NIOSHTIC-2 Publications Search
Study of respirator effect on nasal-oral flow partition.
Harber P; Beck J; Luo J
Am J Ind Med 1997 Oct; 32(4):408-412
The effect of switching the airflow of breathing apparatus used to protect workers from toxicants from the nasal route to the oral route was investigated. Eleven normal healthy volunteers (six males, five females, mean age 29 years, age range 21 to 43) exercised on a calibrated bicycle ergometer while wearing a respirator full face mask with added resistance to breathing, end expiratory pressure (10 centimeters (cm) water) or no load. The inspiratory resistance was approximately 6cm water/liter/second measured at 1 to 2 liters/second flow. Starting from unloaded cycling, the exercise level was increased by 30 watts every 60 seconds until the subject was too fatigued to continue or until 150 watts was attained. The exercise regimen was repeated four times, with a minimum of a 10 minute break between each run. During the no load run the subjects breathed through the full circuit without any added resistance of end expiratory pressure. During the disconnected run the subjects breathed through the respirator mask, but this was completely disconnected from the circuit. During the inspiratory resistance run an inspiratory resistance composed of a single acid mist cartridge was placed in the inspiratory limb of the circuit. During the pressure biased breathing run end expiratory pressure was introduced using a positive end expiratory pressure valve. The use of respirator type loads increased the proportion of oral versus nasal breathing with the switch from nasal to oral breathing at a lower exercise level. The authors conclude that measurements of flow partitioning with an actual respirator be considered when evaluating new designs. Normal interindividual variability in nasal resistance and in flow regimen switch point may partially explain differences in respirator tolerance.
NIOSH-Publication; NIOSH-Grant; Respirators; Humans; Personal-protective-equipment; Respiratory-protection; Pulmonary-function
Medicine University of California School of Medicine Los Angeles, Calif 90024
Issue of Publication
American Journal of Industrial Medicine
University of California Los Angeles, Los Angeles, California
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division