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Sudden upper airway obstruction may affect the normal process of gas exchange of gas exchange in pulmonary-capillary system, resulting in mild to severe changes in arterial blood gases and organ functions according to the duration of the obstruction. Therefore, the immediate restoration of an adequate airway in these patients is lifesaving. It is possible to measure regional tissue PO_2 and PCO_2 and other gas tensions simultaneously and continously because mass spectrometry has been applied to the measurement of gas tensions in tissue recently. So we can understand the organ perfusion status and organ metabolism better than before. Fourteen dogs were ventilated with positive pressure by volume ventilator and 100% O_2 through endotracheal tube(9㎟ I.D.). Of them, 8dogs were subjected to sudden complete endotracheal obstruction clamping with hemostatic forceps until cardiac arrest, and then, physiologic responses were examined. Another 6 dogs were subjected to sudden complete endotracheal obstruction with hemostatic forceps for 5 minutes and were resuscitated using ventilator and 100% O_2 through re-opened endotracheal tubes and their physiologic responses were observed. The following results were obtained. 1. After complete airway obstruction, cardiac arrest occurred in 7min 48sec. (6’18"-10’15"). 2. For 3 minutes following the respiratory obstruction heart rate was decreased more or less, but on the contrary mean arterial pressure was increased. This initial increase was followed by a decrease. 3. Three minutes after the respiratory obstruction, cerebral and myocardial PtO_2 revealed slightly decreased values by -4 and -1%, respectively, in spite of markedly decreased PaO_2 by -90% in comparison. 4. During the first 3 minutes after respiratory obstruction arterial PaCO_2 was markedly increased by 80%, and cerebral and myocardial tissue PtCO_2 were slightly to moderately increased by 15 and 35%, respectively, in comparison with control values. 5. At cardiac arrest, cerebral and myocardial PtO_2 were decreased by 20 and 40% from control values in spite of more 95% decrease of PaO_2. 6. At 15 minutes after the respiratory obstruction, PaO_2 was decreased more than 95% and PaCO_2 increased about 240%, respectively, and cerebral and myocardial PtO_2 decreased 47 and 70%, respectively, PtCO_2 increased 125 and 300%, respectively, compared with control values. 7. Recovery periods of deranged PtO_2 and PtCO_2 in group 2 (respiratory resuscitation group) required more than 15 minutes even though ventilation was assisted.
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