END-TIDAL OXYGEN CONCENTRATION AND PULSE OXIMETRY FOR MONITORING OXYGENATION DURING INTRATRACHEAL JET VENTILATION

Objective. In this study, we evaluated the usefulness of end-tidal oxy gen monitoring during intratracheal jet ventilation (ITJV) for endolar yngeal laser surgery. Methods. A total of 20 consecutive patients of b oth genders scheduled for endolaryngeal procedures under general anest hesia were studied. Inspiratory oxygen concentration and respiratory r ate were varied, with patients serving as their own controls. Readings of pulse oximetry, airway oxygen, and carbon dioxide concentrations w ere recorded, and arterial blood samples for blood gas analysis were t aken. Results. At jet cycle rates of 20 cycles/min, end-tidal oxygen ( ETO(2)) concentration indicated alveolar hypoxia 30 to 60 sec before h ypoxemia was detected by pulse oximetry. Jet mixing of inspiratory and expiratory gas caused a larger difference between end-tidal and arter ial gas concentrations than normally seen with conventional ventilatio n. Correlations between ETO(2) concentrations, oxygen saturations, and arterial oxygen levels depended on respiratory rate and inspiratory o xygen concentration; correlations were stronger at low than at high in spiratory oxygen concentrations and stronger at low than at high respi ratory rates. Conclusions. ETO(2) concentration should be maintained w ell over 21% during ITJV to prevent alveolar and arterial hypoxia. Mon itoring 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.