TY - JOUR
T1 - Effect of hypercapnia on maximal voluntary ventilation and diaphragm fatigue in normal humans
AU - Rafferty, Gerrard F.
AU - Harris, M. Lou
AU - Polkey, Michael I.
AU - Greenough, Anne
AU - Moxham, John
PY - 1999/1/1
Y1 - 1999/1/1
N2 - Relatively little is known about the combined effects of hypercapnia and fatigue on the human diaphragm. We examined the effects of acute hypercapnia and fatigue in seven subjects by measuring changes in transdiaphragmatic pressure (Pdi) elicited by cervical magnetic stimulation after 2 min maximal voluntary ventilation (MVV) while breathing air and also with the inspired PCO2 increased to 8% for 12 min before and during the MVV. Diaphragm strength was assessed before and at 0, 20, 40, 60, and 90 min after the MVV in both studies with the subjects breathing air. There was no difference in the level of ventilation for each run. Mean (± SD) twitch Pdi (TwPdi) fell significantly (p < 0.01) at 20 min after the control and hypercapnic MVV; (30.4 [7.8] to 27.0 [8.1] cm H2O control and 30.3 [4.1] to 27.3 [5.0] cm H2O CO2) and remained significantly (p < 0.01) below baseline. The changes in TwPdi at 20 to 90 min were not significantly different between the control and CO2 runs. The decrease in TwPdi at 0 min after MVV, however, was greater (15%) in the hypercapnic run than in the control run (8.1%) (p < 0.05) when compared with baseline valves. Hypercapnia does not intensify long lasting fatigue but may reduce diaphragm contractility immediately after MVV.
AB - Relatively little is known about the combined effects of hypercapnia and fatigue on the human diaphragm. We examined the effects of acute hypercapnia and fatigue in seven subjects by measuring changes in transdiaphragmatic pressure (Pdi) elicited by cervical magnetic stimulation after 2 min maximal voluntary ventilation (MVV) while breathing air and also with the inspired PCO2 increased to 8% for 12 min before and during the MVV. Diaphragm strength was assessed before and at 0, 20, 40, 60, and 90 min after the MVV in both studies with the subjects breathing air. There was no difference in the level of ventilation for each run. Mean (± SD) twitch Pdi (TwPdi) fell significantly (p < 0.01) at 20 min after the control and hypercapnic MVV; (30.4 [7.8] to 27.0 [8.1] cm H2O control and 30.3 [4.1] to 27.3 [5.0] cm H2O CO2) and remained significantly (p < 0.01) below baseline. The changes in TwPdi at 20 to 90 min were not significantly different between the control and CO2 runs. The decrease in TwPdi at 0 min after MVV, however, was greater (15%) in the hypercapnic run than in the control run (8.1%) (p < 0.05) when compared with baseline valves. Hypercapnia does not intensify long lasting fatigue but may reduce diaphragm contractility immediately after MVV.
UR - http://www.scopus.com/inward/record.url?scp=0032742791&partnerID=8YFLogxK
U2 - 10.1164/ajrccm.160.5.9801114
DO - 10.1164/ajrccm.160.5.9801114
M3 - Article
C2 - 10556122
AN - SCOPUS:0032742791
SN - 1073-449X
VL - 160
SP - 1567
EP - 1571
JO - American Journal of Respiratory and Critical Care Medicine
JF - American Journal of Respiratory and Critical Care Medicine
IS - 5 I
ER -