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Biomedical subjects

A D Sessler

Publications and source records attributed to A D Sessler.

At least 19 recordsLinked to original sources
PubMed1979

Ventilation-perfusion relationship in young healthy awake and anesthetized-paralyzed man.

Distributions of ventilation and perfusion relative to Va/Q were determined in seven young healthy volunteers (24-33 yr) while they were either in the supine or right lateral decubitus position. The subjects were studied first awake and then while anesthetized-paralyzed and breathing 30% oxygen and again while breathing 100% oxygen. In the awake state, no statistically significant differences were observed in the distribution of ventilation and perfusion relative to Va/Q between the supine and right lateral decubitus positions or on changing the inspired oxygen concentrations. After induction of anesthesia-paralysis, Va/Q mismatching increased significantly but only small right-to-left intrapulmonary shunts developed. Ventilating the lungs with 100% oxygen further increased the dispersion of blood flow distribution during anesthesia-paralysis; lung units with low Va/Q or right-to-left intrapulmonary shunts (or both) developed. With induction of anesthesia-paralysis and intubation of the trachea, the anatomic dead space was decreased and the alveolar dead space increased.

Adult↗
PubMed1978

Regional intrapulmonary gas distribution in awake and anesthetized-paralyzed prone man.

The intrapulmonary distribution of inspired gas (ventilation/unit lung volume, VI), functional residual capacity (FRC), closing capacity (CC), and the slope of phase III were determined in five awake and five anesthetized-paralyzed volunteers who were in the prone position with the abdomen unsupported. After induction of anesthesia-paralysis, FRC was less in four of five subjects and CC was consistently less. At FRC there was no difference in the vertical gradient of regional lung volumes between the awake and anesthetized-paralyzed prone subjects. Also, there was no difference in VI between the two states. The normalized slope of phase III decreased consistently with induction of anesthesia-paralysis, but the vertical distribution of a 133Xe bolus inhaled from residual volume was not different between the two states. The data of the study are compatible with 1) a pattern of expansion of the respiratory system during anesthesia-paralysis and mechanical ventilation different than that during spontaneous breathing and 2) a more uniform intraregional distribution of inspired gas and/or a different sequence of emptying during anesthesia-paralysis.

Adult↗
PubMed1977

Regional intrapulmonary gas distribution in awake and anesthetized-paralyzed man.

Intrapulmonary distribution of ventilation/unit lung volume was studied in 28 volunteers in the sitting, supine, or right lateral decubitus position, either awake or anesthetized-paralyzed and mechanically ventilated. We found significant differences between the awake state and anesthesia-paralysis with mechanical ventilation in 1) intrapulmonary gas distribution, and 2) the vertical gradient of regional functional residual capacities for the subjects in the lateral decubitus position, but not for those in the sitting and supine positions. The effect of increasing the tidal volume on distribution of ventilation was significantly different 1) between the three body positions for a given state, and 2) between the two states for a given body position. The data suggest thoracoabdominal mechanics are different in the three body positions and that anesthesia-paralysis and mechanical ventilation may cause a different pattern of expansion of the respiratory system than spontaneous breathing in the awake state.

Adult↗
PubMed1977

Improved oxygenation in patients with acute respiratory failure: the prone position.

To assess the potential benefits of the prone position for gas exchange in patients with acute respiratory failure, we turned 6 patients from supine to prone, supporting the upper thorax and pelvis and allowing the abdomen to protrude. Arterial PO2 increased by a mean of 69 mm Hg (range, 2 to 178 mm Hg) at the same tidal volume, same inspired oxygen concentration, and same level of positive end-expiratory pressure. The maneuver made it possible to reduce the inspired oxygen concentration in 4 of the 5 patients who required mechanical ventilation of the lungs and to defer intubation in the patient who was breathing spontaneously. After subsequent turns from supine to prone, arterial PO2 increased by a mean of 35 mm Hg (range, 4 to 110 mm Hg), permitting a decrease in inspired oxygen concentration or positive end-expiratory pressure when prone (4 patients); arterial PO2 decreased in 12 of 14 instances after the patient was turned from prone to supine. No significant change in mean arterial carbon dioxide tension, respiratory frequency, or effective compliance was observed.

Acute Disease↗
PubMed1976

Single-breath oxygen tests for individual lungs in awake man.

Single-breath oxygen (SBO2) tests for individual lungs were performed in five healthy awake volunteers. In the supine position, all subjects consistently showed a closing volume (CV) for both lungs. In the lateral position, CV was demonstrated in all analyzable SBO2 tests for the dependent and in 20 of 28 for the nondependent lung. CV consistently occurred in the dependent before it occurred in the nondependent lung (asynchronous onset of CV). After CV had been reached in the nondependent lung, a mean of 77 ml of gas was still expired from the dependent lung. No changes in CV for individual lungs were demonstrated with changes in body position. Expiratory flow limitation consistently occurred first in the dependent lung (asynchronous onset of flow limitation). In the lateral position, at high lung volumes, the dependent lung achieved higher flow rates; later in expiration, the nondependent lung contributed progressively more gas to the total expirate (asynchronous emptying). In general, our findings are consistent with both the "asynchronous flow limitation" and the "airway closure" interpretations of CV. However, some of the results are not consistent with either theory.

Adult↗
PubMed1975

General anesthesia and the lung.

In this review, an attempt has been made to select, evaluate, and interpret the pertinent literature relative to general anesthesia and the lung. Concepts of intrapulmonary gas exchange and respiratory system mechanics were synthesized, emphasizing the importance of changes in intrapulmonary gas distribution that are induced by general anesthesia and exploring the possible underlying mechanisms of these changes. The area of control mechanisms and the effects of anesthesia on respiratory regulation were not discussed, nor was the distribution of pulmonary blood flow examined. The following general conclusions can be reached: (1) impaired gas exchange occurs during general anesthesia, with both impaired oxygenation and CO2 elimination; (2) increased venous admixture and increased alveolar dead space impair gas exchange; (3) the distribution of ventilation is changed during general anesthesia, and this change is related to a decrease in FRC in the recumbent positions and to altered chest-wall mechanics. Numerous questions regarding the effect of anesthesia on the lung remain unanswered. The close relationship between advances in pulmonary physiology and the pulmonary effects of anesthetic actions is increasingly apparent, as is the importance of this knowledge in applying mechanical ventilation and end-expiratory pressure to patients with pulmonary disease.

Airway Resistance↗