Hemodynamic effects of positive end-expiratory pressure. Historical perspective.

Mechanical ventilation with positive end-expiratory pressure has been known to increase arterial oxygen content for approximately 40 years. Early experiments demonstrated a diminution of cardiac output with the application of positive end-expiratory pressure, and it was not favored as a therapeutic modality until the 1960s, when it was found to be effective in the treatment of adult respiratory distress syndrome. In recent years, physiologists have methodically scrutinized the effects of positive end-expiratory pressure on each of the major determinants of cardiac output. Review of the progression of thought on this subject reinforces for today's clinician basic principles of cardiac performance and heart-lung interaction.

Tracheal bronchus with regional ventilation and perfusion abnormalities.

Tracheal bronchus is an uncommon anomaly of the tracheobronchial tree. In the case presented, clinical and pathophysiologic abnormalities were associated with this anomaly. The tracheal bronchus supplied the right upper lobe of the lung. The bronchus intermedius arose directly from the trachea in place of the right main bronchus. It was accompanied by marked regional changes in ventilation and perfusion. We discuss the clinical significance of this unusual anomaly.

Noncardiogenic pulmonary edema following blood transfusion.

Noncardiogenic pulmonary edema and acute respiratory failure were found to develop after blood transfusion. Pulmonary antiographic studies and hemodynamic measurements were performed in the presence of pulmonary edema. Normal wedge pressure was observed at the time of angiographic studies, and contrast material appeared to extravasate across the alveolocapillary membrane into the alveoli. The mechanisms of acute injury to the alveolocapillary membranes and of pulmonary edema secondary to reactions to transfusion are discussed.