Cardiovascular responses to short-term head-down positioning in healthy young and older adults.
OBJECTIVE
Isolated head-down postural drainage is assumed to acutely load the cardiovascular system. Consequently, it is considered a relative contraindication in the presence of severe cardiovascular disease. Evidence demonstrating that the head-down manoeuvre as used by physiotherapists does significantly load the cardiovascular system is lacking. The present study documents the cardiovascular responses t short-term 30 degrees head-down positioning in healthy subjects. The results are a point of reference for respiratory patients with and without cardiovascular disease.


METHODS
A quasi-experimental research design was used, with multiple measurements obtained at rest (long sitting and in the head-down position. Twenty-one young subjects (mean age 25 years (standard deviation, (SD) 3 years)) and 19 older subjects (mean age 66 years (SD 6 years)) were studied. Applanation tonometry and sphygmocardiography were used to measure temporal and pressure variables, and indices that estimate myocardial work and coronary blood flow.


RESULTS
Absolute differences existed between the two age groups for all variables at rest (p < 0.001). No age-time interaction was observed for any variable in the head-down position (p > 0.05). Serial measures in the head-down position did not vary across time (p > 0.05). Small (<9%) but significant (p < or = 0.02) decreases in heart rate, relative diastolic duration, mean arterial blood pressure and diastolic time indices, and small (<12%) but significant (p < or = 0.002) increases in cardiac cycle time, ejection duration (relative and absolute) and absolute diastolic duration were observed in the head-down position compared with rest. A small (9%) but significant (p < 0.001) fall in the sub-endocardial viability ratio occurred in the head down position.


CONCLUSIONS
The findings have little consequence in health, but they suggest that head-down postural drainage may be of concern for chest physiotherapy recipients with reduced cardiac reserve or impaired barorefilex function.
Naylor
Justine M
JM
School of Exercise and Sport Sciences, University of Sydney, NSW, Australia. Justine.Naylor@swsahs.nsw.gov.au
Chow
Chin-Moi
CM
McLean
Anthony S
AS
Heard
Robert C
RC
Avolio
Albert
A
D000328:Adult; D000367:Age Factors; D000368:Aged; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure; D018475:Head-Down Tilt / Q000502:physiology*; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption
D010100:Oxygen