Neural respiratory drive assessment and its correlation with inspiratory muscle strength in patients undergoing open-heart surgery: A cross-sectional study.

BACKGROUND AND PURPOSE: Pulmonary dysfunction and inspiratory muscle weakness are frequently observed after cardiac surgery. Understanding the load on and capacity of respiratory muscles can provide valuable insights into the overall respiratory mechanics and neural regulation of breathing. This study aimed to assess the extent of neural respiratory drive (NRD) and determine whether admission-to-discharge differences in NRD were associated with inspiratory muscle strength changes among patients undergoing open-heart surgery. METHODS: This cross-sectional study was conducted on 45 patients scheduled for coronary artery bypass graft or heart valve surgery. NRD was measured using a surface parasternal intercostal electromyogram during resting breathing (sEMGpara tidal) and maximal inspiratory effort (sEMGpara max). Maximal inspiratory pressure (MIP) was used to determine inspiratory muscle strength. Evaluations were performed on the day of admission and discharge. RESULTS: There was a significant increase in sEMGpara tidal (6.9 ± 3.6 µV, p < 0.001), sEMGpara %max (13.7 ± 11.2%, p = 0.008), and neural respiratory drive index (NRDI, the product of EMGpara %max and respiratory rate) (337.7 ± 286.8%.breaths/min, p < 0.001), while sEMGpara max (-43.6 ± 20.4 µV, p < 0.01) and MIP (-24.4 ± 10.7, p < 0.001) significantly decreased during the discharge period. Differences in sEMGpara tidal (r = -0.369, p = 0.045), sEMGpara %max (r = -0.646, p = 0.001), and NRDI (r = -0.639, p = 0.001) were significantly associated with a reduction in MIP. DISCUSSION: The findings indicate that NRD increases after open-heart surgery, which corresponds to a decrease in inspiratory muscle strength.

Beneficial Effect of Water-Based Exercise Training on Exercise Capacity in COPD Patients-a Pilot Study.

Background: Chronic obstructive pulmonary disease (COPD) is a common, preventable, and treatable condition, characterized by persistent airflow limitation. Exercise training is a core component of pulmonary rehabilitation in people with COPD. Water-based exercise has been studied, but it remains unclear whether water-based exercise program leads to the improvement in respiratory function, muscle strength, balance ability, and exercise capacity. We aim to study the effect of an 8-week water-based exercise program on respiratory function, muscle strength, balance ability, and exercise capacity in people with COPD. Methods: Fourteen stable COPD participants (FEV1 56.8 ± 24.6%pred) were recruited and randomized into a water-based exercise or a land-based exercise group. Both groups were trained for 8 weeks, two sessions per week. Pulmonary function, respiratory muscle strength, peripheral muscle strength, balance ability, exercise capacity [6-min walking test (6MWT), incremental shuttle walk test (ISWT), and endurance shuttle walk test (ESWT)] were assessed at baseline and at the end of the program. ANCOVA was used to conduct between-group comparisons of outcomes after adjusting for pre-intervention values. Results: Baseline characteristics of participants were not significantly different between the two groups (p ≥ 0.05). After the 8-week training program, participants in the intervention group achieved larger gains in ESWT (Δ663.4 ± 279.5 vs. Δ45.4 ± 93.2 s, p = 0.001). In addition, maximal inspiratory pressure (MIP) was significantly increased more in the intervention group (Δ11.1 ± 7.8 vs. Δ1.1 ± 5.7 cmH2O, p = 0.026). However, no significant differences in pulmonary function, peripheral muscle strength, balance ability variables, 6MWD (p = 0.248), and ISWT (p = 0.506) were observed between the two groups. Conclusions: The water-based exercise program could be recommended to the COPD rehabilitation program for improving the endurance exercise capacity and inspiratory muscle strength. Clinical Trial Registration: www.thaiclinicaltrials.org, identifier: TCTR20210125005.

Recovery from Strenuous Downhill Running in Young and Older Physically Active Adults.

There is a well-conceived notion that rate of recovery from strenuous exercise gets slower with age. However, it is unclear whether older adults who exercise habitually demonstrate slower rates of recovery. We determined whether older adults who are physically active demonstrate slower rates of recovery from unaccustomed strenuous exercise compared with younger peers. Healthy young sedentary (n=10, 28±2 years), young endurance-trained (n=15, 27±2 years), and older endurance-trained (n=14, 58±2 years) men and women were studied. Participants performed 45 min of downhill running at 65% of their maximal oxygen consumption. Visual analog pain scores of muscle groups increased at 24, 48, and 72 h in all three groups (p<0.05), and changes in the muscular pain scale of the legs was smaller in the older trained group than in the young trained group. Maximum isometric strengths at 90° decreased in all groups at 24 h, but the recovery rates were not different at 72 h among the groups. Plasma creatine kinase activity and myoglobin concentration increased at 24 h following downhill running and returned to baseline at 48 h in both the young and older trained groups. The present findings are not consistent with the prevailing notion that older trained adults have a slower rate of recovery from strenuous exercise.

Effects of heated and thermoneutral yoga interventions on arterial stiffness in middle-aged adults.

The study investigated the efficacy of 12 weeks of heated and thermoneutral Bikram yoga in reducing arterial stiffness in middle-aged adults. Fifty-four sedentary adults (ages 40-60 years) completed 12 weeks of yoga at 40.5 °C (n = 21), yoga at 23 °C (n = 14) or time control (n = 19). Brachial-ankle pulse wave velocity (PWV) was not significantly altered by hot or thermoneutral yoga interventions.

Effects of yoga interventions practised in heated and thermoneutral conditions on endothelium-dependent vasodilatation: The Bikram yoga heart study.

NEW FINDINGS: What is the central question of this study? Does the heated practice environment enhance the effects of Bikram yoga on endothelium-dependent vasodilatation in healthy, middle-aged adults? What is the main finding and its importance? The primary finding from this investigation is that the hatha yoga postures in the Bikram yoga series produce similar enhancements in endothelium-dependent vasodilatation in healthy, middle-aged adults regardless of environmental temperature. These findings highlight the efficacy of yoga postures in producing improvements in vascular health and downplay the necessity of the heated practice environment in inducing vascular adaptations. ABSTRACT: We have previously documented improvements in endothelium-dependent vasodilatation with a Bikram (hot) yoga intervention in middle-aged adults. At present, the effect of environmental temperature in hot yoga on endothelial function is unknown. The purpose of this investigation was to determine the effects of Bikram yoga interventions performed in heated or thermoneutral conditions on endothelium-dependent vasodilatation. Fifty-two sedentary but apparently healthy adults aged 40-60 years were randomly assigned to one of three groups: Bikram yoga practised at 40.5°C (n = 19), Bikram yoga practised at 23°C (n = 14) or sedentary time control (n = 19). The yoga interventions consisted of 90 min Bikram yoga classes three times a week for 12 weeks. Endothelium-dependent vasodilatation was measured non-invasively using brachial artery flow-mediated dilatation (FMD). Body fat percentage determined via dual-energy X-ray absorptiometry was significantly lower in the hot yoga group after the intervention than in the thermoneutral yoga and control conditions. Brachial artery FMD increased (P < 0.05) in the thermoneutral yoga group and tended to increase in the hot yoga group (P = 0.056). No changes occurred in the control group. There were no significant differences in FMD change scores between groups. We conclude that Bikram yoga practised in thermoneutral conditions improved endothelium-dependent vasodilatation in healthy, middle-aged adults. These new findings highlight the effectiveness of hatha yoga postures alone, in the absence of a heated practice environment, in improving vascular health and are of clinical significance given the increased propensity for heat intolerance in ageing adults.

Steady State vs. Pulsatile Blood Pressure Component and Regional Cerebral Perfusion.

BACKGROUND: Arterial blood pressure (BP) can be divided into steady state component that is determined by mean arterial pressure and pulsatile component that is explored by pulse pressure (PP). We determined relationships between BP components and regional cerebral perfusion. METHODS: A total of 52 apparently healthy and cognitively normal adults aged 40-60 years were studied. Regional cerebral perfusion was measured using functional magnetic resonance imaging (MRI) arterial spin labeling technique in 10 a priori regions of interest. RESULTS: There were 5 regions with cerebral perfusion values significantly associated with either pulsatile BP component (i.e., hippocampus, posterior insula, and central white matter) or both steady and pulsatile components (i.e., anterior white matter, and occipitoparietal area). After controlling for body mass index, education, age, and sex, associations between pulsatile BP components and regional cerebral perfusion remained significant in 2 regions (i.e., hippocampus and anterior white matter). Multiple linear regression analyses revealed that brachial systolic pressure (ß = -0.35, P = 0.03) and PP (ß = -0.36, P = 0.02) explained 11 and 12% of the variability in hippocampus perfusion, independent of the entered covariates. CONCLUSIONS: The present preliminary study indicated that pulsatile component of BP was more strongly related to regional cerebral perfusion in areas susceptible to cerebrovascular diseases than steady state component.

Associations of resting heart rate with endothelium-dependent vasodilation and shear rate.

Heart rate is an independent risk factor for cardiovascular disease and a hemodynamic factor that can modulate blood flow as it affects the frequency of shear stimuli acting on the arterial wall. However, the association between heart rate and endothelium-dependent vasodilation remains highly controversial. We determined the association between heart rate at rest and endothelium-dependent vasodilation in 98 apparently healthy adults (18-63 years). The mild and positive association between heart rate and flow-mediated dilation (FMD) was no longer significant when age and sex or baseline diameter were controlled for. The path analyses revealed that heart rate was not directly related to FMD but the association was indirectly mediated by shear rate, which was confirmed by a bias-corrected bootstrap 95% CIs (0.0157-0.1056). We concluded that even though heart rate and endothelium-dependent vasodilation were associated with shear rate, there was no independent relation between heart rate and FMD.

Association between cardiovagal baroreflex sensitivity and baseline cerebral perfusion of the hippocampus.

PURPOSE: A failure to control perfusion pressure due to impaired baroreflex sensitivity (BRS) could potentially cause chronic brain hypoperfusion, leading to cognitive dysfunction. The primary aim of this study was to determine whether BRS was associated with regional cerebral blood flow as measured by MRI arterial spin labeling (ASL) technique. METHODS: Baroreflex sensitivity was measured using the Valsalva maneuver technique in 52 middle-aged normotensive adults (49 ± 1 years), and phase IV of the Valsalva maneuver was used for analyses. Cerebral perfusion was measured using the ASL MRI technique in 10 pre-determined brain regions of interest. RESULTS: Hippocampal perfusion was correlated with BRS (R (2) = 0.17, P = 0.01). No association was observed between BRS and cerebral perfusion in the other brain regions of interest. Partial correlational analyses revealed that BRS was an important predictor of hippocampal perfusion, explaining 11 % of the variability independent of other covariates. When participants were divided into tertiles of BRS (11.8 ± 1.9 and 3.5 ± 0.1 ms/mmHg for the highest and lowest tertiles), regional cerebral perfusion of the hippocampus was significantly lower in the lowest BRS tertile than in the highest tertile (39.1 ± 4.3 and 60.5 ± 8.4 ml/100 g/min). CONCLUSIONS: Baroreflex sensitivity in midlife is positively associated with regional cerebral perfusion of the hippocampus, and impaired BRS appears to be related to brain hypoperfusion even in apparently healthy middle-aged adults. Future longitudinal studies based on the present cross-sectional findings may help to further define the relationship between BRS to cognitive dysfunction.

Moderate intensity of regular exercise improves cardiac SR Ca2+ uptake activity in ovariectomized rats.

The impact of regular exercise in protecting cardiac deteriorating results of female sex hormone deprivation was evaluated by measuring changes in intracellular Ca2+ removal activity of sarcoplasmic reticulum (SR) in ovariectomized rats following 9-wk treadmill running exercise at moderate intensity. Despite induction of cardiac hypertrophy in exercised groups of both sham-operated and ovariectomized rats, exercise training had no effect on SR Ca2+ uptake and SR Ca(2+)-ATPase (SERCA) in hormone intact rat heart. However, exercise training normalized the suppressed maximum SR Ca2+ uptake and SERCA activity in ovariectomized rat heart. While exercise training normalized the leftward shift in pCa (-log[Ca2+])-SR Ca2+ uptake relation in ovariectomized rats, no effect was detected in exercised sham-operated rats. Similar phenomena were also observed on SERCA and on phospholamban (PLB) phosphorylation levels; exercise training in ovariectomized rats enhanced SERCA expression to reach the level as that in sham-operated rats, in which there were no differences in SERCA and phospho-PLB levels between sedentary and exercised groups. In addition, the reduction in phospho-Thr(17) PLB in myocardium of ovariectomized rats was abolished by exercise training. These results showed that regular exercise maintains the molecular activation of cardiac SR Ca2+ uptake under normal physiological conditions and is able to induce a protective impact on cardiac SR Ca2+ uptake in ovarian sex hormone-deprived status.