Hypoxic pulmonary vasoconstriction in man: effects of hyperventilation.

The pulmonary vasoconstriction response to hypoxia was studied in eight anaesthetized supine subjects. One lung was made hypoxic while the other was ventilated with 100% oxygen. This was achieved by separating the tidal gas-distribution to the lungs by means of a double-lumen tracheal catheter.

Hypoxic pulmonary vasoconstriction in the human lung: effect of repeated hypoxic challenges during anesthesia.

Six patients, ages 29-58 yr, were investigated during barbiturate and fentanyl anesthesia. After intubation with a double-lumen bronchial catheter, one lung was ventilated continuously with 100% O2, and the other was rendered hypoxic during three 15-min periods by ventilation with 95% N2 + 5% O2, with intervening 15-min periods of oxygen ventilation. Cardiac output was determined by thermodilution, and the distribution of blood flow between the lungs was assessed from the excretion of a continuously infused poorly soluble gas (SF6).

Hypoxic pulmonary vasoconstriction in the human lung: the effect of prolonged unilateral hypoxic challenge during anaesthesia.

The influence of time on the pulmonary vasoconstrictor response to hypoxia was studied in six subjects during general anaesthesia and artificial ventilation prior to elective surgery. The lungs were intubated separately with a double-lumen bronchial catheter. After preoxygenation of both lungs for 30 min, the test lung was rendered hypoxic for 60 min by ventilation with 5% O2 in N2, with the control lung still being ventilated with 100% O2.

Ventilation and perfusion of each lung during differential ventilation with selective PEEP.

Lung perfusion was studied in 10 patients (mean age 58 yr) in the lateral position during enflurane anesthesia. They were ventilated through a double-lumen endotracheal catheter: 1) by one ventilator with free distribution of ventilation between the lungs, with no (zero) end-respiratory pressure (ZEEP); 2) as above but with a general positive end-expiratory pressure (PEEP) of 9 cmH2O; or 3) by two ventilators with equal distribution of ventilation between the lungs and with a selective PEEP of 8 cmH2O to the dependent lung only. Total ventilation was on average 8 l/min (BTPS) throughout the study.

Variations of regional lung function in acute respiratory failure and during anaesthesia.

Acute respiratory failure and anaesthesia impede ventilation of dependent lung units and perfusion of non-dependent ones, creating considerable ventilation-perfusion (V/Q) mismatch. General PEEP can improve V/Q but it cannot restore it to normal. To improve matching, ventilation must be distributed in proportion to regional blood flow.