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.

Selective PEEP in acute bilateral lung disease. Effect on patients in the lateral posture.

Seven patients with acute respiratory failure due to diffuse and fairly uniform lung disease were studied during mechanical ventilation in the lateral decubital position with: (a) zero end-expiratory pressure (ZEEP) through a double-lumen oro-bronchial tube to permit a recording of the ventilation to each lung; (b) bilateral positive end-expiratory pressure (PEEP) of 1.2 kPa, with maintenance of ventilation distribution between lungs as observed during ZEEP; (c) selective PEEP of 1.2 kPa, applied to the dependent lung only, with ventilation as during ZEEP; and (d) conventional PEEP of 1.

Differential ventilation in acute bilateral lung disease. Influence on gas exchange and central haemodynamics.

Eight patients with acute respiratory failure (ARF) due to diffuse and rather uniform lung disease were intubated with a double-lumen bronchial tube and ventilated in the lateral decubital position by two synchronized ventilators. Ventilation of each lung was individually adjusted to match the expected regional blood flow (differential ventilation). When ventilation with equal volumes (i.

Regional differences in lung function during anaesthesia and intensive care: clinical implications.

Anaesthesia and most frequently acute respiratory failure are accompanied by a lowered functional residual capacity (FRC). This lowering promotes airway closure in dependent lung units and forces ventilation to non-dependent regions. Perfusion, on the other hand, is forced towards dependent lung units.

Pressure-volume and airway closure relationships in each lung in anaesthetized man.

Airway closure, functional residual capacity (FRC) and transpulmonary pressure-volume curves were assessed for each lung separately in the anaesthetized subject by means of a double lumen tracheal catheter. In the supine position airway closure occurred synchronously in the two lungs and 0.2-0.

Ventilation-perfusion distribution during inhalation anaesthesia. Effects of spontaneous breathing, mechanical ventilation and positive end-expiratory pressure.

Ventilation-perfusion (VA/Q) ratios were studied by means of an inert gas elimination technique in healthy subjects with an average age of 51 years in the supine posture (a) when awake, (b) during inhalational anaesthesia, spontaneously breathing, (c) during mechanical ventilation, and (d) when a positive end-expiratory pressure (PEEP) was applied. In the awake subject a bimodal distribution of VA/Q was recovered in most patients, one mode centered around the ratio of 1 and another, smaller mode, within low VA/Q-regions. Any shunt was less than 3% of cardiac output.

Distribution of inspired gas to each lung in anesthetized human subjects.

The distribution of ventilation in man during halothane anesthesia was studied in a two-compartment lung model in which each lung was ventilated separately by means of a double-lumen tracheal tube. Eight subjects were studied prior to scheduled surgery. Tidal volume distribution was even between the lungs in the supine position (horizontal distribution) as was distribution of dynamic lung compliance, resistance and dead space.

Airway closure in each lung of anesthetized human subjects.

Airway closure and functional residual capacity (FRC) were assessed for each lung separately in the anesthetized subject by means of a double-lumen tracheal catheter. Airway closure was studied by argon-bolus and nitrogen-washout techniques, and FRC was calculated from single-breath nitrogen washout. Recordings were done with subjects in the supine and lateral postures.

Airway closure during anaesthesia, and its prevention by positive end expiratory pressure.

Airway closure, functional residual capacity (FRC) and the transpulmonary pressure volume relationship of each lung were studied in the anaesthetized subject in the supine and the left lateral positions. In the supine posture, FRC was of approximately the same size in each lung as was closing capacity (CC). CC exceeded FRC in either lung.

Renal fluoride excretion during and after enflurane anaesthesia: dependency on spontaneous urinary pH-variations.

Renal function, fluoride formation and excretion were studied in seven patients during and after enflurane anaesthesia and surgery. The mean maximal plasma level of fluoride was 17.4 microM.

Renal function and fluoride formation and excretion during enflurane anaesthesia.

Central circulation, renal function, and fluoride formation and excretion were studied in nine patients during enflurane anaesthesia and surgery. Cardiac output and mean systemic arterial pressure remained unchanged compared with preoperative control values. During anaesthesia and surgery, urine flow rate, inulin clearance, PAH clearance and fractional sodium excretion were 60, 65, 55, and 45% of control values, respectively.

Airway closure during anesthesia: a comparison between resident-gas and argon-bolus techniques.

Airway closure was measured in awake and then anesthetized supine healthy subjects with the argon-bolus and the resident-gas (nitrogen) techniques simultaneously. The preinspiratory lung volume for the closing volume maneuver was varied from residual volume to closing capacity (CC). Comparative measurements were also performed in the upright and supine positions in awake subjects.

Studies on intrapulmonary gas distribution in the normal subject. Influence of anaesthesia and artificial ventilation.

Intrapulmonary gas distribution, assessed by a multiple breath, nitrogen washout technique and expressed by the Fowler index NWOD, was studied in subjects with healthy lungs during spontaneous breathing while awake, and during mechanical ventilation under halothane anaesthesia. The distribution index rose from a mean of 32% awake to 56% during anaesthesia. An attempt was also made to differentiate between the contribution of gravitational (airway closure) and non-gravitational (diffuse airway obstruction) inhomogeneity of ventilation.

Fluoride kinetics and renal function during enflurane anaesthesia.

Renal function, fluoride formation and excretion were studied during and after enflurane anaesthesia in seven patients. During anaesthesia, urine flow rate, inulin clearance, PAH clearance and fractional sodium excretion were 13, 78, 65 and 49% of control values, respectively. Renal function was promptly restored postoperatively.

Influence of lung volume history on closing volume measurement during anaesthesia.

Airway closure measurements were made with the bolus technique on eight healthy subjects, who were in a supine position prior to and during anaesthesia. Measurements were made on an expiration following vital capacity (VC) and 30% VC. Closing volume (CV) was calculated prior to anaesthesia, and closing capacity (CC)--functional residual capacity (FRC) was estimated during anaesthesia.

Effects of enflurane on haemodynamics and oxygen uptake with special reference to the influence of surgical stress.

The influence on central haemodynamics of enflurane, in uniform anaesthetic concentration (1.5 MAC), was studied in 10 normocapnic patients undergoing upper abdominal surgery. The patients were studied awake, during anaesthesia prior to surgery, and during surgery.

Renal function during neurolept anaesthesia.

Renal function and central haemodynamics were studied in eight patients, without known histories of renal or cardiovascular disease, during and immediately after upper abdominal surgery under neurolept anaesthesia. Inulin and PAH clearance, fractional sodium and fractional osmolar excretion decreased, while fractional free water reabsorption increased under anaesthesia. Cardiac output, mean systemic arterial pressure and systemic vascular resistance remained virtually unchanged both per- and postoperatively.

The effect of surgical stress on haemodynamics during neurolept anaesthesia.

The influence of surgical stress on haemodynamics during neurolept anaesthesia (NLA) was studied in ten patients, while they were awake, under anaesthesia prior to surgery and peroperatively. Systemic arterial, pulmonary arterial, right atrial and pulmonary capillary wedge pressures, as well as cardiac ouput (Qt), arterial oxygen content and mixed venous oxygen content, were measured. Systemic and pulmonary vascular resistances, arterial-venous oxygen content difference (AVD), oxygen consumption (VO2) and cardiac index (CI) were calculated.