Device for monitoring lung system of subject

Abstract

An apparatus, system, and method for monitoring the lung system of a subject. An optical member for emitting a light signal through a lumen of a lung system of a subject. The optical member and the detector unit are configured to be positioned such that a detected light signal is transmitted from the optical member through the cavity. The control unit is configured to evaluate the detected light signal to determine a physiological state of the pulmonary system of the subject.

Description

[0001] This application is a divisional application of the invention patent application with the application date of April 23, 2020, the application number of CN202080031658.2, and the invention name of "A device for monitoring the pulmonary system of a subject". The entire content of the original parent application is incorporated into this application by reference herein. Technical Field

[0002] The present disclosure relates to examining an inflatable cavity in a human body using an optical device. In particular, the present disclosure relates to a device for monitoring the pulmonary system. Background Art

[0003] The transition of the lungs from the intrauterine environment to normal postnatal air breathing can lead to lung diseases, which are becoming more prevalent as the gestational age of the newborn decreases. With the increasing survival rate of extremely premature infants, the number of infants requiring respiratory support in neonatal care units will increase. Abnormal lung ventilation is common in postnatal lung diseases, such as respiratory distress syndrome due to surfactant deficiency and lung bronchial dysplasia. Despite modern respiratory support methods and minimally invasive surfactant therapy, there is still a risk of life-threatening complications, such as pneumothorax.

[0004] Currently, lung ventilation problems are partially diagnosed by chest X-rays of the lungs. Unfortunately, it can only provide a snapshot of the current condition and can lead to a harmful radiation load when repeated, thus increasing the risk of developing malignancies later.

[0005] Another method is transillumination, in which, in a dark room, a doctor shines a strong light beam through the affected side of the newborn's chest. This procedure is performed to show free air in the area around the lungs (pleural cavity). Transillumination is visually analyzed and is not used for continuous monitoring of the pulmonary system.

[0006] Therefore, there is a clear clinical need for a device and method that can monitor the gas content in the lungs and improve the detection of lung complications while avoiding ionizing radiation as much as possible. It may also be an advantage if the method can include rapid detection of life-threatening complications, such as pneumothorax and bronchial obstruction causing varying degrees of atelectasis.

[0007] Therefore, new and improved devices and methods for monitoring the pulmonary system, particularly for detecting lung ventilation problems, are advantageous. Summary of the Invention

[0008] Accordingly, embodiments of the present disclosure preferably seek to alleviate, mitigate, or eliminate one or more deficiencies, drawbacks, or problems in the art, such as those described above individually or in any combination, in accordance with measuring free gas in a cavity (e.g., the lung). The apparatus, system, or method is adapted to monitor a lung system and detect the state of the lung system, such as detecting ventilation problems, such as pulmonary ventilation problems and / or pulmonary complications, and more particularly diagnosing pneumothorax and / or atelectasis.

[0009] According to a first aspect, an apparatus for monitoring a lung system of a subject is disclosed. The apparatus may include an optical member for emitting an optical signal to pass through a cavity of the subject's lung system, such as the lung. The optical signal may include at least one wavelength. The apparatus may further include a detector unit. The optical member and the detector unit may be configured to be positioned such that the optical signal can be transmitted from the optical member through the cavity to be detected by the detector. The apparatus may further include a control unit for evaluating the detected optical signal to determine the physiological state of the subject's lung system. The physiological state may be determined by evaluating the change in intensity of the optical signal transmitted through the cavity over time.

[0010] The determined state of the lung system (e.g., the lung) may be used as feedback for a medical ventilator. For example, to change the settings of a medical ventilator.

[0011] In some examples, the determined state may relate to the detection of pulmonary complications and / or ventilation problems of the subject.

[0012] In some examples, the detected optical signal may be associated with the same wavelength over time. For example, at least one wavelength of the emitted optical signal is a single wavelength.

[0013] The term "single wavelength" means that the light source is locked at one wavelength rather than a swept frequency. The term should be interpreted as the central wavelength of the light emitted from the light source and encompasses the emitted light having a line width.

[0014] In some examples, the wavelength of the optical signal may be independent of the absorption band of free gas in the cavity (e.g., the lung).

[0015] In some examples, the change in intensity of the detection signal transmitted through the cavity over time may be associated with a change in the volume of the cavity.

[0016] In some examples, the change in volume may be a qualitative measure. For example, an increase or decrease in the intensity signal may be associated with an increase or decrease in the cavity volume. Another example is that the volume change can be detected by obtaining a first transmission signal transmitted through a first cavity (e.g., a first lung) and a second transmission signal transmitted through a second cavity (e.g., the lung). Then the first and second transmission signals are compared with each other to detect the volume change of one cavity relative to the other cavity.

[0017] In some examples, the emitted optical signal can have a wavelength associated with the optical window of the tissue. When the determination of the state of the lung system is based on the evaluation of the intensity of the transmitted signal, the wavelength can be any wavelength that can transmit through the tissue (such as the lung) surrounding the cavity of the lung system being examined.

[0018] In some examples, the emitted optical signal can have a wavelength associated with the absorption band of the free gas in the lung system cavity.

[0019] In some examples of the disclosed device, the optical member can be adapted to be inserted into the subject from the inside using the introduction member.

[0020] In some examples, the optical member can be adapted to be arranged on the skin surface of the subject for emitting an optical signal into the cavity.

[0021] In some examples of the disclosed device, the detector can be configured to be positioned on the skin surface for detecting the optical signal transmitted through the cavity of the subject.

[0022] In some examples of the disclosed device, the control unit can be configured to: determine the state of the lung system by evaluating the intensity of the detected optical signal transmitted through the cavity over time.

[0023] In some examples of the disclosed device, the control unit can be configured to determine the state of the lung system by obtaining the concentration and / or distribution of the free gas from the detected optical signal transmitted through the cavity and evaluating the concentration over time.

[0024] In some examples of the disclosed device, the control unit can be configured to determine the state of the lung system by correlating the intensity of the detected optical signal transmitted through the cavity with the obtained concentration and / or distribution of the free gas over time. In this example, the emitted light used to evaluate the transmission intensity can have the same wavelength as the emitted light used to obtain the concentration and / or distribution of the free gas in the cavity, such as a wavelength associated with the absorption band of the free gas. Alternatively, the emitted light used to evaluate the transmission intensity can have a different wavelength from the emitted light used to obtain the concentration and / or distribution of the free gas in the cavity. For example, the emitted light for intensity evaluation can be any wavelength within the optical window of the tissue, and the emitted light for obtaining the concentration and / or distribution of the free gas can be associated with the absorption band of the free gas.

[0025] In some examples of the disclosed device, when obtaining the concentration and / or distribution of the free gas in the cavity, the emitted light can include at least two different wavelengths. For example, in some examples, at least one of the wavelengths can be associated with the absorption band of a reference gas.

[0026] In some examples of the disclosed apparatus, the free gas can be a physiological gas or a gas mixture, such as any one of oxygen, nitric oxide (NO), carbon dioxide, anesthetic gas, and water vapor.

[0027] In some examples of the disclosed device, the control unit can be configured to control a medical ventilator in response to a determined state of the pulmonary system, such as a detected pulmonary complication and / or ventilation problem.

[0028] It should be emphasized that the term "comprising / including" used in this specification is used to illustrate the presence of the described features, wholes, steps, or components, but does not exclude the presence or addition of one or more other features, wholes, steps, components, or groups thereof.

[0029] Brief Description of the Drawings

[0030] These and other aspects, features, and advantages that the examples of the present disclosure can have will become apparent and elucidated from the following description of the examples of the present disclosure, with reference to the accompanying drawings, in which:

[0031] Figure 1 Examples of the disclosed devices and systems are shown;

[0032] Figures 2A to 2D An example of the arrangement of a light source for measuring lung function in the trachea is shown;

[0033] Figure 3 is a diagram showing another example of the light source configuration for measuring lung function using a bronchoscope;

[0034] Figure 4A and 4B Another example of an arrangement in which the light source is inserted through the esophagus is shown;

[0035] Figure 5 O for inducing atelectasis in four piglets 2 Time evolution of the absorption signal and the corresponding light transmission; and

[0036] Figure 6 Shows O for inducing pneumothorax in four piglets 2 Time evolution of the absorption signal and the corresponding light transmission. Detailed Embodiments

[0037] Specific examples of the present disclosure will now be described with reference to the accompanying drawings. However, the present disclosure can be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these examples are provided so that the present disclosure will be thorough and complete and will fully convey the scope of the present disclosure to those skilled in the art.

[0038] The following disclosure focuses on examples of the present disclosure that are applicable to monitoring a subject's pulmonary system, for example by arranging a light source or an optical component in a cavity, such as in the trachea, or in the digestive system, such as in the esophagus or intestine, such as a part of the digestive tract, and using a detector, such as one or more detectors arranged outside the human body, to detect transmitted light.

[0039] For example, this is advantageous for detecting weak signals resulting from the long path of light through the tissue surrounding the cavity.

[0040] Alternatively, both the detector and the light source can be arranged on the skin. Then, the light source is configured to transmit light into the cavity, and the detector is configured to detect the light that has scattered back after passing through the cavity at least once. Such an arrangement is described in EP1871221, which is incorporated herein by reference.

[0041] Light signals related to free gas, such as absorption spectra, can be used to monitor the pulmonary system to determine the state of the pulmonary system, such as the physiological state of the pulmonary system. Physiological problems can be, for example, ventilation problems and / or pulmonary complications, such as pulmonary ventilation problems, more specifically diagnosed as pneumothorax and / or atelectasis.

[0042] In some examples of the present disclosure, the light source is arranged to transmit light to the tissue with as low a loss as possible, and then the light is detected at the skin surface. By arranging the light source or the optical component internally to reduce the attenuation factor of the light transmitted to the tissue, thereby measuring the free gas in the cavity, the total attenuation factor can be reduced to about 0.001, which is about 1000 times greater than the attenuation factors achieved previously.

[0043] In some examples, the free gas or gas mixture in the cavity of the pulmonary system can be monitored to determine the state of the pulmonary system, such as the physiological state of the pulmonary system. To obtain the concentration and / or distribution of the free gas, the GASMAS technique can be applied.

[0044] When the light source is arranged internally, the disclosed devices, systems, and methods utilize components for injecting the light source into the tissue, such as a bronchoscope, a nasogastric tube, an endoscope, an endotracheal tube, a colonoscope, or similar introduction components.

[0045] A group of patients considered relevant to monitoring the pulmonary system are premature infants. These infants often experience respiratory complications, such as respiratory distress syndrome, dyspnea, and pulmonary function problems. Therefore, premature infants are usually connected to a medical ventilator to help them move air in and out of their lungs. When connected to a medical ventilator, premature infants are intubated with an endotracheal tube. In one example of this specification, it is described how a fiber optic device for transmitting light to a cavity (such as the lung) is combined with an endotracheal tube (such as an endotracheal tube), while detecting the transmitted light at the skin surface.

[0046] In another example of the present specification, it is described how a fiber optic device for delivering light to a cavity (such as the lung) is combined with a nasogastric tube inserted into the esophagus while detecting the transmitted light at the skin surface.

[0047] In addition, in another example, the light from the fiber optic device is distributed over a greater distance or area by a light diffusing material.

[0048] Additionally, and / or alternatively, the transmitted light is detected at the skin surface by one or more skin surface detectors located above a cavity such as the lung. The detector can be configured to be arranged on the skin surface or other devices, such as fiber optics, can be used to collect light at the skin surface and direct the collected light to the detector. In one example, multiple detectors can be used in parallel or sequentially to detect gases or gas distributions or gas concentrations in different parts of the patient's bronchial tree or lung.

[0049] In this way, the results of changes in the settings of a medical ventilator or drug can be directly observed, and the information obtained from the observation can be utilized to optimize the treatment of the patient by using a feedback system.

[0050] In some examples, the detection is frequency-sensitive and / or phase-sensitive. Light from a light source, such as a laser, can be wavelength-modulated at a selected frequency, and synchronous intensity changes can be detected when the modulation is around a gas absorption wavelength. When the modulation is performed near the gas absorption wavelength, as described in S. Svanberg, Gas in Scattering Media Absorption Spectroscopy - from Basic Studies to Biomedical Applications, Lasers and Photonics Reviews 7, 779 (2013), which is incorporated herein by reference, the intensity of the detected light will change rapidly with a small change in wavelength.

[0051] Alternatively, in some examples, the skin area can be detected by an imaging sensor (such as a digital camera) having high-intensity dynamics at the absorption wavelength and a nearby non-absorption wavelength. Then two images can be compared, for example, by division or subtraction, whereby the area affected by the gas can be visualized.

[0052] When using the GASMAS technique, the determination of gas concentration is affected by the path length in the gas-filled cavity that the light interacting with the gas must pass through. Due to multiple scattering, the path length in the tissue is unknown. Therefore, light propagating longer and shorter distances through the tissue can be detected simultaneously. The Beer-Lambert relation commonly used when analyzing gases gives that the intensity of the absorption signal is determined by the product of the gas concentration and the path length (see S. Svanberg, Atomic and Molecular Spectroscopy - Basic Aspects and Practical Applications, 4th Edition, Springer, Berlin, Heidelberg 2004, incorporated herein by reference). When the path length is known, i.e., when measurements are made in non-scattering materials, the gas concentration can be calculated directly.

[0053] When measuring gas concentration using the GSMAS technique, the path length through the gas is unknown; this needs to be taken into account when making gas concentration measurements. Different methods can be used to handle the problem of unknown path length, which are discussed, for example, in L. Mei, G. Somesfalean and S. Svanberg, Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy, Sensors 14, 3871 (2014), incorporated herein by reference.

[0054] One of the most accurate methods is to use the distribution changes in the absorption spectrum, such as the water vapor absorption lines. The change in the water vapor spectral lines depends on the oxygen concentration, see P. Lundin, L. Mei, S. Andersson-Engels and S. Svanberg, Laser Spectroscopic Gas Concentration Measurements in Situations with Unknown Optical Path Length Enabled by Absorption Line Shape Analysis, Appl. Phys. Lett. 103, 034105 (2013), which is incorporated herein by reference. This method requires a good signal-to-noise ratio because the influence of oxygen on the water vapor lines is weak.

[0055] Another option is to perform GSMAS measurements on the gas concentration and water vapor to be determined. It can be assumed that the water vapor concentration is saturated in the tissue and its concentration is determined by the known temperature, see A.L. Buck, Buck Research Manuals; Updated Equation from (1981), which is incorporated herein by reference, and New Equation for Computing Vapor Pressure and Enhancement Factor. J. Appl. Meteorol. 20, 1527 (1996), which is incorporated herein by introduction. Based on the measured water vapor signal, the effective path length of the wavelength used can be calculated. As long as the difference between the wavelengths used is small, the path length obtained may be approximately the same as the path length of the light transmitted through the gas with unknown concentration to be determined (such as oxygen, nitric oxide (NO), or carbon dioxide). Then the gas concentration, such as the concentration of oxygen, nitric oxide (NO), and carbon dioxide, can be directly calculated using the approximate path length. This method works best when the light absorption and light scattering in the tissue for the two measurements are the same, i.e., the case when the wavelengths used for measurement are close. For example, oxygen is usually monitored around some sharp components at about 760 nm in the A band of oxygen molecules. Water vapor has a strong absorption near 935 nm, but due to the different optical properties of different wavelengths, it may be necessary to correct for the wavelength difference compared to oxygen. Therefore, a weaker absorption wavelength of water vapor near 820 nm may be a better choice.

[0056] In a preferred example, the devices, systems, and methods described herein utilize tunable diode laser absorption spectroscopy (TDLAS) to detect gases through multiple light scatterings in tissue, where the absorbed free gas is dispersed in cavities surrounded by a medium. In TDLAS, the wavelength of the light source sweeps across an absorption peak or absorption band. The sweep, where each step can be scaled down to a scale below nanometers.

[0057] Figure 1 An example of an embodiment is shown. The patient 1 in this example is a premature infant. Due to respiratory distress syndrome (RDS) in a common disease condition, the infant is connected to a medical ventilator 2.

[0058] The medical ventilator 2 is connected to the intubated patient 1 through an endotracheal tube 3 inserted into the trachea 4, for example. In this example, two light sources 5, 6 are used to measure gases, such as oxygen at approximately 760 nm and water vapor at about 820 nm. Other wavelengths can be used depending on the gas to be measured. In some examples, other gases besides water vapor can be used as reference gases. The requirement is only that the gas concentration can be calculated without using the path length that the detected light has traveled.

[0059] Alternatively, in other examples, only one light source may be used. In some other examples, more than two light sources may be used to detect additional gases, gas distributions, or gas concentrations.

[0060] Alternatively, when using other methods related to GASMAS described previously herein, other configurations of the light source are possible.

[0061] The light source may be a semiconductor laser, such as a distributed feedback laser (DFBL), a vertical cavity surface emitting laser (VCSEL), or other available types of lasers. The power of the emitted light is preferably in the range of 1 mW to 3000 mW.

[0062] The laser may be driven by a current and temperature regulation unit included in the drive unit 7. The drive unit 7 may be controlled by a control unit 8, such as a computer. The control unit 8 may be used for signal processing and evaluation of measurement data.

[0063] All determinations or calculations described herein may be performed by a control unit or a data processing device (not shown).

[0064] The control unit or data processing device may be implemented by dedicated software (or firmware) running on one or more general-purpose or special-purpose computing devices. In this context, it should be understood that each "element" or "means" of such a computing device refers to the conceptual equivalent of a method step; there is not always a one-to-one correspondence between an element / means and a particular piece of hardware or software routine. A piece of hardware sometimes includes different means / elements. For example, a processing unit serves as one element / means when executing one instruction and as another element / means when executing another instruction. In addition, an element / means may be implemented by one instruction in some cases but by multiple instructions in other cases. Such a software-controlled computing device may include one or more processing units, such as a CPU ("Central Processing Unit"), a DSP ("Digital Signal Processor"), an ASIC ("Application-Specific Integrated Circuit"), discrete analog and / or digital components, or some other programmable logic device such as an FPGA ("Field Programmable Gate Array"). The data processing device 10 may also include a system memory and a system bus that couples the various system components including the system memory to the processing unit. The system bus may be any of a variety of bus structures, including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The system memory may include computer storage media in the form of volatile and / or non-volatile memory, such as read-only memory (ROM), random access memory (RAM), and flash memory. The dedicated software may be stored in the system memory or on other removable / non-removable volatile / non-volatile computer storage media included in or accessible to the computing device, such as magnetic media, optical media, flash memory cards, digital tapes, solid-state RAM, solid-state ROM, etc. The data processing device 10 may include one or more communication interfaces, such as a serial interface, a parallel interface, a USB interface, a wireless interface, a network adapter, etc., and one or more data acquisition devices, such as an A / D converter. The dedicated software may be provided to the control unit or data processing device on any suitable computer-readable medium, including a recording medium and a read-only memory.

[0065] Additionally, in some examples, the control unit 8 may be connected to the controller 9 of the medical ventilator 2 to control the settings of the medical ventilator 2.

[0066] Furthermore, and / or alternatively, the controller 9 may also be used to control the administration of drugs to the patient 1.

[0067] In addition, in some examples, wavelength modulation of a laser may be performed by modulating the drive current at two separate frequencies. The frequencies may typically be in the region of approximately 10 kHz to allow phase-sensitive detection (lock-in detection) for noise reduction.

[0068] By using separate modulation frequencies, different gases such as oxygen, nitric oxide (NO), carbon dioxide, and water vapor can be separated even though the optical injection can be carried out through the same optical fiber 11. The light from each optical fiber connected to light sources such as semiconductor lasers 5, 6 at 12 can be connected to a single injection optical fiber 11.

[0069] In addition, in some examples, a small portion of the light to be injected can be optically steered, for example, through optical fiber 5 to a calibration unit 13. The calibration unit 13 can be a gas chamber including the gases to be detected, such as oxygen, nitric oxide (NO), and carbon dioxide. The gas has a known concentration and the gas chamber has a predetermined length. The calibration unit 13 can also include a water droplet and temperature measurement unit. All parts of the calibration unit 13 can have a common detector unit.

[0070] Alternatively, in some examples, a compact diffuse reflection multi-channel chamber made of a porous material such as ceramic can be used. The porous material can be encapsulated in a compact gas chamber, see T. Svensson, E. Adolfsson, M. Lewander, C. T. Xu and S. Svanberg, Disordered, Strongly Scattering Porous Materials as Miniature Multi-pass Gas Cells, Phys. Rev. Lett. 107, 143901 (2011), which is incorporated herein by reference.

[0071] The main portion of the light with a separate frequency label is guided through the optical fiber 11 downward through the endotracheal tube 3 used in this example.

[0072] In Figures 2B to 2D the example shown, the end of the optical fiber 11 is a diffuser. The diffuser can be a structure on the surface of the optical fiber or a separate component made of a light-scattering material. The diffuser is used to distribute the light over a larger tissue surface to achieve a reduced intensity. The lower intensity may help avoid tissue temperature rise. Another advantage is eye safety if the test is carried out outside the human body.

[0073] In some examples, the injected light transmitted from the end of the optical fiber 11, for example, through the diffuser, can be transmitted to the tissue without passing through any air in the trachea. If the light passes through air, the air may give some background signal in the light detected by the detector 14.

[0074] In one example, an inflatable cuff or balloon made of an optically scattering material and having a reflective material on the inner wall can be used so that as much light as possible is directly transmitted into the tissue, as Figure 2A seen in.

[0075] Figure 2A The example shown gives a good positioning of the optical fiber for monitoring the upper part of the lung. By using a bronchoscope and a diffused fiber tip, light can be injected deeper into the bronchial tree, as Figure 3 shown.

[0076] Alternatively or additionally, in some examples, more than one (e.g., at least two) positions are used for light injection. When multiple positions are used for measurement, the measurements at different positions need to be carried out sequentially. Alternatively, more than one controllable standard optical fiber can be used.

[0077] When multiple positions are used for light injection and a better three-dimensional gas distribution analysis is obtained, diffuse optical tomography can be used, such as in the article J. Swartling, J. Axelsson, S. Svanberg, S. Andersson-Engels, K. Svanberg, G. Ahlgren, K. M. and S. Nilsson, System for Interstitial Photodynamic Therapy with On-line Dosimetry - First Clinical Experiences of Prostate Cancer, J. Biomed. Optics 15, 058003 (2010), which is incorporated herein by reference; and T. Durduran, R. Choe, W. B. Baker and A. G. Yodh, Diffuse Optics for Tissue Monitoring and Tomography, Rep. Progr. Phys. 73, 076701 (2010), which is incorporated herein by reference.

[0078] One or more detectors 14 are adapted to be arranged closely against the skin. The surface size of the detector should be capable of detecting light transmitted through the tissue, e.g., in the range of 0.25 cm 2 to 5 cm 2 e.g., 1 cm 2 . The detector can be made of different materials, such as germanium.

[0079] The detected light is transmitted as an electrical signal to the control unit 8. Digital lock-in techniques can be used to sequentially or parallelly evaluate the signal, as in the article L. Mei, and S. Svanberg, Wavelength Modulation Spectroscopy - Digital detection of Gas Absorption Harmonics based on Fourier Analysis, Applied Optics 54, 2254 (2015), which is incorporated herein by reference.

[0080] Alternatively, in some examples, an analog lock-in amplifier can be used. The analog lock-in amplifier can be connected to the control unit 8.

[0081] In addition, in some examples, a threshold can be selected. When the measured value has reached or exceeded the selected threshold, an alarm 15 can be initiated for healthcare personnel. The alarm 15 can be an acoustic alarm and / or an electronic alarm to a monitoring center.

[0082] Figures 2A to 2D Different examples of how to use a tracheal intubation, such as an endotracheal intubation, are shown.

[0083] Figure 3 An example of injecting diffused light using the working channel of a bronchoscope is shown.

[0084] It can be observed that without using a medical ventilator or a bronchoscope with a tracheal intubation, for example, through a feeding tube, the same device can be used with some modifications to inject light from the outside into the human body through the esophagus. In these cases, the light can be spread and diffused by a scattering medium having a sufficiently large surface (e.g., several square centimeters) and in contact with the skin. Such an arrangement can avoid local elevation of tissue temperature and achieve eye safety.

[0085] Figure 1 An exemplary configuration of the disclosed device and system is illustrated. A patient 1 is connected to a medical ventilator 2 through an introduction member 3 connected to a trachea 4, such as a bronchoscope, a tracheal intubation, or an endotracheal intubation.

[0086] In some other examples, the introduction member 3 can be, for example, a nasogastric feeding tube.

[0087] Light sources 5, 6, such as lasers, whose wavelengths are associated with free gases of interest (e.g., oxygen, nitric oxide (NO), and carbon dioxide) and a reference gas (e.g., water vapor).

[0088] In some examples, other gases than water vapor can be used as the reference gas. The requirement is only that the gas concentration can be calculated without using the path length through which the detected light has propagated.

[0089] Alternatively, in other examples, only one light source may be used. In some other examples, more than two light sources may be used to detect additional gases, gas distributions, or gas concentrations.

[0090] Alternatively, when using other methods related to GASMAS described previously herein, other configurations of the light source are also possible.

[0091] The light source is connected to a drive unit 7 controlled by a control unit 8.

[0092] In some examples, the measured value of the free gas in the lung can be used to affect the controller 9 to control the settings of the medical ventilator 2.

[0093] Alternatively and / or additionally, in some examples, the measured value of the control unit 8 can be used for the administration of the drug 10.

[0094] Light is emitted into the tissue via an optical fiber 11. Light from separate optical fibers 12 connected to the light sources 5, 6 (such as semiconductor lasers) can be connected to a single optical fiber 11.

[0095] Additionally, in some examples, a small portion of the light to be injected can be optically steered, for example via an optical fiber, to a calibration unit 13.

[0096] The detector 14 is configured to be positioned at the skin location of the patient's chest for detecting the transmitted diffused light. The detected light carries information about the gas concentration in the lung or the gas distribution in the lung tissue, such as the oxygen, nitric oxide (NO), and carbon dioxide concentrations or distributions.

[0097] Furthermore, in some examples, an alarm 15 can be activated when the measured value reaches or exceeds a selected threshold.

[0098] Figures 2A to 2D Illustrated are different examples of coupling light from an optical fiber into tissue for measuring lung function.

[0099] Figure 2A An example of an endotracheal tube 3, such as an endotracheal intubation, is shown having an inflatable balloon or cuff 16 to prevent air leakage beside the endotracheal tube 3, and the endotracheal tube 3 includes an optical fiber 11 for transmitting light downward into the trachea.

[0100] Figure 2B An example of an optical fiber 11 is shown descending from an endotracheal tube, such as an endotracheal intubation, to its end. A light diffuser 17 is arranged at the end of the optical fiber 11.

[0101] Figure 2CShows an example of how light in the optical fiber 11 can be connected to the end 18 of an endotracheal tube, such as an endotracheal tube. The end portion is made of a material that does not absorb but strongly scatters light.

[0102] Figure 2D Shows an example of how light from the optical fiber 11 can be coupled to the balloon or cuff 16. The balloon or cuff can be made of a non-absorbing but light-scattering material. In some examples, the inner wall is coated with a light-reflecting material 19.

[0103] In one example, the laser light source is applied through the esophagus rather than the trachea. In this example, the laser light source can be combined with a nasogastric tube used for most infants in neonatal intensive care. Using a nasogastric tube in light application is advantageous because most infants already require insertion of such a device, so no additional device needs to be introduced. This is also advantageous because the esophageal environment is less sensitive to infection. This is also advantageous because the esophagus is usually mostly collapsed, so an inflated cuff may not be needed to create good optical contact between the light source and the tissue. Additionally, the lower part of the lung can also be more easily reached.

[0104] The light source should be located at a point in the esophagus that represents a position close to the lungs. In one example, the optical fiber guiding the laser is combined with a nasogastric feeding tube such that the optical fiber travels along the tube to an appropriate position along the tube. There are markings on the nasogastric feeding tube indicating the depth of insertion of the tube, and these markings can be used to determine the position of the light source in the esophagus.

[0105] In a preferred embodiment, the optical fiber guiding the laser is embedded in the tube wall during the manufacturing process of the nasogastric feeding tube such that the nasogastric feeding tube and the laser light guide are one device.

[0106] In one example, the distal end of the optical fiber is terminated with a light diffuser that distributes the light over a larger area than the area provided only by the tip of the optical fiber. In a preferred example, when the optical fiber is embedded in the tube wall as described above, the diffuser is achieved by designing the tube wall in front of the tip of the optical fiber to have light-scattering properties such that the light scatters along the tube into an area corresponding to the desired diffuser characteristics. In an alternative example, the diffuser is manufactured as a separate component embedded in the tube wall similar to the optical fiber.

[0107] In an alternative example, the diffuser can be made as part of an inflatable cuff similar to the diffuser described above in connection with the trachea.

[0108] The optical fiber can also be positioned in the nasogastric tube in such a way that it can be sequentially moved along the tube to different positions to facilitate obtaining a complete tomographic view of gas distributions, such as oxygen, nitric oxide (NO), and carbon dioxide distributions, using multiple detectors 14, for example.

[0109] Alternatively, multiple optical fibers can be used in parallel at different locations to facilitate the use of multiple detectors 14 to achieve, for example, a complete tomographic view of gas distributions, such as oxygen, nitric oxide (NO), and carbon dioxide distributions.

[0110] In an alternative example, the light source on the nasogastric tube is implemented by placing one or more laser diodes directly at the location where the light source should be located and having wires for driving the laser diodes along the nasogastric tube. This implementation can also be applied to the case of endotracheal intubation.

[0111] Figure 4A Illustrated is an optical fiber 41 in combination with a nasogastric tube 46 inserted into the esophagus 42. Also shown is the relationship with the trachea 43 and the lungs 44. At the distal end of the optical fiber 41, there can be a light diffuser 45. Also shown is the upper part of the stomach 47.

[0112] Figure 4B A close-up of the optical fiber 41 embedded in the wall of the nasogastric tube 46 is shown. The nasogastric tube is inserted into the esophagus 42. In this example, the optical fiber has a diffuser 45 at the distal end of the optical fiber 41. In other examples, the optical fiber 41 may not have a diffuser.

[0113] Alternatively, light transmitted from outside the human body can be used to non-invasively evaluate gas concentration, for example, towards the skin above a cavity containing free gas (such as the lungs). The light that penetrates enough tissue to reach the cavity is scattered and transmitted to a detector placed against the skin. For example, the detector is typically located a few centimeters from the position of the light source. Thus, a non-invasive measurement procedure can be performed.

[0114] When only detecting and evaluating the transmitted signal for determining the state of the lung system, or when correlating the transmission and gas concentration and / or distribution measurements, the same arrangement can be used, where the light source is arranged on the skin.

[0115] In the above examples, the light source or the optical component is described as an optical fiber device connected to a light source (such as a laser), but other devices are equally possible. For example, the light source or the optical component can be a waveguide, or an LED directly arranged in the introducing component.

[0116] When arranging a light probe on the skin surface (i.e., the skin), a fiber arrangement connected to the light source can be used, but in some examples, the light source can be adapted to be directly arranged on the skin surface, such as an LED, a laser, and a waveguide.

[0117] The detector unit can be a photodiode, a photomultiplier tube, an avalanche photodiode, a charge-coupled device, a CCD, or a CMOS photosensitive device. As described herein, the detector can be a single detector or can be multiple detectors.

[0118] The different ways of measuring free gas in a measurement cavity have been described above and these can be used to monitor the lung system and determine the state of the lung system, such as detecting ventilation problems and / or pulmonary complications, such as pulmonary ventilation problems, and more particularly diagnosing pneumothorax and / or atelectasis.

[0119] The same techniques described for introducing an optical signal into a cavity of the lung system and detecting the transmitted light to observe the concentration and / or distribution of free gas in the cavity can be used to measure and evaluate the intensity of the transmitted light. Determination of the state of the lung system can be performed by evaluating changes in the intensity of the transmitted light, such as over time, or by evaluating the shape of the intensity curve over time.

[0120] When evaluating the transmitted light to determine the state of the lung system, such as detecting ventilation problems and / or pulmonary complications, such as pulmonary ventilation problems, and more particularly diagnosing pneumothorax and / or atelectasis, the wavelength can be any wavelength that can penetrate the tissue surrounding the cavity but can still be detected. Preferably, the wavelength lies within the optical window of the tissue that will give a greater penetration depth. Additionally, in some examples, the signal is associated with the same wavelength over time. This means that the wavelength is not scanned but remains constant. For example, by locking the light source to a single wavelength. This wavelength, which is only used when evaluating the intensity signal, may not be related to the absorption band of the free gas. When the wavelength used needs to be associated with the absorption of at least one gas, this is different compared to measuring the concentration or distribution of at least one gas. The term "single wavelength" should be interpreted as the central wavelength of the light emitted by the light source, including where the emitted light has a linewidth.

[0121] The change over time of the intensity of the detected optical signal transmitted through the cavity can be associated with a change in the volume of the cavity. This is related to the fact that the intensity of the detected signal may vary due to the distance the light travels through the cavity. This can be used as a qualitative measurement of the ventilation of the cavity, such as the lung. For example, by monitoring or observing the change over time of the intensity of the optical signal transmitted through the cavity, an increase and / or decrease in intensity can be associated with an increase and / or decrease in the volume of the cavity.

[0122] The volumes of different cavities can also be compared, such as by obtaining a first transmission signal from a first cavity of a first lung and a second transmission signal from a second cavity of a second lung. The first and second transmission signals can then be compared to detect a change in the volume of one of the cavities relative to the other.

[0123] Detecting or monitoring changes in the transmission signal due to volume changes can be used to detect lung ventilation problems. For example, a change in volume may mean that a tube used for aeration is not correctly positioned or has become blocked. Changes in the transmission signal due to volume changes can be used to detect overpressure in at least one lung or collapse of at least one lung, such as partial collapse. It can also be used to detect lung inflammation or sepsis. Detection of volume changes can also be used to detect problems with increased pulmonary mucus.

[0124] Determination of the pulmonary system state can be accomplished by continuously monitoring signals transmitted through the lumen of the pulmonary system (e.g., the lung). Determining the state, such as detecting ventilation problems and / or pulmonary complications, can be accomplished by evaluating detected optical signals transmitted through the lung. Pulmonary complications and / or ventilation problems can be detected by observing changes in the detected optical signals, such as an increase or decrease in the signal over time, or changes in the intensity profile of the optical signal transmitted through the lumen.

[0125] One option can be to obtain the concentration and / or distribution of free gas based on detected optical signals transmitted through the lumen of the pulmonary system. The light should preferably have a wavelength associated with the absorption band of the free gas to be detected. The concentration and / or distribution can be obtained by using the above-described system. Additionally, GASMAS technology can also be applied. The free gas can be a physiological gas or a gas mixture, such as any one of oxygen, nitric oxide (NO), carbon dioxide, anesthetic gas, and water vapor.

[0126] The state of the pulmonary system, such as pulmonary complications and / or ventilation problems, can be detected by observing changes in the concentration and / or distribution of the free gas, such as an increase or decrease in the concentration over time, or changes in the shape of the concentration profile. The concentration of the free gas can be obtained as the absorption signal of the free gas. The absorption signal can have the dimension [%m] and is the product of the relative gas concentration [%] and the absorption path length [m].

[0127] A further option can be to monitor the pulmonary system by correlating the detected light transmitted through the lumen of the pulmonary system (e.g., the lung) with the concentration / distribution signal of the free gas. The emitted light used to evaluate the transmitted intensity can have the same wavelength as the emitted light used to obtain the concentration and / or distribution of the free gas in the lumen, such as a wavelength associated with the absorption band of the free gas. Alternatively, the emitted light used to evaluate the transmitted intensity can have a different wavelength from the emitted light used to obtain the concentration and / or distribution of the free gas in the lumen. For example, the emitted light for intensity evaluation can be any wavelength within the optical window of the tissue, and the emitted light used to obtain the concentration and / or distribution of the free gas can be associated with the absorption band of the free gas.

[0128] To demonstrate that it is possible to monitor the pulmonary system to detect ventilation problems and / or pulmonary complications (e.g., lung ventilation problems), measurements were performed on four piglets. For the measurements, a GASMAS system was used to measure gas absorption at two wavelengths, 764 nm for oxygen absorption and 820 nm for water vapor absorption.

[0129] The relative humidity in the lungs is approximately 100%. Combining the knowledge of tissue temperature and air pressure, the water vapor gas concentration can be theoretically calculated. Therefore, the water vapor gas absorption measured in [%m] provides the absorption path length in [m] for light at 820 nm. Assuming that the average distance traveled by light at 764 nm in the tissue is the same, the measured oxygen absorption [%m] then provides the oxygen concentration in [%.

[0130] The emissions of two diode lasers providing light at 764 nm and 820 nm are focused into an optical fiber. The diode lasers and the optical combination device are encapsulated in a nitrogen-filled box to eliminate offsets in the absorption signal.

[0131] By sequentially scanning the laser wavelength at a rate of 1 kHz on one of the absorption lines of oxygen molecules (O 2 ) at 764 nm and water vapor (H 2 O) at 820 nm, the gas absorption signal is obtained. The two gases are measured sequentially before switching, with a measurement time of 100 s.

[0132] The optical fiber is inserted into a piglet for esophageal light management, and the end of the optical fiber is configured for diffusing light.

[0133] After passing through the tissue, the transmitted light is detected by a photodiode incorporated into a detector probe connected to the skin. The detector probe area is covered with a layer of ultrasonic gel to reduce offsets in the absorption signal. The detected absorption signal is intensity-normalized and frequency-filtered through an electronic platform to obtain the absorption amplitude.

[0134] Partial atelectasis is simulated by inserting a 4Fr embolectomy catheter with a balloon at the tip ( Vascular, Sulzbach, Germany) into the right main bronchus. When the end-tidal CO 2 immediately decreases by 50% after the balloon is inflated, it is confirmed as partial airway obstruction. After approximately 1.5 minutes or if the piglet becomes circulatory unstable, the balloon is deflated. The oxygen signal is continuously measured during the process and repeated 3 times.

[0135] After the piglet's atelectasis is recovered, a small thoracostomy is made 1 cm below the dermal detector probe at the right midaxillary line, a drainage tube is placed and sutured in place. The piglet is ventilated with 100% oxygen while 150 ml of ambient air (21% oxygen) is injected into the pleural cavity through the tube. The oxygen signal is continuously measured during the pneumothorax phase. Approximately 2 minutes after induction, the air is withdrawn from the pleural cavity, followed by lung recruitment. This process is repeated 3 times.

[0136] While continuously monitoring oxygen absorption and light transmission using an internal light source, atelectasis is induced in four piglets, see Figure 5, which shows the time evolution of the oxygen absorption signal and the corresponding light transmission for induced atelectasis. A decrease in oxygen absorption and light transmission at the onset of atelectasis can be seen. The dashed line represents the transmission signal as a percentage, and the solid line represents the absorption in %m. When the balloon is deflated within the bronchus, the absorption and light transmittance are observed to return to their initial values prior to atelectasis in most cases. For pneumothorax measurements, see 2 , which shows the time evolution of the oxygen absorption signal and the corresponding light transmission for induced pneumothorax. Set FiO Figure 6 2 to 1.0, and induce pneumothorax by injecting air into the pleural cavity. When pneumothorax begins, the continuously monitored oxygen absorption decreases. At the same time, an increase in light transmission is detected. The dashed line represents the transmission signal as a percentage, and the solid line represents the absorption in %m. 2 2 2

[0137] To improve the detection of light signals detected in a cavity that has passed through a lung system, such as the lung, different methods can be applied. In some examples, a filter that is transmissive at the wavelength of the emitted light signal can be arranged in front of the detector unit. The filter can pass only long wavelengths (long-pass), only short wavelengths (short-pass), or block wavelength bands of longer and shorter wavelengths (band-pass), or the filter can be a combination of them. The passband can be narrower or wider; the transition between maximum and minimum transmission can be sharp or gradual. Filters with more complex transmission characteristics can be used, such as those with two peaks instead of a single band.

[0138] Additionally and / or alternatively, in some examples, the emitted light signal can be a pulse with gated detection. Gated detection can be, for example, time-gated, whereby the pulsed light source is pulsed at a frequency such as a user-defined frequency. The camera is insensitive for a period of time after the light pulse (referred to as the "gate delay"). Then the camera becomes sensitive for a period of time (referred to as the "gate width").

[0139] Additionally and / or alternatively, in some examples, the emitted light signal can be amplitude-modulated. The modulation can be seen in the detected signal, and by performing a frequency analysis on the detected signal, the amplitude at the modulation frequency will be a measure of the transmission that is less affected by noise and background signals. Additionally, to further suppress the possibility of noise and background, the frequency of the amplitude modulation can also be changed, for example, amplitude-modulate the emitted light signal with a varying modulation frequency and analyze the spectrum of the detected signal at the varying modulation frequencies.

[0140] In some examples, the determined state of the pulmonary system can be used as a feedback signal to a medical ventilator. For example, the settings of the medical ventilator can be changed in response to the detected state, e.g., automatically. This can be achieved by having the control unit send a signal to the medical ventilator or by having the control unit be an integrated part of the medical ventilator.

[0141] The medical ventilator can here be, for example, invasive ventilation (conventional), high-frequency oscillatory ventilation (HFOV) or continuous positive airway pressure ventilation (CPAP). However, the medical ventilator can also mean passive respiratory support, such as high-flow nasal cannula (HFNC).

[0142] One setting that can be changed is the pressure. For example, the control unit can be configured to send a signal to the medical ventilator to increase the pressure when atelectasis is detected and / or to decrease the pressure when the atelectasis decreases.

[0143] The invention has been described above with reference to specific examples. However, within the scope of the present disclosure, other examples than those described above are equally possible. Method steps different from those described above can be provided within the scope of the invention and the method can be carried out by hardware or software. The different features and steps of the invention can be combined in ways different from those described. The scope of the present disclosure is limited only by the appended patent claims.

[0144] The indefinite articles "a" and "an" used in the description and claims should be understood to mean "at least one" unless explicitly stated to the contrary. The phrase "and / or" used in the description and claims should be understood to mean "one or both" of the elements so combined, i.e., elements that are present in combination in some cases and separate in other cases.

Claims

1. An apparatus for monitoring a subject's pulmonary system, said apparatus comprising: an optical member for emitting an optical signal to pass through a cavity of the subject's pulmonary system, wherein the optical signal comprises at least one wavelength, and wherein the at least one wavelength is within an optical window of tissue; a detector unit, wherein the detector is configured to be positioned on the skin surface for detecting the optical signal transmitted through the cavity of the subject; and a control unit for detecting a physiological state of the pulmonary system by correlating over time the intensity of the detected optical signal transmitted through the cavity with the concentration and / or distribution of free gas.

2. The apparatus according to claim 1, wherein the detected optical signal is correlated over time with the same wavelength such that the at least one wavelength of the emitted optical signal is a single wavelength.

3. The apparatus according to any one of claims 1 to 2, wherein the physiological state is related to detecting pulmonary complications and / or ventilation problems.

4. The apparatus according to claim 1, wherein the at least one wavelength of the emitted optical signal is related to an absorption band of free gas in the pulmonary system.

5. The apparatus according to claim 1, wherein the optical member is adapted to be inserted inside a body using an introducing member.

6. The apparatus according to claim 1, wherein the optical member is adapted to be arranged on the skin surface of the subject to emit the optical signal into the cavity.

7. The apparatus according to claim 1, wherein the detected optical signal is provided using tunable diode laser absorption spectroscopy.

8. The apparatus according to claim 1, wherein the optical signal emitted by the optical member comprises at least two different wavelengths.

9. The apparatus according to claim 8, wherein the at least one wavelength is associated with an absorption band of a reference gas to determine the concentration and / or distribution of the free gas.

10. The apparatus according to claim 1, wherein a filter transmitting at the wavelength of the emitted optical signal is arranged in front of the detector unit; and / or wherein the emitted optical signal is pulsed by gated detection; and / or wherein the emitted optical signal is amplitude modulated by a modulation frequency and the spectrum of the detected optical signal is analyzed at the modulation frequency; and / or wherein the emitted optical signal is amplitude modulated at a varying modulation frequency and the spectrum of the detected optical signal is analyzed at the varying modulation frequency.

11. An apparatus for monitoring a subject's pulmonary system, said apparatus comprising: an optical member for emitting an optical signal to pass through a cavity of the subject's pulmonary system, wherein the optical signal comprises at least one wavelength, and wherein the at least one wavelength is within an optical window of tissue; a detector unit, wherein the detector is configured to be positioned on the skin surface for detecting the optical signal transmitted through the cavity of the subject; and A control unit for evaluating the detected optical signal to determine a physiological state of the lung system of the subject by evaluating a change in intensity of the detected optical signal transmitted through the cavity over time, and wherein the control unit is configured to control a medical ventilator based on the detected physiological state of the lung system.

12. The apparatus according to claim 11, wherein the control unit is configured to send a signal to increase the pressure of the medical ventilator when atelectasis is detected.

13. The apparatus according to claim 11, wherein the control unit is configured to send a signal to decrease the pressure of the medical ventilator when the atelectasis decreases.

14. An apparatus for monitoring a lung system of a subject, the apparatus comprising: an optical member for emitting an optical signal through a cavity of the lung system of the subject, wherein the optical signal includes at least one wavelength, and wherein the at least one wavelength is within an optical window of tissue; a detector unit, wherein the detector is configured to be positioned on a skin surface for detecting the optical signal transmitted through the cavity of the subject; and a control unit for evaluating the detected optical signal to determine a physiological state of the lung system of the subject by evaluating a change in intensity of the detected optical signal transmitted through the cavity over time, and wherein the control unit is configured to activate an alarm when the detected signal reaches or exceeds a selected threshold.

15. An apparatus for monitoring a lung system of a subject, the apparatus comprising: a first optical member for emitting a first optical signal through a first cavity of the lung system of the subject, and a second optical member for emitting a second optical signal through a second cavity of the lung system of the subject, wherein the first optical signal and the second optical signal include at least one wavelength, and wherein the at least one wavelength is within an optical window of tissue; a first detector unit, wherein the first detector unit is configured to be positioned on a skin surface for detecting the first optical signal transmitted through the first cavity of the subject, and a second detector unit, wherein the second detector unit is configured to be positioned on a skin surface for detecting the second optical signal transmitted through the second cavity of the subject; and a control unit for detecting a physiological state of the lung system by comparing the first detected optical signal of the first cavity and the second detected optical signal of the second cavity.

16. The apparatus according to claim 15, wherein, the first cavity is a first lung and the second cavity is a second lung.

17. The apparatus according to claim 15, wherein, the detected first optical signal is compared with the detected second optical signal to detect a volume change of one of the first cavity and the second cavity relative to the other cavity.

18. The apparatus according to claim 15, wherein, Compare the detected first optical signal with the detected second optical signal to detect a change in free gas in one of the first cavity and the second cavity relative to the other cavity.

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