Effects of resistive loading on the pattern of breathing.

In order to determine changes in breathing patterns brought about by resistive loading, ventilation was recorded in 11 healthy subjects with four linear resistances (3.57, 5.75, 8.76 and 13.13 cmH2O L(-1) sec) added in a random order throughout the entire breath. At steady state, a breath-by-breath analysis of airflow was used to quantify the pattern of breathing in terms of respiratory variables: TI, TE, Tt, VT, VT/TI, TI/Tt, and by taking TI, TE, VT all together (TRIAD) and also the shape of the entire airflow profile quantified by harmonic analysis (ASTER). Group analysis using ANOVA showed significant changes in all variables. There were increasing changes with increasing loads in all variables, the smallest changes being in TI/Tt. Within to between-individual comparisons between two loads showed that only TI/Tt and the ASTER were more similar within than between-individuals for all comparisons. It was concluded that at steady state mechanisms of load compensation come into play inducing changes in the pattern of breathing proportional to the loads while maintaining some of the individual characteristics.