Inspiratory pressure waveform influences time to failure, respiratory muscle fatigue, and metabolism during resistive breathing

Increased ventilatory work beyond working capacity of the respiratory muscles can induce fatigue, resulting in limited respiratory muscle endurance (Tlim ). Previous resistive breathing investigations all applied square wave inspiratory pressure as fatigue-inducing pattern. Spontaneous breathing pressure pattern more closely approximate a triangle waveform. This study aimed at comparing Tlim , maximal inspiratory pressure (PImax ), and metabolism between square and triangle wave breathing. Eight healthy subjects (Wei = 76 ± 10 kg, H = 181 ± 7.9 cm, age = 33.5 ± 4.8 years, sex [F/M] = 1/7) completed the study, comprising two randomized matched load resistive breathing trials with square and triangle wave inspiratory pressure waveform. Tlim decreased with a mean difference of 8 ± 7.2 min (p = 0.01) between square and triangle wave breathing. PImax was reduced following square wave (p = 0.04) but not for triangle wave breathing (p = 0.88). Higher VO2 was observed in the beginning and end for the triangle wave breathing compared with the square wave breathing (p = 0.036 and p = 0.048). Despite higher metabolism, Tlim was significantly longer in triangle wave breathing compared with square wave breathing, showing that the pressure waveform has an impact on the function and endurance of the respiratory muscles.

Effect of respiratory muscle training in asthma: A systematic review and meta-analysis

BACKGROUND

The last systematic review about respiratory muscle training (RMT) in people with asthma was published almost 10 years ago. Since then, several works have been published.

OBJECTIVE

To review the effect of RMT in people with asthma.

METHODS

We conducted a systematic review of research included up to September 2021 in PubMed/MEDLINE, PEDro, Scopus, Web of Science, CINAHL, LILACS, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov. We included randomized controlled trials and quasi-experimental studies assessing the effect of RMT on respiratory muscle function, rescue medication, asthma-related symptoms, lung function, exercise capacity, healthcare use, health-related quality of life (HRQoL) and adverse effects in people with asthma. Risk of bias and methodological quality were assessed with the Cochrane Risk of Bias assessment tool and the PEDro scale. Meta-analysis was performed whenever possible; otherwise a qualitative approach was followed.

RESULTS

Eleven studies (270 participants) were included, 10 with only adults and were included in the meta-analysis. Inspiratory muscle training (IMT) had beneficial effects on maximal inspiratory pressure (PImax: mean difference [MD] 21.95 cmH₂O [95% confidence interval [CI] 15.05; 28.85]), with no changes in maximal expiratory pressure (MD 14.97 cmH₂O [95%CI -5.65; 35.59]), lung function (forced expiratory volume in 1 sec: MD 0.06 [95%CI -0.14; 0.26] L; force vital capacity: MD 0.39 [95%CI -0.24; 1.02] L) and exercise capacity (standard mean difference [SMD] 1.73 [95%CI -0.61; 4.08]). Subgroup analysis revealed that IMT load >50% PImax and duration >6 weeks were beneficial for exercise capacity. The qualitative analysis suggested that IMT may have benefits on respiratory muscle endurance, rescue medication and exertional dyspnoea, with no adverse effects.

CONCLUSIONS

This systematic review and meta-analysis showed a significant increase in PImax after IMT in adults with asthma and reinforced the relevance of the dose-response principle of training. More evidence is needed to clarify the effect of IMT in respiratory muscle endurance, rescue medication, exercise capacity, healthcare use and HRQoL.

TRIAL REGISTRATION

PROSPERO International Prospective Register of Systematic Reviews CRD42020221939; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=221939.

The effect of inspiratory muscle training and detraining on the respiratory metaboreflex

NEW FINDINGS

What is the central question of this study? Is the attenuation of the respiratory muscle metaboreflex preserved after detraining? What is the main finding and its importance? Inspiratory muscle training increased respiratory muscle strength and attenuated the respiratory muscle metaboreflex as evident by lower heart rate and blood pressure. After 5 weeks of no inspiratory muscle training (detraining), respiratory muscle strength was still elevated and the metaboreflex was still attenuated. The benefits of inspiratory muscle training persist after cessation of training, and attenuation of the respiratory metaboreflex follows changes in respiratory muscle strength.

ABSTRACT

Respiratory muscle training (RMT) improves respiratory muscle (RM) strength and attenuates the RM metaboreflex. However, the time course of muscle function loss after the absence of training or 'detraining' is less known and some evidence suggest the respiratory muscles atrophy faster than other muscles. We sought to determine the RM metaboreflex in response to 5 weeks of RMT and 5 weeks of detraining. An experimental group (2F, 6M; 26 ± 4years) completed 5 weeks of RMT and tibialis anterior (TA) training (each 5 days/week at 50% of maximal inspiratory pressure (MIP) and 50% maximal isometric force, respectively) followed by 5 weeks of no training (detraining) while a control group (1F, 7M; 24 ± 1years) underwent no intervention. Prior to training (PRE), post-training (POST) and post-detraining (DETR), all participants underwent a loaded breathing task (LBT) to failure (60% MIP) while heart rate and mean arterial blood pressure (MAP) were measured. Five weeks of training increased RM (18 ± 9%, P < 0.001) and TA (+34 ± 19%, P < 0.001) strength and both remained elevated after 5 weeks of detraining (MIP-POST vs. MIP-DETR: 154 ± 31 vs. 153 ± 28 cmH2O, respectively, P = 0.853; TA-POST vs. TA-DETR: 86 ± 19 vs. 85 ± 16 N, respectively, P = 0.982). However, the rise in MAP during LBT was attenuated POST (-11 ± 17%, P = 0.003) and DETR (-9 ± 9%, P = 0.007) during the iso-time LBT. The control group had no change in MIP (P = 0.33), TA strength (P = 0.385), or iso-time MAP (P = 0.867) during LBT across all time points. In conclusion, RM and TA have similar temporal strength gains and the attenuation of the respiratory muscle metaboreflex remains after 5 weeks of detraining.

Effects of an incentive spirometer versus a threshold inspiratory muscle trainer on lung functions in Parkinson's disease patients: a randomized trial

Upper airway obstruction, reduced maximal expiratory and inspiratory flows, reduced lung volumes, abnormal ventilatory control, and diaphragmatic dyskinesias are reported in patients with Parkinson's disease (PD). Inspiratory muscle training (IMT) has been reported to be effective in improving respiratory functions; however, no studies have compared the effects of the incentive spirometer (IS) with the threshold inspiratory muscle trainer (TIMT) in patients with PD. The study aimed to compare the effects of IS and TIMT on maximum inspiratory pressure (MIP), 6-min walk distance (6-MWD), forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and peak expiratory flow rate (PEFR) in patients with stage 1-3 according to the Hoehn and Yahr scale. 18 patients were randomly assigned to two groups, i.e., incentive spirometer (IS) and threshold inspiratory muscle trainer (TIMT) group. The IS group received IMT with volume-based IS, and the TIMT group received IMT with TIMT. MIP, 6-MWD, FVC, FEV1, and PEFR were measured before and after six weeks of training. In IS group: A significant increase (p < 0.05) was observed in MIP and 6-MWD by 18.13 and 5%, respectively. In the TIMT group: A significant increase (p < 0.05) was observed in MIP and 6-MWD by 30.15 and 8.94%, respectively. Both groups observed no significant difference (p > 0.05) in FVC, FEV1, and PEFR. When the two groups were compared, a greater increase (p < 0.05) was observed in the MIP and 6-MWD in the TIMT group compared to IS group. IMT with IS or TIMT for six weeks effectively increased MIP and 6-MWD in patients with stage 1-3 (Hoehn and Yahr scale) of PD. No improvement was observed in FVC, FEV1, or PEFR with any of the techniques. TIMT is more effective than IS in improving MIP and 6-MWD.

Respiratory Muscle Interval Training Improves Exercise Capacity in Obese Adolescents during a 3-Week In-Hospital Multidisciplinary Body Weight Reduction Program

The purpose of this study was to determine whether a novel approach of interval training targeted to the respiratory muscles (RMIT; normocapnic hyperpnea with resistance) in addition to a multidisciplinary in-hospital body weight reduction program (BWRP) was able to improve the integrative response to exercise in young patients with obesity. Nine male patients (17.9 ± 4.9 (x ± SD) years; 113.8 ± 16.3 kg) underwent 12 sessions of RMIT and eight age-and sex-matched patients underwent 12 sessions of a sham protocol (CTRL) during the same 3-week BWRP. Before and after the interventions the patients performed an incremental and a heavy-intensity constant work-rate (CWR>GET) cycling exercise to voluntary exhaustion. Body mass decreased by ~4.0 kg after both RMIT (p = 0.0001) and CTRL (p = 0.0002). Peak pulmonary O₂ uptake (V˙O₂) increased after RMIT (p = 0.02) and CTRL (p = 0.0007). During CWR>GET at ISO-time, V˙O₂ (p = 0.0007), pulmonary ventilation (p = 0.01), heart rate (p = 0.02), perceived respiratory discomfort (RPE_R; p = 0.03) and leg effort (p = 0.0003) decreased after RMIT; only RPE_R (p = 0.03) decreased after CTRL. Time to exhaustion increased after RMIT (p = 0.0003) but not after CTRL. In young patients with obesity, RMIT inserted in a 3-week BWRP reduced the cardiorespiratory burden, the metabolic cost, the perceived effort, and improved exercise tolerance during heavy-intensity cycling.

Effects of Inspiratory Muscle Training on Muscle Oxygenation during Vascular Occlusion Testing in Trained Healthy Adult Males

Inspiratory muscle training (IMT) may have an additional effect on cardiovascular autonomic modulation, which could improve the metabolism and vascular function of the muscles.

AIM

To determine the effects of IMT on vascular and metabolic muscle changes and their relationship to changes in physical performance.

METHODS

Physically active men were randomly placed into an experimental (IMTG; n = 8) or IMT placebo group (IMTPG; n = 6). For IMT, resistance load was set at 50% and 15% of the maximum dynamic inspiratory strength (S-Index), respectively. Only the IMTG's weekly load was increased by 5%. In addition, both groups carried out the same concurrent training. Besides the S-Index, a 1.5-mile running test, spirometry, and deoxyhemoglobin (HHb_AUC during occlusion) and reperfusion tissue saturation index (TSI_MB and TSI_MP: time from minimum to baseline and to peak, respectively) in a vascular occlusion test were measured before and after the 4-week training program. In addition, resting heart rate and blood pressure were registered.

RESULTS

IMTG improved compared to IMTPG in the S-Index (Δ = 28.23 ± 26.6 cmH₂O), maximal inspiratory flow (MIF: Δ = 0.91 ± 0.6 L/s), maximum oxygen uptake (Δ = 4.48 ± 1.1 mL/kg/min), 1.5-mile run time (Δ = -0.81 ± 0.2 s), TSI_MB (Δ = -3.38 ± 3.1 s) and TSI_MP (Δ = -5.88 ± 3.7 s) with p < 0.05. ΔVO_2max correlated with S-Index (r = 0.619) and MIF (r = 0.583) with p < 0.05. Both ΔTSI_MB and TSI_MP correlated with ΔHHb_AUC (r = 0.516 and 0.596, respectively) and with Δ1.5-mile run time (r = 0.669 and 0.686, respectively) with p < 0.05.

CONCLUSION

IMT improves vascular function, which is related to additional improvements in physical performance.

Patterns of Changes in Respiratory Muscle Strength over 1 Year in Non-Sarcopenia, Sarcopenia, and Severe Sarcopenia

In this prospective longitudinal cohort study, we explored the characteristics of older people with lower respiratory muscle strength, according to sarcopenia severity, over the course of 1 year. The maximum expiratory pressure (MEP), grip strength, walking speed, and skeletal muscle mass index of 58 participants (28 men, 30 women; mean age, 76.9 ± 7.7 years) were measured at baseline and at the 1-year follow-up. Participants were classified into a decreased MEP group (n = 29; MEP decreased by ≥10% after 1 year) and a non-decreased MEP group (n = 29; MEP decreased by <10%). Sarcopenia status in the mild direction at baseline was significantly associated with MEP decline after one year. Repeated two-way analysis of variance showed significant main effects of measurement time (p < 0.001) and severity of sarcopenia (p = 0.026), as well as a significant interaction effect (p = 0.006). Surprisingly, MEP decreased significantly in the non-sarcopenia and sarcopenia groups, but not in the severe sarcopenia group. Thus, individuals without sarcopenia and those with moderate sarcopenia at baseline are predisposed to MEP decline and should be closely monitored for signs of such decline and associated adverse events.

Pulmonary and Functional Rehabilitation Improves Functional Capacity, Pulmonary Function and Respiratory Muscle Strength in Post COVID-19 Patients: Pilot Clinical Trial

BACKGROUND

Patients affected by COVID-19 may develop an impaired lung function, with reduced lung capacities and volumes, respiratory muscle weakness, changes in radiographic and tomographic findings, limitations in exercising, decreased functional capacity, depression, anxiety and reduced quality of life. Thus, we aimed to analyze the effects of a pulmonary and functional rehabilitation program on the functional capacity, lung function and respiratory muscle strength in patients who were affected by COVID-19 syndrome.

METHODS

This is a pilot clinical trial, composed of post-COVID-19 patients with mild, moderate or severe involvement, in which, they underwent a pulmonary and functional rehabilitation program. Patients were evaluated for functional capacity by the 6 min walk test, pulmonary function by spirometry, respiratory muscle strength by manovacuometry, handgrip strength by dynamometry, quality of life by the COPD Assessment Test and functional status by the PCFS. After the initial assessments, the patients performed the rehabilitation protocol in 16 sessions (inspiratory muscle training, aerobic exercise and peripheral muscle strength) and, at the end, they were evaluated again.

RESULTS

A total of 29 patients completed the program (12.7 ± 2.7 sessions). The functional capacity increased in meters walked from 326.3 ± 140.6 to 445.4 ± 151.1 (p < 0.001), with an increase in the predicted value from 59.7% to 82.6% (p < 0.001). The lung function increased in liters from 2.9 ± 0.8 to 3.2 ± 0.8 (p = 0.004) for forced vital capacity and from 2.5 ± 0.7 to 2.7 ± 0.7 (p = 0.001) for forced expiratory volume in the first second. The respiratory muscle strength increased in cmH₂O from 101.4 ± 46.3 to 115.8 ± 38.3 (p = 0.117) for inspiratory pressure and from 85.8 ± 32.8 to 106.7 ± 36.8 (p < 0.001) for expiratory pressure.

CONCLUSIONS

The pulmonary and functional rehabilitation program provided an improvement in the functional capacity, pulmonary function and respiratory muscle strength in post-COVID-19 patients, restoring their quality of life.

Inspiratory Muscle Training Improves Aerobic Fitness in Active Children

Research on the effect of inspiratory muscle training (IMT) on exercise performance is inconsistent. IMT has not been applied to fit child athletes, who are more likely to develop inspiratory muscle fatigue, and, consequently, to benefit from IMT. Methods: Thirty children (mean age: 10.7 ± 1.2 years) were recruited and randomly assigned to a high-intensity (HG), a low-intensity (LG), or a control group (CG). For both training groups, a double-blind procedure was applied. In the HG, 80% of maximal inspiratory pressure (MIP) was used as the level of training intensity. The LG used 30% MIP. Training groups were trained at 6 breaths a set, 4 sets a day, totaling 24 breaths a day for 6 weeks. Exercise capacity outcomes include maximal and submaximal aerobic capacity, as measured as VO₂max and distance from six-minute walk test (6MWD). Results show improvement in MIP, VO₂max, and 6MWD only in the HG. MIP in the HG significantly increases from 108.7 (100.8-143.3) to 144.4 (130.0-175.6) cmH₂O. VO₂max in the HG increases from 43.0 (40.5-45) to 53.0 (46-63) mL·kg^-1·min^-1. The 6MWD increases from 792.0 (737.5-818.0) to 862.0 (798.5-953.5) m. Data are presented as median (interquartile range). No difference is found in the LG or CG. Conclusion: high-intensity IMT increases MIP, maximal, and submaximal exercise capacity in the HG, but no difference is found in the LG or CG. Therefore, high-intensity type of IMT improves aerobic fitness in fit children by appropriately applying inspiratory muscle strength training.

Inspiratory and leg muscle blood flows during inspiratory muscle metaboreflex activation in heart failure with preserved ejection fraction

The purpose of this study was to determine the cardiovascular consequences elicited by activation of the inspiratory muscle metaboreflex in patients with heart failure with preserved ejection fraction (HFpEF) and controls. Patients with HFpEF (n = 15; 69 ± 10 yr; 33 ± 4 kg/m2) and controls (n = 14; 70 ± 8 yr; 28 ± 4 kg/m2) performed an inspiratory loading trial at 60% maximal inspiratory pressure (PIMAX) until task failure. Mean arterial pressure (MAP) was measured continuously. Near-infrared spectroscopy and bolus injections of indocyanine green dye were used to determine the percent change in blood flow index (%ΔBFI) from baseline to the final minute of inspiratory loading in the vastus lateralis and sternocleidomastoid muscles. Vascular resistance index (VRI) was calculated. Time to task failure was shorter in HFpEF than in controls (339 ± 197 s vs. 626 ± 403 s; P = 0.02). Compared with controls, patients with HFpEF had a greater increase from baseline in MAP (16 ± 7 vs. 10 ± 6 mmHg) and vastus lateralis VRI (76 ± 45 vs. 32 ± 19%) as well as a greater decrease in vastus lateralis %ΔBFI (-32 ± 14 vs. -17 ± 9%) (all, P < 0.05). Sternocleidomastoid %ΔBFI normalized to absolute inspiratory pressure was higher in HFpEF compared with controls (8.0 ± 5.0 vs. 4.0 ± 1.9% per cmH2O·s; P = 0.03). These data indicate that patients with HFpEF exhibit exaggerated cardiovascular responses with inspiratory muscle metaboreflex activation compared with controls.NEW & NOTEWORTHY Respiratory muscle dysfunction is thought to contribute to exercise intolerance in heart failure with preserved ejection fraction (HFpEF); however, the underlying mechanisms are unknown. In the present study, patients with HFpEF had greater increases in leg muscle vascular resistance index and greater decreases in leg muscle blood flow index compared with controls during inspiratory resistive breathing (to activate the metaboreflex). Furthermore, respiratory muscle blood flow index responses normalized to pressure generation during inspiratory resistive breathing were exaggerated in HFpEF compared with controls.

Physiological impact of load carriage exercise: Current understanding and future research directions

Load carriage (LC) refers to the use of personal protective equipment (PPE) and/or load-bearing apparatus that is mostly worn over the thoracic cavity. A commonplace task across various physically demanding occupational groups, the mass being carried during LC duties can approach the wearer's body mass. When compared to unloaded exercise, LC imposes additional physiological stress that negatively impacts the respiratory system by restricting chest wall movement and altering ventilatory mechanics as well as circulatory responses. Consequently, LC activities accelerate the development of fatigue in the respiratory muscles and reduce exercise performance in occupational tasks. Therefore, understanding the implications of LC and the effects specific factors have on physiological capacities during LC activity are important to the implementation of effective mitigation strategies to ameliorate the detrimental effects of thoracic LC. Accordingly, this review highlights the current physiological understanding of LC activities and outlines the knowledge and efficacy of current interventions and research that have attempted to improve LC performance, whilst also highlighting pertinent knowledge gaps that must be explored via future research activities.

A multi-trial, retrospective analysis of the antihypertensive effects of high-resistance, low-volume inspiratory muscle strength training

Above-normal blood pressure (BP) is a primary risk factor for cardiovascular diseases. In a retrospective analysis of five pilot trials, we assessed the BP-lowering effects of high-resistance inspiratory muscle strength training (IMST) in adults aged 18-82 years and the impact of IMST on maximal inspiratory pressure (PIMAX), a gauge of inspiratory muscle strength and independent disease risk factor. Participants were randomized to high-resistance IMST (75% PIMAX) or low-resistance sham (15% PIMAX) training (30 breaths/day, 5-7 days/wk, 6 wk). IMST (n = 67) reduced systolic BP (SBP) by 9 ± 6 mmHg (P < 0.01) and diastolic BP (DBP) by 4 ± 4 mmHg (P < 0.01). IMST-related reductions in SBP and DBP emerged by week 2 of training (-4 ± 8 mmHg and -3 ± 6 mmHg; P ≤ 0.01, respectively) and continued across the 6-wk intervention. SBP and DBP were unchanged with sham training (n = 61, all P > 0.05). Select subject characteristics slightly modified the impact of IMST on BP. Greater reductions in SBP were associated with older age (β = -0.07 ± 0.03; P = 0.04) and greater reductions in DBP associated with medication-naïve BP (β = -3 ± 1; P = 0.02) and higher initial DBP (β = -0.12 ± 0.05; P = 0.04). PIMAX increased with high-resistance IMST and low-resistance sham training, with a greater increase from high-resistance IMST (+20 ± 17 vs. +6 ± 14 cmH2O; P < 0.01). Gains in PIMAX had a modest inverse relation with age (β = -0.20 ± 0.09; P = 0.03) and baseline PIMAX (β = -0.15 ± 0.07; P = 0.04) but not to reductions in SBP or DBP. These compiled findings from multiple independent trials provide the strongest evidence to date that high-resistance IMST evokes clinically significant reductions in SBP and DBP, and increases in PIMAX, in adult men and women.NEW & NOTEWORTHY In young-to-older adult men and women, 6 wk of high-resistance inspiratory muscle strength training lowers casual systolic and diastolic blood pressure by 9 mmHg and 4 mmHg, respectively, with initial reductions observed by week 2 of training. Given blood pressure outcomes with the intervention were only slightly altered by subject baseline characteristics (i.e., age, blood pressure medication, and health status), inspiratory muscle strength training is effective in lowering blood pressure in a broad range of adults.

Effects of Early Resistance Training After Liver Transplantation Procedures: A Randomized Controlled Pilot Trial

BACKGROUND

Exercise interventions improve muscle performance and functionality when applied more than 6 months after liver trans- plantation, but no studies have reported on earlier exercise interventions. Hence, we assessed the effects of early resistance training on functional outcomes in adult liver recipients.

METHODS

The study included 30 liver transplantation patients (53.2 ± 12.4 years) randomly assigned to a training group (n = 15) or a control group (n = 15). Data collected preoperatively and 4 and 8 weeks post-surgery were analyzed, including peripheral and respiratory muscle strength, exercise capacity, physical performance, and fatigue. An 8-week physiotherapy program was applied (training group: standard physiotherapy + resistance training; control group: standard physiotherapy) for 2 sessions/day, 5 days/week.

RESULTS

Baseline data showed a homogeneous distribution in the between-group comparisons. In the within-group analysis; EG showed higher improvements in physical performance (TG: P = .001, CG: P = .05) and fatigue perception (TG: P = .001; CG: P = .006), than the CG. The TG showed eight-week improvements in exercise capacity, peripheral muscle strength, and maximal inspiratory pressure (P = .001), and maximal expiratory pressure (P = .047), while CG remained unchanged (P > .05). In the between-group analysis; the improvements indicated significant differences in deltoid strength and fatigue perception, in favor of the TG (P < .05). A change of 0.9 kg in peripheral muscle strength and >37.8 m in 6-min walk distance (6MWD) was determined, representing clinically significant improvement in liver recipients.

CONCLUSION

Early resistance training may improve muscle strength, exercise capacity, physical performance, and fatigue perception in liver recipients, when added to standard physiotherapy. The estimated minimal clinically important differences are meaningful to clini- cians in setting liver transplanted patient-specific goals.

Inspiratory Muscle Training Strategies in Tracheostomized Critically Ill Individuals

BACKGROUND

Inspiratory muscle training (IMT) strategies can reduce ICU length of stay and optimize recovery in critically ill patients. Our objective was to compare IMT combined with spontaneous breathing with T-piece in tracheostomized subjects.

METHODS

Tracheostomized critically ill subjects who were ready to wean were selected and randomly allocated to one of 2 groups: electronically-assisted IMT (EIMT) or spontaneous breathing with T-piece. Electronically assisted IMT was delivered using 30% of maximal inspiratory pressure (manual EIMT or automatically adjusted loads). The following variables were analyzed: ICU length of stay, weaning time, maximal inspiratory pressure, rapid shallow breathing index, pressure (cm H₂O), power (W), flow (L/s), volume (L), and energy (J).

RESULTS

A total of 132 patients were assessed; 104 subjects were enrolled with EIMT, n = 51 (automatic EIMT, n = 25 and manual EIMT n = 26), or spontaneous breathing with T-piece group, n = 53. The Acute Physiology and Chronic Health Evaluation II score was significantly higher (P = .02) in subjects in the manual EIMT group. Weaning time did not differ significantly between groups (8.55 ± 6.48 d and 10.86 ± 6.48 d, EIMT and spontaneous breathing with T-piece group, respectively; P = .23). Weaning success rates (75%) were lower in the manual EIMT group. Invasive mechanical ventilation time was longer but not significantly different (P = .21) in the spontaneous breathing with T-piece group. Maximal inspiratory pressure was significantly higher in the spontaneous breathing with T-piece and the automatic EIMT groups (P < .001 and P = .007, respectively). Pressure, power, and energy values were significantly higher in the manual EIMT group (P < .001, P = .003, and P = .003, respectively).

CONCLUSIONS

IMT modalities in this trial had no significant impacts on weaning time or successful weaning rates.

Model-based Estimation of Inspiratory Effort using Surface EMG

OBJECTIVE

The quantification of inspiratory patient effort in assisted mechanical ventilation is essential for the adjustment of ventilatory assistance and for assessing patient-ventilator interaction. The inspiratory effort is usually measured via the respiratory muscle pressure (P_mus) derived from esophageal pressure (P_es) measurements. As yet, no reliable non-invasive and unobtrusive alternatives exist to continuously quantify P_mus.

METHODS

We propose a model-based approach to estimate P_mus non-invasively during assisted ventilation using surface electromyographic (sEMG) measurements. The method combines the sEMG and ventilator signals to determine the lung elastance and resistance as well as the neuromechanical coupling of the respiratory muscles via a novel regression technique. Using the equation of motion, an estimate for P_mus can then be calculated directly from the lung mechanical parameters and the pneumatic ventilator signals.

RESULTS

The method was applied to data recorded from a total of 43 ventilated patients and validated against P_es-derived P_mus. Patient effort was quantified via the P_mus pressure-time-product (PTP). The sEMG-derived PTP estimated using the proposed method was highly correlated to P_es-derived PTP ([Formula: see text]), and the breath-wise deviation between the two quantities was [Formula: see text].

CONCLUSION

The estimated, sEMG-derived P_mus is closely related to the P_es-based reference and allows to reliably quantify inspiratory effort.

SIGNIFICANCE

The proposed technique provides a valuable tool for physicians to assess patients undergoing assisted mechanical ventilation and, thus, may support clinical decision making.

Translational Potential of High-Resistance Inspiratory Muscle Strength Training

Age-associated cardiovascular (CV) dysfunction increases the risk for CV diseases. Aerobic exercise training can improve CV function, but only a minority of adults meet aerobic exercise guidelines. High-resistance inspiratory muscle strength training is a time-efficient lifestyle intervention that may promote adherence and improve CV function. However, further investigation is needed to translate inspiratory muscle strength training into the public health domain.

Effect of Chest Resistance and Expansion Exercises on Respiratory Muscle Strength, Lung Function, and Thoracic Excursion in Children with a Post-Operative Congenital Diaphragmatic Hernia

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a life-threatening condition with long-term complications including respiratory tract infections, respiratory muscle weakness, and abnormal lung functions. This study was designed to ascertain the effects of chest resistance and chest expansion exercises on respiratory muscle strength, lung function, and chest mobility in children with post-operative CDH.

METHODS

This randomized controlled clinical study was conducted in the outpatient physiotherapy clinic at Prince Sattam bin Abdulaziz University. Thirty-two children with CDH aged 10-14 years between May 2020 and February 2021 were randomly allocated to the study group (n = 16) and the control group (n = 16). The control group underwent a usual chest physiotherapy program; however, the study group underwent a 12-week chest resistance exercise combined with chest expansion exercise in addition to usual chest physiotherapy, with three sessions per week. Respiratory muscle strength, lung function, and thoracic excursion were assessed pre- and post-treatment.

RESULTS

Using the 2 × 2 repeated ANOVA, significant time × group interactions were detected in favor of the study group, FVC (F = 4.82, 95% CI = -15.6 to -0.97, p = 0.005, and η² = 0.16), FEV1 (F = 4.54, 95% CI = -11.99 to -2.8, p ˂ 0.001, and η² = 0.14), PImax (F = 5.12, 95% CI = -15.71 to -5.3, p ˂ 0.001, and η² = 0.15), and thoracic excursion (F = 4.41, 95% CI = -2.04 to -0.16, p = 0.036, and η² = 0.17).

CONCLUSIONS

Concurrent chest resistance and expansion exercises may improve respiratory muscle strength, lung function, and thoracic excursion in children with post-operative CDH. The study findings suggest that concurrent chest and chest expansion exercises be part of an appropriate pulmonary rehabilitation program in children with a history of CDH.

Respiratory muscle dysfunction in long-COVID patients

Purpose

Symptoms often persistent for more than 4 weeks after COVID-19—now commonly referred to as ‘Long COVID’. Independent of initial disease severity or pathological pulmonary functions tests, fatigue, exertional intolerance and dyspnea are among the most common COVID-19 sequelae. We hypothesized that respiratory muscle dysfunction might be prevalent in persistently symptomatic patients after COVID-19 with self-reported exercise intolerance.

Methods

In a small cross-sectional pilot study (n = 67) of mild-to-moderate (nonhospitalized) and moderate-to-critical convalescent (formerly hospitalized) patients presenting to our outpatient clinic approx. 5 months after acute infection, we measured neuroventilatory activity P0.1, inspiratory muscle strength (PImax) and total respiratory muscle strain (P0.1/PImax) in addition to standard pulmonary functions tests, capillary blood gas analysis, 6 min walking tests and functional questionnaires.

Results

Pathological P0.1/PImax was found in 88% of symptomatic patients. Mean PImax was reduced in hospitalized patients, but reduced PImax was also found in 65% of nonhospitalized patients. Mean P0.1 was pathologically increased in both groups. Increased P0.1 was associated with exercise-induced deoxygenation, impaired exercise tolerance, decreased activity and productivity and worse Post-COVID-19 functional status scale. Pathological changes in P0.1, PImax or P0.1/PImax were not associated with pre-existing conditions.

Conclusions

Our findings point towards respiratory muscle dysfunction as a novel aspect of COVID-19 sequelae. Thus, we strongly advocate for systematic respiratory muscle testing during the diagnostic workup of persistently symptomatic, convalescent COVID-19 patients.

Comparison of disc and wire electrodes to restore cough via lower thoracic spinal cord stimulation

OBJECTIVE

To compare the safety and effectiveness of wire (WE) vs. disc (DE) electrodes to restore cough in subjects with spinal cord injury (SCI).

DESIGN

Clinical trials assessing the effectiveness and clinical outcomes associated with two electrode systems to activate the expiratory muscles.

SETTING

Inpatient hospital setting for DE or WE electrode insertion; outpatient evaluation of cough efficacy and instructions for home use.

PARTICIPANTS

Twenty-nine subjects with SCI; 17 participants with DE and 12 with WE implants.

INTERVENTION

Surgical implantation of WE or DE to restore cough. Daily application of spinal cord stimulation (SCS) at home.

MAIN OUTCOME MEASURE(S)

Airway pressure (P) and peak airflow (F) generation achieved with SCS; clinical parameters including ease in raising secretions, incidence of acute respiratory tract infections (RTI) and side effects.

RESULTS

P and F achieved with DE and WE were not significantly different. For example, at total lung capacity (TLC) with participant effort, P was 128 ± 12 cmH2O and 118 ± 14 cmH2O, with DE and WE, respectively. The degree of difficulty in raising secretions improved markedly in both groups. The incidence of RTI per year fell from 1.3 ± 0.3 and 1.3 ± 0.5-0.3 ± 0.1 and 0.1 ± 0.1 for DE and WE groups, respectively (P < 0.01 for both when compared to pre-implant values and NS between DE and WE groups). The only significant side effect i.e. short-term autonomic dysreflexia was also similar between groups.

CONCLUSIONS

The results of this investigation indicate that both DE and WE result in comparable degrees of expiratory muscle activation, clinical benefits and side effects. Importantly, SCS to restore cough can be achieved with use of WE which can be placed using minimally invasive techniques and associated reduction in cost, surgical time and overall risk.Trial registration: ClinicalTrials.gov identifier: NCT00116337., NCT01659541, FDA IDE: G980267.

Heart Rate Variability and Respiratory Muscle Strength in Patients With Type II Diabetes Practicing Pilates: A Randomized Clinical Trial

PURPOSE

This study aimed to analyze the effect of a Pilates protocol on respiratory muscle strength and heart rate variability (HRV) in patients with type 2 diabetes.

METHOD

A randomized clinical trial (RBR-2gc2qj) was conducted on a type 2 diabetic target population. Patients practiced the Pilates protocol for 8 weeks, with two visits per week. The variables tested were maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), and HRV (time and frequency domains). All variables were tested for normal distribution. Using SPSS 21.0, analysis of variance was performed for variables with normal distribution, and the Wilcoxon and Friedman tests were used for variables that did not show a normal distribution, with a 5% significance level.

RESULTS

Forty-four participants were included in the study (intervention group: 22; control group: 22; mean age: 61.23 ± 8.49 years), most of whom were female (77.3%), married or in a consensual union (59.1%), had complete literacy (31.8%), and had an average body mass index of 26.96 ± 4.35 kg/m². There were no significant differences in MIP and MEP b efore and after the protocol between the intervention and control groups. Regarding HRV, there were significant differences in autonomic modulation, especially between the moments before and during exercise and between the moments during and after exercise; however, it was not possible to determine which system (sympathetic or parasympathetic) is most involved in these changes.

CONCLUSION

The exercise protocol based on the Pilates method did not alter respiratory muscle strength but promoted changes in HRV, especially between the moments before and during exercise and during and after exercise.

Electromyographic study assessing swallowing function in subacute stroke patients with respiratory muscle weakness

BACKGROUND

Dysphagia has been reported to be associated with the descent of the hyolaryngeal complex. Further, suprahyoid muscles play a greater role than infrahyoid muscles in elevation of the hyolarngeal complex. Respiratory muscle training (RMT) can improve lung function, and expiratory muscle strength training can facilitate elevation of the hyoid bone and increase the motor unit recruitment of submental muscles during normal swallowing. This study aimed to investigate the surface electromyography (sEMG) of the swallowing muscles, bilaterally, and the effect of RMT on swallowing muscles in stroke patients with respiratory muscle weakness.

METHODS

Forty patients with first episode of unilateral stroke were included in this retrospective controlled trial. After exclusion of 11 patients with respiratory muscle strength stronger than 70% of the predicted value, 15 were allocated to the RMT group and 14 to the control group. However, eventually, 11 patients in RMT group and 11 patients in control group completed the study. The sEMG of the orbicularis oris, masseter, submental, and infrahyoid muscles were recorded during dry swallowing, water swallowing (2 mL), and forced exhalation against a threshold breathing trainer set at different intensities, at baseline and after 6-week RMT.

RESULTS

Regarding the sEMG of submental muscles, there were significant between-group differences on the latency of the unaffected side (P = .048), significant change from baseline force on the unaffected side (P = .035), and significant between-side difference (P = .011) in the RMT group during dry swallowing. Significant change in the duration from baseline was observed on the affected side of the RMT group when blowing was set at 50% maximal expiratory pressure (MEP; P = .015), and on the unaffected side of the control group when blowing set at 15% MEP (P = .005). Significant difference was observed in the duration between 50% MEP and 15% MEP after 6-week program in the control group (P = .049).

CONCLUSIONS

A 6-week RMT can improve the electric signal of the affected swallowing muscles with more effect on the unaffected side than on the affected side during dry swallowing. Furthermore, RMT with 50% MEP rather than 15% MEP can facilitate greater submental muscle activity on the affected side in stroke patients with respiratory muscle weakness.

Effect of postoperative high load long duration inspiratory muscle training on pulmonary function and functional capacity after mitral valve replacement surgery: A randomized controlled trial with follow-up

Objectives

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.

Design

Prospective randomized controlled trial.

Methods

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).

Results

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.

Conclusion

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 control of respiratory pressures and neuromuscular activation to increase force production in trained martial arts practitioners

PURPOSE

The mechanisms that explain the ability of trained martial arts practitioners to produce and resist greater forces than untrained individuals to aid combat performance are not fully understood. We investigated whether the greater ability of trained martial arts practitioners to produce and resist forces was associated with an enhanced control of respiratory pressures and neuromuscular activation of the respiratory, abdominal, and pelvic floor musculature.

METHODS

Nine trained martial arts practitioners and nine untrained controls were instrumented with skin-surface electromyography (EMG) on the sternocleidomastoid, rectus abdominis, and the group formed by the transverse abdominal and internal oblique muscles (EMG_tra/io). A multipair oesophageal EMG electrode catheter measured gastric (P_g), transdiaphragmatic (P_di), and oesophageal (P_e) pressures and EMG of the crural diaphragm (EMG_di). Participants performed Standing Isometric Unilateral Chest Press (1) and Standing Posture Control (2) tasks.

RESULTS

The trained group produced higher forces normalised to body mass^2/3 (0.033 ± 0.01 vs. 0.025 ± 0.007 N/kg^2/3 mean force in Task 1), lower P_e, and higher P_di in both tasks. Additionally, they produced higher P_g (73 ± 42 vs. 49 ± 19 cmH₂O mean P_g) and EMG_tra/io in Task 1 and higher EMG_di in Task 2. The onset of P_g with respect to the onset of force production was earlier, and the relative contributions of P_g/P_e and P_di/P_e were higher in the trained group in both tasks.

CONCLUSION

Our findings demonstrate that trained martial arts practitioners utilised a greater contribution of abdominal and diaphragm musculature to chest wall recruitment and higher P_di to produce and resist higher forces.

Inspiratory muscle training in neuromuscular patients: Assessing the benefits of a novel protocol

BACKGROUND

Neuromuscular diseases are characterized by the compromise of respiratory muscles, thoracic ventilation, muscle strength and coughing capacity. Patients have low quality of life and increased morbidity and mortality mostly due to respiratory impairment.

OBJECTIVE

To assess the benefits of adding inspiratory muscle training to neuromuscular patients' treatment and their compliance to the approach.

METHODS

We conducted a single-center prospective study with neuromuscular patients with decreased maximal inspiratory pressure. We developed an inspiratory muscle training protocol with three-month duration and once-daily training. The protocol had a progressive intensity that was individually tailored based on patients' baseline characteristics and tolerance. We used Powerbreathe Medic Classic devices to perform the training.

RESULTS

There were 21 patients who met the inclusion criteria and were enrolled in the study. Muscular dystrophy (n= 12, 57.3%) and amyotrophic lateral sclerosis (n= 4, 19%) were the most common diseases. After three months of training, patients increased their maximal inspiratory muscle pressure (p= 0.002) and peak cough flow (p= 0.011). Compliance to the protocol was 99 ± 5.5%.

CONCLUSIONS

This protocol showed significant improvements on pulmonary muscles function and might be considered as an adjunct treatment to neuromuscular treatment. However, these positive results require larger further studies to validate the clinical benefits long-term.