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The level of ventilation attained and breathing patterns adopted during activity have important implications for the distribution and deposition of particles that are inhaled. However, breathing patterns and levels of ventilation adopted during specific physical activities are unknown. We used a noninvasive means of measuring ventilation in subjects performing a variety of activities (bicycling, arm ergometry, lifting, and pulling) during unencumbered (no mouthpiece) breathing and while breathing through a mouthpiece. Minute ventilation (VE), tidal volume (VT), inspiratory time (TI), and total breathing cycle time (TT) were measured initially both spirometrically and from body surface displacements. When a mouthpiece was used, VE and breathing patterns were significantly altered during all activities such that VE, VT, and TT increased by 16, 34, and 20%, respectively. This mouthpiece effect was attenuated at the higher levels of VE. A task dependency of breathing pattern was also noted such that there was much greater variability of VT and TI for a given VE during the lifting activity compared with bicycling (coefficient of variation for VT of 0.39 +/- 0.09 vs. 0.20 +/- 0.07, P less than 0.01; and for TI of 0.38 +/- 0.08 vs. 0.21 +/- 0.08, P less than 0.01). We conclude that a mouthpiece significantly alters breathing pattern during varied types and intensities of activities, and breathing patterns may differ significantly from one activity to another. When the total dose of particulates inhaled in the lung are assessed, the mouthpiece effect and activity effect on breathing pattern must be considered.

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