Clinical Physiology and Functional Imaging最新文献

Near-infrared spectroscopy (NIRS) is used to measure tissue concentrations of oxyhemoglobin (O₂Hb) and deoxyhemoglobin (HHb). In the context of exercise, NIRS confers a higher signal-to-noise ratio than other neuroimaging techniques. However, part of the signal may be influenced by thermoregulatory hyperemia in the superficial cutaneous capillaries of the forehead. The degree to which NIRS signals during exercise reflect cerebral or extracerebral hemodynamic changes is a continuing source of controversy. However, the influence of skin blood flow may be attenuated depending on the NIRS technique (e.g., frequency domain machines with maximal optode separation distances >3.5 cm). The purpose of this study was to compare the changes in forehead skin blood flow and cerebral hemoglobin concentration during incremental exercise versus direct vasodilation of the forehead skin induced by gradual local heating. Thirty participants (12 females, 18 males; age: 20.8 ± 3.2 years; body mass index: 23.8 ± 3.7 kg·m⁻²) participated in the study. Forehead skin blood flow was quantified laser Doppler flux and absolute concentrations of cerebral O₂Hb and HHb were measured by NIRS. Local heating significantly increased the Doppler flux signal across time and these changes were significantly correlated with skin temperature. During incremental exercise, skin temperature, Doppler flux, O₂Hb and HHb increased however, the only significant change that was consistently correlated with Doppler flux was skin temperature. Therefore, a significant change in forehead skin blood flow may not significantly the NIRS hemoglobin data, depending on the type of NIRS device used.

The purpose of this study was to examine the agreement between body fat percentage (%Fat) estimates derived from a standardized ultrasound protocol (%Fat_IASMS), a commonly used skinfold (SKF)-site-based ultrasound protocol (%Fat_JP), and a criterion four-compartment (4C) model (%Fat_4C). For the ultrasound protocols, all measurement sites were marked, measured and analyzed by the same evaluator. Subcutaneous adipose tissue (SAT) thickness was measured manually at the region where the muscle fascia was parallel to the skin and the average value per measurement site was used to calculate body density and subsequently %Fat. A repeated-measures analysis of variance with a priori planned contrasts was used to compare %Fat values between the 4C criterion and both ultrasound methods. Small nonsignificant mean differences were observed between %Fat_IASMS (18.82 ± 14.21%Fat, effect size [ES] = 0.25, p = 0.178), %Fat_JP (18.23 ± 13.32%Fat, ES = 0.32, p = 0.050) and the %Fat_4C criterion (21.70 ± 7.57%Fat); however, %Fat_IASMS did not yield a smaller mean difference than the %Fat_JP (p = 0.287). Additionally, %Fat_IASMS (r = 0.90, p < 0.001, standard error of the estimate [SEE] = 3.29%) and %Fat_JP (r = 0.88, p < 0.001, SEE = 3.60%) were strongly correlated with the 4C criterion, however, %Fat_IASMS did not yield better agreement than %Fat_JP (p = 0.257). Despite slightly underestimating %Fat, both ultrasound techniques demonstrated Good—Very Good agreement with the 4C criterion, with comparable mean differences, correlations, and SEE. The International Association of Sciences in Medicine and Sports (IASMS) standardized protocol using manual calculations of SAT was comparable to the SKF-site-based ultrasound protocol when compared to the 4C criterion. These results indicate that the IASMS (with manually measured SAT) and SKF-site-based ultrasound protocols may be of practical use to clinicians.

Ultrasound has been demonstrated to be a highly accurate and reliable tool for measuring subcutaneous adipose tissue thickness and is robust against changes in hydration status or acute food or fluid intake. However, the effect of prior acute exercise is unexamined. This study examined the impact of an acute endurance exercise and resistance exercise session on standardised brightness-mode ultrasound measurements of subcutaneous adipose tissue thickness compared to skinfolds and dual-energy X-ray absorptiometry body composition estimates. In a randomised cross-over design, 30 active adults (24.2 ± 4.9 years) undertook physique assessment via standardised brightness-mode ultrasound, skinfolds and dual-energy X-ray absorptiometry before, immediately and 45 min after an acute endurance or resistance exercise session. The mean sum of eight subcutaneous adipose tissue thickness measured via standardised brightness-mode ultrasound increased (0.6 mm, p = 0.04) immediately postendurance exercise but was not meaningful when evaluated against the technical error of measurement of the investigator. A significant (p = 0.01) but not meaningful decrease in the sum of eight skinfolds occurred immediately (−1.1 ± 0.4 mm) and 45 min (−1.3 ± 0.4 mm) postresistance exercise. Comparatively, endurance exercise elicited a meaningful decrease of total mass (460 ± 30 g) and trunk lean mass (680 ± 90 g) dual-energy X-ray absorptiometry estimates. Findings from this study indicate standardised client presentation may be unnecessary when employing either standardised brightness-mode ultrasound or skinfolds for body composition assessment unlike dual-energy X-ray absorptiometry.

The pupillary light reflex (PLR) is a method for measuring dynamic responses within the autonomic nervous system, and would have potential value as a point-of-care test in a psychiatry clinic if reproducible results could be obtained in a short period of time. We collected PLR from adult community volunteers and depressed outpatients with the purpose of demonstrating (1) that valid data could be obtained >90% of the time from both the community volunteers and the patients, and (2) that reproducible results could be obtained with repeated measurement over short periods of time. Valid data were captured for 90.3% of 76 participants, allowing for two attempts of the PLR per participant. Success rates were similar for depressed patients and community volunteers. Eighteen of these 76 participants provided repeated paired measurements after 5 and 10 min of dark adaptation, producing high correlations for maximum constriction velocity (MCV) between assay 1 and 2 (Pearson's r = 0.71, p < 0.001), but there was a significant 8% increase in velocity for MCV between assay 1 and 2 (∆ = 0.34 ± 0.59 mm/s, p < 0.05). In contrast, PLR measurements were stable when tested in a separate cohort of 21 additional participants at 10 and 15 min of dark adaptation with an MCV Pearson's correlation of r = 0.84, p < 0.001, with a nonsignificant 1% difference between the two time points. These findings indicate an acceptable rate of collecting valid and reproducible PLR data when contrasting two measurements of PLR after 10 or 15 min of dark adaptation in depressed and suicidal patients.

Trunk muscles may be an overlooked region of deficits following lower-limb amputation (LLA). This study sought to determine the extent that trunk muscle deficits are associated with physical function following amputation. Sedentary adults with a unilateral transtibial- (n = 25) or transfemoral-level (n = 14) amputation were recruited for this cross-sectional research study. Participants underwent a clinical examination that included ultrasound imaging of the lumbar multifidi muscles, the modified Biering-Sorensen Endurance Test (mBSET), and performance-based measures, that is, the Timed Up and Go (TUG), Berg Balance Scale (BBS), and 10-m Walk Test (10mWT). Associations between trunk muscle metrics and performance were explored with regression modeling, while considering covariates known to impact performance postamputation (p ≤ 0.100). Average ultrasound-obtained, lumbar multifidi activity was 14% and 16% for transfemoral- and transtibial-level amputations, respectively, while extensor endurance was 37.34 and 12.61 s, respectively. For TUG, nonamputated-side multifidi activity and an interaction term (level x non-amputated-side multifidi activity) explained 9.4% and 6.2% of the total variance, respectively. For 10mWT, beyond covariates, non-amputated-side multifidi activity and the interaction term explained 6.1% and 5.8% of the total variance, respectively. For TUG, extensor endurance and an interaction term (level x mBSET) explained 11.9% and 8.3% of the total variance beyond covariates; for BBS and 10mWT, extensor endurance explained 11.2% and 17.2% of the total variance, respectively. Findings highlight deficits in lumbar multifidi activity and extensor muscle endurance among sedentary adults with a LLA; reduced muscle activity and endurance may be important factors to target during rehabilitation to enhance mobility-related outcomes.

Hyperthermia increases intravascular adenosine triphosphate (ATP) and is associated with greater hyperthermia-induced cutaneous vasodilation. Hyperthermia may also increase skin interstitial fluid ATP thereby activating cutaneous vascular smooth muscle cells and sweat glands. We evaluated the hypothesis that whole-body heating would increase skin interstitial fluid ATP, and this response would be associated with an increase in cutaneous vasodilation and sweating. Nineteen (8 females) young adults underwent whole-body heating using a water-perfusion suit to increase core temperature by ~1°C during which time cutaneous vascular conductance (CVC, ratio of laser-Doppler blood flow to mean arterial pressure) and sweat rate (ventilated capsule technique) were measured at four forearm skin sites to minimize between-site variations. Dialysate from the skin sites were collected via intradermal microdialysis. Heating increased serum ATP, CVC, and sweat rate (all p ≤ 0.031). However, heating did not modulate dialysate ATP (median, baseline vs. end-heating: 2.38 vs. 2.70 nmol/ml) (p = 0.068), though the effect size was moderate (Cohen's d = 0.566). While the heating-induced increase in CVC was not correlated with changes in serum ATP (r = 0.439, p = 0.060), we observed a negative correlation (r_s = −0.555, p = 0.017) between dialysate ATP and CVC. We did not observe a significant correlation between the heating-induced sweating and serum, dialysate, or sweat ATP (r_s = 0.091 to −0.322, all p ≥ 0.222). Altogether, we showed that passive heating increases ATP in blood and possibly skin interstitial fluid, with the latter potentially blunting cutaneous vasodilation. However, ATP does not appear to modulate sweating.