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Summary: Sleep‐disordered breathing is highly prevalent in individuals with high‐level spinal cord injury. In addition, chest mechanics are known to be altered, leading to paradoxical breathing. Here we investigated the interaction between paradoxical breathing and sleep quality in these patients, and its association with measurements of respiratory function, hypercapnic ventilatory response and peak exercise ventilation. Home‐based polysomnography was performed in 13 patients with spinal cord injury (C4 to T4) untreated for sleep‐disordered breathing. We defined paradoxical breathing as counterphase between thoracic and abdominal movements during slow‐wave and rapid eye movement sleep. Sleep quality, pulmonary function, hypercapnic ventilatory responses and peak exercise ventilation were compared between those with and without paradoxical breathing. Half of individuals presented with nocturnal paradoxical breathing. Despite similar age, body mass index, injury level, time since injury, and respiratory function, those with paradoxical breathing had higher apnea–hypopnea index (13 ± 8 versus 5 ± 3 events per hr) and average sleep heart rate (67 ± 12 versus 54 ± 4 bpm; p < 0.05). Moreover, paradoxical breathing was associated with lower hypercapnic ventilatory response (slope: 0.35 ± 0.17 versus 0.96 ± 0.38) and lower peak exercise ventilation (33 ± 4 versus 48 ± 12 L min−1; p < 0.05). Nocturnal respiratory muscle desynchronization could play a role in the pathophysiology of sleep apnea, and could relate to low ventilatory responses to both hypercapnia and exercise in high‐level spinal cord injury. Polysomnography may be an important diagnostic tool for these patients for whom therapeutic approaches should be considered to treat this abnormality. [ABSTRACT FROM AUTHOR]

Objective: Regulation of blood flow to bone is critical but poorly understood, particularly in humans. This study aims to determine whether nitric oxide (NO), a major regulator of vascular tone to other tissues, contributes also to the regulation of blood flow to bone. Methods: In young healthy adults (n = 16, 8F, 8M), we characterized NO‐mediated vasodilation in the tibia in response to sublingual nitroglycerin and contrasted it to lower leg. Blood flow responses were assessed in supine individuals by continuously measuring tibial total hemoglobin (tHb) via near‐infrared spectroscopy and lower leg blood flow (LBF) as popliteal flow velocity via Doppler ultrasound in the same leg. Results: LBF increased by Δ9.73 ± 0.66 cm/s and peaked 4.4 min after NO administration and declined slowly but remained elevated (Δ3.63 ± 0.60 cm/s) at 10 min. In contrast, time to peak response was longer and smaller in magnitude in the tibia as tHb increased Δ2.08 ± 0.22 μM and peaked 5.3 min after NO administration and declined quickly but remained elevated (Δ0.87±0.22 μM) at 10 min (p =.01). Conclusions: In young adults, the tibial vasculature demonstrates robust NO‐mediated vasodilation, but tHb is delayed and diminishes faster compared to LBF, predominately reflective of skeletal muscle responses. Thus, NO‐mediated vasodilation in bone may be characteristically different from other vascular beds. [ABSTRACT FROM AUTHOR]

To investigate the effects of 2 modes of exercise training, upper-body alone, and the addition of electrical stimulation of the lower body, to attenuate cardiac atrophy and loss of function in individuals with acute spinal cord injury (SCI). Randomized controlled trial. Rehabilitation Hospital. Volunteers (N=27; 5 women, 22 men) who were <24 months post SCI. Volunteers completed either 6 months of no structured exercise (Control), arm rowing (AO), or a combination of arm rowing with electrical stimulation of lower body paralyzed muscle (functional electrical stimulation [FES] rowing). Transthoracic echocardiography was performed on each subject prior to and 6 months after the intervention. The relations between time since injury and exercise type to cardiac structure and function were assessed via 2-way repeated-measures analysis of variance and with multilevel linear regression. Time since injury was significantly associated with a continuous decline in cardiac structure and systolic function, specifically, a reduction in left ventricular mass (0.197 g/month; P =.049), internal diameter during systole (0.255 mm/month; P <.001), and diastole (0.217 mm/month; P =.019), as well as cardiac output (0.048 L/month, P =.019), and left ventricular percent shortening (0.256 %/month; P =.027). These associations were not differentially affected by exercise (Control vs AO vs FES, P >.05). These results indicate that within the subacute phase of recovery from SCI there is a linear loss of left ventricular cardiac structure and systolic function that is not attenuated by current rehabilitative aerobic exercise practices. Reductions in cardiac structure and function may increase the risk of cardiovascular disease in individuals with SCI and warrants further interventions to prevent cardiac decline. [ABSTRACT FROM AUTHOR]

Aerobic exercise induces mast cell degranulation and increases histamine formation by histidine decarboxylase, resulting in an ~150% increase in intramuscular histamine. The purpose of this study was to determine if the increase in skeletal muscle temperature associated with exercise is sufficient to explain this histamine response. Specifically, we hypothesized that local passive heating that mimics the magnitude and time course of changes in skeletal muscle temperature observed during exercise would result in increased intramuscular histamine concentrations comparable to exercising values. Seven subjects participated in the main study in which pulsed short-wave diathermy was used to passively raise the temperature of the vastus lateralis over 60 min. Heating increased intramuscular temperature from 32.6°C [95% confidence interval (CI) 32.0°C to 33.2°C] to 38.9°C (38.7°C to 39.2°C) (P < 0.05) and increased intramuscular histamine concentration from 2.14 ng/mL (1.92 to 2.36 ng/mL) to 2.97 ng/mL (2.57 to 3.36 ng/mL) (P < 0.05), an increase of 41%. In a follow-up in vitro experiment using human-derived cultured mast cells, heating to comparable temperatures did not activate mast cell degranulation. Therefore, it appears that exercise-associated changes in skeletal muscle temperature are sufficient to generate elevations in intramuscular histamine concentration. However, this thermal effect is most likely due to changes in de novo histamine formation via histidine decarboxylase and not due to degranulation of mast cells. In conclusion, physiologically relevant increases in skeletal muscle temperature explain part, but not all, of the histamine response to aerobic exercise. This thermal effect may be important in generating positive adaptations to exercise training. [ABSTRACT FROM AUTHOR]

Cancer cachexia is a muscle-wasting syndrome that results in physical function impairments and decreased survival. While body weight and muscle mass loss predict survival, the prognostic significance of physical function in this population is unclear. Thus, we evaluated the association between physical function, and other routine measures, and overall survival (OS) in cancer patients attending a cachexia support service. Physical function was clinically-assessed using the 30 s sit-to-stand test and handgrip strength. Six-month weight loss, the Patient-Generated Subjective Global Assessment (PG-SGA) total score, C-reactive protein (CRP), albumin, and quality of life were also evaluated. Records from 203 patients (age: 68.6 ± 11.6 years) were included. Handgrip strength did not predict OS. Sit-to-stand repetitions predicted OS in the single variable, but not the multivariable analysis. Multivariable results suggested higher PG-SGA total scores (HR: 1.04, 95% CI: 1.01–1.07), six-month weight loss (HR: 1.02, 95% CI: 1.004–1.04), and elevated CRP (HR: 1.004, 95% CI: 1.0004–1.01) predicted shorter OS. Higher albumin predicted longer OS (HR: 0.93, 95% CI: 0.90–0.97). Six-month weight loss, the PG-SGA total score, CRP, and albumin independently predicted survival, while physical function did not. Functional impairments remain a hallmark of cancer cachexia and the benefit of their routine assessment warrants further exploration, especially in relation to patient quality of life. [ABSTRACT FROM AUTHOR]