The objective was to quantify the Cerebral, and Femoral arterial hemodynamics as well as the calf vein section changes induced by a Tilt up test continuing with a Tilt plus LBNP after a 60 day HDT (WISE).24 healthy volunteers (25-40 y) underwent a 60 day HDT (-6 degree) bedrest: 8 as Control (Co), 8 with Exercise (Ex: treadmill under LBNP and flywheel), 8 with Nutrition (Nut: daily protein supplement). At R+0 all of them underwent a 10 min 80 degree Tilt up test, to which several LBNP period of 3 min were added (from -10 to -50 mmHg by steps of 10 mmHg) until presyncopal stage. Cerebral and Femoral flow changes were assessed by Doppler. Posterior Tibial, and Gastrocnemian vein were investigated by echography.At Post HDT 10 min Tilt: cerebral flow decreased similarly in the 3 groups, but more in the non finishers than in the finishers, while the femoral decreased similarly in all groups. Leg vascular resistance and cerebral/femoral flow ratio increased less in the Co and Nut gr than in the Ex gr, and also in the non finishers than in the finishers. Percent increase in Gastrocnemian and Tibial section was higher in Co and Nut gr than in Ex gr, and in non finishers than in finishers.Non exercise and non finisher subjects showed a lack of leg vasoconstriction, and a higher calf vein distensibility at post HDT Tilt test.
Cardiovascular monitoring is important to prevent diseases from progressing. The jugular venous pulse (JVP) waveform offers important clinical information about cardiac health, but is not routinely examined due to its invasive catheterisation procedure. Here, we demonstrate for the first time that the JVP can be consistently observed in a non-contact manner using a novel light-based photoplethysmographic imaging system, coded hemodynamic imaging (CHI). While traditional monitoring methods measure the JVP at a single location, CHI's wide-field imaging capabilities were able to observe the jugular venous pulse's spatial flow profile for the first time. The important inflection points in the JVP were observed, meaning that cardiac abnormalities can be assessed through JVP distortions. CHI provides a new way to assess cardiac health through non-contact light-based JVP monitoring, and can be used in non-surgical environments for cardiac assessment.
Our understanding of the impact of long-duration head-down bed rest (HDBR) on sympathetic neurovascular regulation during orthostatic stress remains incomplete. Through retrospective analysis of the WISE-2005 long-duration bed rest trial, this study aimed to investigate the impact of 60 days of -6° HDBR on the transduction of integrated muscle sympathetic nerve activity (MSNA; peroneal microneurography) into total peripheral resistance (TPR; Finometer Modelflow) responses during rest and graded lower body negative pressure (LBNP; -20, -30, and -45 mmHg). Signal averaging quantified sympathetic transduction for 12 cardiac cycles (ECG) following integrated MSNA bursts in healthy females ( n = 12; 25-40 years). Mixed-effects modeling and post-hoct-tests assessed the impact of HDBR on sympathetic transduction during rest (5-min) and graded LBNP (3-min per level). Data are presented as mean ± SD. Long-duration HDBR did not affect resting total MSNA (pre-HDBR: 909 ± 368 AU/min, post-HDBR: 910 ± 254 AU/min; p = 0.999). HDBR did not affect total MSNA responses to -20 mmHg LBNP (pre-HDBR: 1430 ± 599 AU/min, post-HDBR: 1823 ± 433 AU/min), -30 mmHg LBNP (pre-HDBR: 1574 ± 549 AU/min, post-HDBR: 1924 ± 587 AU/min), or -45 mmHg LBNP (pre-HDBR: 1950 ± 819 AU/min, post-HDBR: 2328 ± 880 AU/min; p = 0.191). HDBR did not affect resting sympathetic transduction to TPR (pre-HDBR: 0.002 ± 0.16 mmHg/L/min, post-HDBR: -0.091 ± 0.12 mmHg/L/min; p = 0.296). However, HDBR augmented TPR transduction responses to graded LBNP (HDBR-by-LBNP interaction: p = 0.050). Pre-HDBR, TPR transduction responses were unchanged with graded LBNP (all p > 0.05). In contrast, post-HDBR, TPR transduction responses increased progressively with graded LBNP (rest: -0.09 ± 0.12 mmHg/L/min, -20 mmHg: 0.22 ± 0.31 mmHg/L/min, -30 mmHg: 0.30 ± 0.34 mmHg/L/min, -45 mmHg: 0.44 ± 0.12 mmHg/L/min; all p < 0.005). The same effect of HDBR was observed when sympathetic transduction of mean arterial pressure was analyzed (data not shown). These data suggest that long-duration HDBR augments sympathetic neurovascular responses to integrated MSNA bursts during orthostatic stress among females. This work was supported by the Canadian Space Agency, the French “Centre National d’Etudes Spatiales”, the European Space Agency, and the National Aeronautics and Space Administration of the USA. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Cardiovascular monitoring is important to prevent diseases from progressing. The jugular venous pulse (JVP) waveform offers important clinical information about cardiac health, but is not routinely examined due to its invasive catheterisation procedure. Here, we demonstrate for the first time that the JVP can be consistently observed in a non-contact manner using a novel light-based photoplethysmographic imaging system, coded hemodynamic imaging (CHI). While traditional monitoring methods measure the JVP at a single location, CHI's wide-field imaging capabilities were able to observe the jugular venous pulse's spatial flow profile for the first time. The important inflection points in the JVP were observed, meaning that cardiac abnormalities can be assessed through JVP distortions. CHI provides a new way to assess cardiac health through non-contact light-based JVP monitoring, and can be used in non-surgical environments for cardiac assessment.
We investigated the pattern of activity and heart rate (HR) during daily living on the International Space Station (ISS) compared to on Earth in 7 long-duration astronauts to test the hypotheses that the HR responses on the ISS would be similar to preflight values, although the pattern of activity would shift to a dominance of arm activity, and postflight HR would be elevated compared to preflight during similar levels of activity.HR and ankle and wrist activity collected for 24-h periods before, during, and after spaceflight were divided into night, morning, afternoon, and evening segments. Exercise was excluded and analyzed separately.Consistent with the hypotheses, HR during daily activities on the ISS was unchanged compared to preflight; activity patterns shifted to predominantly arm in space. Contrary to the hypothesis, only night time HR was elevated postflight, although this was very small (+4 +/- 3 bpm compared to preflight). A trend was found for higher postflight HR in the afternoon (+10 +/- 10 bpm) while ankle activity level was not changed (99 +/- 48, 106 +/- 52 counts pre- to postflight, respectively). Astronauts engaged in aerobic exercise 4-8 times/week, 30-50 min/session, on a cycle ergometer and treadmill. Resistance exercise sessions were completed 4-6 times/week for 58 +/- 14 min/session.Astronauts on ISS maintained their HR during daily activities; on return to Earth there were only very small increases in HR, suggesting that cardiovascular fitness was maintained to meet the demands of normal daily activities.
Lower body negative pressure (LBNP) and head down bed rest (HDBR) are protocols used to simulate hypovolemia and cardiovascular deconditioning, causing an alteration of autonomic control of circulation. The objective of this study was to investigate the combined effects of LBNP and bed rest on cardiac baroreflex sensitivity (BRS). RR and systolic blood pressure (SBP) recordings from seven volunteers were analyzed during a mild LBNP protocol consisting of three different levels of LBNP (-10 mmHg, -20 mmHg, -30 mmHg) before (pre-HDBR) and on day 50 of a HDBR study. Spectra of RR and SBP were computed and BRS was assessed in the low frequency (LF) and high frequency (HF) bands through a bivariate model that takes into account the causal relationships between heart rate (HR) and arterial blood pressure. HR significantly increased from BL in HDBR for LBNP≤-20 mmHg. BRS gain decreased significantly in the LF band with increasing levels of LBNP in both conditions. BRS gain was significantly lower on day 50 of HDBR with respect to pre-HDBR at -20 mmHg. These data suggest that BRS in the LF range is reduced in bed rest, and these changes may be due primarily to a reduction in plasma volume associated with bed rest, which impact the physiological responses of autonomic control of circulation.
