Sex-specific effect of blood O2 carrying capacity on orthostatic tolerance in older individuals

2021 ◽  
Author(s):  
Candela Diaz-Canestro ◽  
David Montero
Keyword(s):  
Older Women ◽  
Carrying Capacity ◽  
Lower Body Negative Pressure ◽  
Specific Effect ◽  
Left Ventricular ◽  
Orthostatic Tolerance ◽  
Activity Levels ◽  
Older Individuals ◽  
Total N ◽  
End Diastolic Volume

Abstract Blood oxygen (O2) carrying capacity is reduced with ageing and has been previously linked with the capacity to withstand the upright posture, i.e., orthostatic tolerance (OT). This study experimentally tested the hypothesis that a definite reduction in blood O2 carrying capacity via hemoglobin (Hb) manipulation differently affects the OT of older women and men as assessed by lower body negative pressure (LBNP). Secondary hemodynamic parameters were determined with transthoracic echocardiography throughout incremental LBNP levels for 1 hour or until presyncope in healthy older women and men (total n=26) matched by age (64±7 vs. 65±8 yr, P<0.618) and physical activity levels. Measurements were repeated within a week period after a 10 % reduction of blood O2 carrying capacity via carbon monoxide rebreathing and analyzed via two-way ANCOVA. In the assessment session, OT time was similar between women and men (53.5±6.1 vs. 56.4±6.0 min, P=0.238). Following a 10 % reduction of blood O2 carrying capacity, OT time was reduced in women compared with men (51.3±7.0 vs. 58.2±2.8 min, P=0.003). The effect of reduced O2 carrying capacity on OT time differed between sexes (mean difference (MD)=-5.30 min, P=0.010). Prior to presyncope. reduced O2 carrying capacity resulted in lower left ventricular end-diastolic volume (MD=-8.11 ml∙m -2, P=0.043) and stroke volume (MD=-8.04 ml∙m -2, 95 % CI=-14.36, -1.71, P=0.018) in women relative to men, even after adjusting for baseline variables. In conclusion, present results suggest that reduced blood O2 carrying capacity specifically impairs OT and its circulatory determinants in older women.

scholarly journals Beneficial effects of elevating cardiac preload on left-ventricular diastolic function and volume during heat stress: implications toward tolerance during a hemorrhagic insult

2014 ◽  
Vol 307 (8) ◽  
pp. R1036-R1041 ◽  
Author(s):  
R. M. Brothers ◽  
Redi Pecini ◽  
M. Dalsgaard ◽  
Morten Bundgaard-Nielsen ◽  
Thad E. Wilson ◽  
...  
Keyword(s):  
Heat Stress ◽  
Diastolic Function ◽  
Lower Body Negative Pressure ◽  
Left Ventricular Diastolic Function ◽  
Left Ventricular ◽  
Stress Conditions ◽  
Volume Loading ◽  
Ventricular Diastolic Function ◽  
Beneficial Effects ◽  
End Diastolic Volume

Volume loading normalizes tolerance to a simulated hemorrhagic challenge in heat-stressed individuals, relative to when these individuals are thermoneutral. The mechanism(s) by which this occurs is unknown. This project tested two unique hypotheses; that is, the elevation of central blood volume via volume loading while heat stressed would 1) increase indices of left ventricular diastolic function, and 2) preserve left ventricular end-diastolic volume (LVEDV) during a subsequent simulated hemorrhagic challenge induced by lower-body negative pressure (LBNP). Indices of left ventricular diastolic function were evaluated in nine subjects during the following conditions: thermoneutral, heat stress, and heat stress after acute volume loading sufficient to return ventricular filling pressures toward thermoneutral levels. LVEDV was also measured in these subjects during the aforementioned conditions prior to and during a simulated hemorrhagic challenge. Heat stress did not change indices of diastolic function. Subsequent volume infusion elevated indices of diastolic function, specifically early diastolic mitral annular tissue velocity ( E′) and early diastolic propagation velocity ( E) relative to both thermoneutral and heat stress conditions ( P < 0.05 for both). Heat stress reduced LVEDV ( P < 0.05), while volume infusion returned LVEDV to thermoneutral levels. The reduction in LVEDV to LBNP was similar between thermoneutral and heat stress conditions, whereas the reduction after volume infusion was attenuated relative to both conditions ( P < 0.05). Absolute LVEDV during LBNP after volume loading was appreciably greater relative to the same level of LBNP during heat stress alone. Thus, rapid volume infusion during heat stress increased indices of left ventricular diastolic function and attenuated the reduction in LVEDV during LBNP, both of which may serve as mechanisms by which volume loading improves tolerance to a combined hyperthermic and hemorrhagic challenge.

scholarly journals Females have greater left ventricular twist mechanics than males during acute reductions to preload

2016 ◽  
Vol 311 (1) ◽  
pp. H76-H84 ◽  
Author(s):  
Alexandra M. Williams ◽  
Rob E. Shave ◽  
Mike Stembridge ◽  
Neil D. Eves
Keyword(s):  
Sex Differences ◽  
Lower Body Negative Pressure ◽  
Left Ventricular ◽  
Rapid Infusion ◽  
Systolic Volume ◽  
End Diastolic Volume ◽  
Apical Rotation ◽  
Left Ventricular Twist ◽  
End Systolic Volume ◽  
And Function

Compared to males, females have smaller left ventricular (LV) dimensions and volumes, higher ejection fractions (EF), and higher LV longitudinal and circumferential strain. LV twist mechanics determine ventricular function and are preload-dependent. Therefore, the sex differences in LV structure and myocardial function may result in different mechanics when preload is altered. This study investigated sex differences in LV mechanics during acute challenges to preload. With the use of conventional and speckle-tracking echocardiography, LV structure and function were assessed in 20 males (24 ± 6.2 yr) and 20 females (23 ± 3.1 yr) at baseline and during progressive levels of lower body negative pressure (LBNP). Fourteen participants (8 males, 6 females) were also assessed following a rapid infusion of saline. LV end-diastolic volume, end-systolic volume, stroke volume (SV), and EF were reduced in both groups during LBNP ( P < 0.001). While males had greater absolute volumes ( P < 0.001), there were no sex differences in allometrically scaled volumes at any stage. Sex differences were not detected at baseline in basal rotation, apical rotation, or twist. Apical rotation and twist increased in both groups ( P < 0.001) with LBNP. At −60 mmHg, females had greater apical rotation ( P = 0.009), twist ( P = 0.008), and torsion ( P = 0.002) and faster untwisting velocity ( P = 0.02) than males. There were no differences in mechanics following saline infusion. Females have larger LV twist and a faster untwisting velocity than males during large reductions to preload, supporting that females have a greater reliance on LV twist mechanics to maintain SV during severe reductions to preload.

scholarly journals Supine cycling plus volume loading prevent cardiovascular deconditioning during bed rest

2010 ◽  
Vol 108 (5) ◽  
pp. 1177-1186 ◽  
Author(s):  
Shigeki Shibata ◽  
Merja Perhonen ◽  
Benjamin D. Levine
Keyword(s):  
Exercise Training ◽  
Exercise Capacity ◽  
Orthostatic Intolerance ◽  
Lower Body Negative Pressure ◽  
Bed Rest ◽  
Left Ventricular ◽  
Orthostatic Tolerance ◽  
Volume Loading ◽  
Cardiac Atrophy ◽  
Cardiac Filling

There are two possible mechanisms contributing to the excessive fall of stroke volume (and its contribution to orthostatic intolerance) in the upright position after bed rest or spaceflight: reduced cardiac filling due to hypovolemia and/or a less distensible heart due to cardiac atrophy. We hypothesized that preservation of cardiac mechanical function by exercise training, plus normalization of cardiac filling with volume infusion, would prevent orthostatic intolerance after bed rest. Eighteen men and three women were assigned to 1) exercise countermeasure ( n = 14) and 2) no exercise countermeasure ( n = 7) groups during bed rest. Bed rest occurred in the 6° head-down tilt position for 18 days. The exercise regimen was prescribed to compensate for the estimated cardiac work reduction between bed rest and ambulatory periods. At the end of bed rest, the subjects were further divided into two additional groups for post-bed rest testing: 1) volume loading with intravenous dextran to normalize cardiac filling pressure and 2) no volume loading. Dextran infusion was given to half of the exercise group and all of the sedentary group after bed rest, leading ultimately to three groups: 1) exercise plus volume infusion; 2) exercise alone; and 3) volume infusion alone. Exercise training alone preserved left ventricular mass and distensibility as well as upright exercise capacity, but lower body negative pressure (LBNP) tolerance was still depressed. LBNP tolerance was maintained only when exercise training was accompanied by dextran infusion. Dextran infusion alone following bed rest without exercise maintained neither orthostatic tolerance nor upright exercise capacity. We conclude that daily supine cycle exercise sufficient to prevent cardiac atrophy can prevent orthostatic intolerance after bed rest only when combined with plasma volume restoration. This maintenance of orthostatic tolerance was achieved by neither exercise nor dextran infusion alone. Cardiac atrophy and hypovolemia are likely to contribute independently to orthostatic intolerance after bed rest.

Evidence for increased cardiac compliance during exposure to simulated microgravity

1998 ◽  
Vol 275 (4) ◽  
pp. R1343-R1352 ◽  
Author(s):  
Steven C. Koenig ◽  
Victor A. Convertino ◽  
John W. Fanton ◽  
Craig A. Reister ◽  
F. Andrew Gaffney ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Stroke Volume ◽  
Simulated Microgravity ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Left Ventricular ◽  
Continuous Exposure ◽  
Orthostatic Tolerance ◽  
Experimental Conditions ◽  
Ventricular Compliance

We measured hemodynamic responses during 4 days of head-down tilt (HDT) and during graded lower body negative pressure (LBNP) in invasively instrumented rhesus monkeys to test the hypotheses that exposure to simulated microgravity increases cardiac compliance and that decreased stroke volume, cardiac output, and orthostatic tolerance are associated with reduced left ventricular peak dP/d t. Six monkeys underwent two 4-day (96 h) experimental conditions separated by 9 days of ambulatory activities in a crossover counterbalance design: 1) continuous exposure to 10° HDT and 2) ∼12–14 h per day of 80° head-up tilt and 10–12 h supine (control condition). Each animal underwent measurements of central venous pressure (CVP), left ventricular and aortic pressures, stroke volume, esophageal pressure (EsP), plasma volume, α1- and β1-adrenergic responsiveness, and tolerance to LBNP. HDT induced a hypovolemic and hypoadrenergic state with reduced LBNP tolerance compared with the control condition. Decreased LBNP tolerance with HDT was associated with reduced stroke volume, cardiac output, and peak dP/d t. Compared with the control condition, a 34% reduction in CVP ( P= 0.010) and no change in left ventricular end-diastolic area during HDT was associated with increased ventricular compliance ( P = 0.0053). Increased cardiac compliance could not be explained by reduced intrathoracic pressure since EsP was unaltered by HDT. Our data provide the first direct evidence that increased cardiac compliance was associated with headward fluid shifts similar to those induced by exposure to spaceflight and that reduced orthostatic tolerance was associated with lower cardiac contractility.

Changes in ventricular twist and untwisting with orthostatic stress: endurance athletes versus normally active individuals

2010 ◽  
Vol 108 (5) ◽  
pp. 1259-1266 ◽  
Author(s):  
Ben T. Esch ◽  
Jessica M. Scott ◽  
Mark J. Haykowsky ◽  
Ian Paterson ◽  
Darren E. R. Warburton ◽  
...  
Keyword(s):  
Stroke Volume ◽  
Orthostatic Intolerance ◽  
Lower Body Negative Pressure ◽  
Left Ventricular ◽  
Endurance Athletes ◽  
Compensatory Mechanism ◽  
Filling Rate ◽  
Systolic Volume ◽  
End Diastolic Volume ◽  
Early Filling

Endurance-trained individuals exhibit larger reductions in left ventricular (LV) end-diastolic volume in response to lower body negative pressure (LBNP) compared with normally active individuals. However, the relationship between LV torsion and untwisting and the LV volume response to LBNP in endurance athletes is unknown. Eight endurance-trained athletes [maximal oxygen consumption (V̇o2max): 66.4 ± 7.2 ml·kg−1·min−1] and eight normally active individuals (V̇o2max: 41.9 ± 9.0 ml·kg−1·min−1) (all men) underwent two cardiac magnetic resonance imaging (MRI) assessments, the first during supine rest and the second during −30 mmHg LBNP. Right ventricular (RV) and LV volumes were assessed, myocardial tagging was applied in order to quantify LV peak torsion and peak untwisting rate, and filling rates were measured with phase-contrast MRI. In response to LBNP, endurance-trained individuals had greater reductions in RV and LV end-diastolic volume and stroke volume ( P < 0.05). Endurance athletes had reduced untwisting rates (20.3 ± 8.7°/s), while normally active individuals had increased untwisting rates (−16.2 ± 32.1°/s) in response to LBNP ( P < 0.05). Changes in peak untwisting rate were significantly correlated with change in peak torsion ( R = −0.87, P < 0.05), with the change in early filling rate and V̇o2max, but not with changes in end-diastolic or end-systolic volume ( P > 0.05). We conclude that increased untwisting rates in normally active subjects may mitigate the drop in early filling rate with LBNP and thus may be a compensatory mechanism for the reduction in stroke volume with volume unloading. The opposite response in athletes, who showed a decreased untwisting rate, may contribute to their larger reductions in LV end-diastolic and stroke volumes with volume unloading and their orthostatic intolerance.

Hemodynamic effects of unloading the old heart

1999 ◽  
Vol 277 (5) ◽  
pp. H1863-H1871 ◽  
Author(s):  
Amit Nussbacher ◽  
Gary Gerstenblith ◽  
Frances C. O'connor ◽  
Lewis C. Becker ◽  
David A. Kass ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Stroke Volume ◽  
Left Ventricular ◽  
Stroke Work ◽  
Older Individuals ◽  
Maximum Increase ◽  
End Diastolic Volume ◽  
Exercise Thallium Scintigraphy ◽  
Carotid Arterial ◽  
Ejection Phase

A reduction in upright exercise capacity with aging in healthy individuals is accompanied by acute left ventricular (LV) dilatation and impaired LV ejection. To determine whether acute vasodilator administration would improve LV ejection during exercise, sodium nitroprusside (NP) was administered to 16 healthy subjects, ages 64–84 yr, who had been screened for the absence of coronary heart disease by prior exercise thallium scintigraphy. Infusion of NP (0.3–1.0 μg ⋅ kg−1 ⋅ min−1), titrated to reduce the resting mean arterial pressure 10% (and eliminate the late augmentation of carotid arterial pressure), increased LV ejection fraction (EF) compared with placebo during upright, maximal graded cycle exercise at all work rates and permitted an equivalent stroke volume and stroke work from a smaller end-diastolic volume. The maximum increase in exercise EF in older subjects during NP infusion was equal to that in healthy, younger (22–39 yr) control subjects. The maximum cycle work rate and cardiac index were unchanged compared with placebo. Thus combined preload and afterload reduction with NP in older individuals improves overall LV ejection phase function: exercise LV stroke work is reduced, EF is increased, and stroke volume is maintained in the setting of a reduced ventricular size. These findings suggest that at least some of the age-associated decline in cardiac function during maximal aerobic exercise may be secondary to adverse loading conditions.

scholarly journals Sex and age interaction in fundamental circulatory volumetric variables at peak working capacity

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Candela Diaz-Canestro ◽  
David Montero
Keyword(s):  
Physical Activity ◽  
Older Women ◽  
Vigorous Physical Activity ◽  
Age Groups ◽  
Left Ventricular ◽  
Older Age ◽  
Peak Exercise ◽  
Lower Heart Rate ◽  
End Diastolic Volume ◽  
Cardiac Filling

Abstract Background Whether the fundamental hematological and cardiac variables determining cardiorespiratory fitness and their intrinsic relationships are modulated by major constitutional factors, such as sex and age remains unresolved. Methods Transthoracic echocardiography, central hemodynamics and pulmonary oxygen (O2) uptake were assessed in controlled conditions during submaximal and peak exercise (cycle ergometry) in 85 healthy young (20–44 year) and older (50–77) women and men matched by age-status and moderate-to-vigorous physical activity (MVPA) levels. Main outcomes such as peak left ventricular end-diastolic volume (LVEDVpeak), stroke volume (SVpeak), cardiac output (Qpeak) and O2 uptake (VO2peak), as well as blood volume (BV), BV–LVEDVpeak and LVEDVpeak–SVpeak relationships were determined with established methods. Results All individuals were non-smokers and non-obese, and MVPA levels were similar between sex and age groups (P ≥ 0.140). BV per kg of body weight did not differ between sexes (P ≥ 0.118), but was reduced with older age in men (P = 0.018). Key cardiac parameters normalized by body size (LVEDVpeak, SVpeak, Qpeak) were decreased in women compared with men irrespective of age (P ≤ 0.046). Older age per se curtailed Qpeak (P ≤ 0.022) due to lower heart rate (P < 0.001). In parallel, VO2peak was reduced with older age in both sexes (P < 0.001). The analysis of fundamental circulatory relationships revealed that older women require a higher BV for a given LVEDVpeak than older men (P = 0.024). Conclusions Sex and age interact on the crucial circulatory relationship between total circulating BV and peak cardiac filling, with older women necessitating more BV to fill the exercising heart than age- and physical activity-matched men.

Diastolic ventricular interactions in endurance-trained athletes during orthostatic stress

2007 ◽  
Vol 293 (1) ◽  
pp. H409-H415 ◽  
Author(s):  
Ben T. A. Esch ◽  
Jessica M. Scott ◽  
Mark J. Haykowsky ◽  
Don C. McKenzie ◽  
Darren E. R. Warburton
Keyword(s):  
Left Ventricle ◽  
Stroke Volume ◽  
Lower Body Negative Pressure ◽  
Left Ventricular ◽  
Lower Body ◽  
End Diastolic Volume ◽  
Cardiac Responses ◽  
Ventricular Compliance ◽  
Body Positive ◽  
Ventricular Interactions

Enhanced left-ventricular (LV) compliance is a common adaptation to endurance training. This adaptation may have differential effects under conditions of altered venous return. The purpose of this investigation was to assess the effect of cardiac (un)loading on right ventricular (RV) cavity dimensions and LV volumes in endurance-trained athletes and normally active males. Eight endurance-trained (Vo2max, 65.4 ± 5.7 ml·kg−1·min−1) and eight normally active (Vo2max, 45.1 ± 6.0 ml·kg−1·min−1) males underwent assessments of the following: 1) Vo2max, 2) orthostatic tolerance, and 3) cardiac responses to lower-body positive (0–60 mmHg) and negative (0 to −80 mmHg) pressures with echocardiography. In response to negative pressures, echocardiographic analysis revealed a similar decrease in RV end-diastolic cavity area in both groups (e.g., at −80 mmHg: normals, 21.4%; athletes, 20.8%) but a greater decrease in LV end-diastolic volume in endurance-trained athletes (e.g., at −80 mmHg: normals, 32.3%; athletes, 44.4%; P < 0.05). Endurance-trained athletes also had significantly greater decreases in LV stroke volume during lower-body negative pressure. During positive pressures, endurance-trained athletes showed larger increases in LV end-diastolic volume (e.g., at +60 mmHg; normals, 14.1%; athletes, 26.8%) and LV stroke volume, despite similar responses in RV end-diastolic cavity area (e.g., at +60 mmHg: normals, 18.2%; athletes, 24.2%; P < 0.05). This investigation revealed that in response to cardiac (un)loading similar changes in RV cavity area occur in endurance-trained and normally active individuals despite a differential response in the left ventricle. These differences may be the result of alterations in RV influence on the left ventricle and/or intrinsic ventricular compliance.

Sex differences in cardiorespiratory fitness are explained by blood volume and oxygen carrying capacity

2021 ◽  
Author(s):  
Candela Diaz-Canestro ◽  
Brandon Pentz ◽  
Arshia Sehgal ◽  
David Montero
Keyword(s):  
Sex Differences ◽  
Blood Volume ◽  
Cardiorespiratory Fitness ◽  
Carrying Capacity ◽  
Left Ventricular ◽  
Adult Women ◽  
Activity Levels ◽  
O2 Uptake ◽  
Mature Adult ◽  
Adult Lifespan

Abstract Aims  Intrinsic sex differences in fundamental blood attributes have long been hypothesized to contribute to the gap in cardiorespiratory fitness between men and women. This study experimentally assessed the role of blood volume and oxygen (O2) carrying capacity on sex differences in cardiac function and aerobic power. Methods and results  Healthy women and men (n = 60) throughout the mature adult lifespan (42–88 yr) were matched by age and physical activity levels. Transthoracic echocardiography, central blood pressure, and O2 uptake were assessed throughout incremental exercise (cycle ergometry). Main outcomes such as left ventricular end-diastolic volume (LVEDV), stroke volume (SV), cardiac output (Q), and peak O2 uptake (VO2peak), as well as blood volume (BV) were determined with established methods. Measurements were repeated in men following blood withdrawal and O2 carrying capacity reduction matching women’s levels. Prior to blood normalization, BV and O2 carrying capacity were markedly reduced in women compared with men (P &lt; 0.001). Blood normalization resulted in a precise match of BV (82.36 ± 9.83 vs. 82.34 ± 7.70 ml·kg−1, P = 0.993) and O2 carrying capacity (12.0 ± 0.6 vs. 12.0 ± 0.7 g·dl−1, P = 0.562) between women and men. Body size-adjusted cardiac filling and output (LVEDV, SV, Q) during exercise as well as VO2peak (30.8 ± 7.5 vs. 35.6 ± 8.7 ml·min−1·kg−1, P &lt; 0.001) were lower in women compared with men prior to blood normalization. VO2peak did not differ between women and men after blood normalization (30.8 ± 7.5 vs. 29.7 ± 7.4 ml·min−1·kg−1, P = 0.551). Conclusions  Sex differences in cardiorespiratory fitness are abolished when blood attributes determining O2 delivery are experimentally matched between adult women and men.

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