title: Single-breath DLCO maneuver causes cardiac output to fall during and after cycling.
abstract: The purpose of this study was to evaluate the influence of the single-breath pulmonary diffusing capacity (DLCO) breath-hold maneuver on central hemodynamics. Ten men (mean age 24 yr) were studied at rest, during 40 min of cycling at 40 and 60% of peak O2 uptake, and 10 min into recovery. DLCO was measured in the seated position during a 10-s breath hold at total lung capacity. At rest the breath hold caused a significant fall in stroke volume (SV, -16%) and an increase in heart rate (HR, +20%) with no change in cardiac output (Q). The resting DLCO of 36.5 ml.min-1.mmHg-1 increased by 28 and 48%, respectively, during the low- and moderate-intensity cycling. The breath hold while cycling caused a significant decrease in SV and Q, but HR did not change. Likewise, during recovery SV and Q fell with the breath hold but again HR did not change. A significant fall in systolic (-17%), diastolic (-12.5%), and mean arterial pressure (-15%) occurred during the breath hold at rest and during and after the exercise. The reduction observed in SV and blood pressure most likely reflected a decrease in venous return. The differences observed in the HR response before, compared with during and after exercise, were consistent with a resetting or shift in the operating point of the arterial baroreflex. Because blood flow fell during the exercise and recovery breath-hold maneuver, the "true" DLCO may have been underestimated during and after cycling.
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Wright State University, Dayton, Ohio 45401-0927.
authors.forename: D S
authors.initials: DS
authors.lastname: Miles
authors.forename: R W
authors.initials: RW
authors.lastname: Gotshall
authors.forename: M R
authors.initials: MR
authors.lastname: Motta
authors.forename: C A
authors.initials: CA
authors.lastname: Duncan
mesh_terms: D000328:Adult; D002302:Cardiac Output; D004058:Diffusion; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D008297:Male; D012016:Reference Values; D012119:Respiration; D013318:Stroke Volume