title: Variability of resting respiratory drive and timing in healthy subjects.
abstract: Studies of breathing pattern have focused primarily on changes in the mean values of the breathing pattern components, whereas there has been minimal investigation of breath-to-breath variability, which should provide information on the constancy with which respiration is controlled. In this study we examined the variability of breathing pattern both on a breath-to-breath and day-to-day basis by calculating the coefficient of variation (i.e., the standard deviation expressed as a percentage of the mean). By examining breath-to-breath data, we found that the coefficients of variation of tidal volume (VT) and fractional inspiratory time (TI/TT, an index of timing) obtained with an inductive plethysmograph and spirometer were within 1% of each other. Examination of breath-to-breath variability in breathing pattern over a 15-min period in 65 subjects revealed large coefficients of variation, indicating the need to base calculations on a relatively large number of breaths. Less breath-to-breath variability was observed in respiratory frequency [f, 20.8 +/- 11.5% (SD)] and TI/TT (17.9 +/- 6.5%) than in VT (33 +/- 14.9%) and mean inspiratory flow (VT/TI, an index of drive; 31.6 +/- 12.6%; P less than 0.0001). Older subjects (60-81 yr) displayed greater breath-to-breath variability than young subjects (21-50 yr). Use of a mouthpiece did not affect the degree of variability.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Pulmonary Medicine, University of Texas Health Science Center, Houston 77030.
authors.forename: M J
authors.initials: MJ
authors.lastname: Tobin
authors.forename: M J
authors.initials: MJ
authors.lastname: Mador
authors.forename: S M
authors.initials: SM
authors.lastname: Guenther
authors.forename: R F
authors.initials: RF
authors.lastname: Lodato
authors.forename: M A
authors.initials: MA
authors.lastname: Sackner
mesh_terms: D000328:Adult; D000375:Aging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010507:Periodicity; D010991:Plethysmography; D012016:Reference Values; D012119:Respiration; D013990:Tidal Volume; D013997:Time Factors