PubMed Health⌕ Search

Biomedical subjects

R W Virtue

Publications and source records attributed to R W Virtue.

At least 19 recordsLinked to original sources
PubMed1983

Quantitative recovery of expired nitrogen and nitrous oxide from venous gas emboli.

It has not been previously established whether venous gas emboli dissolve from pulmonary blood vessels into adjacent airways, or pass as microbubbles directly into the systemic circulation. We reported here the quantitative recovery of embolized gases from the airways, in amounts which substantiate the complete elimination of such gases by dissolution. A computer controlled quadrupole mass spectrometer was used to measure the net expired volumes of N2 or N2O following the injection of 40 ml boluses of these gases into the airways (AW) or right ventricles (RV) of 5 mongrel dogs. Every 20 ms, linearized flow signals were multiplied by gas concentrations, and the products summed for inspired and expired volumes of each breath. Intubated dogs were ventilated with 100% oxygen under Na-pentobarbital and either succinylcholine chloride or pancuronium bromide anesthesia; Swan-Ganz catheters were used for RV injections and for monotoring cardiovascular parameters. The overall mean % volume recoveries were 70.4 for AW-N2O, 68.2 for RV-N2O, 83.7 for AW-N2, and 46.7 for RV-N2. As expected, the AW percent volume recoveries increased with decreasing aqueous solubilities, and represented maximal values obtainable for RV emboli, due to alveolar reabsorption of gases excreted from the pulmonary circulation. Although all RV-N2O could thus be accounted for, RV-N2 recoveries were significantly less than AW-N2. The remaining RV-N2 did not pass as bubbles into the pulmonary veins, but continued to obstruct the pulmonary arterioles, as demonstrated with the use of nitrous oxide challenges in the inspired gas mixture.

Animals↗
PubMed1979

Nitrous oxide levels in operating room air with various gas flows.

Monitoring of nitrous oxide concentrations in operating rooms disclosed some leaks that had hitherto been unrecognized. Because nitrous oxide concentrations reported before 1967 had been obtained for the most part with high flows of the gas and without information concerning room air exchange, measurements were made of nitrous oxide levels during operations with an infra-red analyzer. after correction of leaks. Measurements were made at six sites in the operating-room suite, with and without scavenging. Flows that varied 0.1 to 2.5 litres of nitrous oxide were used in rooms that had 20 changes per hour of fresh air. Without scavenging, the highest time-weighted average value inhaled by any of the personnel (anaesthetists) was 31 ppm, when flow of 500 ml of nitrous oxide per minute were employed. The lowest reported deleterious concentration (unconfirmed) is 50 ppm. Lower flows produced lower values. With good scavenging, using flows as high as 2.51/min of nitrous oxide, the highest average value (anaesthetist) was 7.2 ppm. A short discussion is given concerning reasons for using low flows, including the cost of wasting agents and pollution of the entire atmosphere.

Air Pollutants↗
PubMed1979

A closed lung system study of inert gas absorption.

The demonstration that the rate of rise of the alveolar fraction of nitrous oxide is enhanced when the inspired N2O concentration is high is termed the "concentration effect." A similar effect on a second gas has been termed the "second gas effect". These effects have been observed in open systems and attributed to differential changes between inspired and expired ventilation. The purpose of this investigation is to study these effects in a closed system. A breath-holding maneuver was utilized with a high and a low N2O concentration in argon and oxygen. The results indicate that breath holding with a high N2O concentration "concentrates" both the alveolar fraction of N2O and argon. These results are attributable to alveolar volume shrinkage as a consequence of the large absorption of N2O by the pulmonary blood. A mathematical model verifies this interpretation and suggests that volume shrinkage can be important in breath-holding maneuvers designed for noninvasive measurement of cardiac output and lung tissue volume.

Argon↗
PubMed1966

Your reputation.

Explore the source record for details and available documents.

Anesthesiology↗