Component analysis of task-related respiratory patterns.

The pattern of breathing, determined by time, volumetric and respiratory shape parameters was examined in male students subjected to mental arithmetic tasks, sustained attention tasks, a relaxation task and four levels of graded exercise. Also, the relationships among the respiratory time parameters were determined by performing a factor analysis on a pooled matrix containing the parameter correlations across all experimental conditions. Relative to baseline, the experimental tasks induced rather distinct breathing patterns. During exercise the breathing curves resembled a triangular shape which was caused by a decrease in total breath duration coupled to an increase in both the depth of breathing and the inspiratory duty cycle time. For both the sustained attention and mental arithmetic conditions there was a slight decrease in the depth of breathing and a more pronounced decrease in inspiration time. However, during mental arithmetic the decrease in inspiration was linked to an increase in expiration duration, exhibiting a breathing curve that resembled a 'saw tooth'. In contrast, the attention tasks induced a slight decrease in expiration duration showing a sinusoidal breathing curve which was more similar to the baseline and relaxation breathing pattern. The factor analysis revealed two respiratory factors: a time factor reflecting inspiration, expiration and total cycle duration and a factor related to the inspiratory duty cycle time. We conclude that analysis of breathing patterns with components other than rate and depth of breathing is a potentially useful research tool.