The Effect of Inspired Oxygen Concentration on the Ventilation–Perfusion Distribution in Inhomogeneous Lungs

✍ Scribed by J.P. WHITELEY; D.J. GAVAGHAN; C.E.W. HAHN

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 296 KB
• Volume: 204
• Category: Article
• ISSN: 0022-5193
• DOI: 10.1006/jtbi.2000.2036

✦ Synopsis

The coupled conservation of mass equations for oxygen, carbon dioxide and nitrogen are written down for a lung model consisting of two homogeneous alveolar compartments (with di!erent ventilation}perfusion ratios) and a shunt compartment. As inspired oxygen concentration and oxygen consumption are varied, the #ux of oxygen, carbon dioxide and nitrogen across the alveolar membrane in each compartment varies. The result of this is that the expired ventilation}perfusion ratio for each compartment becomes a function of inspired oxygen concentration and oxygen consumption as well as parameters such as inspired ventilation and alveolar perfusion. Another result is that the &&inspired ventilation''}perfusion ratio and the &&expired ventilation''}perfusion ratio di!er signi"cantly, under some conditions, for poorly ventilated lung compartments. As a consequence, we need to distinguish between the &&inspired ventilation''}perfusion distribution, which is independent of inspired oxygen concentration and oxygen consumption, and the &&expired ventilation''}perfusion distribution, which we now show to be strongly dependent on inspired oxygen concentration and less dependent oxygen consumption. Since the multiple inert gas elimination technique (MIGET) estimates the &&expired ventilation''}perfusion distribution, it follows that the distribution recovered by MIGET may be strongly dependent on inspired oxygen concentration.