Centralized hospital monitoring system for automatically detecting upper airway instability and for preventing and aborting adverse drug reactions

Abstract

A system and method for the automatic diagnosis of obstructive sleep apnea in a centralized hospital critical care monitoring system for the monitoring of a plurality of patients in at least one of a critical care, step down, and cardiac ward by telemetry. The system includes a central processor having a display, and a plurality of telemetry unit for mounting with patients, each of the telemetry units has a plurality of sensors for connection with each patient, the telemetry unit is capable of the transmission of multiple signals derived from the sensors to the central processor, in one preferred embodiment the method comprising steps of programming the system to analyze the signals and to automatically identify the presence and severity of obstructive sleep apnea and to provide an indication of the identification.

Description

[0001] This application claims priority of prior application Ser. No. 10 / 150,582, filed May 17, 2002; provisional applications 60 / 291,692 and 60 / 291,687, both filed May 17, 2001 and provisional application 60 / 295,484 filed Jun. 10, 2001, the disclosures and contents of each of which is incorporated by reference as if completely disclosed herein.FIELD OF THE INVENTION [0002] This invention relates to centralized hospital monitoring systems and particular to the organization, analysis, and automatic detection of patterns indicative of upper airway instability during sleep, deep sedation, and analegia. BACKGROUND AND SUMMARY OF THE INVENTION [0003] The high number of unnecessary deaths in the hospital due to errors related to pharmaceutical administration such as sedative and narcotics has been a recent focus of US government studies and much discussion in the literature and press. The present inventors recognized that these adverse events occur not only due to improper dosage of medic...

AI Technical Summary

Benefits of technology

[0007] To understand the criticality of recognizing airway instability in real-time it is important to consider the significance of the combined effect that oxygen therapy and narcotics or sedation may have in the patient care environment in the hospital, for example, in the management of a post-operative obese patient after upper abdominal surgery. Such a patient may be at particular risk for increased airway instability in association with narcotic therapy in the through 3rd post-operative day due to sleep deprivation, airway edema, and sedation. Furthermore, in the second and third postoperative day monitoring the vigilance of hospital personnel may diminish due to perceived stability, and rebound rapid eye movement (REM) sleep which can increase upper airway instability may occur due to antecedent sleep deprivation. Indeed, many of these patients have significant sleep apnea prior to admission to the hospital which is unknown to the surgeon or the anesthesiologist due to the subtly of symptoms. Such patients, even with severe sleep apnea, are relatively safe at home because of an intact arousal response; however, in the hospital, narcotics and sedatives often remove this “safety net. The administration of post-operative narcotics can shift the arousal curve to the right and this can significantly increase the danger of airway instability and, therefore, place the patient at substantial risk. Many of these patients are placed on electrocardiographic monitoring but the alarms are generally set at high and low limits. Hypoxemia, induced by airway instability generally does not generally produce marked levels of tachycardia; therefore, airway instability is poorly identified by simple electrocardiographic monitoring without the identification of specific pattern of clusters of the pulse rate. In addition, simple oximetry evaluation is also a poor method to identify airway instability. Conventional hospital oximeters often have averaging intervals, which attenuate the dynamic desaturations. Even when the clustered desaturations occur they are often thought to represent false alarms because they are brief. When desaturations are recognized as potentially real this often results in the simple and often misguided addition of nasal oxygen. However, nasal oxygen may prolong the apneas and potentially increase functional airway instability. From a monitoring perspective, the addition of oxygen therapy can be seen to potentially hide the presence of significant airway instability by attenuation of the level of desaturation and reduction in the effectiveness of the oximeter as a monitoring tool in the diagnosis of this disorder.

[0034] It is further the purpose of the present invention to provide real time protection to patients against adverse drug and to provide a data matrix comprising matched time series of physiologic signals with a time series of drug infusion so that hospital personnel can readily match specific patterns of pathophysiologic perturbations to specific types of medications and ranges of medication dosage for patients hospital wide.

Problems solved by technology

Administration of “standard acceptable dosages” to patients with potentially unstable physiology can produce an insidious and deadly occurrence of relative drug excess, which will not be prevented by simple computer matching of patient name and drug.

Further, the present nventors recognized that failure to timely interrupt infusion upon the occurrence of physiologic instability represented a major cause of death.

In hospitals, throughout the United States monitored patients are experiencing profound physiologic instability before and during medication infusion producing patterns as shown in FIG. 2 and yet still are being subjected to continuous infusion of further destabilizing and potentially deadly narcotics and sedation simply because the hospital monitors do not recognize the patterns nor are they programmed to warn the hospital worker or to lock out the infusion based on such recognition.

A major factor in the development of respiratory failure (one of the most common causes of death in the hospital) is airway instability, which results in airway collapse during sedation, stroke, narcotic administration, or stupor.

Subgroups of patients in the hospital are at considerable risk from this type of instability.

In addition patients with otherwise relatively stable airways may have instability induced by sedation or narcotics.

For these reasons thousands of patients each day enter and leave hospital-monitored units with unrecognized sleep apnea and ventilation and airway instability.

This failure of conventional hospital based patient monitors to timely and / or automatically detect cluster patterns indicative of airway instability can be seen as a major health care deficiency indicative of a long unsatisfied need.

Because obstructive sleep apnea, a condition derived from airway instability, is so common, the consequence of the failure of conventional hospital monitors to routinely recognize upper airway instability clusters means that many of patients with this disorder will never be diagnosed in their lifetime.

A second group of patients will have a complication in the hospital due to the failure to timely recognize airway instability.

Without recognition of the inherent instability, a patient may be extubated too early after surgery or given too much narcotic (the right drug, the right patient, the ordered dose but unknowingly a “relative drug excess”).

Such a patient may be at particular risk for increased airway instability in association with narcotic therapy in the through 3rd post-operative day due to sleep deprivation, airway edema, and sedation.

Furthermore, in the second and third postoperative day monitoring the vigilance of hospital personnel may diminish due to perceived stability, and rebound rapid eye movement (REM) sleep which can increase upper airway instability may occur due to antecedent sleep deprivation.

Indeed, many of these patients have significant sleep apnea prior to admission to the hospital which is unknown to the surgeon or the anesthesiologist due to the subtly of symptoms.

Such patients, even with severe sleep apnea, are relatively safe at home because of an intact arousal response; however, in the hospital, narcotics and sedatives often remove this “safety net.

The administration of post-operative narcotics can shift the arousal curve to the right and this can significantly increase the danger of airway instability and, therefore, place the patient at substantial risk.

Hypoxemia, induced by airway instability generally does not generally produce marked levels of tachycardia; therefore, airway instability is poorly identified by simple electrocardiographic monitoring without the identification of specific pattern of clusters of the pulse rate.

In addition, simple oximetry evaluation is also a poor method to identify airway instability.

Even when the clustered desaturations occur they are often thought to represent false alarms because they are brief.

When desaturations are recognized as potentially real this often results in the simple and often misguided addition of nasal oxygen.

However, nasal oxygen may prolong the apneas and potentially increase functional airway instability.

From a monitoring perspective, the addition of oxygen therapy can be seen to potentially hide the presence of significant airway instability by attenuation of the level of desaturation and reduction in the effectiveness of the oximeter as a monitoring tool in the diagnosis of this disorder.

Oxygen and sedatives can be seen as a deadly combination in patients with severely unstable airways since the sedatives increase the apneas and the oxygen hides them from the oximeter.

A fall in afferent output from the brain controller to the airway dilators results in upper airway collapse.

Alternatively, a fall in afferent output to the pump muscles causes hypoventilation.

The first and most traditionally considered potential effect of narcotics or sedation is the suppression by the narcotic or sedative of the brains afferent output to pump muscle such as the diaphragm and chest wall, resulting in inadequate tidal volume and associated fall in minute ventilation and a progressive rise in carbon dioxide levels.

The rise in carbon dioxide levels causes further suppression of the arousal response, therefore, potentially causing respiratory arrest.

However, in the presence of oxygen administration, oximetry is a poor indicator of ventilation.

In addition, patients may have a combined cause of ventilation failure induce by the presence of both upper airway instability and decreased diaphragm output as will be discussed, this complicates the output patterns of CO2 monitors making recognition of evolving respiratory failure due to hypoventilation more difficult for conventional threshold alarm based systems.

This reduction in airway tone results in dynamic airway instability and precipitates monomorphic cluster cycles of airway collapse and recovery associated with the arousal response as the patient engages in a recurrent and cyclic process of arousal based rescue from each airway collapse.

If, despite the development of significant cluster of airway collapse, the narcotic administration or sedation is continued, this can lead to further prolongation of the apneas, progression to dangerous polymorphic desaturation, and eventual respiratory arrest.

There is, therefore, a dynamic interaction between suppression of respiratory drive, which results in hypoventilation and suppression of respiratory drive, which results in upper airway instability.

At any given time, a patient may have a greater degree of upper airway instability or a greater degree of hypoventilation.

Unfortunately, this has been one of the major limitations of carbon dioxide monitoring.

The upper airway obstruction may result in drop out of the nasal carbon dioxide signal due to both the upper airway obstruction, on one hand, or due to conversion from nasal to oral breathing during a recovery from the upper airway obstruction, on the other hand.

Although breath by breath monitoring may show evidence of apnea, conversion from nasal to oral breathing can reduce the ability of the CO2 monitor to identify even severe hypoventilation in association with upper airway obstruction, especially if the signal is averaged or sampled at a low rate.

For this reason, conventional tidal CO2 monitoring when applied with conventional monitors without out cluster pattern recognition may be least effective when applied to patients at greatest risk, that is, those patients with combined upper airway instability and hypoventilation.

In addition, the present inventors recognized that the complexity and time course variability of these patterns commonly overwhelms hospital workers so that timely intervention is often not applied, resulting in unnecessary death or patient injury.

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