ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Gas-exchange units in the lung with low &OV0312;/&OV0422; give rise to an oxygen partial pressure lower in arterial blood than alveolar gas (A-aDi>.) an N2partial pressurehigherin arterial blood than in “ideal” mixed alveolar gas (a-ADx2). Both &OV0312;/&OV0422; maldistribution and direct right-to-left shunts can contribute to the A-aDo, but only low &OV0312;/&OV0422; will cause an a-ADx2. Twenty patients from an intensive care unit were studied by measurement of the A-aDo2. and a-ADx. In 14 patients breathing an enriched oxygen mixture A-aDo.’s averaged 183 mm Hg and a-ADx.’s, 69 mm Hg. In six patients breathing room air the mean A-aDo. was 47 mm Hg; three had no a-ADx.; the other three had a mean a-ADx. of 19 mm Hg. Hence, 17 of the 20 patients showed evidence of &OV0312;/&OV0422; mismatching. Using a two-compartment model, a mixing equation was derived to calculate the percentage flow (&OV0422;o/&OV0422;T) in a compartment with a &OV0312;/&OV0422; of essentially 0 necessary to produce the measured a-ADx,. This value ranged from 9 to 46 per cent of the cardiac output in those patients with a-ADx,’s. The classic technique of separating the &OV0312;/&OV0422; component of the A-aDo, by 100 per cent oxygen breathing was found to be misleading in eight of ten cases when compared with the a-ADx, method of assessing maldistribution. It appeared that units with low &OV0312;/&OV0422; became atelectatic when 100 per cent oxygen was breathed. It was postulated that the areas of low &OV0312;A/&OV0422; occur as a result of intermittent airway closure in the most dependent areas of the lung and also in the case of interstitial pulmonary edema with airway narrowing.

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Intrapulmonary gas distribution of individual lungs was studied in five healthy anesthetized, paralyzed, and mechanically ventilated adult volunteers in the supine and both lateral decubitus positions. Comparison of the results with previous findings in conscious and spontaneously-breathing man indicated that the distribution of inspired gas during mechanical ventilation in anesthetized subjects is different. Inspired gas was more uniformly distributed within the individual lungs of mechanically ventilated anesthetized subjects in the supine position. There was a preferential distribution of tidal volume to the nondependent lung, in contrast to the preferential ventilation of the dependent lung in conscious, spontaneously-breathing man in the lateral position. Although relative end-expiratory lung volumes (that is, functional residual capacity) of individual lungs in persons ventilated mechanically in both positions were similar to those reported for the conscious, spontaneously-breathing subject, preferential ventilation of the nondependent lung and lesser ventilation of the dependent lung resulted in similar nitrogen clearances from the two lungs when the subjects were in the lateral position. This finding is in contrast to the significant differences between nitrogen clearances of the two lungs in spontaneously-breathing man in the lateral position.

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

Anesthetized dogs were mechanically ventilated using tidal volumes (VT) of 15, 24, 43, and 15 ml/kg with an end-expiratory pressure of 10 cm H2O (continuous positive-pressure ventilation). Pulmonary edema was then induced by injecting oleic acid into the right ventricle and the ventilatory patterns were repeated. Prior to pulmonary edema the only significant finding was that of decreased shunt and cardiac output during CPPV. With pulmonary edema, shunt and PaO2, were significantly improved during ventilation with a VTof 43 ml/kg and CPPV, compared with ventilation with a VTof 15 ml/kg. Ventilation with a tidal volume of 24 ml/kg not only failed to improve the shunt and PaO2seen at a VTof 15 ml/kg, but also significantly depressed cardiac output.

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

The effects of 5, 13, 20, and 30 per cent cyclopropane, alone and with either reserpine or spinal anesthesia, on cerebral blood flow (CBF) and metabolic rate for oxygen (CMRO2) were investigated in three groups of nine dogs each. With cyclopropane alone, CBF increased abruptly in eight of nine dogs as the concetration was increased, while CMRO2changed insignificantly. After pretreatment with reserpine, CBF decreased significantly with 13 per cent cyclopropane, but at higher concentrations increased abruptly in four of nine dogs. CMRO2decreased with 13 per cent cyclopropane and remained decreased at the higher concentrations. During spinal anesthesia, CBF and CMRO2decreased significantly with increases in cyclopropane. In a single dog, during spinal anesthesia and 20 per cent cyclopropane, CBF and CMRO2increased during intravenous infusions of both epinephrine (0.1 and 0.25 μ/kg/min) and norepinephrine (0.25 μ/kg/min). The authors conclude that the unusual and variable effects of increasing concentrations of cyclopropane on CBF and CMRO2are secondary to the increases in circulating catecholamine levels resulting from the sympathoadrenal stimulatory effects of this anesthetic.

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

The metabolism of methohexital and its hypnotic effect were studied in rats. Twelve minutes after intraperitoneal administration, 58 per cent of the methohexital present in the liver existed as free hydroxylated or conjugated hydroxylated metabolic breakdown products. Small amounts of the unconjugated metabolites, but no conjugated metabolites, were present in the brain. Neither metabolite, but a high level of unchanged methohexital, was present in adipose tissue. Administration of nalorphine 30 minutes prior to methohexital significantly increased the deep time produced by methohexital and the barbiturate levels in the brain and liver but did not affect the metabolic biotransformation of methohexital.

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

A 12-compartment analog computer multiple model of the uptake and distribution of halothane in man is described. In this model an uptake and distribution model is combined with a circulatory model so that the two continuously influence each other. Cardiac output and its regional distribution were each controlled by the halothane concentration in any one of three compartments: arterial blood, brain (gray matter), and myocardium. Curves generated by this model differ significantly from those generated by a standard (linear) model. The magnitude of inspired concentration, but not the type of compartmental control, influences the rise time of alveolar concentration significantly. The circulation is influenced by both factors, particularly compartmental controls. The model is useful not only for predicting halothane concentrations, but also for gaining new insight into halothane-induced changes in the circulation: mean arterial pressure, cardiac output, and regional blood flows.

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID

摘要:

The changes in Pao2, P&OV0456;co2, and cisternal CSF Po2, were followed in eight goats after abruptly changing the Flo2from 1.0 to 0.21 during a period of constant hyperventilation (Paco230 torr). The half times (tj's) for oxygen content in the arterial, venous, and cisternal compartments were 0.57,1.01, and 3.60 minutes, respectively; the oxygen stores of the CSF were shown to be extremely labile and limited in nature.

ISSN:0003-3022    

出版商:OVID    

年代:1972

数据来源: OVID