Effects of body positions on arterial stiffness as assessed by pulse wave velocity.

BACKGROUND: Assessing arterial stiffness through pulse wave velocity (PWV) usually requires participants to be in a supine position. If this position is not feasible, adjustments such as tilting the bed or bending the knees may be made. The Vicorder device also recommends tilting the upper body to prevent jugular vein interference in the recorded carotid pulse. OBJECTIVE: To examine the impact of varying body positions on PWV. METHODS: Seventy adults were studied in the fully supine (0°) to 40° upper body tilted-up positions with and without knee bend. Carotid-femoral PWV (cfPWV) was measured using two different testing devices (Omron VP-1000plus and Vicorder) and brachial-ankle PWV (baPWV) was measured using Omron. RESULTS: cfPWV measured at 10° tilt-up was not different from 0° position while baPWV increased significantly from 10°. Elevations in cfPWV were 7% at 20° and 15% at 40° compared with 0° position. Knee bend did not affect cfPWV but decreased baPWV at each angle ( P  < 0.05). Jugular vein interference on the Vicorder was observed in 78% of participants in supine position, decreasing as body angle increased (7% at 30°). However, cfPWV values measured by Vicorder were consistent with those obtained by Omron even with jugular vein interference. CONCLUSION: Arterial stiffness assessed by PWV increased gradually and significantly in semi-Fowler's position ≥20°. Knee bend decreased baPWV but did not seem to affect cfPWV. PWV should be measured in supine position if possible. If the supine posture is not tolerated, knee bend followed by a slight incline position may be recommended.

Feasibility and Performance of Hemoglobin A1C Self-Testing During COVID-19 Among African Americans With Type 2 Diabetes.

PURPOSE: The purpose of the study was to determine the feasibility of implementing A1C self-testing at home using the A1CNow® Self Check and to compare the accuracy of the A1CNow to a reference standard in African Americans with type 2 diabetes (T2D). METHODS: African American adults with T2D were recruited from 13 different churches (N = 123). Phase 1, conducted during the early phase of the COVID-19 pandemic, examined the feasibility of A1C assessment using the A1CNow performed at home by untrained participants. Phase 2, conducted when in-person research resumed, compared A1C values concurrently measured using the A1CNow and the DCA Vantage™ Analyzer (reference standard) collected by research staff at church testing sites. RESULTS: In Phase 1, 98.8% of participants successfully completed at least 1 at-home A1C test; the overall failure rate was 24.7%. In Phase 2, the failure rate of staff-performed A1CNow testing was 4.4%. The Bland-Altman plot reveals that A1CNow values were 0.68% lower than DCA values, and the mean differences (A1CNow minus DCA) ranged from -2.6% to 1.2% with a limit of agreement between -1.9% to 0.5%. CONCLUSIONS: A1C self-testing is feasible for use in community settings involving African American adults with T2D. The A1CNow Self-Check underestimated A1C values when compared with the reference standard. Ongoing improvements in point-of-care devices have the potential to expand research and clinical care, especially in underserved communities.

Vascular responses to simulated breath-hold diving involving multiple reflexes.

Breath-hold diving evokes a complex cardiovascular response. The degrees of hypertension induced by the diving reflex are substantial and accentuated by the underwater swimming. This condition provides a circulatory challenge to properly buffer and cushion cardiac pulsations. We determined hemodynamic changes during the diving maneuver and hypothesized that central artery compliance would be augmented during simulated breath-hold diving. A total of 20 healthy young adults were studied. Hemodynamics were measured during exercise on a cycle ergometer, apnea, face immersion in cold water (trigeminal stimulation), and simulated breath-hold diving. Arterial compliance was measured by recording the carotid artery diameter from images derived from an ultrasound machine at the cephalic portion of the common carotid artery 1-2 cm proximal to the carotid bulb, whereas arterial pressure waveforms were obtained using an arterial tonometry placed on the contralateral carotid artery and recorded on a data acquisition software. The change in diameter was divided by the change in blood pressure to calculate arterial compliance. Arterial compliance increased with simulated diving compared with rest (P = 0.007) and was elevated compared with exercise and apnea alone (P < 0.01). A significant increase in heart rate was observed with exercise, apnea, and facial immersion when compared with rest (P < 0.001). However, simulated diving brought the heart rate down to resting levels. Cardiac output increased with all conditions (P < 0.001), with an attenuated response during simulated diving compared with exercise and facial immersion (P < 0.05). Mean blood pressure was elevated during all conditions (P < 0.001), with a further elevation observed during simulated diving compared with exercise (P < 0.001), apnea (P = 0.016), and facial immersion (P < 0.001). Total peripheral resistance was decreased during exercise and facial immersion compared with rest (P < 0.001) but was increased during simulated diving compared with exercise (P < 0.001), apnea (P = 0.008), and facial immersion (P = 0.003). We concluded that central artery compliance is augmented during simulated breath-hold diving to help buffer cardiac pulsations.