An evaluation of oxygen delivery using nasal prongs.

Oxygen delivery using nasal prongs was assessed using a lung model for spontaneous ventilation. The analogue lung was attached to a manikin, which provided a model of the 'face and pharynx' to which the nasal prongs were applied. Oxygen concentrations were measured in the model trachea at varying fresh gas inflow and peak inspiratory flows. The study demonstrated enormous variability in the both the peak-inspired (26.3-90.0%) and end-expired concentrations (25.2-78.6%) of oxygen delivered to the trachea. There was a regular relationship between the ratio of peak inspiratory flows, expressed over fresh gas inflow and the end-expired oxygen concentrations which could allow estimation of inspired oxygen concentration.