Acute Respiratory Failure and Chronic Obstructive Lung Disease

Abstract

The approach to acute respiratory failure in patients with chronic obstructive lung disease (COPD) requires a special understanding of factors regarding diagnosis, patient evaluation, interpretation of laboratory data, and management that is inherent to this group of patients. Although the term COPD as commonly used encompasses a wide variety of patients with the underlying common denominator of limitation of airflow, most of these patients fall into the major categories of chronic bronchitis, asthma, and emphysema. ~1any of these patients manifest an overlap syndrome made up of several or all of the components. The term chronic bronchitis denotes a clinical syndrome characterized by chronic or recurrent bronchial hypersecretion clinically diagnosed by the presence of chronic productive cough with no other cause such as infection, neoplasm, or cardiac disease. The sputum may be mucous, purulent, or eosinophilic in character. 2. 22 The mechanisms of airflow limitation are related to generalized hypcrtrophy and hyperplasia of the mucus-secreting bronchial glands, diffuse inflammation with thickening of the tracheobronchial submucosa, and secretions in the airways. Asthma is characterized by an increased responsiveness of the tracheobronchial tree to various stimuli and is manifested by diffuse narrowing of the airways, which is reversible either spontaneously or as a result of therapy. The airflow limitation results from a combination of mucous plugging of the airways, smooth muscle hypertrophy and constriction, goblet cell hyperplasia, and diffuse mucosal edema. 2 Pulmonary emphysema is defined pathologically as an abnormal enlargement of the airspaces distal to the terminal bronchioles associated with destruction of the alveolar walls. 2 Airflow limitation results from the collapse of small airways due to loss of the elastic recoil of the lung parenchyma, which aids in maintaining the patency of the small bronchioles.

Canadian Guidelines for the Management of Acute Exacerbations of Chronic Bronchitis

“…In addition, hypoxemia can increase the risk of myocardial ischemia in the elderly COPD population and can have neuropsychiatric side effects. Low-flow oxygen should be administered if hypoxemia is present (168)(169)(170)(171). Excess use of oxygen should be avoided as this may lead to progressive hypercapnia, either by decreasing hypoxic ventilatory drive or by worsening ventilation-perfusion mismatching within the lung (172,173).…”

Canadian Guidelines for the Management of Acute Exacerbations of Chronic Bronchitis: Executive Summary

“…Low flow oxygen should be administered if hypoxemia is present (46)(47)(48)(49). Excess use of oxygen should be avoided, because this may lead to progressive hypercapnia (50,51).…”

Neurologic Manifestations of Lung Disease

“…Additional therapeutic measures, when indicated, include venesection for polycythemia, bronchodilators, treatment of bronchopulmonary infection, and relief of cardiac decompensation. 1,2…”