In recent years there has been a growing awareness of respiratory patients, particularly Asthmantic patients, being unable to properly perceive their shortness-of-breath (dyspnea) signals.
This can vary from mild unawareness of little consequence, to severe impairment, this to the point of being unable to detect severe dyspnea signals due to developing serious disease conditions. It is clear this impaired ability to detect dyspnea signals is a major factor in Asthma deaths, some 5,000 a year in the United States alone. This is a medical tragedy, as almost all Asthmatics may be saved, if only they came to medical attention early in their Asthmatic deterioration.
The Dyspnea Perception System is specifically designed to improve on the presently available tests to detect blunted dyspnea awareness.
The implications of the report by Dr. Yoshihiro Kikuchi and colleagues are indeed profound. These investigators reported in the New England Journal Of Medicine in 1994 a striking lack of dyspnea sensations in a group of asthmatic patients who had near-fatal asthma attacks. (See: Chemosensitivity and Perception of Dyspnea in Patients with a History of Near-Fatal Asthma; Kikuchi, Yoshihro et al, New England Journal of Medicine, v. 130 No. 19 p. 1329, May 12, 1994--See also editorial Blunted Perception and Death from Asthma p.1383.) Of note, a number of other investigators have also reported decreased dyspnea awareness in asthmatic patients.
In recent years there has been a worldwide alarming increase in the incidence of Asthmatic deaths, despite the fact that much more is now known about Asthma, and many potent Asthma medications are now available. In the United States alone there are about 5,000 Asthma deaths yearly, and despite major professional and public health efforts to improve this tragic mortality there has been essentially no significant improvement.
Unfortunately, clinical predictors of risk for potential Asthmatic fatality are rather crude. Many of these deaths have been unexpected, in patients who did not appear to fit the usual criteria of risk of potential fatal attacks. The reason(s) for increasing Asthma mortality are uncertain, but it is generally thought there is a group of patients, numbering perhaps 5 to 15 percent of Asthmatics, who may be relatively unaware they are getting into serious difficulty with an Asthma attack. It is thought that these patients, unaware of the normal dyspnea distress signals, therefore delay coming to expert medical attention until it is too late.
Any test that could screen the Asthmatic population for blunted dyspnea awareness to an increasing inspiratory respiratory load (which basically what an Asthmatic attack is) holds promise of identifying these susceptible individuals for special attention and early intervention, and therefore prevent these unnecessary deaths.
The Dyspnea Perception System is designed specifically to address this problem, by providing a more standardized, specific and sensitive test to detect individuals at risk.
It is important to understand that any test for dyspnea, in provoking dyspnea during the testing procedure, will automatically introduce methodology bias and potential error into the testing procedure. This is because breathing control has a cognitive aspect, and patients will normally react to the dyspnea sensation by attempting to relieve their distress by overriding the basic breathing regulatory mechanisms to a greater or lesser degree.
See for example the Rescue Breathing Pattern or click on Theory & Papers in the Navigation Bar.
The result will be an uncertain distortion of the breathing pattern, therefore introducing a testing bias factor between the normal population and patients with blunted dyspnea perception. The Sierra Biotechnology method is the only dyspnea testing method that controls this bias factor. Likewise, this method is the only one that standardizes for Tidal Volume and Inspiratory Pressure / Load in order to make valid comparisons between different subjects.
The validity of subjective reporting of patients symptoms is always a problen in clinical and scientific inquiry. In any test that must depend on patient subjective reporting, such as the Borg Dyspnea Scale, the more the testing variabilities are controlled, the more confidence one has in the patient's subjective response.
Because of these methodology advancements, this testing procedure holds promise of becoming a standard test for dyspnea, and with potential widespread applications.
For example, in Pulmonary Rehabilitation Programs, which have some difficulty in providing objective measurements of improvement, an objective demonstration of improvement in the primary complaint of dyspnea following rehabilitation would more likely satisfy third party payers. Insurance companies and federal entitlement programs are understandably often reluctant to pay for these services, without demonstrable proof of therapeutic benefit, and as a result many worthy Pulmonary Rehabilitation Programs have payment problems and financial difficulties. This results in restriction of services, to the detriment of good patient care.
The overall Dyspnea Perception Systemtm is as follows:
The patient breathes through a testing interface device, which is attached to flowmeter and pressure sensing transducers. This data is input to a computer, and the computer generates an output signal to automatically adjust the level of inspiratory resistance.
The testing procedure is rigidly standardized by having the patient interact with a BIS Display © , which controls their breathing, and can quality control the breathing performance. (Please refer to the section on Biofeedback Incentive Systemtm for details on the BIS system, and the Phantom Line concept of quality control means.)
The patient is prompted to move an indicating device to the level of Borg dyspnea units at least once every minute, or whenever they feel there has been a change in their dyspnea level. This Borg data is also entered into the computer, and an overall graphic report is generated.
This first report display basically reproduces the original method of Kikuchi, with the important exception of breathing control with the BIS technology. In order to further standardize the test to account for both large and small individuals, or patients with greater or lesser amounts of lung tissue, the Tidal Volume breath is set at a fixed percentage (e.g. 50%) of a predetermined Vital Capacity breath.
Note the stepwise increase in inspiratory pressure every two minutes. Also displayed are three curvilinear displays of Borg dyspnea responses. The middle one is for a normal patient, with dyspnea normally increasing with time and an increasing inspiratory load. To the left and above is a hypersensitive patient with Hyperventilation Syndrome, and to the right and below is a patient with blunted dyspnea perception, which is typical of the at-risk Asthmatic. NOTE: The Borg scale is on the left, and Inspiratory Pressure on the right.
This second report display is the preferred testing embodiment. Here the patient breathes at a constant inspiratory load. This load is determined from a previously determined Maximum Inspiratory Pressure, (e.g. 50% of MIP), in order to standardize the test for patients with stronger or weaker respiratory muscles. As before, breathing control is with the BIS biofeedback technology, and the Tidal Volume is standardized as a percentage of the Vital Capacity breath. NOTE: The Borg scale is on the left, and Inspiratory Pressure on the right.
Again note the three Borg responses; the middle for a normal patient, the upper for a hypersensitive patient (with Hyperventilation Syndrome), and the lower for a patient with diminished dyspnea perception (and therefore at risk for fatal Asthma attacks). The line at the top is the peak inspiratory pressure. Note that it remains relatively constant (because of the BIS breathing control), but near the end begins to diminish, as the patient fatigues and is unable to keep up the respiratory effort as defined by the BIS biofeedback prompting.
The Dyspnea Perception Systemtm has great potential to better evaluate the elusive sensation of dyspnea in a wide variety of applications, and specifically to favorably influence the tragedy of fatal Asthma attacks by identifying those at risk, in order that these vulnerable patients be given more intense monitoring and and specialized care. More advanced Asthma programs have demonstrated that more intense monitoring and and specialized care can substantially improve on the tragedy of needless Asthmatic deaths.
In recent years there has been great interest in the Lung Volume Reduction Surgery (LVRS) procedure to relieve dyspnea in patient's with advanced Emphysema, and to make them more functional. The Dyspnea Perception System holds considerable promise in evaluation and follow-up in this important area of concern.