[Multicenter study on the usefulness of the NasOral system for the denitrogenation and apneic oxygenation in anesthesia]

V Martínez-Pons, V Madrid, R Company, F J Belda, H Pérez Moya, M T Ibáñez, R Ortiz
Revista Española de Anestesiología y Reanimación 2001, 48 (2): 53-8

OBJECTIVES: To study the usefulness of the NasOral system for denitrogenation prior to anesthetic induction for improving pulmonary oxygen storage that maintains SpO2 within the normal range during induced apnea and facilitates apneic oxygenation.

MATERIAL AND METHODS: To establish the study population of 125, five hospitals of the Valencian Community (Spain) enrolled patients scheduled for elective procedures under general anesthesia. The patients were preoxygenated using the NasOral system (denitrogenation). For two minutes, the patients inhaled oxygen through the nose (FiO2 1) at a flow rate of 8-10 l/min (never less than the patient's own minute volume) and exhaled orally through a unidirectional valve. We measured time of apnea with SpO2 > or = 96% to assess the usefulness of the device for denitrogenation. We also measured PetCO2 after endotracheal intubation and after maximum time of apnea (< or = 10 minutes) to assess use of the device for apneic oxygenation during laryngoscopy.

RESULTS: We found no significant differences with regard to age, sex, ASA or Mallampati classification among patient groups enrolled at the participating hospitals. Cox's regression analysis was used to determine relative risk of SpO2 < 96%. At 10 minutes post-apnea, 88.8% of all patients maintained SpO2 > or = 96%. However, SpO2 > 96% was maintained by 94.1% in the Mallampati I group and by 84.1% in the Mallampati II group. SpO2 fell below the cut-off (< 96%) in 33.3% of obese patients and in 7.5% of non-obese patients. Analysis of the likelihood of SpO2 < 96% associated with the variables of obesity, sex, age, ASA and Mallampati classification was significant only for obesity, for which a risk of 1.95 was calculated relative to non-obesity (95% CI 1.14-3.35). The NasOral system allows performance of direct laryngoscopy for oral tracheal intubation, maintaining oxygen flow through the permeable airway to facilitate apneic oxygenation.

CONCLUSIONS: The NasOral system facilitates denitrogenation before induction of anesthesia in all patients with permeable nasal fossae as well as apneic oxygenation during laryngoscopy.

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