Do females and males exhibit a similar sarcopenic response as a consequence of normoxic and hypoxic bed rest?

The effect of implementation of pain neuroscience education and rehabilitation exercise on post-operative pain and recovery after laparoscopic colorectal surgery: a prospective randomized controlled trial

PURPOSES

To optimize the efficacy of analgesia and post-operative recovery for patients undergoing laparoscopic colorectal surgery by integrating a composite psycho-somatic analgesia algorithm involving peri-operative rehabilitation exercise and pain neuroscience education into multi-modal analgesia.

METHODS

A prospective randomized controlled trial was conducted to compare conventional peri-operative analgesia (group CA) and the addition of rehabilitation exercise and pain neuroscience education into it (group REPNE) for patients undergoing laparoscopic colorectal surgery. Acute and chronic post-operative pain, characteristics of pain (pain catastrophizing, sensitization, and trends of neuropathic transformation), and quality of post-operative recovery calibrated with EuroQol Five Dimensions Questionnaire (EQ-5D-5L) were investigated and compared between two groups.

RESULTS

A total of 175 patients consented to participate in this study. Compared with those receiving conventional analgesia (group CA, N = 89), patients in group REPNE (N = 86) reported reduced intensity of pain 24 h after surgery, less risk of pain catastrophizing and sensitization, and better quality of life during hospitalization recovery till 1 month after surgery (p < 0.05). No statistical difference was found for neuropathic transformation of post-operative pain or for the incidence of chronic post-operative pain (p > 0.05).

CONCLUSIONS

The addition of peri-operative rehabilitation exercise and pain neuroscience education into multi-modal analgesia provided better analgesic effect compared with routine practice for patients receiving laparoscopic colorectal surgery and also facilitated better post-operative recovery. This composite psycho-somatic algorithm for peri-operative analgesia merits further application in clinical practice.

Case Report: Muscle Wasting during Severe Sustained Hypoxia in Two Professional Mountaineers

PURPOSE

Chronic exposure to hypoxia can induce muscle wasting in unaccustomed individuals. Detailed assessment of the effects of hypoxia on muscle tissue adaptation in elite mountaineers has not been performed. This study aims to assess muscle volume after exposure to normobaric hypoxia.

METHODS

Two professional mountaineers (A and B) participated in a 35-d intervention of graded normobaric hypoxia with the aim of 14 d exposure to 8% oxygen corresponding to 7112-m altitude. Volume of the shank, thigh, and hip muscles was assessed by magnetic resonance imaging pre- and postintervention. Dietary intake and physical activity were monitored throughout the study from food images and accelerometry analysis, together with blood analysis and anthropometric measurements.

RESULTS

Hypoxia reduced total leg muscle volume by 3.3% ± 6.0% in A and by 9.4% ± 7.3% in B. A lost 288 g and B 642 g of muscle mass, whereas dietary intake only declined by ~23% in the last intervention week. Arterial oxygen saturation declined from 95% and 86% to 77% and 72% in A and B, respectively. In hypoxia, participants could not maintain their physical activity levels. Notably, muscle loss varied substantially across muscle groups amounting to 5.4% ± 3.0%, 8.3% ± 5.2%, and 4.1% ± 8.6% for hip, thigh, and shank muscles, respectively.

CONCLUSIONS

Our results indicate that hypoxia and resultant reductions in physical activity and caloric intake lead to substantial loss of muscle mass that was accentuated in proximal muscle as opposed to distal muscles. Surprisingly, thigh muscle wasting during this intervention is comparable with that observed during strict 56-d bed rest.

Adult Female Sleep During Hypoxic Bed Rest

Purpose

Hypobaric hypoxic habitats are currently being touted as a potential solution to minimise decompression procedures in preparation for extra vehicular activities during future space missions. Since astronauts will live in hypoxic environments for the duration of such missions, the present study sought to elucidate the separate and combined effects of inactivity [simulated with the experimental bed rest (BR) model] and hypoxia on sleep characteristics in women.

Methods

Twelve women (Age = 27 ± 3 year) took part in three 10-day interventions, in a repeated measures cross-over counterbalanced design: (1) normobaric normoxic BR (NBR), (2) normobaric hypoxic BR (HBR; simulated altitude of 4,000 m), and (3) normobaric hypoxic ambulatory (HAMB; 4,000 m) confinement, during which sleep was assessed on night 1 and night 10 with polysomnography. In addition, one baseline sleep assessment was performed. This baseline assessment, although lacking a confinement aspect, was included statistically as a fourth comparison (i.e., pseudo normobaric normoxic ambulatory; pNAMB) in the present study.

Results

Hypoxia decreased sleep efficiency (p = 0.019), increased N1% sleep (p = 0.030), decreased N3 sleep duration (p = 0.003), and increased apnea hypopnea index (p < 0.001). BR impaired sleep maintenance, efficiency, and architecture [e.g., N2% sleep increased (p = 0.033)]. Specifically, for N3% sleep, the effects of partial pressure of oxygen and activity interacted. Hypoxia decreased N3% sleep both when active (pNAMB vs HAMB; p < 0.001) and inactive (NBR vs HBR; p = 0.021), however, this decrease was attenuated in the inactive state (–3.8%) compared to the active state (–10.2%).

Conclusion

A 10-day exposure to hypoxia and BR negatively impacted sleep on multiple levels as in macrostructure, microstructure and respiratory functioning. Interestingly, hypoxia appeared to have less adverse effects on sleep macrostructure while the participants were inactive (bed ridden) compared to when ambulatory. Data were missing to some extent (i.e., 20.8%). Therefore, multiple imputation was used, and our results should be considered as exploratory.

Heterogeneity of Hematological Response to Hypoxia and Short-Term or Medium-Term Bed Rest

Hematological changes are commonly observed following prolonged exposure to hypoxia and bed rest. Typically, such responses have been reported as means and standard deviations, however, investigation into the responses of individuals is insufficient. Therefore, the present study retrospectively assessed individual variation in the hematological responses to severe inactivity (bed rest) and hypoxia. The data were derived from three-bed rest projects: two 10-d (LunHab project: 8 males; FemHab project: 12 females), and one 21-d (PlanHab project: 11 males). Each project comprised a normoxic bed rest (NBR; P_IO₂=133mmHg) and hypoxic bed rest (HBR; P_IO₂=91mmHg) intervention, where the subjects were confined in the Planica facility (Rateče, Slovenia). During the HBR intervention, subjects were exposed to normobaric hypoxia equivalent to an altitude of 4,000m. NBR and HBR interventions were conducted in a random order and separated by a washout period. Blood was drawn prior to (Pre), during, and post bed rest (R1, R2, R4) to analyze the individual variation in the responses of red blood cells (RBC), erythropoietin (EPO), and reticulocytes (Rct) to bed rest and hypoxia. No significant differences were found in the mean ∆(Pre-Post) values of EPO across projects (LunHab, FemHab, and PlanHab; p>0.05), however, female EPO responses to NBR (Range - 17.39, IQR – 12.97 mIU^.ml⁻¹) and HBR (Range – 49.00, IQR – 10.91 mIU^.ml⁻¹) were larger than males (LunHab NBR Range – 4.60, IQR – 2.03; HBR Range – 7.10, IQR – 2.78; PlanHab NBR Range – 7.23, IQR – 1.37; HBR Range – 9.72, IQR – 4.91 mIU^.ml⁻¹). Bed rest duration had no impact on the heterogeneity of EPO, Rct, and RBC responses (10-d v 21-d). The resultant hematological changes that occur during NBR and HBR are not proportional to the acute EPO response. The following cascade of hematological responses to NBR and HBR suggests that the source of variability in the present data is due to mechanisms related to hypoxia as opposed to inactivity alone. Studies investigating hematological changes should structure their study design to explore these mechanistic responses and elucidate the discord between the EPO response and hematological cascade to fully assess heterogeneity.

Heterogeneity of human adaptations to bed rest and hypoxia: a retrospective analysis within the skeletal muscle oxidative function

This retrospective study was designed to analyze the interindividual variability in the responses of different variables characterizing the skeletal muscle oxidative function to normoxic (N-BR) and hypoxic (H-BR) bed rests and to a hypoxic ambulatory confinement (H-AMB) of 10 and 21 days. We also assessed whether and how the addition of hypoxia to bed rest might influence the heterogeneity of the responses. In vivo measurements of O₂ uptake and muscle fractional O₂ extraction were carried out during an incremental one-leg knee-extension exercise. Mitochondrial respiration was assessed in permeabilized muscle fibers. A total of 17 subjects were included in this analysis. This analysis revealed a similar variability among subjects in the alterations induced by N-BR and H-BR both in peak O₂ uptake (SD: 4.1% and 3.3% after 10 days; 4.5% and 8.1% after 21 days, respectively) and peak muscle fractional O₂ extraction (SD: 5.9% and 7.3% after 10 days; 6.5% and 7.3% after 21 days), independently from the duration of the exposure. The individual changes measured in these variables were significantly related (r = 0.66, P = 0.004 after N-BR; r = 0.61, P = 0.009 after H-BR). Mitochondrial respiration showed a large variability of response after both N-BR (SD: 25.0% and 15.7% after 10 and 21 days) and H-BR (SD: 13.0% and 19.8% after 10 and 21 days); no correlation was found between N-BR and H-BR changes. When added to bed rest, hypoxia altered the individual adaptations within the mitochondria but not those intrinsic to the muscle oxidative function in vivo, both after the short- and medium-term exposures.

Substantial and Reproducible Individual Variability in Skeletal Muscle Outcomes in the Cross-Over Designed Planica Bed Rest Program

To evaluate the individual responses in skeletal muscle outcomes following bed rest, data from three studies (21-day PlanHab; 10-day FemHab and LunHab) were combined. Subjects (n = 35) participated in three cross-over campaigns within each study: normoxic (NBR) and hypoxic bed rest (HBR), and hypoxic ambulation (HAMB; used as control). Individual variability (SDIR) was investigated as √(SDExp 2 -SDCon 2 ), where SDExp and SDCon are the standard deviations of the change score (i.e., post - pre) in the experimental (NBR and HBR) and the control (HAMB) groups, respectively. Repeatability and moderators of the individual variability were explored. Significant SDIR was detected for knee extension torque, and thigh and calf muscle area, which translated into an individual response ranging from 3 to -17% for knee extension torque, -2 to -12% for calf muscle area, and -1 to -8% for thigh muscle area. Strong correlations were found for changes in NBR vs. HBR (i.e., repeatability) in thigh and calf muscle area (r = 0.65-0.75, P < 0.0001). Change-scores in knee extension torque, and thigh and calf muscle area strongly correlated with baseline values (P < 0.001; r between -0.5 and -0.9). Orthogonal partial least squares regression analysis explored if changes in the investigated variables could predict calf muscle area alterations. This analysis indicated that 43% of the variance in calf muscle area could be attributed to changes in all of the other variables. This is the first study using a validated methodology to report clinically relevant individual variability after bed rest in knee extension torque, calf muscle area, and (to a lower extent) thigh muscle area. Baseline values emerged as a moderator of the individual response, and a global bed rest signature served as a moderately strong predictor of the individual variation in calf muscle area alterations.