Effects of the self-contained breathing apparatus on left-ventricular function at rest and during graded exercise.
The purpose of this study was to examine the effects of the self-contained breathing apparatus (SCBA) on left-ventricular (LV) function at rest and during mild- to moderate-intensity exercise, using 2-dimensional echocardiography. Twenty-three healthy male volunteers exercised on a stair-climber at work rates equivalent to 50%, 60%, 70%, and 80% of peak oxygen consumption. Esophageal pressure LV diastolic and systolic cavity areas, and myocardial areas were acquired during the final minute of each stage of exercise. As expected, the esophageal pressure response during SCBA breathing revealed significantly lower (more negative) inspiratory pressures and higher (more positive) expiratory pressures and, consequently, higher pressure swings, than free breathing (FB). End-diastolic cavity area (EDCA) and end-systolic cavity area (ESCA) were lower with the SCBA than with FB. LV contractility was higher (p < 0.05) with the SCBA, which can partially be explained by decreases in end-systolic wall stress. Therefore, the SCBA was found to decrease LV preload during moderate-intensity exercise, but did not negatively affect stroke area because of a similar reduction in ESCA.
Mayne
Jonathan R
JR
Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G 2H9, Canada.
Haykowsky
Mark J
MJ
Nelson
Michael D
MD
Hartley
Timothy C
TC
Butcher
Scott J
SJ
Jones
Richard L
RL
Petersen
Stewart R
SR
D000328:Adult; D004452:Echocardiography; D004947:Esophagus / Q000502:physiology; D015444:Exercise; D045853:Exhalation; D005390:Fires; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D016272:Occupational Health; D010101:Oxygen Consumption; D011312:Pressure; D012134:Respiratory Protective Devices; D013147:Spirometry; D016277:Ventricular Function, Left