Human Oxygenation by Air During Anaesthesia: The Relation of Ventilatory Volume and Arterial Oxygen Saturation

Abstract

Ventilation and arterial oxygen saturation have been measured in 18 patients during anaesthesia with ether or halothane carried in air. All patients were ventilated artificially with a Jefferson ventilator at a frequency of 16 breaths per minute and variable tidal volume. Ventilation has been expressed as a percentage of Radford's standard, Nunn's standard and the patient's pre-operative resting ventilation. 110 per cent of both Radford's and Nunn's standard ventilation and 98 per cent of the patient's own resting ventilation were found to yield a mean arterial oxygen saturation of 95 per cent. Below this the mean saturation fell sharply with decreasing ventilation. Cyanosis was never visible even with a saturation as low as 70 per cent, although desaturation was evident in the colour of the arterial blood when sampled.

Evaluation of Agent-Specific and Universal PAC Drawover Anesthesia Devices Using a Procine Model

“…This equation demonstrates that the alveolar oxygen tension is increased with increasing barometric pressure and fractional inspired oxygen concentration; whereas it is decreased by increased arterial carbon dioxide tension. Therefore, it follows that the SaO 2 would improve in patients receiving supplemental oxygen or under controlled respiration (Wakai, 1963;Mackie, 1987;Nunn, 1987) Supplemental oxygen is the preferred method for ensuring that a patient is adequately oxygenated. Our data and reports by others show that a good SaO 2 levels may be maintained by introducing low flows of 02 into the breathing circuit.…”

A Review of the Pharmacology of Halothane

“…The E.M.O. inhaler has been utilized as a draw-over system for halothane anaesthesia, but here again inadequate oxygenation associated with the use of halothane and air mixtures may be sufficient to cause cyanosis, and the addition of oxygen or the initiation of controlled respiration may be necessary (Cole and Parkhouse, 1963;Wackai, 1963).…”