Arturo Arce

Biphasic responses of the brachial artery diameter following forearm occlusion: A blunted response in the elderly

BackgroundThe purpose was to examine the temporal response of the brachial artery diameter following 5 minutes of forearm occlusion in young men. A secondary objective was to compare the main features of the temporal pattern between young and old.MethodsSixteen young (28 ± 8 yrs) and fifteen older (85 ± 8 yrs) men underwent high-resolution ultrasonography of the brachial artery before and after five minutes of forearm occlusion.ResultsFollowing release of the pressure cuff the brachial artery diameter exhibits a temporal biphasic response. Initially, there is a significant reduction in brachial diameter (NIL) compared to baseline (BASE), followed by a rapid increase to a PEAK at 41 sec post release. When comparing the magnitude of the decrease in diameter and the Brachial Artery Flow Mediated Dilation (BAFMD) between Young and Old, older subjects demonstrated a blunted response (Magnitude of Decrease: Young: 2.0%; Old: 0.4%, p = 0.015, and BAFMD: Young: 7.7%; Old: 2.3%, p = 0.001). Finally, a significant relationship was noted between the magnitude of decrease and BAFMD (r = -0.44, p = 0.04).ConclusionExamination of the temporal response of the brachial artery diameter following 5 minutes of forearm occlusion reveals a biphasic pattern in all participants. Specific features of this pattern are blunted in older adults compared with younger subjects. Finally, the magnitude of the drop in diameter following forearm occlusion correlates with the magnitude of the BAFMD.

Brachial artery dimensions, flow-mediated reactivity and physical function in older adults

Human aging is associated with deterioration in physical functional ability. The causes are complex and multifactorial, but are presumed to include the presence and extent of cardiovascular disease. Purpose: To examine the associations between brachial artery (BA) dimensions, flow-mediated dilation (BAFMD) and physical function in 28 older adults (age: 84.6±10.9, range 66 to 98 yrs). Methods: High-resolution ultrasonography was used to measure BA diameters at rest and following 5min of forearm occlusion. Physical function was assessed using the Continuous Scale-Physical Function Performance (CS-PFP) test. Results: Pearson correlation revealed that BAFMD (r =-.39), and all physical function parameters of the CS-PFP declined with age at an alpha of p= .04 and p 5%, thus the sample was biased towards “non-responders.” Conclusion: These results appear to confirm predicted trends for

Influence of Venous Emptying on Reactive Hyperemic Blood Flow and Exercise Performance

Recent work by Tschakovsky & Hughson (Am J Physiol Heart Circ Physiol 279: H1007, 2000) indicates that venous emptying serves as a stimulus for vasodilation. This suggests the importance of recognizing the potential influence of venous volume on reactive hyperemic blood flow (RHBF) following occlusion. Purpose: To examine the influence of venous emptying on RHBF. Methods: Non-dominant forearm in-flow, venous capacitance and outflow were examined in 21 individuals [age=23±2.27y]. Forearm arterial inflow, venous capacitance, and outflow were obtained two times using strain gauge plethysmography. Forearm blood inflow was estimated at rest and following 5 min of upper arm occlusion. Forearm venous capacitance and outflow were obtained following 5 min of upper arm venous occlusion pressure at 7 mmHg below diastolic blood pressure. Prior to the second measure the arm was passively elevated for 2 minutes. Immediately before returning the arm to its original position the upper arm cuff was again inflated to 240mmHg. Subsequently, RHBF and venous measures were obtained. Results: Average resting in-flow was 2.84±1.22 ml/100ml/min. RHBF was significantly greater following venous emptying (Before: 18.15±3.80; After: 23.70±5.93 ml/100ml/min, p=0.0001). Venous capacitance was also greater (Before: 1.96±0.82; After: 2.94±0.82 %, p=0.0001), whereas venous outflow (Before: 37.06±10.50; After: 39.00±10.72 ml/100ml/min, p=0.17) remained unaffected after venous emptying. Summary: Venous emptying prior to upper arm occlusion results in a significant greater RHBF response and venous capacitance. A potential explanation for the observation is a decrease in the pressure gradient across the tissue bed and/or withdrawal of the venoarteriolar reflex constriction.