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Biomedical subjects

E P Didier

Publications and source records attributed to E P Didier.

At least 19 recordsLinked to original sources
PubMed1990

Ventilation-perfusion distribution after aortic valve replacement.

In eight patients, the ventilation-perfusion (Va/Q) relationships after uncomplicated aortic valve replacement were studied by the multiple inert gas technique. Postoperatively, all patients had a right-to-left intrapulmonary shunt (Qsp/Qt) (range 2.4% to 14.4%) and abnormal distribution of Va/Q patterns to varying degrees. No single mechanism was identified that defined gas exchange in all patients. In three patients, moving from the supine to the right lateral decubitus position resulted in improved oxygenation which occurred because of better matching of Va/Q, not because of a decrease in Qsp/Qt.

Adult↗
PubMed1989

Position and motion of the human diaphragm during anesthesia-paralysis.

Regional motion of the human diaphragm was determined by high-speed, three-dimensional x-ray computed tomography. Six healthy volunteers were studied first while awake and breathing spontaneously and again while anesthetized-paralyzed and their lungs ventilated mechanically. Tidal volume (VT) and respiratory frequency were similar during both conditions. Three subjects were studied while they were supine and three while they were prone. During spontaneous breathing, movement of dependent diaphragm regions was greater than that of nondependent regions in four of six subjects. In five of the six subjects, dorsal diaphragm movement exceeded ventral movement regardless of body position. The volume displaced by the diaphragm (delta Vdi) was similar to VT in supine subjects but tended to be less than VT in prone subjects. After induction of anesthesia-paralysis, the end-expiratory position of the diaphragm did not change consistently in supine subjects, whereas a consistent cephalad volume shift occurred in prone subjects. During anesthesia-paralysis and mechanical ventilation, delta Vdi was reduced to approximately 50% of VT in both body positions. In the supine position, the pattern of diaphragm motion during mechanical inflation was nearly uniform. By contrast, in the prone position, the motion was nonuniform, with most motion occurring in the dorsal (nondependent) regions. It is concluded that the dominant influence on diaphragm motion may be some anatomical difference between the crural and costal diaphragm regions rather than the abdominal hydrostatic pressure gradient.

Adult↗
PubMed1987

Quantification of thoracic volumes by three-dimensional imaging.

End-expiratory thoracic cavity volume (Vthx) was measured in eight volunteers lying supine by three-dimensional X-ray computed tomography using the Dynamic Spatial Reconstructor. Untrapped end-expiratory pulmonary gas volume at functional residual capacity (FRC) was determined by nitrogen clearance. Both measurements were done before and after induction of anesthesia-paralysis. After induction of anesthesia-paralysis, Vthx and FRC were consistently and significantly (P less than 0.01) reduced by 0.28 +/- 0.22 (SD) and 0.59 +/- 0.24 liter, respectively. The reduction of FRC was larger than the reduction of Vthx (delta Vthx) in six of the eight subjects, a finding suggesting that intrathoracic fluid (blood) plus trapped gas volume (Vtt) increased. Changes in Vthx were partitioned into volume changes from the thoracic rib cage (delta Vrc) and from shape and/or position changes of the diaphragm (delta Vdi). delta Vrc contributed significantly (0.17 +/- 0.15 liter, P less than 0.02) to delta Vthx, whereas delta Vdi contributed only in four of the eight subjects. We conclude that delta Vrc, delta Vdi, and delta Vtt contribute to the reduction of FRC after induction of anesthesia-paralysis in humans; the relative contribution of them varies among subjects.

Adult↗
PubMed1984

Gas transport and pulmonary perfusion during high-frequency ventilation in humans.

Regional pulmonary 133Xe clearances, regional 133Xe washins, regional distribution of pulmonary blood flow, and pulmonary gas exchange were determined during high-frequency small-volume ventilation (HFV, oscillation frequencies 12 or 18 Hz, stroke volumes 1.2-0.8 ml/kg) in six healthy anesthetized-paralyzed volunteers lying supine. Adequate pulmonary gas exchange was maintained by HFV; the efficiency of oxygenation during HFV did not differ significantly from that during conventional mechanical ventilation at similar mean lung volumes. During HFV regional pulmonary clearances and washins of tracer gas were different among regions. Apical nondependent lung regions cleared faster and had greater regional longitudinal gas conductances than did basal nondependent or dependent regions. The vertical gradient for pulmonary perfusion was preserved during HFV. Apparently the rate of interregional gas mixing is small during HFV at 12 and 18 Hz in anesthetized-paralyzed humans.

Adult↗
PubMed1983

Sedation and respiratory mechanics in man.

The effects of sedation with halothane, enflurane or midazolam on respiratory mechanics and lung volumes were studied in young healthy volunteers, in the supine position. Functional residual capacity increased with halothane sedation, but was unchanged with sedation produced by enflurane or midazolam. Sedation with halothane and enflurane, but not midazolam, tended to increase lung static recoil pressure. Total lung capacity was decreased during sedation with midazolam. No evidence was found that sedation with these three agents increased airway resistance. These findings imply that changes in respiratory mechanics induced by the residual effects of anaesthetic agents are unlikely to contribute significantly to the impairment in pulmonary gas exchange which may occur in the period immediately after operation.

Adult↗
PubMed1981

Inspiratory flow and intrapulmonary gas distribution.

The effect of flow of inspired gas on intrapulmonary gas distribution was examined by analysis of regional pulmonary 133Xe clearances and of total pulmonary 133Xe clearance measured at the mouth after equilibration of the lungs with 133Xe. Five awake healthy volunteers (24 to 40 yr of age) and another 5 healthy, anesthetized-paralyzed volunteers (26 to 28 yr of age) were studied while they were in the right lateral decubitus position. The awake subjects were studied at 3 inspiratory flows (0.4, 0.7, and 1.0 L/s) and the anesthetized-paralyzed subjects at 4 inspiratory flows (0.2, 0.5, 1.1, and 1.6 L/s). Interregional differences in 133Xe clearances along the vertical axis were significantly less during anesthesia-paralysis and mechanical ventilation than during spontaneous breathing in the awake state. No differences in the regional or total pulmonary 133Xe clearances were detected at these different flows in either of the two states, i.e., the difference between the awake and anesthetized-paralyzed states persisted.

Adult↗
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↗
PubMed1979

Preoperative pulmonary preparation of patients with chronic obstructive pulmonary disease: a prospective study.

A group of 157 patients with chronic obstructive pulmonary disease who were treated before surgery using a standardized pulmonary preparation underwent physiologic assessment both before and after the prophylactic program. The postoperative course of each patient also was evaluated to assess the incidence of respiratory morbidity and mortality. Although many physiologic values were statistically improved after the pulmonary preparation, most of the changes are of doubtful functional significance. It is difficult to determine which patients will develop pulmonary complications not requiring mechanical ventilation, but the group requiring this type of support appears to be predictable on the basis of the severity of their pulmonary functional impairment and their lack of response to the standard pulmonary preparation used. The single most reliable test for this purpose was the mean forced expiratory flow during the middle half of the forced vital capacity. The frequency of postoperative respiratory complications was related to the type of operation, with the highest incidence occurring in the group that had extensive upper-abdominal surgery. While the occurrence of these complications was significantly reduced in patients undergoing a standard preoperative pulmonary preparation, the explanation for the beneficial effect of this procedure is not apparent.

Aged↗