Premium
Effects of respiratory muscle work on blood flow distribution during exercise in heart failure
Author(s) -
Olson Thomas P.,
Joyner Michael J.,
Dietz Niki M.,
Eisenach John H.,
Curry Timothy B.,
Johnson Bruce D.
Publication year - 2010
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2009.186056
Subject(s) - respiratory system , heart failure , medicine , cardiac output , blood flow , cardiology , vascular resistance , work of breathing , cardiac index , ejection fraction , hemodynamics , anesthesia
Heart failure (HF) patients have a reduced cardiac reserve and increased work of breathing. Increased locomotor muscle blood flow demand may result in competition between respiratory and locomotor vascular beds. We hypothesized that HF patients would demonstrate improved locomotor blood flow with respiratory muscle unloading during activity. Ten patients (ejection fraction = 31 ± 3%) and 10 controls (CTL) underwent two cycling sessions (60% peak work). Session 1 (S1): 5 min of normal breathing (NB), 5 min respiratory muscle unloading with a ventilator, and 5 min of NB. Session 2 (S2): 5 min NB, 5 min of respiratory muscle loading with inspiratory resistance, and 5 min of NB. Measurements included: leg blood flow (LBF, thermodilution), cardiac output , and oesophageal pressure ( P pl , index of pleural pressure). S1: P pl was reduced in both groups (HF: 73 ± 8%; CTL: 60 ± 13%, P < 0.01). HF: increased (9.6 ± 0.4 vs. 11.3 ± 0.8 l min −1 , P < 0.05) and LBF increased (4.8 ± 0.8 vs. 7.3 ± 1.1 l min −1 , P < 0.01); CTL: no changes in (14.7 ± 1.0 vs. 14.8 ± 1.6 l min −1 ) or LBF (10.9 ± 1.8 vs. 10.3 ± 1.7 l min −1 ). S2: P pl increased in both groups (HF: 172 ± 16%, CTL: 220 ± 40%, P < 0.01). HF: no change was observed in (10.0 ± 0.4 vs. 10.3 ± 0.8 l min −1 ) or LBF (5.0 ± 0.6 vs. 4.7 ± 0.5 l min −1 ); CTL: increased (15.4 ± 1.4 vs. 16.9 ± 1.5 l min −1 , P < 0.01) and LBF remained unchanged (10.7 ± 1.5 vs. 10.3 ± 1.8 l min −1 ). These data suggest HF patients preferentially steal blood flow from locomotor muscles to accommodate the work of breathing during activity. Further, HF patients are unable to vasoconstrict locomotor vascular beds beyond NB when presented with a respiratory load.