Which of the following statement(s) is/are true concerning pulmonary edema?
A. Pulmonary edema effectively narrows bronchi and increases pulmonary vascular resistance B. Ventilation and perfusion are decreased equally C. Positive pressure ventilation improves gas exchange by decreasing lung edema D. The condition is frequently caused by decreased plasma protein levels
Pulmonary edema effectively narrows bronchi and increases pulmonary vascular resistance-the causes of pulmonary edema are: 1) increased hydrostatic pressure; 2) increased capillary permeability and 3) decreased plasma oncotic pressure. the latter, however, is rarely a problem unless the concentration of plasma protein is very low. when fluid begins to collect in the lung interstitium, it migrates to the loose areolar portion of the lung microanatomy that surround the small bronchioles and pulmonary arteries. the edema in these areas has the effect of narrowing bronchi and increasing resistance in the pulmonary vasculature. this will decrease both ventilation and perfusion in the edematous area, but ventilation is often affected more than blood flow, resulting in a decreased / ratio, with all of its attendant effects on gas exchange. ventilator treatment of pulmonary edema which increases airway pressure tends to hold the alveoli open, spreading out the space available for water accumulation and overcomes the effect of small bronchial occlusion. positive pressure ventilation does not, therefore, affect the amount of edema in the lung, only its manifestations.