Holmer et al

Breath Air Flow Rates During Treadmill Walking

Using Filter Respirators

I. Holmér, K. Kuklane, and C. Gao

Lund University, Department of Ergonomics

Box 118, Lund 22100, Sweden

Respiratory minute volumes and instantaneous breath flow rates were measured in 8 subjects during treadmill work using (a) a particle filter respirator(Sundstroem SR200) and (b) a control breathing mask (Metamax I, Cortex). Work comprised five consecutive bouts of walking at 5 km/h with an increase in elevation of the treadmill by 5 % every 5 minutes. Minute ventilationincreased in a curvilinear manner with oxygen uptake and reached 88±20 and 93±20 l/min at 5 km/h (20%) with the control mask and SR200, respectively. Peak inspiratory flow rate (PIFR), measured as the average of several breath cycles (in 30 sec), was 273±38 for Control and 300±36 for SR200 at the same work rate. During standardized speech communication, minute volumes decreased. In contrast, PIFR increased by about 100 % at low work rates and about 30 % at 5 km/h (20%) compared to no speech condition, reaching a highest value of 373±42 for Control and 407±48 for SR200. The time of the inhalation cycle was between 50-60 % of the total breath cycle in Control and 46-53 in SR200. During speech inhalation time was 14 and 19 % at the lowest work rate for Control and SR200, respectively. Corresponding values for the highest work rate were 38 and 33 % of total breath time. At the highest work rate mean inspiratory flow rate was 192±43 l/min for SR200. It was calculated that at the three highest work rates the mask air flow rate exceeded 95 l/min for more than 60 % of the inhalation time. During speech conditions this result was valid also for the two lowest work rates.