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Review Series: Lung function made easy: Assessing gas exchange

National Heart and Lung Institute, Imperial College Faculty of Medicine, Hammersmith Hospital Campus, London, UK, mike.hughes{at}imperial.ac.uk

In clinical practice there are two sorts of measurements, a) arterial oxygen and carbon dioxide partial pressure (PaO₂, PaCO₂) or arterial oxygen saturation (SaO₂), and b) the transfer capacity for carbon monoxide (TLCO). The former measures the output or performance of the lung as a gas exchanger, and the latter estimates the available surface area or potential for gas exchange. As gas exchange deteriorates (PaO₂ falls and PaCO₂ rises), the body compensates by increasing ventilation and lowering PaCO ₂. Therefore, a high PaCO₂ represents chronic respiratory or "compensation" failure, either chemo-insensitivity ("won't breathe") or neuromuscular weakness/increased work of breathing ("cannot breathe"). Chronic respiratory failure may progress to acute failure in which PaCO₂ falls and PaCO₂ rises progressively, assisted ventilation is usually required. The TLCO is a laboratory test which measures the integrity of the blood-gas barrier, it is particularly useful in the assessment of emphysema, interstitial disease and pulmonary vascular disease. Chronic Respiratory Disease 2007; 4: 205—214

Key Words: altitude • arterial blood gases • carbon monoxide • diffusion • hypoventilation • KCO • normal values • pulse oximetry • transfer factor • ventilation-perfusion ratio

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Chronic Respiratory Disease, Vol. 4, No. 4, 205-214 (2007)
DOI: 10.1177/1479972307084446


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This Article Abstract Free Full Text (Free PDF) Free Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Hughes, J.M.B. Search for Related Content PubMed PubMed Citation Articles by Hughes, J.M.B. Social Bookmarking                         What's this?