Effects of Breathing Pattern on Oxygen Delivery Via a Nasal or Pharyngeal Cannula

摘要

BACKGROUND: During sedation for upper gastrointestinal endoscopy, oxygen delivery via a nasal cannula is often necessary. However, the influences of the oxygen delivery route and breathing pattern on the F-IO2 have not been thoroughly investigated. The aim of this simulation study was to investigate the difference in the F-IO2 with a pharyngeal cannula versus nasal cannula during high- or low-tidal volume (V-T) ventilation and open- or closed-mouth breathing. METHODS: Six healthy volunteers were asked to breathe using 2 patterns of ventilation (high or low V-T) via a sealed face mask connected to an endotracheal tube that was retrogradely inserted into the trachea of a mannequin. The mannequin also had a pharyngeal or nasal cannula inserted into the pharynx or attached to the nose, through which oxygen (2 or 5 L/min) was delivered. The mouth of the mannequin was kept open or closed by packing. We measured the F-IO2 of every breath for 1 min at each setting. RESULTS: During low-and high-V-T ventilation, the F-IO2 was highest at a flow of 5 L/min with a pharyngeal cannula. Oxygen delivery was higher with the pharyngeal cannula compared with the nasal cannula at all settings. Differences in flow did not result in significant differences in the F-IO2 with high- and low-V-T ventilation. At a flow of 5 L/min via a pharyngeal cannula, open-mouth breathing resulted in a significantly higher F-IO2 compared with closed-mouth breathing. Conclusions: A pharyngeal cannula provided a higher F-IO2 compared with a nasal cannula at the same oxygen flow. Open-mouth breathing resulted in a higher F-IO2 compared with closed-mouth breathing when 5 L/min oxygen was delivered via a pharyngeal cannula. The breathing pattern did not affect the F-IO2 in this study.