Determinants of exercise performance in normal men with externally imposed expiratory flow limitation.
To understand how externally applied expiratory flow limitation (EFL) leads to impaired exercise performance and dyspnea, we studied six healthy males during control incremental exercise to exhaustion (C) and with EFL at approximately 1. We measured volume at the mouth (Vm), esophageal, gastric and transdiaphragmatic (Pdi) pressures, maximal exercise power (W(max)) and the difference (Delta) in Borg scale ratings of breathlessness between C and EFL exercise. Optoelectronic plethysmography measured chest wall and lung volume (VL). From Campbell diagrams, we measured alveolar (PA) and expiratory muscle (Pmus) pressures, and from Pdi and abdominal motion, an index of diaphragmatic power (W(di)). Four subjects hyperinflated and two did not. EFL limited performance equally to 65% W(max) with Borg = 9-10 in both. At EFL W(max), inspiratory time (TI) was 0.66s +/- 0.08, expiratory time (TE) 2.12 +/- 0.26 s, Pmus approximately 40 cmH2O and DeltaVL-DeltaVm = 488.7 +/- 74.1 ml. From PA and VL, we calculated compressed gas volume (VC) = 163.0 +/- 4.6 ml. The difference, DeltaVL-DeltaVm-VC (estimated blood volume shift) was 326 ml +/- 66 or 7.2 ml/cmH2O PA. The high Pmus and long TE mimicked a Valsalva maneuver from which the short TI did not allow recovery. Multiple stepwise linear regression revealed that the difference between C and EFL Pmus accounted for 70.3% of the variance in DeltaBorg. DeltaW(di) added 12.5%. We conclude that high expiratory pressures cause severe dyspnea and the possibility of adverse circulatory events, both of which would impair exercise performance.
Iandelli
Iacopo
I
Fondazione Don Gnocchi, I-50020 Pozzolatico, Italy.
Aliverti
Andrea
A
Kayser
Bengt
B
Dellacà
Raffaele
R
Cala
Stephen J
SJ
Duranti
Roberto
R
Kelly
Susan
S
Scano
Giorgio
G
Sliwinski
Pawel
P
Yan
Sheng
S
Macklem
Peter T
PT
Pedotti
Antonio
A
D000328:Adult; D001810:Blood Volume / Q000502:physiology; D003964:Diaphragm / Q000502:physiology; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005540:Forced Expiratory Flow Rates / Q000502:physiology*; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology*; D008297:Male; D005082:Physical Exertion / Q000502:physiology; D010991:Plethysmography; D011312:Pressure; D012123:Pulmonary Ventilation / Q000502:physiology*; D012016:Reference Values; D014109:Total Lung Capacity / Q000502:physiology