Work of nasal breathing: measurement of each nostril independently using a split mask.

The work of nasal breathing was determined in human subjects as a measure of impedance to respiratory airflow. The nasal cavities were examined separately and simultaneously with a split mask; flow and pressure signals were fed to a microprocessor for on-line computation and printout of respired volumes and work of nasal breathing. An alternating resistive nasal cycle of 3--4 hours' duration was demonstrated in the majority of normal, resting subjects. Reciprocity of the resistive changes in each nasal cavity maintained a constant total nasal respiratory work load of about 0.2 Joules/litre. Moderate changes in breathing rate and tidal volume had little influence on work. Inspiratory work was 1.6 times that of expiration. Increases in resistance of the dependent nostril were seen when the lateral decubitus position was adopted. Increase in cephalic venous pressure and pathological nasal obstruction increased the work of nasal breathing.