IngentaConnect Stratification does not limit O2 uptake in rabbit lungs

Authors: HELLER¹; SCHUSTER¹

Source: Acta Physiologica, Volume 162, Number 1, January 1998 , pp. 21-26(6)

Abstract:

This study was performed to assess the role of stratification, i.e. axial gas mixing deficit within alveolar space, in limiting alveolar gas exchange for oxygen. The single-breath method for varying breath-holding time with oxygen-labelled carbon dioxide, C¹⁸O₂, was applied to 10 anaesthetized, paralysed and artificially ventilated rabbits. Alveolar partial pressure of C¹⁸O₂ was analysed using respiratory mass spectrometry. Starting from residual volume, the lungs were rapidly inflated using 40 mL of indicator gas mixture (1% C¹⁸O₂ in nitrogen). After executing breath-holding, the lungs were rapidly deflated. Pulmonary diffusing capacity of carbon monoxide was determined in the same way. On the basis of a serial compartment model, the lower limit of the stratificational conductance of oxygen was estimated, using the rate constant of C¹⁸O₂ removal from alveolar space (4 s⁻¹) and Graham's law. We found that the stratificational conductance in rabbits amounts to at least 13.5 mL mmHg⁻¹ min⁻¹. The pulmonary diffusing capacity of oxygen was calculated by multiplying the carbon monoxide diffusing capacity of rabbit lungs by a factor of 1.2, yielding a value of 0.77 mL mmHg⁻¹ min⁻¹. These results show that stratificational conductance is at least 17.5 times higher than pulmonary oxygen diffusing capacity, indicating that stratification does not limit oxygen uptake in rabbit lungs.

Keywords: alveolar space; axial gas mixing deficit; compartment model; oxygen-labelled carbon dioxide; rabbit; single-breath method; stratification

Document Type: Original article

DOI: 10.1046/j.1365-201X.1998.0281f.x

Affiliations: 1: Department of Physiology, University of Bonn, Bonn

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