Causes of Oxygenation Impairment During Anesthesia
Mild to moderate hypoxemia (arterial oxygen saturation of between 85–90%) occurs in about half of all patients undergoing anesthesia and elective surgery, despite an inspired oxygen fraction (FiO2) of 0.3–0.4 . In 20% of the patients the saturation is below 81% for up to 5 min . It maybe argued that such hypoxemia does not cause any harm in most patients, but it can hardly be considered a desirable condition and the causes of such hypoxemia should be identified and prevented, if possible. Moreover, post-operative pulmonary complications occur in 1–3% of patients undergoing elective thoracic or abdominal surgery, and the complication rate may increase to 20% in emergency surgery [2, 3]. To what extent post-operative complications are caused by a respiratory dysfunction during anesthesia is not clear. However, atelectasis that has developed during anesthesia remains in the post-operative period, and impairment in arterial oxygenation and decrease in forced spirometry correlate to the size of the atelectasis . Moreover, in view of the large number of anesthestics that are given in the western world, some 30–50000 per million inhabitants, a moderate complication rate will have considerable social and economic consequences.
KeywordsSpontaneous Breathing Functional Residual Capacity Compute Tomog Lung Region Hypoxic Pulmonary Vasoconstriction
Unable to display preview. Download preview PDF.
- 5.Nunn JF (1993) Nunn’s applied respiratory physiology. 4th ed. Oxford, Heinemann, pp 407–408Google Scholar
- 11.Prutow RJ, Dueck R, Davies NJH, et al (1982) Shunt development in young adult surgical patients due to inhalational anesthesia. Anesthesiology 57: A477 (Abst)Google Scholar
- 12.Bindslev L, Hedenstierna G, Santesson J, et al (1981) Ventilation-perfusion distribution during inhalation anaesthesia. Effect of spontaneous breathing, mechanical ventilation and positive end-expiratory presssure. Acta Anaesthesiol Scand 25: 360–371Google Scholar
- 17.Dantzker DR, Wagner PD, West JB (1975) Instability of lung units with low VA/Q ratios during 02 breathing. J Appl Physiol 38: 886–895Google Scholar
- 23.Warner DO, Warner MA, Ritman EL (1995) Human chest wall function while awake and during halothane anesthesia 1. Quiet breathing. Anesthesiology; 82: 6–19Google Scholar
- 24.Milic–Emili J, Henderson JAM, Dolovich MB, et al (1966) Regional distribution of inspired gas in the lung. J Appl Physiol 21–749–759Google Scholar
- 34.Hedenstierna G, Tokics L, Lundh B, et al (1989) Pulmonary densities during anaesthesia. An experimental study on lung histology and gas exchange. Eur Respir J 2: 528–535Google Scholar
- 37.Joyce CJ, Williams AB (1999) Kinetics of absorption atelectasis during anesthesia: A mathematical model. J Appl Physiol 86: 1116–1125Google Scholar