Question

What are the pathophysiologic changes in COPD and how does it differ from asthma?

Discuss the use of oxygen therapy in patients with a diagnosis of COPD.

What are the benefits and the potential pitfalls?

Answer 1

Pathophysiologic changes in COPD

Two core clinical entities are there in COPD

Emphysema and chronic broncitis

• emphysema: smoking causes inflammation of airways. Neutrophils and immune cells are recruited in smaller airways. Structural changes and loss of elastic recoil occur in airways and cause air trapping, lesser expiratory flow rates, airway collapse and hyperinflation of chest.
• Chronic bronchitis: inflammation causes fibrosis of walls of bronchioles/ bronchi, increased mucus secretion, edema of airways, and constriction of airways. patient develops breathing difficulty and chronic cough.

Emphysema is enlargement of distal airspaces

Chronic bronchitis manifested by sputun on most days for 3 consecutive months over 2 consecutive years

AIRWAY NARROWING IS FULLY REVERSIBLE IN ASTHMA BUT NOT FULLY REVERSIBLE IN COPD

EMPHYSEMA IS TYPICAL IN COPD BUT NOT USUALLY SEEN IN ASTHMA

oxygen therapy in COPD

• COPD patients usually have hypoxic drive. Hence, Oxygen therapy should be cautiously given to such patients
• Resting PaO2 of 56-59mmKg with dependent edema, p pulmonale and polycythemia or resting PaO2 < 55 mmHg require continuous oxygen use.
• Desaturation (SPO2 < 88%) with activity or at night require intermittent oxygen use.
• Supplemental oxygen can be provided with mask, prongs, CPAP, Bipap or ventilation as required based on patient condition

Oxygen therapy helps to relieve breathlessness, dyspnea and improves oxygen saturation. But in patients with hypoxic drive continuus oxygen therapy may affect respiratory drive

Reference

http://www.pathophys.org/copd/