End-tidal oxygen concentration and pulse oximetry for monitoring oxygenation during intratracheal jet ventilation

Abstract

Objective. In this study, we evaluated the usefulness of end-tidal oxygen monitoring during intratracheal jet ventilation (ITJV) for endolaryngeal laser surgery.Methods. A total of 20 consecutive patients of both genders scheduled for endolaryngeal procedures under general anesthesia were studied. Inspiratory oxygen concentration and respiratory rate were varied, with patients serving as their own controls. Readings of pulse oximetry, airway oxygen, and carbon dioxide concentrations were recorded, and arterial blood samples for blood gas analysis were taken.Results. At jet cycle rates of 20 cycles/min, end-tidal oxygen (ETo₂) concentration indicated alveolar hypoxia 30 to 60 sec before hypoxemia was detected by pulse oximetry. Jet mixing of inspiratory and expiratory gas caused a larger difference between end-tidal and arterial gas concentrations than normally seen with conventional ventilation. Correlations between ETo₂ concentrations, oxygen saturations, and arterial oxygen levels depended on respiratory rate and inspiratory oxygen concentration; correlations were stronger at low than at high inspiratory oxygen concentrations and stronger at low than at high respiratory rates.Conclusions. ETo₂ concentration should be maintained well over 21% during ITJV to prevent alveolar and arterial hypoxia. Monitoring of respiratory oxygen concentrations at jet cycle rates of 20 cycles/min and less verifies safe oxygen levels during laser surgery, and confirms adequate alveolar oxygenation.