Tracheal Oxygen Concentrations with a Nasal Cannula during Oral and Nasal Breathing

Abstract

Although the nasal cannula is commonly used to administer supplemental oxygen, it is not known whether the device is less effective when a patient breathes through the mouth rather than the nose. We used a medical mass spectrometer to measure oxygen and carbon dioxide concentrations in the trachea of a trained subject who breathed first nasally and then orally while receiving oxygen by nasal cannula at five arbitrarily chosen rates of flow. Depending upon the rate of flow of oxygen and the pattern of breathing of the subject, peak tracheal oxygen concentrations varied widely. In every instance the peak concentration of oxygen in the trachea was greater with nasal breathing than with oral breathing.