Chronic obstructive pulmonary disease
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Chronic obstructive pulmonary disease (COPD)refers primarily to two related disease: chronic bronchitis and emphisema, both characterized by irreversible obstruction of the air flow through the airways.
#Emphysema is an anatomic condition manifest by degeneration of alveolar walls and loss of capillary architecture leading to a reduction in the intrinsic elastic support to the terminal bronchioles that collapse due to a lack of radial retraction
- Patients with COPD have high residual volumes that reflect premature closure of the airway at high lung volumes; air remains trapped in the distal airways causing an abundance of dead space; this leads to mild hypoxemia with minimal elevation of the CO2
- PaCO2 is often normal in mild cases of COPD largely because any rise in PaCO2 rapidly stimulates chemoreceptors to augment alveolar ventilation; an increase in PaCO2 caused by fatigue related to the increased work of breathing will drive up the oxygen consuption
- When weaning emphysema patients from the ventilator it is best to drop the FIO2 first and then the rate because the primary respiratory drive in these patients is PaO2 changes, thus dropping the FIO2 will drive the respiratory center
- Patients with COPD should be fed low carbohydrate, high fat diet because of the high respiratory quotient for carbohydrates (1.0) versus the low respiratory quotient for fat (0.7)
- Treatment: 1. anti-inflammatories ( inhaled or oral steroids); 2. broncodilators; 3. antibiotics.