Pulmonary Gas Exchange in the Intensive Care Unit

  • R. Naeije
Conference paper


Acute respiratory failure is an acute insufficiency of the gas exchange function of the lungs. Respiratory failure is always associated with abnormal arterial blood gases, in the sense that the gradient between alveolar PO2 (PAO2) and arterial PO2 (PaO2) (AaPO2) is increased, while PaCO2 is increased, normal or decreased. Respiratory failure therefore is classically defined using arterial blood gases criteria, generally by a PaO2 lower than 60 mmHg and a PaCO2 higher than 50 mmHg. Accordingly, pulmonary gas exchange in patients admitted to the intensive care unit are evaluated with repetitive arterial blood gas analysis. However, PaO2 and PaCO2 are determined not only by the gas exchange function of the lungs, but also by extrapulmonary factors including inspired PO2 (PIO2) and mixed venous PO2 (PvO2) which in turn depends on cardiac output (Q), O2 extraction, haemoglobin, and P50. Also, the tolerance to abnormal PaO2 and PaCO2 is largely dependent on the patient’s past history and current illness.


Chronic Obstructive Pulmonary Disease Interstitial Lung Disease Adult Respiratory Distress Syndrome Hypoxic Pulmonary Vasoconstriction Mixed Venous Blood 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    JB West (1991) Pulmonary physiology: The essentials. Williams and Wilkins, BaltimoreGoogle Scholar
  2. 2.
    JB West (1985) Pulmonary pathophysiology: The essentials. Williams and Wilkins BaltimoreGoogle Scholar
  3. 3.
    Mélot C, Naeije R, Hallemans R et al (1987) Hypoxic pulmonary vasoconstriction and pulmonary gas exchange in normal man. Respir Physiol 68:11–27PubMedCrossRefGoogle Scholar
  4. 4.
    Mélot C, Hallemans R, Mols P et al (1984) Deleterious effects of nifedipine on pulmonary gas exchange in chronic obstructive pulmonary disease. Am Rev Respir Dis 130:612–616PubMedGoogle Scholar
  5. 5.
    Mélot C, Lejeune P, Leeman M et al (1989) Prostaglandin E1 in the adult respiratory distress syndrome: benefit for pulmonary hypertension and cost for pulmonary gas exchange. Am Rev Respir DisGoogle Scholar

Copyright information

© Springer-Verlag Italia 1999

Authors and Affiliations

  • R. Naeije
    • 1
  1. 1.Dept. of Intensive Care, Erasme University HospitalFree University of BrusselsBrusselsBelgium

Personalised recommendations