Introduction: Impairments caused by the chronic disorder of the respiratory system generally result from irreversible loss of pulmonary functional capacity (ventilatory impairment, gas exchange impairment, or a combination of both). The most common symptom attributable to these disorders is dyspnea on exertion. Cough, wheezing, sputum production, hemoptysis, and chest pain may also occur, but need not be present. However, since these symptoms are common to many other diseases, evaluation of impairments of the respiratory system requires a history, physical examination, and chest roentgenogram to establish the diagnosis of a chronic respiratory disorder. Pulmonary function testing is required to provide a basis for assessing the impairment, once the diagnosis is established by appropriate clinical findings.
Alteration of ventilatory function may be due primarily to chronic obstructive pulmonary disease (emphysema, chronic bronchitis, chronic asthmatic bronchitis) or restrictive disorders with primary loss of lung volume (pulmonary resection, thoracoplasty, chest cage deformity as seen in kyphoscoliosis), or infiltrative interstitial disorders (diffuse fibrosis). Impairment of gas exchange without significant airway obstruction may be produced by interstitial disorders (diffuse fibrosis). Primary disease of pulmonary circulation may produce pulmonary vascular hypertension and, eventually, heart failure. Whatever the mechanism, any chronic progressive pulmonary disorder may result in cor pulmonale or heart failure. Chronic infection caused, most frequently by mycobacterial or mycotic organisms, may produce extensive lung destruction resulting in marked loss of pulmonary functional capacity. Some disorders such as bronchiectasis and asthma may be characterized by acute, intermittent illnesses of such frequency and intensity that they produce a marked impairment apart from intercurrent functional loss, which may be mild.
Most chronic pulmonary disorders may be adequately evaluated on the basis of history, physical examination, chest roentgenogram, and ventilatory function tests. Direct assessment of gas exchange by exercise arterial blood gas determination or diffusing capacity is required only in specific relatively rare circumstances, depending on the clinical features and specific diagnosis.
Mycobacterial and mycotic infections of the lung will be evaluated on the basis of the resulting impairment to pulmonary function. Evidence of infectious or active mycobacterial or mycotic infection, such as positive cultures, increasing lesions, or cavitation, is not, by itself, a basis for determining that the individual has a severe impairment which is expected to last 12 months. However, if these factors are abnormally persistent, they should not be ignored. For example, in those unusual cases where there is evidence of persistent pulmonary infection caused by mycobacterial or mycotic organisms for a period closely approaching 12 consecutive months, the clinical findings, complications, treatment considerations, and prognosis must be carefully assessed to determine whether, despite the absence of impairment of pulmonary function, the individual has a severe impairment that can be expected to last for 12 consecutive months.
When a respiratory impairment is episodic in nature, as may occur in complications of bronchiectasis and asthmatic bronchitis, the frequency of severe episodes despite prescribed treatment is the criterion for determining the level of impairment. Documentation for episodic asthma should include the hospital or emergency room records indicating the dates of treatment, clinical findings on presentation, what treatment was given and for what period of time, and the clinical response. Severe attacks of episodic asthma, as listed in section 3.03B, are defined as prolonged episodes lasting at least several hours, requiring intensive treatment such as intravenous drug administration or inhalation therapy in a hospital or emergency room.
Documentation of ventilatory function tests. The results of ventilatory function studies for evaluation under tables I and II should be expressed in liters or liters per minute (BTPS). The reported one second forced expiratory volume (FEV1 ) should represent the largest of at least three attempts. One satisfactory maximum voluntary ventilation (MVV) is sufficient. The MVV should represent the observed value and should not be calculated from FEV1 . These studies should be repeated after administration of a nebulized bronchodilator unless the prebronchodilator values are 80 percent or more of predicted normal values or the use of bronchodilators is contraindicated. The values in tables I and II assume that the ventilatory function studies were not performed in the presence of wheezing or other evidence of bronchospasm or, if these were present at the time of the examination, that the studies were repeated after administration of a bronchodilator. Ventilatory function studies performed in the presence of bronchospasm, without use of bronchodilators, cannot be found to meet the requisite level of severity in tables I and II.
The appropriately labeled spirometric tracing, showing distance per second on the abscissa and the distance per liter on the ordinate, must be incorporated in the file. The manufacturer and model number of the device used to measure and record the ventilatory function should be stated. If the spirogram was generated other than by direct pen linkage to a mechanical displacement-type spirometer, the spirometric tracing must show the calibration of volume units through mechanical means such as would be obtained using a giant syringe. The FEV1 must be recorded at a speed of at least 20 mm. per second. Calculation of the FEV1 from a flow volume loop is not acceptable. The recording device must provide a volume excursion of at least 10 mm. per liter. The MVV should be represented by the tidal excursions measured over a 10- to 15-second interval. Tracings showing only cumulative volume for the MVV are not acceptable. The ventilatory function tables are based on measurement of the height of the individual without shoes. Studies should not be performed during or soon after an acute respiratory illness. A statement should be made as to the individual's ability to understand the directions and cooperate in performing the test.
Documentation of chronic impairment of gas exchange—Arterial blood gases and exercise tests.
Introduction: Exercise tests with measurement of arterial blood gases at rest and during exercise should be purchased when not available as evidence of record in cases in which there is documentation of chronic pulmonary disease, but the existing evidence, including properly performed ventilatory function tests, is not adequate to evaluate the level of the impairment. Before purchasing arterial blood gas tests, medical history, physical examination, report of chest roentgenogram, ventilatory function tests, electrocardiographic tracing, and hematocrit must be obtained and should be evaluated by a physician competent in pulmonary medicine. Arterial blood gas tests should not be purchased where full development short of such purchase reveals that the impairment meets or equals any other listing or when the claim can be adjudicated on some other basis. Capillary blood analysis for PO2 or PCO2 is not acceptable. Analysis of arterial blood gases obtained after exercise is stopped is not acceptable.
Generally individuals with an FEV1 greater than 2.5 liters or an MVV greater than 100 liters per minute would not be considered for blood gas studies unless diffuse interstitial pulmonary fibrosis was noted on chest x-ray or documented by tissue diagnosis. The exercise test facility should be provided with the clinical reports, report of chest roentgenogram, and spirometry results obtained by the DDS. The testing facility should determine whether exercise testing is clinically contraindicated. If an exercise test is clinically contraindicated, the reason for exclusion from the test should be stated in the report of the exercise test facility.
Methodology. Individuals considered for exercise testing first should have resting PaO2 , PaCO2 , and pH determinations by the testing facility. The samples should be obtained in the sitting or standing position. The individual should be exercised under steady state conditions, preferably on a treadmill for a period of 6 minutes at a speed and grade providing a workload of approximately 17 ml. O2 /kg./min. If a bicycle ergometer is used, an exercise equivalent of 450 kgm./min., or 75 watts, should be used. At the option of the facility, a warm-up period of treadmill walking may be performed to acquaint the applicant with the procedure. If, during the warm-up period, the individual cannot exercise at the designated level, a lower speed and/or grade may be selected in keeping with the exercise capacity estimate. The individual should be monitored by electrocardiogram throughout the exercise and representative strips taken to provide heart rate in each minute of exercise. During the 5th or 6th minute of exercise, an arterial blood gas sample should be drawn and analyzed for PO 2 , PCO2 , and pH. If the facility has the capability, and at the option of the DDS and the facility, minute ventilation (BTPS) and oxygen consumption per minute (STPD) and CO2 production (STPD) should be measured during the 5th or 6th minute of exercise. If the individual fails to complete 6 minutes of exercise, the facility should comment on the reason.
The report should contain representative strips of electrocardiograms taken during the exercise, hematocrit, resting and exercise arterial blood gas value, speed and grade of the treadmill or bicycle ergometer exercise level in watts or kgm./min., and duration of exercise. The altitude of the test site, barometric pressure, and normal range of blood gas values for that facility should also be reported.
Evaluation. Three tables are provided in Listing 3.02C1 for evaluation of arterial blood gas determinations at rest and during exercise. The blood gas levels in Listing 3.02C1, Table III-A, are applicable at test sites situated at less than 3,000 feet above sea level. The blood gas levels in Listing 3.02C1, Table III-B, are applicable at test sites situated at 3,000 through 6,000 feet above sea level. The blood gas levels in Lising 3.02C1, Table III-C, are applicable for test sites over 6,000 feet above sea level. Tables III-B and C, take into account the lower blood PaO2 normally found in individuals tested at the higher altitude. When the barometric pressure is unusually high for the altitude at the time of testing, consideration should be given to those cases in which the PaO2 falls slightly above the requirements of Table III-A, III-B, or III-C, whichever is appropriate for the altitude at which testing was performed.