Clinical Practice Guideline

for

CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

 

Overview: Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the U.S., and its incidence is increasing, with about 12 million people currently diagnosed and another 12 million estimated with early undiagnosed disease.  It is a syndrome of progressive airflow limitation caused by chronic inflammation of the airways and lung parenchyma.  Smoking is the major causal factor for COPD, with alpha-1 antitrypsin deficiency as the etiology in a small number of cases.  While there is disagreement regarding classification, COPD as used here encompasses emphysema, chronic bronchitis, or a combination of both.  The pathogenesis of COPD involves destruction of the alveoli (emphysema), obstruction of the large and small airways (chronic bronchitis), or an interplay of both mechanisms.

 

In adults after age 30, the forced expiratory volume in one second (FEV1) typically declines about 30 ml per year.  The development of COPD is associated with an accelerated decline in FEV1, but the decline is still gradual enough that patients rarely note symptoms early in the course of disease.  While most patients have a mixture of emphysema and chronic bronchitis, it is also true that one or the other usually predominates; this has important implications both for presentation and for aeromedical disposition.  The classic emphysema patient develops gradual airflow obstruction without associated reactivity or sputum production, and thus tends to present quite late.  In those areas of the lung most affected by alveolar membrane destruction, resistance to airflow is accompanied by loss of the capillary bed, such that ventilation and perfusion remain more or less matched and oxygenation is reasonably well maintained.  The “moth-eaten” parenchyma is at risk for barotrauma from rapid pressure changes.  With predominant chronic bronchitis, the patient will experience significant sputum production, usually accompanied by wheezing and variable obstruction on spirometry.  (Since the airflow obstruction is often accompanied by a degree of reversibility, distinguishing chronic bronchitis from moderate or severe persistent asthma can be difficult.)  Patients with chronic bronchitis commonly have significant ventilation-perfusion mismatching, so arterial hypoxemia is more usual than with emphysema.  Between this and the airway hyper-reactivity, chronic bronchitis is less likely to be waiverable than would be the case with emphysema with an equivalent degree of obstruction.

 

The major goals of COPD therapy include smoking cessation, symptomatic relief, improvement of physiologic function, and limitation of complications.  Smoking cessation is the only intervention known to be effective in modifying the disease, and can lead to a 50% sustained reduction in the decline rate of lung function in COPD patients.  Therapies for COPD include inhaled bronchodilators, inhaled anticholinergics, oxygen, antibiotics, short courses of systemic corticosteroids, pulmonary rehabilitation, lung volume reduction surgery, and lung transplantation.  Also, COPD patients should receive pneumococcal vaccination and annual influenza vaccination.

 

Aeromedical Concerns: The aerospace environment includes physiological stressors such as decreased barometric pressures, hypoxic cabin altitudes, and accelerative forces.  Patients with COPD, especially chronic bronchitis, have abnormal lung ventilation/perfusion which can cause arterial hypoxemia in the aerospace environment, affecting higher cognitive functions (i.e., sensory perception, judgment, and memory), psychomotor skills, and exercise tolerance.

 

The aircraft life support environment is designed with the normally oxygenated individual in mind.  Cabin altitudes that allow acceptable oxygenation in normal individuals may be insufficient for COPD patients.  While several papers have addressed the tolerance of COPD patients to commercial cabin altitudes, they were exploring the issue of acute cardiopulmonary decompensation, and were not designed to address cognitive ability or exercise tolerance.  Thus, the USAF requires near normal arterial oxygenation at rest for military aviation.  It is important when evaluating baseline oxygenation to account for ambient altitude, so that the aviator in Colorado meets the same standard as the aviator in Delaware.  The alveolar-arterial (A-a) gradient is the most reasonable measure of oxygenation.  Normal A-a gradient is about 8 mm Hg at age 20, rising to 16 mm Hg in normal 60 year olds.  A-a gradients of equal to or less than 20 mm Hg are considered acceptable for FC II.

 

Dyspnea is a distressing and even frightening symptom, and if present in any significant degree, is likely to be aeromedically incapacitating.  In COPD, dyspnea appears to result from a perception of the increased work of breathing.  While the likelihood of dyspnea is in part related to the severity of obstruction, an important factor is the rate at which airflow obstruction develops.  Thus, the intermittent asthmatic may experience dyspnea whenever he or she becomes even mildly obstructed, whereas the patient with “dry” emphysema will tend to ascribe the gradually decreasing exercise tolerance to deconditioning or age, and not present for evaluation until the disease has become severe.

 

Accelerative forces can further aggravate ventilation/perfusion defects, causing even more unoxygenated blood to be shunted into the systemic circulation, leading to increased hypoxemia.  Furthermore, emphysematous bullae may expand during ascent to altitude or during rapid decompression, compressing on the adjacent lung tissues or causing a pneumothorax, leading to sudden incapacitation.  In addition, hypoxia is the single strongest stimulus for increasing the pulmonary vascular resistance, potentially leading to pulmonary hypertension and more serious sequelae such as cor pulmonale, right-sided congestive heart failure, arrhythmia, and syncope.

 

Medical Work-up: The aviator needs a detailed history and physical to include smoking history and statement that member has discontinued smoking, as well as a consultation report from a pulmonary or internal medicine specialist.  Testing results should include spirometry results including pre- and post-bronchodilator challenge and all chest x-ray reports and arterial blood gas measurements at room air with calculated A-a gradient.  If the aviator is military, he or she may require medical board results.

 

Aeromedical Disposition:

 

Air Force: COPD is disqualifying for all flying classes in the US Air Force.  Waiver consideration is based on the extent of the disease process and the degree of pulmonary insufficiency.  Most patients with moderate or advanced COPD will not be suited for the aviation environment, though the occasional patient with moderate emphysema may be considered for categorical waiver.  An aviator with early COPD (likely to be an incidental finding on spirometry performed for another indication) could qualify for flying as long as he or she stops smoking, is reasonably physically fit, has a normal chest x-ray, and has adequate oxygenation.

 

Army: Chronic Obstructive Pulmonary Disease (COPD) is not named in the Army regulations as disqualifying, though the components of COPD such as emphysema, pulmonary fibrosis, reactive airway disease, etc. are specifically disqualifying.  The aeromedical concerns for Army aviation are the same as for the Air Force and the required information is similar.  Waivers may be considered for designated aviators only.  A favorable disposition will be entertained only if: (1) There is no cardiovascular decompensation; (2) Exercise tolerance is unimpaired; (3) The patient does not require medications; and (4) There are no bullae evident.

 

Navy: Waivers may be considered for designated aviators only on a case-by-case basis if there is no cardiovascular decompensation, exercise tolerance is unimpaired, the patient does not require any medications, and there are no bullae evident on radiographs. Pulmonary function testing should be normal. Aviation personnel meeting these criteria will be restricted from high-performance aircraft.

INFORMATION REQUIRED:

1.     Internal medicine or pulmonology consultation

2.     Chest x-ray and/or CT to exclude bullae

3.     Complete PFT including bronchodilator challenge

4.     Cardiology consultation (if there is evidence of RVH)

 

Civilian: The Federal Aviation Administration allows airmen with COPD to pilot aircraft for any class providing the FVC, FEV1, or FEV1/FVC is 50% or greater.  The airman will require a complete current status of their illness by the treating physician.  This should include all the medications plus mention of the presence of side effects.  In select cases the Aeromedical Certification Division may require the airman perform an exercise tolerance test with pulse oximetry.  Some cases may be sent to a pulmonary medicine consultant for a recommendation.  All medications that are used in the treatment of COPD are allowed; this includes the beta agonist inhalers.  An equivalent dose of greater than 20 mg Prednisone daily is not permitted.

 

Waiver Experience:

 

Air Force: Query of AIMWTS revealed only four cases with a history of COPD.  There were no initial pilot training submissions.  All of these cases were granted waivers.  However, these cases were mild and did not require pharmacologic therapy.

 

Army: The Aeromedical Epidemiological Data Repository (AEDR) catalogs all Army flight physicals since 1960.  There have been approximately 160,000 individual aircrew entered in this database.  There are 7 non-rated people in the database with this diagnosis, one was suspended and 6 were granted waivers. There were 11 pilots including 4 applicants with this diagnosis and none of them were given waivers.

 

Navy: Not available at this time.

 

Civilian:  As of June 30, 2010 there are currently issued: 4 first-, 71 second- and 347 third-class airmen with this condition for a total of 422.

 

ICD9 Codes for COPD

491.20

Chronic bronchitis

492.8

Emphysema

496

Chronic airway obstruction

 

=======================================================================================================================

References:

 

Barnes PJ.  Chronic obstructive pulmonary disease.  N Engl J Med.  Jul 2000; 343(4): 269-80.

 

Berg BW, Dillard TA, Derderian SS, Rajagopal KR.  Hemodynamic effects of altitude exposure and oxygen administration in chronic obstructive pulmonary disease.  Am J Med, Apr 1993; 94:  407-12.

 

Djukanovic R, Gadola SD.  Virus infection, asthma, and chronic obstructive pulmonary disease.  N Engl J Med.  Nov 2008; 359(19):  2062-4.

 

Grimes GC, Manning JL, Patel P, and Via MR.  Medications for COPD: A Review of Effectiveness.  Am Fam Physician, 2007; 76(8):  1141-8.

 

Hogg JC, Chu F, Utokaparch S, et al.  The nature of small-airway obstruction in chronic obstructive pulmonary disease.  N Engl J Med, 2004; 350(26):  2645-53.

 

Hunter MH, King DE.  COPD: Management of Acute Exacerbations and Chronic Stable Disease.  Am Fam Physician, 2001; 64(4): 603-12.

 

Lacasse Y, Ferreira I, Brooks D, et al.  Critical appraisal of clinical practice guidelines targeting chronic obstructive pulmonary disease.  Arch Intern Med, 2001; 161: 69-74.

 

Lategola MT, Flux M, Lyne PJ.  Altitude Tolerance of General Pilots with Normal or Partially Impaired Spirometric Function.  Aviat Space Environ Med, 1978; 49(9): 1123-5.

 

Lategola MT, Flux M, Lyne PJ.  Spirometric Assessment of Potential Respiratory Impairment in General Aviation Airmen.  Aviat Space Environ Med, 1977; 48(6): 508-11.

 

Niederman MS, ed.  Mechanisms and management of COPD.  Chest, 1998; 113(4): 233S-234S.

 

Rayman RB, Hastings JD, Kruyer WB, Levy RA.  Clinical Aviation Medicine.  New York:  Castle Connolly, 2000.

 

Singh JM, Palda VA, Stanbrook MB, and Chapman KRl.  Corticosteroid therapy for patients with acute exacerbations of chronic obstructive pulmonary disease.  Arch Intern Med, 2002; 162: 2527-36.

 

Sutherland ER and Cherniack RM.  Management of chronic obstructive pulmonary disease.  N Engl J Med, 2004; 350(26):  2689-97.

 

Voelker R.  New tool helps primary care clinicians with diagnosis and treatment of COPD.  JAMA, 2007; 298(24):  2855-6.

 

 

Prepared by Drs Dai Tran and Dan Van Syoc

Date: September 26, 2010