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Introduction This narrative review summarizes current knowledge on the physiology and pathophysiology of expiratory muscle function in ICU patients, as shared by academic professionals from multidisciplinary, multinational backgrounds, who include clinicians, clinical physiologists and basic physiologists. Results The expiratory muscles, which include the abdominal wall muscles and some of the rib cage muscles, are an important component of the respiratory muscle pump and are recruited in the presence of high respiratory load or low inspiratory muscle capacity. Recruitment of the expiratory muscles may have beneficial effects, including reduction in end-expiratory lung volume, reduction in transpulmonary pressure and increased inspiratory muscle capacity. However, severe weakness of the expiratory muscles may develop in ICU patients and is associated with worse outcomes, including difficult ventilator weaning and impaired airway clearance. Several techniques are available to assess expiratory muscle function in the critically ill patient, including gastric pressure and ultrasound. Conclusion The expiratory muscles are the \"neglected component\" of the respiratory muscle pump. Expiratory muscles are frequently recruited in critically ill ventilated patients, but a fundamental understanding of expiratory muscle function is still lacking in these patients.

This randomized controlled trial aimed to compare abdominal muscle thickness between intensive care patients and healthy controls, and to evaluate the impact of IMT on expiratory muscle thickness using ultrasound. In this single-blind randomized controlled trial, 20 post-extubation intensive care patients were randomly assigned to either an a conventional physiotherapy (CP) group or IMT + CP group. Both interventions were applied for five days. An additional 10 healthy individuals served as controls for comparison. Abdominal muscle thicknesses—including external oblique (EOA), internal oblique (IOA), transversus abdominis (TRA), and rectus abdominis (RA)—were measured using ultrasound. Maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) were also recorded. At baseline, healthy controls had significantly higher MIP, MIP% predicted, MEP, MEP% predicted, and RA muscle thickness compared to both patient groups (p < 0.05). Following intervention, both IMT and CP groups showed significant improvements in MIP (p < 0.05), but only the IMT group demonstrated significant increases in MEP, MEP% predicted, IOA, and RA muscle thickness (p < 0.05). The IMT group showed significantly greater improvements in MIP, MEP, IOA, and RA muscle thickness compared to the CP group (p < 0.05). Post-extubation IMT may improve not only inspiratory but also expiratory muscle strength and abdominal wall thickness. These findings suggest that IMT could support weaning processes in intensive care, although larger studies are needed. •Rectus abdominis thickness, MIP, MIP% predicted, MEP and MEP% predicted are higher in the healthy individiuals than in ICU patients•IMT increasesinternal oblique and rectus abdominis thickness in respiratory ICU patients.•IMT improves both MIP,MEPand predict

Cold temperatures (<−15°C) increase exercise‐induced bronchoconstriction (EIB), while hypoxic‐induced hyperventilation exacerbates respiratory muscle fatigue for a given exercising task. This study aimed to determine the individual and combined effects of cold and normobaric hypoxia on the respiratory system responses to high‐intensity exercise. Fourteen trained male runners (V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}{\\mathrm{max}}}$ : 64 ± 5 mL/kg/min) randomly performed an incremental cardiopulmonary exercise test (CPET) to volitional exhaustion under four environmental conditions: normothermic (18°C) normoxia (FIO2 ${{F}_{{\\mathrm{I}}{{{\\mathrm{O}}}_2}}}$ : 20.9%) and hypoxia (FIO2 ${{F}_{{\\mathrm{I}}{{{\\mathrm{O}}}_2}}}$ : 13.5%), and cold (−20°C) normoxia and hypoxia. Ventilatory responses during exercise and lung function (LF), maximal inspiratory (MIP) and expiratory (MEP) pressure measurements before and after exercise were evaluated. Volume of air forcefully exhaled in 1 s (FEV1), FEV1/forced vital capacity (FVC), peak expiratory flow, forced expiratory flow during the mid (25–75%) portion of the FVC, and maximal expiratory flow at 50% of FVC were affected by cold exposure. No significant pre‐ to post‐exercise change in MIP and MEP was found, independent of environmental conditions. Greater LF impairments in cold‐normoxia and coldhypoxia were associated with the lowest peak ventilatory responses during exercise. Cold exposure was found to negatively impact peak ventilatory responses and post‐exercise LF, further highlighting a relationship between EIB presence and the blunted ventilatory response in the cold. Respiratory muscle strength remained unchanged after exercise regardless of the environmental condition, suggesting no detrimental effect of hypoxia on this parameter when intermittent short‐duration high‐intensity exercises are performed. Future studies should investigate the combined cold‐hypoxic effect on longer exercise durations at a sustained high intensity, accounting for differences between normobaric and hypobaric hypoxia exposures. What is the central question of this study? What are the independent and combined effects of cold and normobaric hypoxia on respiratory responses to high‐intensity exercise? What is the main finding and its importance? Cold exposure impaired lung function and peak ventilatory responses during high‐intensity exercise, with greater impairments observed under combined cold‐hypoxia condition. The findings highlight a link between exercise‐induced bronchoconstriction and reduced ventilatory capacity in cold environments. Respiratory muscle strength remained unaffected post‐exercise across all conditions, suggesting no detrimental impact of hypoxia during short‐duration high‐intensity tasks.

Objective This study investigated the influence of Coronavirus Disease 2019 (COVID-19) on lung function in early convalescence phase. Methods A retrospective study of COVID-19 patients at the Fifth Affiliated Hospital of Sun Yat-sen University were conducted, with serial assessments including lung volumes (TLC), spirometry (FVC, FEV1), lung diffusing capacity for carbon monoxide (DLCO),respiratory muscle strength, 6-min walking distance (6MWD) and high resolution CT being collected at 30 days after discharged. Results Fifty-seven patients completed the serial assessments. There were 40 non-severe cases and 17 severe cases. Thirty-one patients (54.3%) had abnormal CT findings. Abnormalities were detected in the pulmonary function tests in 43 (75.4%) of the patients. Six (10.5%), 5(8.7%), 25(43.8%) 7(12.3%), and 30 (52.6%) patients had FVC, FEV1, FEV1/FVC ratio, TLC, and DLCO values less than 80% of predicted values, respectively. 28 (49.1%) and 13 (22.8%) patients had PImax and PEmax values less than 80% of the corresponding predicted values. Compared with non-severe cases, severe patients showed higher incidence of DLCO impairment (75.6%vs42.5%, p  = 0.019), higher lung total severity score (TSS) and R20, and significantly lower percentage of predicted TLC and 6MWD. No significant correlation between TSS and pulmonary function parameters was found during follow-up visit. Conclusion Impaired diffusing-capacity, lower respiratory muscle strength, and lung imaging abnormalities were detected in more than half of the COVID-19 patients in early convalescence phase. Compared with non-severe cases, severe patients had a higher incidence of DLCO impairment and encountered more TLC decrease and 6MWD decline.

Purpose This study aimed to compare the effects of manual lymphatic drainage and bandaging (MLDB) combined with calf muscle exercise training (CMT) and/or inspiratory muscle training (IMT) on edema, muscle strength, functional capacity, functionality, and quality of life (QoL) in patients with secondary lower limb lymphedema (LLL). Method A total of 76 patients (mean age: 47.06 ± 16.16 years; 84.2% female) with LLL were included in the study and randomized into four groups: MLDB alone (Group 1), MLDB + CMT (Group 2), MLDB + IMT (Group 3), and MLDB + CMT + IMT (Group 4). The training programs were administered for 30 min per day, five days per week, over three weeks. Edema was assessed using circumference measurements (CM) and tissue dielectric constant (TDC). Muscle strength was evaluated using maximum inspiratory/expiratory pressure (MIP/MEP) and a dynamometer. Functional capacity was assessed with the 6-Minute Walk Test (6MWT), functionality with the Lower Extremity Functional Scale (LEFS), and QoL with the Lymphedema Quality of Life Scale (LYMQOL). Results In the intra-group analyses, all assessments improved in all groups, except for MIP, MEP, and gastrocnemius muscle strength in Group 1 and MIP in Group 2 (p < 0.05). In the inter-group analyses, Group 3 showed the largest effect sizes (ES) for reductions in TDC (ES: 2.34) and improvements in LYMQOL (ES: 1.74), MEP (ES: 1.46), and LEFS (ES: 1.44) (p < 0.001 for all). Group 4 had the largest ES for increases in MIP (ES: 1.42, p < 0.001). Group 2 showed the largest ES for improvements in gastrocnemius muscle strength (ES: 1.41, p < 0.001). However, there were no significant differences among the groups in CM or 6MWT results (p > 0.05). Conclusion Compared to enhancing leg muscle strength, improving respiratory muscle function in addition to MLDB had a greater impact on reducing edema and enhancing functionality and QoL. Trial Registration Number NCT05609526. Registration Date: 14.11.2022.

Although, pre-operative inspiratory muscle training has been investigated and reported to be an effective strategy to reduce postoperative pulmonary complications, the efficacy of postoperative inspiratory muscle training as well as the proper load, frequency, and duration necessary to reduce the postoperative pulmonary complications has not been fully investigated. This study was designed to investigate the effect of postoperative high-load long-duration inspiratory muscle training on pulmonary function, inspiratory muscle strength, and functional capacity after mitral valve replacement surgeries. Prospective randomized controlled trial. A total of one hundred patients (mean age 38.3±3.29years) underwent mitral valve replacement surgery were randomized into experimental (n = 50) and control (n = 50) groups. The control group received conventional physiotherapy care, while experimental group received conventional care in addition to inspiratory muscle training, with 40% of the baseline maximal inspiratory pressure targeting a load of 80% by the end of the 8 weeks intervention protocol. Inspiratory muscle training started on the patient's first day in the inpatient ward. Lung functions, inspiratory muscle strength, and functional capacity were evaluated using a computer-based spirometry system, maximal inspiratory pressure measurement and 6MWT respectively at 5 time points and a follow-up assessment was performed 6 months after surgery. Repeated measure ANOVA and post-hoc analyses were used (p <0.05). Group-time interactions were detected for all the studied variables (p<0.001). Between-group analysis revealed statistically significant postoperative improvements in all studied variables in the experimental group compared to the control group (p <0.001) with large effect size of η2 ˃0.14. Within-group analysis indicated substantial improvements in lung function, inspiratory pressure and functional capacity in the experimental group (p <0.05) over time, and these improvements were maintained at follow-up. High intensity, long-duration postoperative inspiratory muscle training is highly effective in improving lung function, inspiratory muscle strength, and functional capacity after mitral valve replacement surgeries.

The inspiratory muscles contribute to balance via diaphragmatic contraction and by increasing intra-abdominal pressure. We have shown inspiratory muscle training (IMT) improves dynamic balance significantly with healthy community-dwellers. However, it is not known how the magnitude of balance improvements following IMT compares to that of an established balance program. This study compared the effects of 8-week of IMT for community-dwellers, to 8-week of the Otago exercise program (OEP) for care-residents, on balance and physical performance outcomes. Nineteen healthy community-dwellers (74 ± 4 years) were assigned to self-administered IMT. Eighteen, healthy care-residents (82 ± 4 years) were assigned to instructor-led OEP. The IMT involved 30 breaths twice-daily at ~50% of maximal inspiratory pressure (MIP). The OEP group undertook resistance and mobility exercises for ~60 minutes, twice-weekly. Balance and physical performance were assessed using the mini Balance Evaluation System Test (mini-BEST) and time up and go (TUG). After 8-week, both groups improved balance ability significantly (mini-BEST: IMT by 24 ± 34%; OEP by 34 ± 28%), with no between-group difference. Dynamic balance sub-tasks improved significantly more for the IMT group (P < 0.01), than the OEP group and vice versa for static balance sub-tasks (P = 0.01). The IMT group also improved MIP (by 66 ± 97%), peak inspiratory power (by 31 ± 12%) and TUG (by -11 ± 27%); whereas the OEP did not. IMT and OEP improved balance ability similarly, with IMT eliciting greater improvement in dynamic balance, whilst OEP improved static balance more than IMT. Unlike IMT, the OEP did not provide additional benefits in inspiratory muscle function and TUG performance. Our findings suggest that IMT offers a novel method of improving dynamic balance in older adults, which may be more relevant to function than static balance and potentially a useful adjunct to the OEP in frailty prevention.

Abstract Rationale The pathophysiologic causes of obstructive sleep apnea (OSA) likely vary among patients but have not been well characterized. Objectives To define carefully the proportion of key anatomic and nonanatomic contributions in a relatively large cohort of patients with OSA and control subjects to identify pathophysiologic targets for future novel therapies for OSA. Methods Seventy-five men and women with and without OSA aged 20–65 years were studied on three separate nights. Initially, the apnea-hypopnea index was determined by polysomnography followed by determination of anatomic (passive critical closing pressure of the upper airway [Pcrit]) and nonanatomic (genioglossus muscle responsiveness, arousal threshold, and respiratory control stability; loop gain) contributions to OSA. Measurements and Main Results Pathophysiologic traits varied substantially among participants. A total of 36% of patients with OSA had minimal genioglossus muscle responsiveness during sleep, 37% had a low arousal threshold, and 36% had high loop gain. A total of 28% had multiple nonanatomic features. Although overall the upper airway was more collapsible in patients with OSA (Pcrit, 0.3 [−1.5 to 1.9] vs. −6.2 [−12.4 to −3.6] cm H2O; P <0.01), 19% had a relatively noncollapsible upper airway similar to many of the control subjects (Pcrit, −2 to −5 cm H2O). In these patients, loop gain was almost twice as high as patients with a Pcrit greater than −2 cm H2O (−5.9 [−8.8 to −4.5] vs. −3.2 [−4.8 to −2.4] dimensionless; P = 0.01). A three-point scale for weighting the relative contribution of the traits is proposed. It suggests that nonanatomic features play an important role in 56% of patients with OSA. Conclusions This study confirms that OSA is a heterogeneous disorder. Although Pcrit-anatomy is an important determinant, abnormalities in nonanatomic traits are also present in most patients with OSA.

BackgroundRespiratory complications remain a leading cause of morbidity and mortality in people with acute and chronic tetraplegia. Respiratory muscle weakness following spinal cord injury-induced tetraplegia impairs lung function and the ability to cough. In particular, inspiratory muscle strength has been identified as the best predictor of the likelihood of developing pneumonia in individuals with tetraplegia. We hypothesised that 6 weeks of progressive respiratory muscle training (RMT) increases respiratory muscle strength with improvements in lung function, quality of life and respiratory health.MethodsSixty-two adults with tetraplegia participated in a double-blind randomised controlled trial. Active or sham RMT was performed twice daily for 6 weeks. Inspiratory muscle strength, measured as maximal inspiratory pressure (PImax) was the primary outcome. Secondary outcomes included lung function, quality of life and respiratory health. Between-group comparisons were obtained with linear models adjusting for baseline values of the outcomes.ResultsAfter 6 weeks, there was a greater improvement in PImax in the active group than in the sham group (mean difference 11.5 cmH2O (95% CI 5.6 to 17.4), p<0.001) and respiratory symptoms were reduced (St George Respiratory Questionnaire mean difference 10.3 points (0.01–20.65), p=0.046). Significant improvements were observed in quality of life (EuroQol-Five Dimensional Visual Analogue Scale 14.9 points (1.9–27.9), p=0.023) and perceived breathlessness (Borg score 0.64 (0.11–1.17), p=0.021). There were no significant improvements in other measures of respiratory function (p=0.126–0.979).ConclusionsProgressive RMT increases inspiratory muscle strength in people with tetraplegia, by a magnitude which is likely to be clinically significant. Measurement of baseline PImax and provision of RMT to at-risk individuals may reduce respiratory complications after tetraplegia.Trial registration numberAustralian New Zealand Clinical Trials Registry (ACTRN 12612000929808).

Purpose Respiratory muscle weakness frequently develops in critically ill patients and is associated with adverse outcome, including difficult weaning from mechanical ventilation. Today, no drug is approved to improve respiratory muscle function in these patients. Previously, we have shown that the calcium sensitizer levosimendan improves calcium sensitivity of human diaphragm muscle fibers in vitro and contractile efficiency of the diaphragm in healthy subjects. The main purpose of this study is to investigate the effects of levosimendan on diaphragm contractile efficiency in mechanically ventilated patients. Methods In a double-blind randomized placebo-controlled trial, mechanically ventilated patients performed two 30-min continuous positive airway pressure (CPAP) trials with 5-h interval. After the first CPAP trial, study medication (levosimendan 0.2 µg/kg/min continuous infusion or placebo) was administered. During the CPAP trials, electrical activity of the diaphragm (EA di ), transdiaphragmatic pressure ( P di ), and flow were measured. Neuromechanical efficiency (primary outcome parameter) was calculated. Results Thirty-nine patients were included in the study. Neuromechanical efficiency was not different during the CPAP trial after levosimendan administration compared to the CPAP trial before study medication. Tidal volume and minute ventilation were higher after levosimendan administration (11 and 21%, respectively), whereas EA di and P di were higher in both groups in the CPAP trial after study medication compared to the CPAP trial before study medication. Conclusions Levosimendan does not improve diaphragm contractile efficiency.