| Abstract: | The effects of a filtering device, an air-line breathing apparatus and a self-contained breathing apparatus ( SCBA ) on pulmonary ventilation, oxygen consumption and heart rate were studied in 12 well-trained firemen aged 21-35 years. Their average maximal oxygen consumption (VO2 max) was 64.9 ml X min-1 X kg-1. Sequential tests without and with the respirator were performed on a treadmill. The continuous test contained five components, each of which lasted 5 min: sitting at rest, walking at 20%, 40%, and 60% of the individual VO2 max, and recovery sitting. During the higher submaximal work levels and recovery, ventilation, heart rate, and oxygen consumption in particular increased more with respirators than without them. At the highest work level the increments in oxygen consumption caused by the respirators were 13%, (8.7 ml X min-1 X kg-1), 7% (4.4 ml X min-1 X kg-1), and 20% (12.7 ml X min-1 X kg-1) of VO2 max. All three respirators hampered respiration, resulting in hypoventilation. The additional effort of breathing and the weight of the apparatus (15 kg with the SCBA ) increased the subjects' cardiorespiratory strain so clearly that the need for rest periods and the individual's work capacity when the respirators are worn must be carefully considered, particularly with the SCBA . |
