Ventilation-perfusion ratios
Schaffartzik, W.
Der Anaesthesist 43(10): 683-697
1994
ISSN/ISBN: 0003-2417 PMID: 7818053 Document Number: 434763
Knowledge of normal and impaired pulmonary gas exchange is essential to the anaesthesiologist. Analysis of an arterial blood sample allows evaluation of whether or not pulmonary gas exchange is normal. For this purpose comparison with the oxygenation index or the alveolar-arterial PO-2 difference is helpful. Pathological changes of these variables are mainly caused by ventilation-perfusion ( ovrhdot V-A/ ovrhdot Q) mismatch. In daily practice, venous admixture or intrapulmonary shunt can be calculated using arterial and mixed-venous blood By analysing arterial and expired PCO-2, dead-space ventilation can be determined, but extended analyses of ovrhdot V-A/ ovrhdot Q distribution are not possible in daily practice. However, knowledge of the principles of typical disturbances of pulmonary gas exchange in acute and chronic lung disease allows the use of therapeutic strategies based on the pathophysiological changes.