Neonatal continuous positive airway pressure device

Abstract

A neonatal continuous positive airway pressure (nnCPAP) system and method, comprising an inspiratory preparation portion comprising an oxygen inlet for a pressurized oxygen source, an ambient inlet for an ambient air source, a blender, a blower, an oxygen flow sensor, a blended flow sensor, an oxygen sensor, an inspiratory pressure sensor, an expiratory reception portion comprising an expiratory pressure sensor to measure expiratory pressure; and a control system having a processor and memory and being configured to determine a pressure at a patient interface based on measurements from the inspiratory pressure sensor and the expiratory pressure sensor, and control a blended air ratio using a dual control system

Description

[0001] NEONATAL CONTINUOUS POSITIVE AIRWAY PRESSURE DEVICE

[0002] BACKGROUND

[0003] The present disclosure relates generally to the respiratory support field and more specifically to an improved neonatal continuous positive airway pressure (nnCPAP) device for neonates with Respiratory Distress Syndrome (RDS).

[0003] Clinicians characterize respiratory distress (RD) in newborns as difficulty breathing and poor oxygen saturation of varying severity, with Respiratory Distress Syndrome (RDS) leading to the most severe cases. RDS is most common in premature infants; each year, roughly 3.2 million globally are thought to suffer from RD that CPAP could treat. The main goal of treatment is to maintain appropriate oxygenation (measured as SpO2).

[0004] Although the mortality rate of RDS without treatment is nearly 100%, it is only 2% when appropriately treated. However, in low-income countries with poor health outcomes, the mortality rate remains as high as 75%. While multiple factors contribute to this high mortality rate, significant factors involved in current CPAP therapy failure include the need for consistent monitoring, as current solutions only work when the nasal prongs are fully occluded within the infant’ s nares, and the high baby: nurse ratio found in low-income countries that does not allow nurses to provide sufficient oversight to all neonates and CPAP machines.

[0005] Accordingly, improved systems, devices, and methods for nnCPAP are desired.

[0004] SUMMARY

[0005] Wherefore, it is an object of one or more embodiments of the presently disclosed invention to overcome one or more of the above mentioned shortcomings and drawbacks associated with the current technology. One or more embodiments of the presently disclosed invention are directed to methods and apparatuses that satisfy the above shortcomings and drawbacks.

[0006] The presently disclosed invention relates to methods, treatments and neonatal continuous positive airway pressure (nnCPAP) systems comprising an inspiratory preparation portion comprising an oxygen inlet for a pressurized oxygen source, anambient inlet for an ambient air source, a blender coupled to the first and second inlets to blend pressurized oxygen and ambient air from the oxygen and ambient inlets, respectively, a blower coupled to the blender and configured to generate an airflow directed to a patient from the blended air, an oxygen flow sensor arranged to detect a flow of the pressurized oxygen, a blended flow sensor arranged to detect a flow of blended air, an oxygen sensor configured to measure an oxygen concentration of the blended air, and an inspiratory pressure sensor to measure inspiratory pressure, an expiratory reception portion comprising an expiratory pressure sensor to measure expiratory pressure, and a control system having a processor and memory and being configured to determine a pressure at a patient interface based on measurements from the inspiratory pressure sensor and the expiratory pressure sensor, and control a blended air ratio using a dual control system that initially uses flow measurements of the oxygen flow sensor and the blended flow sensor to adjust an oxygen concentration of the blended air to near a target concentration and then uses oxygen concentration measurements from the oxygen sensor to adjust the oxygen concentration further toward the target concentration. According to a further embodiment, the nnCPAP system comprises a proportional valve coupled to the oxygen inlet, wherein the control system is configured to control the proportional valve to adjust the oxygen concentration. According to a further embodiment, the control system is configured to calculate an initial fraction of inspired oxygen delivered in the blended air based on a purity value of the pressurized oxygen, an oxygen level of room air, a value of the flow of pressurized oxygen, and a value of the flow of blended air. According to a further embodiment, the control system is configured to determine an initial fraction of inspired oxygen delivered in the blended air according to the formula FiO2D= 100 * (Purity * Fox+ 0.21 * (Finsp- Fox)) / Finsp, where FiO2Dis a fraction of inspired oxygen delivered, Purity is an oxygen concentration of the pressurized oxygen, Finsp is a value of the flow of blended air, and FOx is a value of the flow of pressurized oxygen. According to a further embodiment, the control system is configured to initially set the value of Purity to 1.00. According to a further embodiment, the control system determines the oxygen concentration value from the oxygen sensor, and uses that value to recalculate the Purity value and the fraction of inspired oxygen delivered. Accordingto a further embodiment, the control system is configured to calibrate the oxygen sensor at least once in a time period, wherein the time period is between 0.5 days and 7.0 days. According to a further embodiment, the control system is configured to calibrate the oxygen sensor while delivering treatment by shutting off pressurized oxygen momentarily, flushing substantially all of the pressurized oxygen out of the system, performing a calibration based on ambient air, and turning the oxygen back on for the patient, in less than 0.50 seconds. According to a further embodiment, the oxygen sensor is an electrochemical non-consumable oxygen sensor with a life span of at least two years. According to a further embodiment, the control system is configured to perform a calibration procedure to determine pneumatic characteristics of a patient circuit coupled to the system. According to a further embodiment, the calibration procedure includes determining coefficients for calculating pressure drops through an inspiratory portion and a patient interface of the patient circuit. According to a further embodiment, the control system is configured to calculate a theoretical maximum pressure that could be delivered safely to the patient based on a current system state, and to limit an output of the blower if the theoretical maximum pressure exceeds a maximum pressure threshold. According to a further embodiment, the nnCPAP system comprises a battery, wherein the control system is configured to selectively disable features of the system based on a charge state of the battery and a voltage level of a mains power received. According to a further embodiment, the nnCPAP system comprises that when the nnCPAP system is not receiving power from a mains power then when a voltage in the battery falls below a first threshold, an alarm is initiated and power is discontinued to a humidifier heater plate, when the voltage falls below a second threshold, power is discontinued to a heater wire, and when the voltage falls below a third threshold, the blower reduces speed and maintains a small positive flow of air and a further alarm is activated. According to a further embodiment, the nnCPAP system comprises a patient circuit comprising an inspiratory circuit attached to the inspiratory module, an expiratory circuit attached to the expiratory module, a nasal interface connecting the inspiratory circuit to the expiratory circuit, and the control system being configured to calculate a delivered pressure (Pbaby) that is delivered to the neonatal patient from the nasal interface based on measurements from the sensors andthe determined pneumatic characteristics of the inspiratory circuit and nasal interface. According to a further embodiment, the control system is further configured to calculate an expiratory flow (Fex) based on the measured expiratory pressure (Pex). According to a further embodiment, the expiratory flow is calculated using the equation Fex= a*Pexb. According to a further embodiment, a is a value between 1.40 and 1.60 and b is a value between 0.40 and 0.60. According to a further embodiment, the value of a is between 1.470 and 1.490 and the value of b is between 0.500 and 0.520. According to a further embodiment, the value of a is 1.48 and the value of b is 0.511. According to a further embodiment, the memory stores an inspiratory circuit coefficient (Cinsp) and a nasal interface coefficient (Cieak) calculated during the calibration process. According to a further embodiment, the processor is configured to calculate a pressure drop through the inspiratory circuit using the equation: Pinsp- Pckt= Cinsp*Finsp^2, wherein Pcktis a calculated circuit pressure, wherein Finspis a flow through the inspiratory circuit, as measured by the inspiratory flow sensor, and wherein Pinspis a pressure measured by the inspiratory pressure sensor. According to a further embodiment, the processor is configured to calculate a pressure drop through the nasal interface using the equation: Pckt- Pbaby= Cleak*Fleak^2, wherein Fleakis a calculated flow out the nasal interface, and wherein Pcktis a calculated circuit pressure. According to a further embodiment, the processor is configured to calculate a pressure of air delivered to the neonatal patient using the equation: Pbaby= Pckt- Cleak*Fleak^2, wherein Fleakis a calculated flow out the nasal interface, and wherein Pcktis a calculated circuit pressure. According to a further embodiment, the processor is configured to limit blower speed based on a calculated theoretical maximum pressure (Pmax_theoretical). According to a further embodiment, the processor is configured to limit blower speed based on a calculated theoretical maximum pressure (Pmax_theoretical), and to calculate the P max_theoretical based on values of Pinsp, Cinsp, and Finsp. According to a further embodiment, the processor is configured to calculate the theoretical maximum pressure using the equation: Pmax_theoretical= [(Pinsp- Cinsp*Finsp^2) + (m*Finsp^n + p*Finsp^2 + q*Finsp+ s)] / 2. According to a further embodiment, the processor is configured to calculate the theoretical maximum pressure using the equation: Pmax_theoretical= [(Pinsp- Cinsp*Finsp^2) + (0.1423*Finsp^1.8446 + 0.00218*Finsp^2 + 0.0623*Finsp- 0.0817)] / 2.According to a further embodiment, the processor is configured to limit blower speed so that Pbaby does not exceed 3.0 cm of H2O pressure above a target pressure. According to a further embodiment, the oxygen sensor is connected to a battery voltage, such that the oxygen sensor is energized even when the nnCPAP device is turned off. According to a further embodiment, substantially the only item that requires maintenance in a five- year period is changing one or more filters once a year each. According to a further embodiment, the nnCPAP system comprises when the oxygen sensor detects oxygen levels deviating more than 10.0% from FiO2 setpoint, an alarm is initiated. According to a further embodiment, the nnCPAP system comprises a pressure regulator upstream of a proportional valve that limits pressurized oxygen flow to less than 15.0 psi. According to a further embodiment, the nnCPAP system comprises a spring biased normally open / powered closed pressure relief valve that provides an open air pathway to the patient interface when power to the machine shuts off. According to a further embodiment, the nnCPAP system comprises a housing and a fan arranged in or adjacent to the housing and the control module being configured such that when the nnCPAP system is powered on, before any heating components are powered, the fan turns on and circulates exterior air into a housing interior and interior air out of the system. According to a further embodiment, the nnCPAP system comprises a pressure sensor upstream of a proportional valve.

[0007] The presently disclosed invention further relates to methods, treatments and neonatal continuous positive airway pressure (nnCPAP) systems comprising an inspiratory preparation portion comprising an oxygen inlet for a pressurized oxygen source, an ambient inlet for an ambient air source, a blender coupled to the oxygen and ambient inlets to blend pressurized oxygen and ambient air from the first and second inlets, respectively, a blower coupled to the blender and configured to generate an airflow directed to a patient from the blended air, and an inspiratory pressure sensor to measure inspiratory pressure, an expiratory reception portion comprising an expiratory pressure sensor to measure expiratory pressure, and a control system having a processor and memory and being configured to determine a pressure at a patient interface based on measurements from the inspiratory pressure sensor and the expiratory pressure sensor, and control a blended air ratio using a dual control system that initially usesflow measurements of the oxygen flow sensor and the blended flow sensor to adjust an oxygen concentration of the blended air to near a target concentration and then uses oxygen concentration measurements from the oxygen sensor to adjust the oxygen concentration further toward the target concentration. According to a further embodiment, the nnCPAP system comprises a proportional valve coupled to the oxygen inlet, wherein the control system is configured to control the proportional valve to adjust the oxygen concentration. According to a further embodiment the control system is configured to calculate an initial fraction of inspired oxygen delivered in the blended air based on a purity value of the pressurized oxygen, an oxygen level of room air, a value of the flow of pressurized oxygen, and a value of the flow of blended air. According to a further embodiment the control system is configured to determine an initial fraction of inspired oxygen delivered in the blended air according to the formula FiO2D= 100 * (Purity * Fox+ 0.21 * (Finsp- Fox)) / Finsp, where FiO2Dis a fraction of inspired oxygen delivered, Purity is an oxygen concentration of the pressurized oxygen, Finsp is a value of the flow of blended air, and Foxis a value of the flow of pressurized oxygen. According to a further embodiment the control system is configured to initially set the value of Purity to 1.00. According to a further embodiment the control system determines the oxygen concentration value from a measured oxygen concentration from the oxygen sensor, and uses the measured oxygen concentration value to recalculate the Purity value and the fraction of inspired oxygen delivered. According to a further embodiment the control system is configured to calibrate the oxygen sensor at least once in a time period, wherein the time period is between 0.5 days and 7.0 days. According to a further embodiment the control system is configured to calibrate the oxygen sensor while delivering treatment by shutting off oxygen momentarily, flushing all of the oxygen out of the system, performing a calibration based on ambient air, and turning the oxygen back on for the patient, in under 0.50 seconds. According to a further embodiment the oxygen sensor is an electrochemical non-consumable oxygen sensor with a life span of at least two years. According to a further embodiment, the nnCPAP system comprises a battery, wherein the control system is configured to selectively disable features of the system based on a charge state of the battery and a voltage level of a mains power received. According to a further embodiment, thennCPAP system comprises that when the nnCPAP system is not receiving power from a mains power then when a voltage in the battery falls below a first threshold, an alarm is initiated and power is discontinued to a humidifier heater plate, when the voltage falls below a second threshold, power is discontinued to a heater wire, and when the voltage falls below a third threshold, the blower reduces speed and maintains a small positive flow of air and a further alarm is activated. According to a further embodiment only one oxygen sensor and only two flow sensors are provided. According to a further embodiment, the nnCPAP system comprises a pressure regulator upstream of a proportional valve that limits pressurized oxygen flow to less than 15.0 psi. According to a further embodiment, the nnCPAP system comprises a spring biased open powered closed pressure relief valve that provides an open air pathway to the patient interface when power to the machine shuts off. According to a further embodiment, the nnCPAP system comprises a housing and a fan arranged in or adjacent to the housing and the control module being configured such that when the nnCPAP system is powered on, before any heating components are powered, the fan turns on and circulates exterior air into a housing interior and interior air out of the system. According to a further embodiment, the nnCPAP system comprises an additional pressure sensor upstream of a proportional valve.

[0008] The presently disclosed invention further relates to methods, treatments and neonatal continuous positive airway pressure (nnCPAP) systems comprising an inspiratory preparation portion comprising an oxygen inlet for a pressurized oxygen source, an ambient inlet for an ambient air source, a blender coupled to the oxygen and ambient inlets to blend pressurized oxygen and ambient air from the first and second inlets, respectively, a blower coupled to the blender and configured to generate an airflow directed to a patient from the blended air, an oxygen flow sensor arranged to detect a flow of the pressurized oxygen, a blended flow sensor arranged to detect a flow of blended air, an oxygen sensor configured to measure an oxygen concentration of the blended air, and a control system having a processor and memory and being configured to control a blended air ratio using a dual control system that initially uses flow measurements of the oxygen flow sensor and the blended flow sensor to adjust an oxygen concentration of the blended air to near a target concentration and thenuses oxygen concentration measurements from the oxygen sensor to adjust the oxygen concentration further toward the target concentration. According to a further embodiment the control system is configured to perform a calibration procedure to determine pneumatic characteristics of a patient circuit coupled to the system. According to a further embodiment the calibration procedure includes determining coefficients for calculating pressure drops through an inspiratory portion and a patient interface of the patient circuit. According to a further embodiment the control system is configured to calculate a theoretical maximum pressure that could be delivered safely to the patient based on a current system state, and to limit an output of the blower if the theoretical maximum pressure exceeds a maximum pressure threshold. According to a further embodiment, the nnCPAP system comprises a battery, wherein the control system is configured to selectively disable features of the system based on a charge state of the battery and a voltage level of a mains power received. According to a further embodiment, the nnCPAP system comprises that when the nnCPAP system is not receiving power from a mains power then when a voltage in the battery falls below a first threshold, an alarm is initiated and power is discontinued to a humidifier heater plate, when the voltage falls below a second threshold, power is discontinued to a heater wire, and when the voltage falls below a third threshold, the blower reduces speed and maintains a small positive flow of air and a further alarm is activated. According to a further embodiment, the nnCPAP system comprises a patient circuit comprising an inspiratory circuit attached to the inspiratory module, an expiratory circuit attached to the expiratory module, a nasal interface connecting the inspiratory circuit to the expiratory circuit, and the control system being configured to calculate a delivered pressure (Pbaby) that is delivered to the neonatal patient from the nasal interface based on measurements from the sensors and the determined pneumatic characteristics of the inspiratory circuit and nasal interface. According to a further embodiment the control system is further configured to calculate an expiratory flow (Fex) based on the measured expiratory pressure (Pex). According to a further embodiment the expiratory flow is calculated using the equation: Fex= a*Pex^b. According to a further embodiment a is a value between 1.40 and 1.60 and b is a value between 0.40 and 0.60. According to a further embodiment the value of a is between 1.470 and 1.490 and the value of b isbetween 0.500 and 0.520. According to a further embodiment the value of a is 1.48 and the value of b is 0.511. According to a further embodiment the memory stores an inspiratory circuit coefficient (Cinsp) and a nasal interface coefficient (Cieak) calculated during the calibration process. According to a further embodiment the processor is configured to calculate a pressure drop through the inspiratory circuit using the equation Pinsp- Pckt= Cinsp*Finsp^2, wherein Pcktis a calculated circuit pressure, wherein Finspis a flow through the inspiratory circuit, as measured by the inspiratory flow sensor, and wherein Pinspis a pressure measured by the inspiratory pressure sensor. According to a further embodiment the processor is configured to calculate a pressure drop through the nasal interface using the equation: Pckt- Pbaby= Cleak*Fleak^2, wherein Fleakis a calculated flow out the nasal interface, and wherein Pcktis a calculated circuit pressure. According to a further embodiment the processor is configured to calculate a pressure of air delivered to the neonatal patient using the equation: Pbaby= Pckt- Cleak*Fleak^2, wherein Fleakis a calculated flow out the nasal interface, and wherein Pcktis a calculated circuit pressure. According to a further embodiment the processor is configured to limit blower speed based on a calculated theoretical maximum pressure (P max theoretical ). According to a further embodiment the processor is configured to limit blower speed based on a calculated theoretical maximum pressure (P max theoretical), and to calculate the Pmax_theoreticai based on values of Pinsp, Cinsp, and Finsp. According to a further embodiment, the processor is configured to calculate the theoretical maximum pressure using the equation: Pmax_theoretical= [(Pinsp- Cinsp*Finsp^2) + (m*Finsp^n + p*Finsp^2 + q*Finsp+ s)] / 2. According to a further embodiment the processor is configured to calculate the theoretical maximum pressure using the equation: Pmax_theoretical= [(Pinsp- Cinsp*Finsp^2) + (0.1423*Finsp^1.8446 + 0.00218*Finsp^2 + 0.0623*Finsp- 0.0817)] / 2. According to a further embodiment the processor is configured to limit blower speed so that Pbaby does not exceed 3 cm of H2O in pressure above a target pressure. According to a further embodiment the oxygen sensor is connected to a battery voltage, such that the oxygen sensor 48 is energized even when the nnCPAP device 2 is turned off. According to a further embodiment substantially an only item that requires maintenance in a five year period is changing one or more filters once a year each. According to a further embodiment, the nnCPAP system compriseswhen the oxygen sensor detects oxygen levels deviating more than 10.0% from FiO2 setpoint, an alarm is initiated. According to a further embodiment, the nnCPAP system comprises a pressure regulator upstream of a proportional valve that limits pressurized oxygen flow to less than 15.0 psi. According to a further embodiment, the nnCPAP system comprises a spring biased open powered closed pressure relief valve that provides an open air pathway to the patient interface when power to the machine shuts off. According to a further embodiment, the nnCPAP system comprises a housing and a fan arranged in or adjacent to the housing and the control module being configured such that when the nnCPAP system is powered on, before any heating components are powered, the fan turns on and circulates exterior air into a housing interior and interior air out of the system. According to a further embodiment, the nnCPAP system comprises a pressure sensor upstream of a proportional valve.

[0009] Various objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components. The present invention may address one or more of the problems and deficiencies of the current technology discussed above. However, it is contemplated that the invention may prove useful in addressing other problems and deficiencies in a number of technical areas. Therefore, the claimed invention should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various embodiments of the invention and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of the invention. It is to be appreciated that the accompanying drawings are not necessarily to scale since the emphasis is instead placed on illustrating the principles of the invention. The invention will now be described, by way of example, with reference to the accompanying drawings in which:

[0012] Fig. 1 is a schematic view of an embodiment of the neonatal continuous positive airway pressure (nnCPAP) device as presently disclosed delivering air to a neonatal patient; and

[0013] Figs. 2A and 2B are schematic images depicting the flow and pressure of air at various points along a therapeutic path to and from the neonatal patient.

[0014] DETAILED DESCRIPTION

[0015] The present invention will be understood by reference to the following detailed description, which should be read in conjunction with the appended drawings. It is to be appreciated that the following detailed description of various embodiments is by way of example only and is not meant to limit, in any way, the scope of the present invention. In the summary above, in the following detailed description, in the claims below, and in the accompanying drawings, reference is made to particular features (including method steps) of the present invention. It is to be understood that the disclosure of the invention in this specification includes all possible combinations of such particular features, not just those explicitly described. For example, where a particular feature is disclosed in the context of a particular aspect or embodiment of the invention or a particular claim, that feature can also be used, to the extent possible, in combination with and / or in the context of other particular aspects and embodiments of the invention, and in the invention generally. The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and grammatical equivalents and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures, are used herein to mean that other components, ingredients, steps, etc. are optionally present. For example, an article “comprising” (or “which comprises”) components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also one or more other components. The singular forms “a,” “and” and “the” include plural references unless the context clearly dictates otherwise. Where reference is made herein to a method comprising two or more defined steps, the defined steps can be carried out in any order or simultaneously (except where the context excludes that possibility), and the method can include one or more other steps which are carried outbefore any of the defined steps, between two of the defined steps, or after all the defined steps (except where the context excludes that possibility).

[0016] The term ‘‘at least” followed by a number is used herein to denote the start of a range beginning with that number (which may be a range having an upper limit or no upper limit, depending on the variable being defined). For example, “at least 1” means 1 or more than 1. The term “at most” followed by a number is used herein to denote the end of a range ending with that number (which may be a range having 1 or 0 as its lower limit, or a range having no lower limit, depending upon the variable being defined). For example, “at most 4” means 4 or less than 4, and “at most 40% means 40% or less than 40%. When, in this specification, a range is given as “(a first number) to (a second number)” or “(a first number)-(a second number),” this means a range whose lower limit is the first number and whose upper limit is the second number. For example, 25 to 100 mm means a range whose lower limit is 25 mm, and whose upper limit is 100 mm.

[0017] The embodiments set forth the below represent the necessary information to enable those skilled in the art to practice the invention and illustrate the best mode of practicing the invention. For the measurements listed, embodiments including measurements plus or minus the measurement times 5%, 10%, 20%, 50% and 75% are also contemplated. For the recitation of numeric ranges herein, each intervening number there between with the same degree of precision is explicitly contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated.

[0018] The term “substantially” means that the property is within 80% of its desired value.In other embodiments, “substantially” means that the property is within 90% of its desired value. In other embodiments, “substantially” means that the property is within 95% of its desired value. In other embodiments, “substantially” means that the property is within 99% of its desired value. For example, the term “substantially complete” means that a process is at least 80% complete, for example. In other embodiments, the term “substantially complete” means that a process is at least 90% complete, for example. In other embodiments, the term “substantially complete” means that a processis at least 95% complete, for example. In other embodiments, the term “substantially complete” means that a process is at least 99% complete, for example.

[0019] The term “substantially” includes a value that is within 10% less than or greater than the indicated value. In certain embodiments, the value is within 5% less than or greater than of the indicated value. In certain embodiments, the value is within 2.5% less than or greater than of the indicated value. In certain embodiments, the value is within 1% less than or greater than of the indicated value. In certain embodiments, the value is within 0.5% less than or greater than of the indicated value.

[0020] The term “about” includes when value is within 10% of the indicated value. In certain embodiments, the value is within 5% of the indicated value. In certain embodiments, the value is within 2.5% of the indicated value. In certain embodiments, the value is within 1% of the indicated value. In certain embodiments, the value is within 0.5% of the indicated value.

[0021] In addition, the invention does not require that all the advantageous features and all the advantages of any of the embodiments need to be incorporated into every embodiment of the invention.

[0022] Turning now to Fig. 1, a brief description concerning the various components of the present invention will now be briefly discussed. As can be seen in this embodiment, the neonatal continuous positive airway pressure (nnCPAP) device 2 comprises an inspiratory preparation portion 4, an expiratory reception portion 6, a patient circuit 8 connecting the two, a user interface 10, and a control system 12.

[0023] In operation, the inspiratory preparation portion 4 prepares heated, humidified, blended air 14 to be delivered to a neonate patient 16. The process begins with an oxygen source 18 delivering preferably pressurized oxygen 19 through an oxygen hose 20 to an oxygen inlet in 22 the housing 23 of the nnCPAP device 2, and through a pressure regulator 24. From the pressure regulator 24, the pressurized oxygen 19 continues on an oxygen path 26 to a proportional valve 28. The proportional valve 28 preferably can open wide enough to utilize oxygen 19 from a low-pressure source 18 and also have a fine enough control to utilize oxygen 19 from a high-pressure source 18. From the proportional valve 28, the pressurized oxygen 19 continues past an oxygen flow sensor 30 to a blender 31, and then a blower 32. Concurrently, ambient air 34 issupplied to an ambient inlet 36 in the housing 23 of the nnCPAP device 2, then through an air filter 38 and along an ambient path 40. A mitigation fan 41 is also located in or adjacent to the housing 23. The oxygen path 26 and ambient path 40 merge in the blender 31 and form a blended air path 42 that flows into the blower 32. After the blower 32, the blended air path 42 flows past an inspiratory flow sensor 46 and into a manifold 44, which includes an oxygen sensor 48 (such as an Oxycell™ sensor), an inspiratory pressure sensor 50, and a pressure relief valve 52. Though the oxygen sensor 48 is located downstream from the inspiratory flow sensor 46 in the embodiment shown, the oxygen sensor 48 may also be located at other locations, including other locations downstream of the blender 31 and upstream of the patient circuit 8. The pressure relief valve 52 provides preferably one of a spring biased normally open I energized closed or a biased closed valved fluid passage from the blended air path 42 out of the housing 23, such that when the air pressure in the blended air path 42 exceeds a set amount, the blended air 14 may exit the nnCPAP device 2 through the pressure relief valve 52. Continuing, the blended air path 42 exits the housing 23 and an enclosed portion of the inspiratory preparation portion 6 through an outlet check valve 68 and then flows into a preferably removable humidifier chamber 54 through a chamber inlet 56. The humidifier chamber 54 preferably sits in a recess of the housing 23. The humidifier chamber 54 preferably incases a sufficient quantity of water 58 to humidify the blended air 14 that passes in a space over the water 58. A preferably spring loaded heater plate 60, preferably under the humidifier chamber 54, supplies heat to the water 58. A heater plate temperature sensor 62 monitors the temperature of the heater plate 60 and / or the water 58. An optical sensor 63 is preferably arranged under the heater plate 60 and detects when the heater plate 60 is depressed by an installed humidifier chamber 54, and power is preferably only supplied to the heater plate 60 when a humidifier chamber 54 is installed. The blended air path 42 leaves the humidifier chamber 54 through a chamber outlet 64, leaves the inspiratory preparation portion 4 of the nnCPAP device 2, and enters the patient circuit 8.

[0024] The patient circuit 8 comprises an inspiratory circuit 70, a patient interface 72, and an expiratory circuit 74. The inspiratory circuit 70 includes line tubing 76 with a first end connected to the chamber outlet 64 and includes a heater wire 78 extending alonga length of one of the inside (shown) and the outside (not shown) of the inspiratory circuit 70. Adjacent to the heating wire 78 on a first end, preferably closer to the chamber outlet 64 and distal to the neonatal patient 16, is a distal temperature sensor 66. Adjacent to the heating wire 78 on a second opposite end, preferably further from the chamber outlet 64 and proximate to the patient 16, is a proximate temperature sensor 80. The heater wire 78, distal temperature sensor 66, and proximate temperature sensor 80 are functionally connected to the control system 12 by one or more wires (not shown). The inspiratory circuit 70 terminates at, and its second end is fluidly connected to, the patient interface 72. The patient interface 72 has one or more openings or vents 82 that allow the blended air 14 to be delivered to a preferably neonate patient 16 at a location inside or near the patient's mouth or nose 84. The patient interface 72 forms a transition from the blended air path 42 received from the inspiratory circuit 70 to the expiratory air path 86 provided to the expiratory circuit 74. Continuing, the patient interface 72 is fluidly connected to the expiratory circuit 74. The expiratory circuit 74 similarly includes line tubing 76, with a first end connected to the patient interface 72 and a second end connected to the housing 23 through an expiratory inlet 88 of the expiratory reception portion 6 of the nnCPAP device 2.

[0025] After the expiratory inlet 88, the expiratory air path 86 continues into the expiratory reception portion 6, carrying expiratory air 90 past an expiratory pressure sensor 92, and terminates at a preferably fixed orifice 94 that allows the expiratory air 90 to exit the housing 23 of the nnCPAP device 2.

[0026] The user interface 10 preferably includes one or more screens that include a temperature display 96, a pressure display 98, and / or a FiCT (fraction of inspired oxygen ) display 100, each value referring to the blended air 14 delivered to the patient 16. The user interface 10 preferably includes one or more screens that display operation instructions 102 of the nnCPAP device 2. The user interface 10 preferably further includes one or more input devices 104, such as buttons, keys, switches, scanners, touch screens, and / or knobs to input instructions and / or data into the nnCPAP device 2. The user interface also includes one or more alerts and or alarms 106. In an embodiment, long visual status light 108 is positioned on a top surface of the nnCPAP device 2. The status light 108 can display a solid first color when the nnCPAP device 2 is functioningproperly, and may display a solid or flashing first or second color(s) if the nnCPAP device 2 is not functioning properly. An improper function could include delivering air 14 to the patient 16 where the temperature, the pressure, the flow rate, the FiO2, and / or some other quality of the air 14 is outside of a predetermined window, or detecting other malfunctioning issues with the nnCPAP device 22 such as loss of power or low battery conditions, for example, or detecting malfunctioning issues with the nnCPAP device’s 2 use with the patient 16. In an embodiment, one or more of the long visual status light(s) 108 is positioned at a top of a handle 110 for the nnCPAP device 2. In a further embodiment, the handle 110 is fixed in an upward position.

[0027] The control system 12 controls the functioning of the nnCPAP device 2 and is functionally connected to send power and send and / or receive data / information and / or instructions to and / or from the elements of the inspiratory preparation portion 4, the expiratory reception portion 6, the patient circuit 8, and / or the user interface 10. The control system 12 preferably includes a processor 112, a non-volatile memory 114, a removable memory 116, a wireless transmitter / receiver 118, a first further control system module 120, and a second further control system module 122, such as one or more of analog to digital converters, digital to analog converters, pulse width modulators, and / or USB interface 120, 122, for example. An external power source 124 is preferably connected to the control system 12 via a power cord 126 to a power supply unit (not shown) of the nnCPAP device to power the nnCPAP device 2 and the various constituent parts. The external power source 124 is preferably a mains power such as an A / C current, which is preferably converted to DC current by the power supply unit. Alternatively, and / or additionally one or more batteries 128 are provided to power the power source of nnCPAP device 2 and / or for providing auxiliary and / or backup and / or emergency power for the nnCPAP device 2.

[0028] Operation

[0029] In operation, some embodiments of the nnCPAP device have one or more of a variable oxygen pressure dual control system, a patient pressure determination, a low 02 safety feature, a high-pressure safety feature, a dynamic max pressure safety feature, a low battery safety feature, a no power safety feature, an 02 fire safety feature, a User Interface Guide feature, and a visual status safety feature. Contrasting with otherCPAP devices that maintain a constant flow, such that pressure would fluctuate when external factors occur, embodiments of the nnCPAP device 2 disclosed preferably maintains a constant pressure.

[0030] In operation, the user preferably sets a target pressure and a target FiO2, and the control system 12 modulates the flow via modulation of one of the proportional valve 28, the blower 32, and both the proportional valve 28 and the blower 32 to achieve the target FiO2. The nnCPAP device 2 is designed to accept pressurized oxygen 19 from either a high-pressured source 18, such as an oxygen tank or a central supply in a hospital, or a lower-pressured source 18 such as a concentrator and is designed to compensate for varieties in pressure and purity of the oxygen 19 supplied from the oxygen source 18.

[0031] Variable Oxygen Pressure Dual Control System / FiO2 Algorithm

[0032] Determining FiO2

[0033] When the nnCPAP device 2 powers and / or initiates a therapy session, the control system 12 determines a flow-calculated FiO2 (“FiO2pc”) level using the flow rate of the blended air 14 and flow rate of the pressurized oxygen 19, and then the control system 12 adjusts the blend rate to achieve a delivered FiO2 (“FiO2o”) level that approximates a predetermined target FiO2 (“FiO2r”) level. Next or concurrently, the oxygen sensor 48 senses a measured FiO2 (“F102M”) level in the blended air 14. Utilizing the FiO2M value, the control system 12 adjusts the proportional valve 28 accordingly to achieve the FiO2 r rate in the FiO2o. A benefit of this method is that an approximate FiO2pc, which is therapeutically sufficiently close to the FiO2p rate, can be achieved quickly with data from just the two flow sensors 30, 46; and then an FiO2 that is preferably closer to the F1O2T can be achieved at a later point in time with a more accurate F102M data from the oxygen sensor 48.

[0034] To calculate the FIO2FC, the inventors invented an algorithm with the following variables. Fiuspis the blended air 14 flow through the inspiratory circuit, as measured by the inspiratory flow sensor 46. Foxis the flow of oxygen 19, as measured by the oxygen flow sensor 30 on the oxygen path 26. Purity is the calculated concentration of pressurized oxygen 19 provided by the oxygen source 18. From a tank 18, the oxygen 19 concentration is likely 100% oxygen. From an oxygen concentrator 18, the oxygen19 concentration is likely between 80-96% oxygen (0.80 to 0.96). O2measured is the oxygen concentration of the blended air 14 as measured by the oxygen sensor 48. O2mesured is equal to F1O2M. FlowRatio is the proportion of the total flow of ambient air 34 that comes from the oxygen source 18. FactorpiowRatio is the correction factor to account for pressurized oxygen 19 being supplied at less than 100% purity, and is equal to Purity minus 0.21.

[0035] The Fi02o can be calculated as the concentration of oxygen 19 from the oxygen source 18 times the flow of oxygen 19 measured by the oxygen flow sensor 30 plus the flow of ambient (e.g., “room”) air 34 times 21.0%, divided by the total inspiratory flow rate measured by the inspiratory flow sensor 46. The following formula may represent the FiO2o value:FiO2D= 100 * (Purity * Fox+ 0.21 * (Finsp- Fox)) / Finsp

[0036] The inventors created the term “FlowRatio” as being equal to [100 * Fox / Finsp]. This may simplify the delivered FiO2 value formula to:FiO2 D = (Purity - 0.21) * FlowRatio + 21

[0037] The inventors created a further new variable “FactorpiowRatio” as being equal to the [Purity - 21] term. This further simplifies the delivered FiO2 value formula to:FiO2o = FactorpiowRatio * FlowRatio + 21

[0038] With the nnCPAP device 2, a starting assumption may be that the oxygen source 18 is pure and that the FactorpiowRatio = 0.79. Using this initial assumed FactorpiowRatio, the proportional valve 28 may be adjusted to rapidly achieve an FiO2pc value equal to the target, where the FiO2o is approximately the FiO2. When the control system determines the FiO2pc is achieved, the oxygen sensor 48 can find the O2measured value. With the O2measured value, the FactorpiowRatio may be recalculated using the equation:FactorpiowRatio = (O2measured - 21) / (100 * FlowRatio),

[0039] This recalculated FactorpiowRatio may then be used to calculate the Purity of the pressurized oxygen from the oxygen source 18 and true F1O2D and / or to make rapid changes if the user changes the FiO2 setpoint. With these values, the proportional valve 28 may be quickly adjusted to better align Fi02o with FiO2p.

[0040] In further embodiments, the oxygen sensor 48 regularly monitors the FiO2o of the blended air 14 to ensure that the amount and purity of the pressurized oxygen areconsistent with the O2measured, and the control system 12 adjusts the FactorpiowRatio and proportional valve further as needed.

[0041] The oxygen sensor 48 is preferably an electrochemical non-consumable oxygen sensor 48, such as the Oxycell TM sensor, that works according to the principle of an oxygen pump. In the oxygen sensor 48, there is preferably a measuring electrode, a reference electrode and a counter-electrode in the electrolyte. A description of an embodiment of such an oxygen sensor 48 follows. Such an oxygen sensor 48 is electronically operated using a potentiostat switch so that oxygen is reduced at the measuring electrode: O2 + 4H++ 4e’ — 2H2O / Simultaneously, water is electrolyzed at the counter-electrode: 2H2O -^ 62 + 4H++ 4e". Overall, the oxygen that arrives at the measuring side of the oxygen sensor 48 is then returned at the counter-electrode side, without the oxygen sensor 48 being changed. This produces an electrical current that, depending on the gas influx, is proportional to the 02 concentration in the gas being monitored. This type of oxygen sensor 48 can measure 02 concentration from between 0% to 100%, have a response time of under 800 ms, have an operating temperature of between 0 and 50 degrees Celsius, and have a useful life of about five years or more. Using this type of oxygen sensor 48 sensor has material benefits in deploying the nnCPAP device 2 in regions of the world where a requirement of regular maintenance, which may be difficult to procure, may impede functionality and utility of other devices. The nnCPAP device may preferably operate for multiple years without replacing any of the sensors or other hardware, with the exception of the air filter 38.

[0042] Oxygen sensor calibration

[0043] In a further embodiment, the oxygen sensor 48 is calibrated every 24 hours to 7.0 days. During oxygen sensor 48 calibration, the proportional valve 28 is closed and the ambient path 40 is substantially purged of pressurized oxygen 19. After the purging, the oxygen sensor 48 is calibrated on ambient air 34.

[0044] As some neonatal patients may be receiving therapy from the nnCPAP device 2 for months at a time, the calibration may be done while a neonatal patient 16 is receiving treatment. The patient may receive a reduced FiO2o for a preferably very short period of time during the oxygen sensor 48 calibration, but will still preferably receive warm, humidified air of normal oxygen levels. The oxygen sensor 48 calibration willpreferably last between 0.01 and 10.00 seconds, more preferably between 0.10 and 5.00 seconds, and most preferably around 2.50 seconds.

[0045] In a further embodiment, the oxygen sensor is calibrated every 24 hours when not providing therapy to preserve oxygen measurement accuracy. The proportional valve is closed, and the blower purges oxygen from the gas pathway so the oxygen sensor calibration can be performed under standard atmospheric conditions.

[0046] In a further embodiment, oxygen sensor calibration is not performed during therapy to ensure that critical therapy is not interrupted. If preferably between 5 and 15 days, and more preferably 10 days of continuous therapy are conducted without an oxygen sensor calibration, the oxygen display may be modified to indicate a potential accuracy reduction. This alerts the user to reduced accuracy conditions without performing a calibration. In such an embodiment, continuous therapy takes priority over strict oxygen accuracy. In a further embodiment of this embodiment, if therapy is being performed without pressurized oxygen (FiO2 setpoint left at 21%), the oxygen sensor calibration is preferably performed every 24 hours, as such a calibration would not interfere with therapy.

[0047] Q2 level safety

[0048] During operation, an oxygen source 18 may deliver a variable amount of oxygen 19. For example, a tank 18 may be the oxygen source 18, and the tank may start to run out of oxygen 19. A volume of gas might still be flowing into the nnCPAP device 2 through the oxygen inlet 22, but the amount of oxygen 19 could be decreasing. The oxygen sensor 48 ensures that not just flow of gas is maintained, but level of oxygen 18 is as well. If FiO2M deviates from an expected amount by more than a predetermined level, the control system may attempt to address the change by opening or closing the proportional valve, and / or may alert a user of the change in oxygen level.

[0049] Pretreatment Calibration

[0050] Turning to Figs. 2A and 2B, further aspects of the nnCPAP device 2 are discussed.According to an embodiment, the nnCPAP device 2 may determine a pressure of blended air 14 delivered to the patient 16, preferably without a pressure sensor located in the patient circuit 8, and preferably such determination may be made substantially agnostic to brand or manufacturer of line tubing 76 or patient interface 72 are attachedto the inspiratory preparation portion 4 or expiratory reception portion 6. This may be achieved based on measurements taken during a calibration procedure to determine pneumatic characteristics of a patient circuit coupled to the system.

[0051] The calibration procedure may be initiated by connecting the line tubing 76 and patient interface 72 that will be used with the patient 16, but without the patient connected to the nnCPAP device 2 such that the patient interface 72 is open to the environment at whatever the ambient air pressure is (e.g., the arrangement in Fig. 1, but without the patient). The control system 12 then causes air to be blown through the nnCPAP device 2 at preferably between 2 and 10 different pressures and / or between 2 and 10 different flow rates, more preferably between 4 and 8 different pressures and / or between 4 and 8 different flow rates, most at 6 different pressures and / or 6 different flow rates, beginning at approximate pressure of 1.0 cmH20 at the patient interface and increasing until the approximate pressure of 12.0 cmH20 at the patient interface is reached. The control system 12 measures the flow and pressure out of the inspiratory preparation portion 4 with the FinSp flow sensor 46 and Pisuppressure sensor 50, respectively, and pressure into the expiratory reception portion 6 via the PeXp pressure sensor 92. The processor 112 may then use the resulting measurements averaged to determine the factors Cinsp and Cleak that are specific to this patient circuit (line tubing 76) and use such determined Cinsp and Cleak factors to determine the resultant patient pressure (Pbaby) at the patient interface during therapy. In addition, if oxygen is connected and flowing during the circuit calibration, the proportional valve control for oxygen is calibrated to the oxygen flow rate, thus speeding up the time to reach the FiO2 setpoint for therapy. The processor 112 may additionally use the measurements to build a model, such as the following pressure algorithm.

[0052] Pressure Algorithm

[0053] Referring to Figs. 2A and 2B, key variables are defined in determining the pressure algorithm.

[0054] FinSp is the flow through the inspiratory circuit 70, as measured by the inspiratory flow sensor 46;

[0055] Pinsp is the pressure measured by the inspiratory pressure sensor 50 before the air leaves the inspiratory preparation portion 4;

[0056] Pexis the pressure as measured by the expiratory flow sensor 92 after the air returns to the expiratory reception portion 6;

[0057] Fexis the flow through the expiratory circuit 74, calculated from Pex;

[0058] Pckt is the pressure at the junction of the inspiratory circuit 70, expiratory circuit 74, and patient interface 72. It may be calculated from Pex(and Fex);

[0059] Fieak is the flow out of the vent 82 of the patient interface 72, calculated as the difference between FinSp and Fex;

[0060] Pbaby is the pressure delivered to the baby / patient 16. It may be calculated using the characteristics of the inspiratory circuit 70 and patient interface 72 and some or all of the pressure and flow measurements;

[0061] Psetpoint is a user selected target pressure for Pbaby.

[0062] Cmsp is the inspiratory circuit coefficient calculated during the calibration procedure; it indicates how significant the pressure drop is through the inspiratory circuit 70; and

[0063] Cicak is the patient interface coefficient calculated during the calibration procedure.It indicates how significant the pressure drop is through a given patient / nasal interface 72.

[0064] The inventors empirically determined that the relationship between Pexand Fexis represented by a power series where Fexis roughly proportional to the square root of Pex, with pressure measured in cmH₂O and flow measured in liters per minute (though these units omitted in the equations below). According to one embodiment, a relationship between Pexand Fexmay be:Fex = a*Pexb, where a and b are determined values.Which was determined in one embodiment as:Fex = 1.480* Pex0'511.Which may be approximated further as:p > 1 5* p 05rex — 1. J r ex

[0065] In cases where a theoretical Pexneeds to be solved for based on a known Fex, in some embodiments the general relationship between Fexand Pexcan be approximated as (again, with units omitted):Pex= c*Fexd, where c and d are determined values.Which was determined in one embodiment as:Pex = 0.464 * FeX1959Which may be approximated further as:Pex= 0.5 * Fex2- This can become relevant in the over-pressurization safety method described below.

[0066] The pressure drop through the expiratory circuit may be represented by a single polynomial. According to one embodiment, the polynomial is represented by:Pckt - Pex = e* Fex2+ f* Fex+ g, where e, f, and g are determined values.

[0067] The inventors empirically determined an embodiment for such a formula by measurements taken from 5 expiratory circuits, as followsPckt - Pex = 0.00218 * Fex2+ 0.0623 * Fex- 0.0817

[0068] The circuit pressure (Pckt) may calculated from Pexin this formula using:Pckt-ex = Pex + 0.00218 * Fex2+ 0.0623 * Fex- 0.0817

[0069] The circuit pressure (Pckt) may also be calculated using this formula:Pcktjnsp = Pckt-ex + 0.0033 * Fcx2+ 0.0156 * Fex + 0.0033 * Finsp2+ 0.0156 * Finsp- 0.044

[0070] Continuing, the circuit pressure (Pckt) may also be calculated as the average of PCkt_ex and Pckt_ jnsp using the formula:Pckt—(Pckt_ex + Pcktjnsp)

[0071] The pressure drop through the inspiratory circuit 70 and through the nasal interface 72 are roughly proportional to the square of the flow through them. The pressure drop through the inspiratory circuit 70 may be represented by:Pinsp “ Pckt — Cinsp^ Finsp •And the pressure drop through the nasal interface 72 may be represented by:Pckt - Pbaby=Cleak* Fieak”.The coefficients of the squared flows may be different based on the specific circuit and nasal interface used and are calculated during circuit calibration. PCkt is the pressure at the junction of the inspiratory circuit 70, expiratory circuit 74, and nasal interface 72.

[0072] CinSp and Cieak may be calculated during a circuit test. Fieak and Pbaby may then be calculated.

[0073] Fieak may be calculated from the difference in FjnSand Fexsuch thatFie k — Finsp " Fex

[0074] During the calibration process, the vent 82 (such as mask opening or prongs, for example) 82 is open to the ambient pressure, so Pbaby = 0. Cieak may then be calculated from Pckt - 0 = Cieak * Fieak2such thatCieak=Pckl I Fieak2

[0075] Cinsp may be calculated from Pinsp- Pcktjsnp = Cinsp * Finsp2such thatCinsp = t VP1insp - P ck,t_isnp i / ' / F insp2

[0076] Determining Pressure at the Patient

[0077] Based on the measurements and calculations during the calibration process, the processor 112 builds a model of what the pressure is at the patient’s nose 84, without requiring any pressure sensor outside of the housing 23, and preferably using only the FinSp flow sensor 46, Pisnppressure sensor 50, and the Pexppressure sensor 92 measurements for such calculations. This allows substantially any consumables, such as various line tubing 76 and various patient interfaces 72, to be used.

[0078] During therapy, the pressure delivered to the patient (Pbaby) is equal to the circuit pressure (PCkt) minus the pressure drop through the nasal interface 72. PCkt can be calculated multiple ways after calibration has been completed, for example, as the inspiratory pressure minus the pressure drop through the inspiratory circuit, p > p. _r\ * p. 2xckt_insp ~1insp mspAinspor as the expiratory pressure plus the pressure drop through the expiratory circuit Pckt ex = Pex +h * Fex2+j* Fex+ k, where h, j, and k are determined valuessuch as in one embodiment, where h, j, and k for this formula was found to equal:Pckt-ex = Pex + 0.00218 * Fex2+ 0.0623 * Fex - 0.0817.

[0079] Pckt may be calculated in both ways (Pcktjnspand Pckt_ex), and the average of the two (Pckt av) may be used in the following formula to determine the pressure at the patient / neonate’s nose:P1=P - C * p 2baby1ckt_avg '—leak1leak.

[0080] Therefore, after calibration and during therapy, the control system may periodically or consistently calculate the pressure that is delivered to the neonatal patient 16 from the nasal or other patient interface 72 based on real-time measurements from the Fiuspflowsensor 46, Pjsnppressure sensor 50, and the Pexppressure sensor 92 during therapy and patient circuit 8 characteristics determined during the calibration procedure.

[0081] Over-pressurization Risk Mitigation

[0082] Under some embodiments, the nnCPAP device 2 is monitoring the PiSnPand the Pexp, and calculating Pbaby, and moderating flow rate and pressure to maintain a target pressure at Pbaby. During operation, if there is a leak at the nasal interface 72 which lower calculated Pbaby, there may be a risk that if the nnCPAP device 2 increases Pisnpto compensate, and then the leak is plugged suddenly, the Pbaby could spike high enough to harm the patient 16. One example is if the prongs 72 come completely out of the patient’s nose 84, the blower 32 may ramp up to try and reach the target pressure at Pbaby so the patient will still receive therapeutic oxygen even though the prongs 72 are out. But if a nurse then, noticing the dislodged prongs 72, quickly replaces the prongs 72 back into the patient’s nose 84, the potential pressure spikes may be quite high.

[0083] Thus, the inventors were concerned that if all the air put out by the blower 32 (Fins) in such a situation suddenly went to the patient 16 (Fieak = 0), the high pressure would harm the patient 16. To prevent this over-pressurization, a safety algorithm based on a theoretical maximum safe pressure is preferably run on the nnCPAP device 2 during operation. To calculate this theoretical pressure (Pmax.theoreticai), the following may be used:Ficak — 0 and Fex— FjnSpP — P. _ C * F. 2rckt 1rinsp '‘-'insp1inspPckt-2 = Pex + 0.00218 * Fex2+ 0.0623 * Fex- 0.0817

[0084] Instead of using the measured Pex, a theoretical maximum Pexmay be calculated using the previously described equation for the previously described embodiment:Pex = 1.039 * Fex1'656.So for the scenario where Fex= Finspthis yields:Pckt_2 = (1.039 * Finsp1 656) + 0.00218 * Finsp2+ 0.0623 * Finsp- 0.0817.

[0085] Because in this scenario: Fieak= 0, then Pmax_theoreticai = Pckt-avg., andPmax_theoretical=[(Pinsp — CiiisP*FinspA2) + (m*FiuspAn + p*FinsPA2 + q*FinSp + S)] I 2, where m, n, p, q, and s are determined values.

[0086] Written out in terms of measured values in one embodiment:Pmax_theoretical — [(Pinsp - C insp^ Pinsp ) + (0.464 * Pinsp1 959+ 0.00218 * Finsp + 0.0623 * FiuSp - 0.0817)] / 2

[0087] For increased safety, if Pmax_theoreticai ever exceeds Psetpoint + 3 cmH₂O, the blower speed is preferably decreased until Pmax_theoreticai < ( Psetpoint + 3 cmH20 ).

[0088] Battery Safety Shutdown

[0089] In an embodiment of the nnCPAP device 2, the device 2 may function fully if power from the mains 124 is no longer supplied, such as in mains 124 power outage, if the power cord 126 was unplugged from the mains 124 while the nnCPAP was powered on, or if the nnCPAP device 2 was turned with the power cord 126 unplugged, for example, and the power instead being supplied by the battery 128. However, in situations where the battery 128 is supplying power, a potential risk is that the battery 128 runs down while therapy is still required for the patient 16. To balance the competing priorities of the fullness of functionality with the longevity of functioning when operating on potentially limited power, a hierarchy of function may be implemented, increasing efficiency as a battery level falls. In an embodiment, the nnCPCP device 2 successively shuts down different elements, starting with less critical elements and moving to more critical elements.

[0090] In one embodiment where mains 124 power is not provided, at a first battery energy level, all nnCPAP device 2 elements are powered. When the battery energy level falls below a first threshold and enters a second battery energy level, the heater plate 60 is preferably shut off, but preferably most or all other functioning is maintained. When the battery energy level falls below a second threshold and enters a third battery energy level, other heating elements, like the heating wire 78, are preferably shut off, but the blower 32 is still functioning at normal power, and, e.g., proportional valve and sensors are preferably still active. When the battery energy level falls below a third threshold and enters a fourth battery energy level, most elements would preferably be powered off and the blower 32 may function at a reduced level, so as to prolong a time period that a sufficient level of air flows through the patient interface 72 to the patient 16. In an embodiment, at the fourth battery energy level the blower 32 would blow air such that a flow rate of air out of the interface 72 is substantially sufficient to ensure the patient’s 16 normal respiration volume is provided.

[0091] In an embodiment, one or more alarms will signal at one or more or each of the battery energy levels. In an embodiment, an increasing volume of audible alarms and / or an increasing number and / or brightness and / or strobing of visual alarms accompany the progression from the first to the fourth energy level.

[0092] In an embodiment, the first battery energy level is entered when the battery 128 is at a full charge and the nnCPAP device is not receiving power from the mains power 124, the second battery energy level is entered when the battery 128 is a full charge minus 4.0 volts, the third battery energy level is entered when the battery 128 is a full charge minus 5.0 volts, the fourth battery energy level is entered when the battery 128 is a full charge minus 6.0 volts, for example.

[0093] In an embodiment, an automatic sounding audible critical power alarm may automatically sound when power falls below a certain threshold, and the nnCPAP device 2 machine is in the on position. The critical power alarm may be self-powered with a separate power source and / or battery, preferably charged by mains power 124. This critical power alarm is preferably designed to be loud enough to be heard from rooms away, such as between 55 and 85 db, or more preferably between 60 and 80 db, and most preferably between 65 and 75 db.

[0094] In an embodiment, there is full battery monitoring, with a battery level displayed on the front of the nnCPAP device 2 user interface 10. This may be displayed at all times, when the battery 128 is providing power alone, and / or when the battery power level decreases from a full level.

[0095] Failsafe patient breathing pathway

[0096] In some embodiments, depending on the patient interface 72, if power fails and airflow into the patient interface 72 stops or falls below a level required for adequate patient respiration, the patient 16 may suffer. In such a catastrophic situation, one or more emergency valves may be provided that are normally / spring-biased open, but are powered closed, such as a normally open solenoid valve. This emergency valve would preferably remain closed during normal operation of the nnCPAP device 2, but if the nnCPAP device 2 shuts off, the emergency valve could automatically open, and provide an air pathway from outside air to the patient 16. The emergency valve may be located in various positions, including right adjacent to the inspiratory preparationportion 4 connecting to the patient circuit 8 and / or right adjacent to the expiratory reception portion 6 connecting to the patient circuit 8, for example. Alternatively or additionally, in an embodiment, the pressure relief valve 52 may also be designed as a spring-biased open, powered closed emergency relief valve, such that when the nnCPAP device 2 shuts off, the pressure relief valve 52 opens so that air can then go through the pressure relief valve 52, and the patient's nose 84 is not plugged. The emergency valve may also be designed to open automatically before nnCPAP device 2 power falls to zero, but opens when power falls below a level necessary to cause the blower 32 to blow a sufficient flow of air through the patient interface to the patient 16 for patient 16 respiration.

[0097] Preventing Oxygen Fire Risk

[0098] In an embodiment, oxygen 19 may collect inside the housing 23 when the nnCPAP device 2 is powered off, but the oxygen source 18 is still connected, creating a hyperoxygenated environment. This could potentially create a fire risk when the heating plate 60 is powered on. To help mitigate such risk, a mitigation fan 41 may be provided. When the nnCPAP device 2 is turned on, preferably before one, some, or any high-power elements such as the heating elements, like the heater plate 60 and / or heating wire 78, are powered, the mitigation fan 41 is activated and circulates exterior air into the interior of the housing 23, flushing some, most, or all of any collected hyperoxygenated air from the interior of the nnCPAP device 2. The mitigation fan 41 may run for a mitigation period of preferably between 4.0 and 20.0 seconds, more preferably between 5.0 and 10.0 seconds, to provide a sufficient flushing volume of ambient air to help mitigate a risk caused by an oxygen leak. After the mitigation fan has run for the mitigation period, the nnCPAP device 2 may preferably continue powering on. Alternatively, or additionally, in a further embodiment, the blower 32 may act as a mitigation fan and selectively blow ambient air 34 through the nnCPAP device 2 when the nnCPAP device 2 is turned on before any heating elements are turned on.

[0099] Rapid over-pressurization prevention

[0100] In an embodiment, the pressure of oxygen 19 may change rapidly because of a malfunction with the oxygen source 18, including increasing to an undesirable ordangerously high level. To prevent such an increase in pressure from harming the patient 16 receiving therapy, the pressure regulator 24 is positioned upstream of the proportional valve 28, such that the proportional valve 28 prevents pressure at a safe upper level, such as 15 psi, for example.

[0101] Non-technical operation and maintenance

[0102] In an embodiment, all or most of the operating instructions and maintenance instructions are provided in the memory 114 and the respective instructions are displayed to the user in sequential steps when required. This helps ensure that the nnCPAP device 2 is operated properly and maintained when needed, and no physical operations or maintenance booklet is required, which addresses common problems in encountered in long term operation of the nnCPAP device 2 in developing countries.

[0103] In an embodiment, when the nnCPAP device 2 is powered on, a display screen instructs the user on the process of setting up for delivering therapy. There may be buttons to scroll through the setup screens.

[0104] In an embodiment, there may be specific troubleshooting instructions displayed for most or all of the various alarms.

[0105] In a further embodiment, an additional, upstream pressure sensor is additionally placed upstream of the proportional valve 28. This would allow an increased amount of data about the pressure of the pressurized oxygen and, thus, a potentially faster determination of a preferable opening amount of the proportional valve 28.

[0106] High Flow Nasal Cannula

[0107] According to a further High Flow Nasal Cannula (HFNC) embodiment of the nnCPAP device 2, alternatively termed a Heated Humidified High Flow Nasal Cannula (HHHFNC) embodiment, the expiratory reception portion 6 may be omitted, and the patient circuit 8 may include the inspiratory circuit 70 and the patient interface 72, but have no expiratory circuit 74. The HFNC embodiment nnCPAP device 2 is preferably a flow-controlled therapy, such that the user sets a flow and an FiO2 (oxygen concentration) for the patient 16. The blower 32 adjusts its speed to keep the flow rate measured by the inspiratory pressure sensor 50 equal to the target flow set by the user. The HFNC embodiment nnCPAP device 2HFNC embodiment uses the inspiratory flow sensor 46 and the inspiratory pressure sensor 50, along with an algorithm describedbelow, to calculate what pressure air the infant 16 receives without requiring a second pressure sensor.

[0108] The calculated pressure Pbaby is preferably displayed on a screen but is preferably not used in setting blower 32 speed. To do this, an initial pressure calibration is done before therapy is initiated on a new patient 16 or before using new patient circuit 8 accessories.

[0109] Preferably, the air is also heated and humidified.

[0110] According to an HFNC embodiment, a “single-limb circuit” is used. This means one tube (the inspiratory circuit 70 and the patient interface 72) goes from the HFNC embodiment nnCPAP device 2 to the baby 16, without a second tube (expiratory circuit 74) returning to the HFNC embodiment nnCPAP device 2 from to the baby 16.

[0111] Oxygen Sensor Power

[0112] In some embodiments, the oxygen sensor 48 may be partially or fully powered by the power supply and / or the power source. In a further embodiment, the oxygen sensor 48 may alternatively or additionally be connected to the battery 128 voltage to keep the oxygen sensor 48 energized even when the nnCPAP device 2 is turned off. By keeping the oxygen sensor 48 energized during power shutdown, the oxygen sensor 48 maintains accuracy immediately at startup. Without this battery 128 voltage connection, the oxygen sensor 48 may need a warmup period of several minutes upon turning the nnCPAP device 2 on, during which oxygen level readings may be inaccurate.

[0113] The invention illustratively disclosed herein suitably may explicitly be practiced in the absence of any element which is not specifically disclosed herein. Though the nnCPAP device 2 has many advantages for the treatment of neonatal patients, this device may be used on natal, pediatric, adolescent, adult, and elderly patients as well. While various embodiments of the present invention have been described in detail, it is apparent that various modifications and alterations of those embodiments will occur to and be readily apparent those skilled in the art. However, it is to be expressly understood that such modifications and alterations are within the scope and spirit of the present invention, as set forth in the appended claims. Further, the invention(s) described herein is capable of other embodiments and of being practiced or of being carried out in various other related ways. The present disclosure also contemplatesother embodiments “comprising,” “consisting of’ and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items, while only the terms “consisting of’ and “consisting only of’ are to be construed in the limitative sense.

Claims

Wherefore, I / we claim:

1. A neonatal continuous positive airway pressure (nnCPAP) system, comprising:an inspiratory preparation portion comprisingan oxygen inlet for a pressurized oxygen source,an ambient inlet for an ambient air source,a blender coupled to the first and second inlets to blend pressurized oxygen and ambient air from the oxygen and ambient inlets, respectively,a blower coupled to the blender and configured to generate an airflow directed to a patient from the blended air,an oxygen flow sensor arranged to detect a flow of the pressurized oxygen, a blended flow sensor arranged to detect a flow of blended air,an oxygen sensor configured to measure an oxygen concentration of the blended air, andan inspiratory pressure sensor to measure inspiratory pressure;an expiratory reception portion comprising an expiratory pressure sensor to measure expiratory pressure; anda control system having a processor and memory and being configured todetermine a pressure at a patient interface based on measurements from the inspiratory pressure sensor and the expiratory pressure sensor, andcontrol a blended air ratio using a dual control system thatinitially uses flow measurements of the oxygen flow sensor and the blended flow sensor to adjust an oxygen concentration of the blended air to near a target concentration and then uses oxygen concentration measurements from the oxygen sensor to adjust the oxygen concentration further toward the target concentration.

2. The nnCPAP system of claim 1, further comprising a proportional valve coupled to the oxygen inlet, wherein the control system is configured to control the proportional valve to adjust the oxygen concentration.

3. The nnCPAP system of claim 2, wherein the control system is configured to calculate an initial fraction of inspired oxygen delivered in the blended air based on a purity value of the pressurizedoxygen, an oxygen level of room air, a value of the flow of pressurized oxygen, and a value of the flow of blended air.

4. The nnCPAP system of claim 3, wherein the control system is configured to determine an initial fraction of inspired oxygen delivered in the blended air according to the formulaFiO2D= 100 * (Purity * Fox+ 0.21 * (Finsp- Fox)) I FmSp,where Fi02o is a fraction of inspired oxygen delivered, Purity is an oxygen concentration of the pressurized oxygen, FinSp is a value of the flow of blended air, and Foxis a value of the flow of pressurized oxygen.

5. The nnCPAP system of claim 4, wherein the control system is configured to initially set the value of Purity to 1.00.

6. The nnCPAP system of claim 5, wherein the control system determines the oxygen concentration value from the oxygen sensor, and uses that value to recalculate the Purity value and the fraction of inspired oxygen delivered.

7. The nnCPAP system of claim 1, wherein the control system is configured to calibrate the oxygen sensor at least once in a time period, wherein the time period is between 0.5 days and 7.0 days.

8. The nnCPAP system of claim 7 wherein the control system is configured to calibrate the oxygen sensor while delivering treatment by shutting off pressurized oxygen momentarily, flushing substantially all of the pressurized oxygen out of the system, performing a calibration based on ambient air, and turning the oxygen back on for the patient, in less than 0.50 seconds.

9. The nnCPAP system of claim 1 wherein the oxygen sensor is an electrochemical nonconsumable oxygen sensor with a life span of at least two years.

10. The nnCPAP system of claim 1, wherein the control system is configured to perform a calibration procedure to determine pneumatic characteristics of a patient circuit coupled to the system.

11. The nnCPAP system of claim 10, wherein the calibration procedure includes determining coefficients for calculating pressure drops through an inspiratory portion and a patient interface of the patient circuit.

12. The nnCPAP system of claim 10, wherein the control system is configured to calculate a theoretical maximum pressure that could be delivered safely to the patient based on a current system state, and to limit an output of the blower if the theoretical maximum pressure exceeds a maximum pressure threshold.

13. The nnCPAP system of claim 1, further comprising a battery, wherein the control system is configured to selectively disable features of the system based on a charge state of the battery and a voltage level of a mains power received.

14. The nnCPAP system of claim 13 further comprising that when the nnCPAP system is not receiving power from a mains power thenwhen a voltage in the battery falls below a first threshold, an alarm is initiated and power is discontinued to a humidifier heater plate;when the voltage falls below a second threshold, power is discontinued to a heater wire; andwhen the voltage falls below a third threshold, the blower reduces speed and maintains a small positive flow of air and a further alarm is activated.

15. The nnCPAP system of claim 10 further comprisinga patient circuit comprisingan inspiratory circuit attached to the inspiratory module;an expiratory circuit attached to the expiratory module;a nasal interface connecting the inspiratory circuit to the expiratory circuit; andthe control system being configured to calculate a delivered pressure (Pbaby) that is delivered to the neonatal patient from the nasal interface based on measurements from the sensors and the determined pneumatic characteristics of the inspiratory circuit and nasal interface.

16. The nnCPAP system of claim 15, wherein the control system is further configured to calculate an expiratory flow (Fex) based on the measured expiratory pressure (Pex).

17. The nnCPAP system of claim 16 wherein the expiratory flow is calculated using the equation:Fex= a*PexAb18. The nnCPAP system of claim 17 wherein a is a value between 1.40 and 1.60 and b is a value between 0.40 and 0.60.

19. The nnCPAP system of claim 17 wherein the value of a is between 1.470 and 1.490 and the value of b is between 0.500 and 0.520.

20. The nnCPAP system of claim 17 wherein the value of a is 1.48 and the value of b is 0.511.

21. The nnCPAP system of claim 16, whereinthe memory stores an inspiratory circuit coefficient (Cinsp) and a nasal interface coefficient (Cieak) calculated during the calibration process.

22. The nnCPAP system of claim 21, wherein the processor is configured to calculate a pressure drop through the inspiratory circuit using the equation:Pinsp ■ Pckt=Cinsp*Finsp 2,wherein Pckt is a calculated circuit pressure;wherein Finspis a flow through the inspiratory circuit, as measured by the inspiratory flow sensor; andwherein Pinspis a pressure measured by the inspiratory pressure sensor.

23. The nnCPAP system of claim 21, wherein the processor is configured to calculate a pressure drop through the nasal interface using the equation:Pckt - Pbaby = Cleak*Fleak^2,wherein Fieak is a calculated flow out the nasal interface, andwherein PCkt is a calculated circuit pressure.

24. The nnCPAP system of claim 21, wherein the processor is configured to calculate a pressure of air delivered to the neonatal patient using the equation:Pbaby = Pckt - Cleak*FleakA2,wherein Fieak is a calculated flow out the nasal interface, andwherein Pckt is a calculated circuit pressure.

25. The nnCPAP system of claim 16, wherein the processor is configured to limit blower speed based on a calculated theoretical maximum pressure (Pmax theoretical).

26. The nnCPAP system of claim 22, wherein the processor is configured tolimit blower speed based on a calculated theoretical maximum pressure (Pmax.theoreticai), and to calculate the Pmax_theoreticai based on values of Pjasp, Cinsp, and F;llsp.

27. The nnCPAP system of claim 26, wherein the processor is configured to calculate the theoretical maximum pressure using the equation:PmaX theoretical=[(Pinsp—CinsP*Finsp 2) + (m*Finsp n + P*FinspA2 + q*Finsp + S)] I 1 '.

28. The nnCPAP system of claim 26, wherein the processor is configured to calculate the theoretical maximum pressure using the equation:Pmax_tlieoretical=[(Pinsp - Cinsp*FinsPA2) + (0. 1423*FinSpAl.8446 + 0.00218*FinspA2 + 0.0623*Finsp-0.0817)] / 2.

29. The nnCPAP system of claim 25, wherein the processor is configured to limit blower speed so that Pbaby does not exceed 3.0 cm of H2O pressure above a target pressure.30 The nnCPAP system of claim 1, wherein the oxygen sensor is connected to a battery voltage, such that the oxygen sensor is energized even when the nnCPAP device is turned off.31 The nnCPAP system of claim 1, wherein substantially an only item that requires maintenance in a five year period is changing one or more filters once a year each.32 The nnCPAP system of claim 1, further comprising when the oxygen sensor detects oxygen levels deviating more than 10.0% from FiO2 setpoint, an alarm is initiated.33 The nnCPAP system of claim 1 further comprises a pressure regulator upstream of a proportional valve that limits pressurized oxygen flow to less than 15.0 psi.34 The nnCPAP system of claim 1 further comprising a spring biased normally open I powered closed pressure relief valve that provides an open air pathway to the patient interface when power to the machine shuts off.35 The nnCPAP system of claim 1 further comprisinga housing anda fan arranged in or adjacent to the housing andthe control module being configured such that when the nnCPAP system is powered on, before any heating components are powered, the fan turns on and circulates exterior air into a housing interior and interior air out of the system.36 The nnCPAP system of claim 1 further comprising a pressure sensor upstream of a proportional valve.

37. A neonatal continuous positive airway pressure (nnCPAP) system, comprising:an inspiratory preparation portion comprisingan oxygen inlet for a pressurized oxygen source,an ambient inlet for an ambient air source,a blender coupled to the oxygen and ambient inlets to blend pressurized oxygen and ambient air from the first and second inlets, respectively,a blower coupled to the blender and configured to generate an airflow directed to a patient from the blended air, andan inspiratory pressure sensor to measure inspiratory pressure;an expiratory reception portion comprising an expiratory pressure sensor to measure expiratory pressure; anda control system having a processor and memory and being configured todetermine a pressure at a patient interface based on measurements from the inspiratory pressure sensor and the expiratory pressure sensor, andcontrol a blended air ratio using a dual control system thatinitially uses flow measurements of the oxygen flow sensor and the blended flow sensor to adjust an oxygen concentration of the blended air to near a target concentration and then uses oxygen concentration measurements from the oxygen sensor to adjust the oxygen concentration further toward the target concentration.

38. The nnCPAP system of claim 37, further comprising a proportional valve coupled to the oxygen inlet, wherein the control system is configured to control the proportional valve to adjust the oxygen concentration.

39. The nnCPAP system of claim 38, wherein the control system is configured to calculate an initial fraction of inspired oxygen delivered in the blended air based on a purity value of the pressurized oxygen, an oxygen level of room air, a value of the flow of pressurized oxygen, and a value of the flow of blended air.

40. The nnCPAP system of claim 39, wherein the control system is configured to determine an initial fraction of inspired oxygen delivered in the blended air according to the formula FiO2o = 100 * (Purity * Fox+ 0.21 * (Finsp- Fox)) I Finsp,where Fi02o is a fraction of inspired oxygen delivered, Purity is an oxygen concentration of the pressurized oxygen, Finspis a value of the flow of blended air, and Foxis a value of the flow of pressurized oxygen.

41. The nnCPAP system of claim 40, wherein the control system is configured to initially set the value of Purity to 1.00.

42. The nnCPAP system of claim 41, wherein the control system determines the oxygen concentration value from a measured oxygen concentration from the oxygen sensor, and uses the measured oxygen concentration value to recalculate the Purity value and the fraction of inspired oxygen delivered.

43. The nnCPAP system of claim 37, wherein the control system is configured to calibrate the oxygen sensor at least once in a time period, wherein the time period is between 0.5 days and 7.0 days.

44. The nnCPAP system of claim 43 wherein the control system is configured to calibrate the oxygen sensor while delivering treatment by shutting off oxygen momentarily, flushing all of the oxygen out of the system, performing a calibration based on ambient air, and turning the oxygen back on for the patient, in under 0.50 seconds.

45. The nnCPAP system of claim 37 wherein the oxygen sensor is an electrochemical nonconsumable oxygen sensor with a life span of at least two years.

46. The nnCPAP system of claim 37, further comprising a battery, wherein the control system is configured to selectively disable features of the system based on a charge state of the battery and a voltage level of a mains power received.

47. The nnCPAP system of claim 46 further comprising that when the nnCPAP system is not receiving power from a mains power thenwhen a voltage in the battery falls below a first threshold, an alarm is initiated and power is discontinued to a humidifier heater plate;when the voltage falls below a second threshold, power is discontinued to a heater wire; andwhen the voltage falls below a third threshold, the blower reduces speed and maintains a small positive flow of air and a further alarm is activated.

48. The nnCPAP system of claim 1, wherein only one oxygen sensor and only two flow sensors are provided.

49. The nnCPAP system of claim 37 further comprises a pressure regulator upstream of a proportional valve that limits pressurized oxygen flow to less than 15.0 psi.

50. The nnCPAP system of claim 37 further comprising a spring biased open powered closed pressure relief valve that provides an open air pathway to the patient interface when power to the machine shuts off.

51. The nnCPAP system of claim 37 further comprisinga housing anda fan arranged in or adjacent to the housing andthe control module being configured such that when the nnCPAP system is powered on, before any heating components are powered, the fan turns on and circulates exterior air into a housing interior and interior air out of the system.

52. The nnCPAP system of claim 37 further comprising an additional pressure sensor upstream of a proportional valve.

53. A neonatal continuous positive airway pressure (nnCPAP) system, comprising:an inspiratory preparation portion comprisingan oxygen inlet for a pressurized oxygen source,an ambient inlet for an ambient air source,a blender coupled to the oxygen and ambient inlets to blend pressurized oxygen and ambient air from the first and second inlets, respectively,a blower coupled to the blender and configured to generate an airflow directed to a patient from the blended air,an oxygen flow sensor arranged to detect a flow of the pressurized oxygen, a blended flow sensor arranged to detect a flow of blended air,an oxygen sensor configured to measure an oxygen concentration of the blended air, anda control system having a processor and memory and being configured tocontrol a blended air ratio using a dual control system thatinitially uses flow measurements of the oxygen flow sensor and the blended flow sensor to adjust an oxygen concentration of the blended air to near a target concentration and then uses oxygen concentration measurements from the oxygen sensor to adjust the oxygen concentration further toward the target concentration.

54. The nnCPAP system of claim 53, wherein the control system is configured to perform a calibration procedure to determine pneumatic characteristics of a patient circuit coupled to the system.

55. The nnCPAP system of claim 53, wherein the calibration procedure includes determining coefficients for calculating pressure drops through an inspiratory portion and a patient interface of the patient circuit.

56. The nnCPAP system of claim 53, wherein the control system is configured to calculate a theoretical maximum pressure that could be delivered safely to the patient based on a current system state, and to limit an output of the blower if the theoretical maximum pressure exceeds a maximum pressure threshold.

57. The nnCPAP system of claim 53, further comprising a battery, wherein the control system is configured to selectively disable features of the system based on a charge state of the battery and a voltage level of a mains power received.

58. The nnCPAP system of claim 57 further comprising that when the nnCPAP system is not receiving power from a mains power thenwhen a voltage in the battery falls below a first threshold, an alarm is initiated and power is discontinued to a humidifier heater plate;when the voltage falls below a second threshold, power is discontinued to a heater wire; andwhen the voltage falls below a third threshold, the blower reduces speed and maintains a small positive flow of air and a further alarm is activated.

59. The nnCPAP system of claim 53 further comprisinga patient circuit comprisingan inspiratory circuit attached to the inspiratory module;an expiratory circuit attached to the expiratory module;a nasal interface connecting the inspiratory circuit to the expiratory circuit; and the control system being configured to calculate a delivered pressure (Pbaby) that is delivered to the neonatal patient from the nasal interface based on measurements from the sensors and the determined pneumatic characteristics of the inspiratory circuit and nasal interface.

60. The nnCPAP system of claim 59, wherein the control system is further configured to calculate an expiratory flow (Fex) based on the measured expiratory pressure (Pex).

61. The nnCPAP system of claim 60 wherein the expiratory flow is calculated using the equation:Fex= a*Pex^b.

62. The nnCPAP system of claim 61 wherein a is a value between 1.40 and 1.60 and b is a value between 0.40 and 0.60.

63. The nnCPAP system of claim 61 wherein the value of a is between 1.470 and 1.490 and the value of b is between 0.500 and 0.520.

64. The nnCPAP system of claim 61 wherein the value of a is 1.48 and the value of b is 0.511.

65. The nnCPAP system of claim 60, whereinthe memory stores an inspiratory circuit coefficient (Cinsp) and a nasal interface coefficient (Cieak) calculated during the calibration process.

66. The nnCPAP system of claim 65, wherein the processor is configured to calculate a pressure drop through the inspiratory circuit using the equation:Pinsp = Pckt — Cinsp*Finsp^2,wherein Pckt is a calculated circuit pressure;wherein Finspis a flow through the inspiratory circuit, as measured by the inspiratory flow sensor; andwherein Pinspis a pressure measured by the inspiratory pressure sensor.

67. The nnCPAP system of claim 65, wherein the processor is configured to calculate a pressure drop through the nasal interface using the equation:Pckt - Pbaby = Cleak*Fleak^2,wherein Ficak is a calculated flow out the nasal interface, andwherein PCkt is a calculated circuit pressure.

68. The nnCPAP system of claim 65, wherein the processor is configured to calculate a pressure of air delivered to the neonatal patient using the equation:Pbaby = Pckt - Cleak*FleakA2,wherein Fieak is a calculated flow out the nasal interface, andwherein Pckt is a calculated circuit pressure.

70. The nnCPAP system of claim 59, wherein the processor is configured to limit blower speed based on a calculated theoretical maximum pressure (Pmax_theoreticai).

71. The nnCPAP system of claim 67, wherein the processor is configured tolimit blower speed based on a calculated theoretical maximum pressure (P max_theoretical), and to calculate the Pmax_theoreticai based on values of Pinsp, Cinsp, and FinSp.

72. The nnCPAP system of claim 71, wherein the processor is configured to calculate the theoretical maximum pressure using the equation:Pmax_theoretical = [(Pinsp — Cinsp*Finsp^2) + (m*Finsp^n + p*Finsp^2 + q*Finsp + s)] / 2.

73. The nnCPAP system of claim 71, wherein the processor is configured to calculate the theoretical maximum pressure using the equation:Pmax_theoretical = [(Pinsp - Cinsp*Finsp^2) + (0.1423*Finsp^1.8446 + 0.00218*Finsp^2 + 0.0623*Finsp -0.0817)] / 2.

74. The nnCPAP system of claim 70, wherein the processor is configured to limit blower speed so that Pbaby does not exceed 3 cm of H2O in pressure above a target pressure.

75. The nnCPAP system of claim 53, wherein the oxygen sensor is connected to a battery voltage, such that the oxygen sensor is energized even when the nnCPAP device is turned off.

76. The nnCPAP system of claim 53, wherein substantially an only item that requires maintenance in a five year period is changing one or more filters once a year each.

77. The nnCPAP system of claim 53, further comprising when the oxygen sensor detects oxygen levels deviating more than 10.0% from FiO2 setpoint, an alarm is initiated.

78. The nnCPAP system of claim 53 further comprises a pressure regulator upstream of a proportional valve that limits pressurized oxygen flow to less than 15.0 psi.

79. The nnCPAP system of claim 53 further comprising a spring biased open powered closed pressure relief valve that provides an open air pathway to the patient interface when power to the machine shuts off.

80. The nnCPAP system of claim 53 further comprisinga housing anda fan arranged in or adjacent to the housing andthe control module being configured such that when the nnCPAP system is powered on, before any heating components are powered, the fan turns on and circulates exterior air into a housing interior and interior air out of the system.

81. The nnCPAP system of claim 53 further comprising a pressure sensor upstream of a proportional valve.

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