Specific diseases which cause decreased ability of the lungs to perform their function of ventilation. These diseases include chronic bronchitis, emphysema, small airway disease, asthma, and bronchiectasis. The obstruction is characterized by chronic airflow obstruction with reversible or irreversible mechanisms or both. Airflow obstruction is a reduction in the ratio of forced expiratory volume in the first second (FEV-1) to forced vital capacity (FVC) (FEV1/FVC).

Although each type of chronic obstructive pulmonary disease (COPD) is a separate clinical entity, patients usually have two or more types. COPD usually refers to some combination of chronic bronchitis (see Diagnostic Code: 6600 Chronic bronchitis), emphysema (see Diagnostic Code: 6603 Emphysema pulmonary), and small airway disease, while asthma (see Diagnostic Code: 6602 Asthma, bronchial) and bronchiectasis (see Diagnostic Code: 6601 Bronchiectasis) are usually considered distinct entities.

A combination of genetic tendency and environmental exposure leads to COPD. The most common environmental risk factor is smoking. It is believed to contribute to more than 80% of cases. Smoking contributes to airway obstruction by causing an inflammatory reaction that may or may not cause the production of mucus. Other environmental exposures include pollution and occupational contacts. Being male, having low socioeconomic status, and having had a childhood respiratory illness are other etiologic factors.

Cough, increased sputum production, dyspnea, and wheezing are the most common symptoms. Potential disabling symptoms increase as patients age (over 50). A cough that produces mucus usually begins several years after a person starts to smoke. The cough may be mild, or more severe causing syncope, vomiting, or stress incontinence. The amount of sputum may vary from less than one teaspoon to several tablespoons. Larger quantities or greenish or yellowish sputum suggest infection or, less commonly, bronchiectasis. As obstruction of the airway advances, hypoxemia may develop slowly, resulting in subtle signs of brain dysfunction, e.g., inability to concentrate, and diminished short-term memory (STM). In addition, if hypoxemia goes unnoticed, hypercapnia may develop and slowly lead to brain edema. Signs of severe obstruction are not apparent in all patients with COPD. However, they are clear-cut when they do appear. A characteristic sign is pursed-lips breathing which delays airway closure, and allows a larger tidal volume and more efficient function of the respiratory muscles.

Chest x-rays are not sensitive to early or moderate obstructive disease. Spirometry measures the obstructive component of the disease. Pulmonary function tests show the distinctive pattern of volume-dependent airway obstruction. Obstruction is usually considered present when the FEV-1 is less than 80% of the FVC. ABG levels are typically abnormal in moderate and severe COPD. The patient may present with hypoxemia.

Depending on the patient's respiratory reserve, the physician may suggest that the patient minimize activities of daily living (ADL) to decrease oxygen requirements. Patients who have a sufficient respiratory reserve are usually started on a graduated exercise program. Supplemental oxygen may be indicated for some patients. The primary goal of drug therapy is to reduce dyspnea. Other treatment goals are aimed to control cough and sputum production. Preventive measures are instituted to prevent influenza and bacterial infections, e.g., receiving annual influenza vaccinations, and a pneumococcal vaccination every 5-10 years. In addition, patients are placed on antibiotics at the first sign of purulent sputum. Moreover, increased use of bronchodilators and oral corticosteroids may also be necessary if a patient is experiencing an acute infection.

Generally, patients should receive long-term home oxygen supplementation if the PaO2 is 55 mm Hg or less, or if the PaO2 is 56-59 mm Hg accompanied by symptoms that suggest cardiac involvement, e.g., peripheral edema or elevated blood count. In addition, for cases of right-sided heart failure or biventricular heart failure, treatment includes administration of diuretics with caution, and correcting electrolyte imbalances, (e.g., hypokalemia). Finally, ventilatory support may be indicated if hypercapnia accompanied by rapidly rising levels of pCO2 and low levels of pH are revealed via ABGs. These signs would indicate tired respiratory muscles.

Recurrence of bronchitis in patients with COPD usually results from viruses, Hemophilus influenzae, and Streptococcus pneumoniae. Acute hypoxemia that may occur with a respiratory infection may lead to confusion and restlessness. Uncorrected hypoxemia leads to pulmonary hypertension, cor pulmonale, reduced free water clearance in the kidney, arrhythmias, polycythemia, and altered mental status. Some patients with severe COPD survive up to 15 years after diagnosis. Death is generally caused by medical complications, e.g., acute respiratory failure, severe pneumonia, pneumothorax, cardiac arrhythmia, or pulmonary embolism.

• May be entitled to special monthly compensation where the Veteran has a single service-connected disability rated as 100% with additional service-connected disability or disabilities independently ratable at 60% or more, which are separate and distinct from the 100% service-connected disability and involves different anatomical segments or bodily systems. See  38 CFR 3.350(i)(1) – Special Monthly Compensation (SMC).

• Review 38 CFR 3.809a for eligibility for entitlement to Special Home Adaptation grants under 38 U.S.C. 2101(b)

• Consider entitlement to service connection based on chronic effects of exposure to mustard gas and Lewisite under 38 CFR 3.316(a)(2)

• Review special provisions regarding the evaluation of specific respiratory conditions under 38 CFR 4.96(a) - Rating co-existing respiratory conditions and 38 CFR 4.96(d) - Special provisions for the application of evaluation criteria for diagnostic codes 6600, 6603, 6604, 6825–6833, and 6840–6845.