title: Effects of respiratory muscle work on blood flow distribution during exercise in heart failure.
abstract: 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 (Q), 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: Q 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 Q (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 Q(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.
authors.affiliation: Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Olson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Joyner
authors.forename: Niki M
authors.initials: NM
authors.lastname: Dietz
authors.forename: John H
authors.initials: JH
authors.lastname: Eisenach
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Curry
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Johnson
mesh_terms: D000328:Adult; D000465:Algorithms; D002302:Cardiac Output / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007866:Leg / Q000098:blood supply / Q000502:physiology; D008168:Lung / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000502:physiology; D011312:Pressure; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000502:physiology; D012132:Respiratory Muscles / Q000503:physiopathology*; D013815:Thermodilution
references.citation: J Physiol. 2009 Jul 15;587(Pt 14):3665-77
references.pmid: 19451206
references.citation: Am Rev Respir Dis. 1984 Feb;129(2 Pt 2):S60-2
references.pmid: 6696343
references.citation: J Physiol. 1985 Sep;366:233-49
references.pmid: 4057091
references.citation: Am J Respir Crit Care Med. 1999 Dec;160(6):1804-11
references.pmid: 10588589
references.citation: J Appl Physiol (1985). 1999 Aug;87(2):643-51
references.pmid: 10444624
references.citation: Chest. 2000 Feb;117(2):321-32
references.pmid: 10669670
references.citation: Am J Physiol Heart Circ Physiol. 2002 May;282(5):H1732-8
references.pmid: 11959638
references.citation: Arch Intern Med. 1983 Mar;143(3):429-33
references.pmid: 6830378
references.citation: Heart. 2002 Nov;88(5):453-9
references.pmid: 12381630
references.citation: Am J Med. 1979 Sep;67(3):460-6
references.pmid: 474591
references.citation: J Appl Physiol Respir Environ Exerc Physiol. 1978 Dec;45(6):885-92
references.pmid: 730593
references.citation: Circulation. 2000 Jun 20;101(24):2774-6
references.pmid: 10859280
references.citation: J Appl Physiol (1985). 1998 Jul;85(1):68-75
references.pmid: 9655757
references.citation: Am J Cardiol. 1985 Apr 1;55(8):1037-42
references.pmid: 3984864
references.citation: Schweiz Z Sportmed. 1992 Jun;40(2):55-64
references.pmid: 1626272
references.citation: Chest. 1990 Oct;98(4):816-20
references.pmid: 2209136
references.citation: Exerc Sport Sci Rev. 2006 Oct;34(4):194-201
references.pmid: 17031258
references.citation: Am J Physiol Heart Circ Physiol. 2007 Jan;292(1):H580-92
references.pmid: 16997896
references.citation: Am J Physiol Heart Circ Physiol. 2008 Jun;294(6):H2465-72
references.pmid: 18375714
references.citation: Jpn Circ J. 1999 Feb;63(2):97-103
references.pmid: 10084371
references.citation: J Am Coll Cardiol. 1997 Mar 1;29(3):590-6
references.pmid: 9060898
references.citation: Respir Med. 1998 Dec;92(12):1321-5
references.pmid: 10197224
references.citation: Am J Physiol. 1993 Nov;265(5 Pt 2):H1721-6
references.pmid: 8238585
references.citation: J Am Coll Cardiol. 1994 Oct;24(4):972-81
references.pmid: 7930233
references.citation: Cardiol Clin. 1993 May;11(2):215-27
references.pmid: 8508448
references.citation: Eur Heart J. 1983 Jan;4 Suppl A:67-83
references.pmid: 6840124
references.citation: J Appl Physiol (1985). 1997 May;82(5):1573-83
references.pmid: 9134907
references.citation: Chest. 2006 Jul;130(1):164-71
references.pmid: 16840397
references.citation: Annu Rev Physiol. 1981;43:455-76
references.pmid: 6452090
references.citation: J Appl Physiol (1985). 1998 Aug;85(2):609-18
references.pmid: 9688739
references.citation: J Appl Physiol (1985). 1992 May;72(5):1818-25
references.pmid: 1601791
references.citation: J Appl Physiol (1985). 2000 Jul;89(1):131-8
references.pmid: 10904044
references.citation: J Appl Physiol (1985). 1999 Apr;86(4):1388-95
references.pmid: 10194227
references.citation: Circulation. 2001 Feb 20;103(7):916-8
references.pmid: 11181463
references.citation: J Appl Physiol (1985). 2000 May;88(5):1650-8
references.pmid: 10797126
references.citation: J Appl Physiol Respir Environ Exerc Physiol. 1982 Jul;53(1):280-5
references.pmid: 7118642