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R S Sikand

Publications and source records attributed to R S Sikand.

8 recordsLinked to original sources
PubMed1976

Convective and diffusive gas mixing in human lungs: experiments and model analysis.

Equilibration of inspired with lung residual gas was studied by a single-breath technique for varying breath-holding time with He, Ar, and SF6 as test gases. The ratio of end-expired (FE') to mean lung concentration after expiration (FL) was always below unity, indicating imperfect mixing of gas in the lung. The ratio of FL/FE' for all gases increased with tB, for any tB the ratio was smallest for SF6 and greatest for He. Similarly, Bohr dead space (VD) at any given tB was greatest for SF6 and smallest for He, with VD decreasing toward an asymptotic value common for all gases as tB increased. The results were analyzed quantitatively on a serial three-compartment model of the lung. Model analysis suggests that both diffusion and convection are effective in equilibrating test gases in the lung during breath holding. Further, stratified inhomogeneities in the absence of convective gas mixing in the alveolar space would seriously limit alveolar respiratory gas exchange; with convection, however, stratification is likely to impose only moderate constraints on resting gas exchange.

Computers↗
PubMedDate not supplied

Rebreathing and single breath pulmonary CO diffusing capacity in man at rest and exercise studied by C18O isotope.

The pulmonary diffusing capacity for carbon monoxide, Dco, was estimated in normal subjects, using both a single breath technique (DcoSB) and a rebreathing technique (DcoRB). In order to measure CO by mass spectrometry, the stable isotope C(18)O was used. In three normal subjects Dco was measured at different lung volumes at rest, and at different levels of bicycle exercise. DcoRB was found on the average 30% higher than DcoSB when compared at the same mean lung volume, and both increased slightly during exercise. The advantages and drawbacks of the rebreathing method are critically discussed.

Acetylene↗