Blood pressure (BP) response to the onset of lower body negative pressure (LBNP): Effect t of age

To test the hypothesis that hypotension would be transiently present at the onset of low level of LBNP with aging, we compared the changes in BP (Finapres) and heart rate (HR) in 5 young (29±4yr) and 5 older (65±3yr) healthy subjects between LBNP -15 and -40 torr. The initial response, an average of the first 10 beats of BP and HR after the onset of LBNP was achieved (∼4 to 5 sec), and the later response, an average of the following 1-min beat-to-beat data, were compared to the baseline (averaged 1-min data prior to the application of LBNP), see table. Although there was an initial hypotension associated with a tachycardia observed LBNP Young Older Torr Baseline Initial Later Baseline Initial Later HR -15 59±4 6l±3 59±3 56±3 59±3 59±3 bpm -40 59±5 71 ±2*68±3*57±3 62±2*62±3*SBP -15 119±7 115±14 118±6 130±8 128±11 129±11 mmHg -40 120±6 105±7*117*6 134±10 112±7*123±11 MRP -15 82±3 76±3 79±3 93±5 89±7 91±7 mmHg -40 85±3 72±3*81±3 98±8 80±6*91±8 PP -15 53±7 53±4 54±7 60±5 60±6 59±6 mmHg -40 51±5 46±3*50±5 59±5 49±3*51±5 at -40 torr, -15 torr did not significantly change BP in both groups, indicating an absence of ihe perturbation of the arterial baroreceptors at low level LBNP. The older subjects showed a greater hypotension with less tachycardia in the initial response to -40 torr of LBNP. We concluded that the cardiovascular reflex was compromised with aging in response to the onset of orthostatic challenge.