Individuality of breathing patterns in adults assessed over time

Sixteen healthy adult subjects underwent two studies separated by 4-5 years to test whether their resting pattern of breathing was reproducible over time. From breath-by-breath analysis of airflow, measured with a pneumotachometer, the pattern of breathing was quantified in terms of individual respiratory variables; inspiratory time (Ti), expiratory time (Te), total breath duration (Ttot), tidal volume (Vt), Vt/Ti, Ti/Ttot, and by taking Ti, Te and Vt all together (TRIAD). Also, the shape of the entire airflow profile was quantified by harmonic analysis (ASTER). A statistical analysis was designed to compare differences between the 1st and the 2nd recording within individuals with those differences observed between random pairs of recordings from the two studies in the same 16 individuals. It was found that all variables were significantly more similar within-individuals than between-individuals; this is best demonstrated when considering the ASTER and/or the TRIAD. It was concluded that the individuality of breathing pattern is maintained over a long period despite changes in smoking habit, weight, mild respiratory diseases, and other changes which occurred between the two studies in our subjects.