Document Detail

Indirect measures of human vagal withdrawal during head-up tilt with and without a respiratory acidosis.
MedLine Citation:
PMID:  19340559     Owner:  NLM     Status:  MEDLINE    
Human ECG records were analyzed during supine (SUP) rest and whole body 80 degrees head-up tilt (HUT), with a respiratory acidosis (5%CO(2)) and breathing room air (RA). HUT increased heart rate in both conditions (RA(SUP) 60 +/- 13 vs. RA(HUT) 79 +/- 16; 5%CO(2SUP) 63 +/- 12 vs. 5%CO(2HUT) 79 +/- 14 beats min(-1)) and decreased mean R-R interval, with no changes in the R-R interval standard deviation. When corrected for changes in frequency spectrum total power (NU), the high frequency (0.15-0.4 Hz) component (HF(NU)) of heart rate variability decreased (RA(SUP) 44.01 +/- 21.57 vs. RA(HUT) 24.05 +/- 13.09; 5%CO(2SUP) 69.23 +/- 15.37 vs. 5%CO(2HUT) 47.64 +/- 21.11) without accompanying changes in the low frequency (0.04-0.15 Hz) component (LF(NU)) (RA(SUP) 52.36 +/- 21.93 vs. RA(HUT) 66.58 +/- 19.49; 5%CO(2SUP) 22.97 +/- 11.54 vs. 5%CO(2HUT) 40.45 +/- 21.41). Positive linear relations between the tilt-induced changes (Delta) in HF(NU) and R-R interval were recorded for RA (DeltaHF(NU) = 0.0787(DeltaR-R) - 11.3, R (2) = 0.79, P < 0.05), and for 5%CO(2) (DeltaHF(NU) = 0.0334(DeltaR-R) + 1.1, R (2) = 0.82, P < 0.05). The decreased HF component suggested withdrawal of vagal activity during HUT. For both RA and 5%CO(2), the positive linear relations between DeltaHF(NU) and DeltaR-R suggested that the greater the increase in heart rate with HUT, the greater the vagal withdrawal. However, a reduced range of DeltaHF during HUT with respiratory acidosis suggested vagal withdrawal was lower with a respiratory acidosis.
S J Brown; T Mundel; M Barnes; J A Brown
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Publication Detail:
Type:  Journal Article     Date:  2008-11-30
Journal Detail:
Title:  The journal of physiological sciences : JPS     Volume:  59     ISSN:  1880-6546     ISO Abbreviation:  J Physiol Sci     Publication Date:  2009 Jan 
Date Detail:
Created Date:  2009-04-02     Completed Date:  2009-07-07     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101262417     Medline TA:  J Physiol Sci     Country:  Japan    
Other Details:
Languages:  eng     Pagination:  31-6     Citation Subset:  IM    
Institute of Food, Nutrition and Human Health, Massey University, Auckland, New Zealand.
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MeSH Terms
Acidosis, Respiratory / physiopathology*
Cardiovascular System / innervation
Heart Rate / physiology*
Hypercapnia / physiopathology*
Respiratory Mechanics / physiology*
Supine Position / physiology
Tilt-Table Test
Vagus Nerve / physiology*
Young Adult

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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