This essay looks at the historical significance of four APS classic papers that are freely available online: Fenn WO, Rahn H, and OTIS AB. A theoretical study of the composition of the alveolar air at altitude. Am J Physiol 146: 637-653. 1946 (http://ajplegacy.physiology.org/cgi/reprint/146/5/637). Rahn H. A concept of mean alveolar air and the ventilation-bloodflow relationships during pulmona...

Lungs evolved to increase diffusing capacity by compartmentalizing and reducing the size of individual gas exchange units. This increased the potential for gas exchange limitations from ventilation-perfusion heterogeneity. However, comparative studies on reptiles, birds, and mammals show that heterogeneity is independent of lung complexity.

The authors used albumin aggregates whose diameters were stated to range from 15 μm to 50 μm. Assuming radioactivity relates to particle mass, not diameter, 50 μm particles would be 37 times hotter than 15 μm particles ((50/15) = 37). If the abnormal vascular channels at their narrowest exceeded 50 μm diameter, this inhomogeneity of size may have posed no problem. If any were less than 50 μm bu...

The lung is characterized morphologically by establishing a very large surface and an exceedingly thin barrier between air and blood. A model for relating these structural features to the lung's gas exchange function is first developed. It is then shown that DO2 estimated by morphometry is about two times larger than that estimated by physiology; there are possible reasons for this. Comparing a...

Although important alterations in structure and function develop with age, the hypothesis that the lungs are capable of maintaining adequate gas exchange for the maximum human life span is generally accepted. This hypothesis was examined by measuring arterial oxygen and carbon dioxide tension (Pa,O2 and Pa,CO2) alveolo-arterial differences in oxygen and carbon dioxide tension (PA-a,O2 and Pa-A,...

Increased ventilation-perfusion (VA/Q) inequality is observed in approximately 50% of humans during heavy exercise and contributes to the widening of the alveolar-arterial O2 difference (A-aDO2). Despite extensive investigation, the cause remains unknown. As a first step to more direct examination of this problem, we developed an animal model. Eight Yucatan miniswine were studied at rest and du...

A reanalysis of results from a recent paper on the effect of oscillation on gas exchange through leaves of cottonwood (Populus deltoides, Marsh) is presented. Mass flow of air through the leaf cannot account for the observed increase in gas exchange during oscillation in that experiment. Consideration of various published data shows that in the field, mass flow will not constitute more than a f...

Distribution of contact pressure between the bipolar plate and gas diffusion layer considerably affect the performance of proton exchange membrane fuel cell. In this regard, an adaptive neuro-fuzzy inference system (ANFIS) is developed to predict the contact pressure distribution on the gas diffusion layer due to dimensional errors of the bipolar plate ribs in a proton exchange membrane fuel ce...

in order to evaluate the effect of different levels of drought stress on some physiological parameters in grapevine, a potted experiment with iranian grapevine cultivars ‘sahani’, ‘bidane-sefid’ and ‘farkhii’ was conducted in summer of 2008. the experiment was performed while employing four drought stress (water potential of soil, ?s= -0.2, -0.6, -1, -1.5 mpa) treatments each in three replicati...