Reducing tidal volume does not affect oxygenation in ASA I-II patients during anesthesia
Mehmet Tugrul, Emre Çamci, Aysen Yavru, Simru Turnaoglu, Sevinay Karakoca, Tülay Özkan, Kamil Pembeci, Lütfi Telci

The aim of this study was to evaluate the need of high tidal volumes for mechanical ventilation during general anesthesia.

We studied the effects of different tidal volumes (T1 baseline- 9.7 ml/kg, T2- 8.8 ml/kg, T3- 7.8 ml/kg and T4- 6.9 ml/kg) and minute ventilation on arterial blood gases, airway pressures and arterial to end-tidal PCO2 difference in 69 adult ASA physical status I and II patients (Group A). Arterial oxygenation was also evaluated in 33 patients (Group B) in which the order of tidal volume steps was reversed.

In Group A there were no significant changes in arterial oxygen tension, oxygen saturation and arterial to end-tidal PCO2 difference during tidal volume reduction. Comparison of T1-T2, T2-T3 and T3-T4 showed significant differences in arterial carbon dioxide tension (29.7 ± 4.7 mmHg, 31.7 ± 5.3 mmHg, 33.5 ± 5.6 mmHg, 34.6 ± 5.6 mmHg) (p < 0.001, p < 0.001 and p < 0.05, respectively), end-tidal PCO2 (p < 0.001, p < 0.001 and p < 0.01, respectively), peak (26.3 ± 6.4 cmH2 O, 23.5 ± 5.7 cmH2 O, 20.8 ± 4.9 cmH2O, 18.5 ± 4.6 cmH2 O) (p < 0.001 for all comparisons), plateau (p < 0.001 for all comparisons) and mean (p < 0.001, p < 0.001 and p < 0.05, respectively) airway pressures. Arterial pH showed a significant difference between T1-T2 (p < 0.001).

There were no significant changes in arterial oxygen tension and oxygen saturation in Group B. Comparison of those parameters between equal tidal volume steps in Groups A and B did not show a significant difference.

In conclusion, we suggest that lower tidal volumes of 7 or 8 ml/kg lead to more favorable arterial carbon dioxide tension, pH and airway pressure values without having any detrimental effects on arterial oxygenation or on the efficacy of ventilation during general anesthesia.

Keywords: Anaesthesia, general lung, gas exchange, Monitoring, ventilation, tidal volume

Applied Cardiopulmonary Pathophysiology 8: 29-35, 1999

Autorenanschrift:

Mehmet Tugrul, M.D.
I.Ü.Istanbul Tip Fakültesi
Anesteziyoloji Anabilim Dali
34390, Çapa, Istanbul
Turkey
Phone: 90-212-6318767
Fax: 90-212-5332083