Inspiratory muscle training in children and adolescents living with neuromuscular diseases: A pre-experimental study

Inspiratory muscle training in children with neuromuscular disorders

Background

Progressive respiratory muscle weakness and ineffective cough contribute to morbidity and mortality in children with neuromuscular disorders (NMD). Inspiratory muscle training (IMT) aims to preserve or improve respiratory muscle strength and reduce respiratory morbidity. This study aimed to determine the safety and efficacy of IMT in children with NMD.

Methods/design

A randomised cross-over study compared a 3-month intervention (IMT) with control periods (no IMT). Children diagnosed with NMD (5 years - 18 years) performed 30 breaths (at 30% of maximum inspiratory mouth pressure [Pimax]) with an electronic threshold device, twice daily. During the control period, participants did not perform any IMT.

Discussion

Twenty three children (median [interquartile range {IQR}] age of 12.33 [10.03-14.17] years), mostly male (n = 20) and non-ambulant (n = 14) participated. No adverse events related to IMT were reported. No difference in median patient hospitalisation and respiratory tract infection (RTI) rates between non-training and intervention periods (p = 0.60; p = 0.21) was found. During IMT, Pimax and peak cough flow improved with a mean ± standard deviation (s.d.) of 14.57 ± 15.67 cmH2O and 32.27 ± 36.60 L/min, compared to 3.04 ± 11.93 cmH2O (p = 0.01) and -16.59 ± 48.29 L/min (p = 0.0005) during the non-training period. Similar to other studies, spirometry did not show a significant change.

Conclusion

A 3-month IMT programme in children with NMD appears safe and well-tolerated, with significant improvement in respiratory muscle strength and cough efficacy.

Clinical implications

Inspiratory muscle training could be considered a cost-effective adjunct to respiratory management in children with NMD.

Trial Registration

Pan African Clinical Trial Registry, PACTR201506001171421, https://pactr.samrc.ac.za.

Future Directions for Respiratory Muscle Training in Neuromuscular Disorders: A Scoping Review

BACKGROUND

Respiratory muscle training (RMT) aims to improve inspiratory and/or expiratory muscle function in neuromuscular disorders (NMDs). A comprehensive overview of the available literature is lacking. This scoping review explores methodological characteristics, (adverse) effects, and adherence of RMT studies in NMDs. Moreover, it identifies limitations and research gaps in the literature and provides future research directions.

SUMMARY

Eligible studies were identified using MEDLINE, Embase, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials databases. Three reviewers independently selected articles. Inclusion criteria were English language, original research articles on RMT using a device, patients with an NMD, and pulmonary function tests or respiratory muscle strength as outcome measures. We included NMDs with slow, intermediate and fast progression. Exclusion criteria were critically ill patients, weaning from mechanical ventilation, other neurological disorders, and RMT combined with non-respiratory interventions. One reviewer extracted the data on patients' characteristics, methodological characteristics, results of outcome measures, adverse events, and patient adherence. Forty-five studies were identified. We found a large diversity in study designs and training protocols. The effects of RMT on respiratory muscle strength and/or endurance are variable. Patient adherence was high and no serious adverse events were reported.

KEY MESSAGES

The diversity in studies across the available literature precludes definitive conclusions regarding the effects of RMT on respiratory muscle function and clinically relevant outcomes in NMDs. Therefore, well-powered and -designed studies that focus on clinically relevant outcomes and assess whether RMT can improve or offset deterioration of respiratory muscle weakness in NMDs are needed.

Suitability of the Respicheck questionnaire and Epworth sleepiness scale for therapy monitoring in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is an autosomal dominant trinucleotide disorder that often leads to respiratory dysfunction resulting in hypoventilation symptoms, reduced quality of life and causing premature death if untreated. To early identify symptoms of hypoventilation, the Respicheck questionnaire was developed as a screening tool. Symptomatic therapies like inspiratory muscle training (IMT) are recommended to strengthen respiratory muscles and reduce or even prevent hypoventilation symptoms. Our study aimed to evaluate the Respicheck questionnaire's suitablility to monitor the efficacy of IMT. Patients with genetically confirmed DM1 were randomly assigned to either IMT - endurance or strength training, or control group. At baseline, end of study and four interim visits, pulmonary function tests, Respicheck questionnaire and Epworth sleepiness scale were assessed. While patients in training groups achieved a substantial improvement after nine months of regular IMT in pulmonary function tests, the Respicheck score did not improve likewise. Similarly, the ESS score did not change significantly in both training and control groups. Consequently, we conclude that either improvement of respiratory function is not necessarily associated with clinical improvement, or respiratory muscle weakness was not the only reason for hypoventilation syndrome, or both questionnaires are not sensitive enough to detect slight clinical changes.

The RESISTANT study (Respiratory Muscle Training in Patients with Spinal Muscular Atrophy): study protocol for a randomized controlled trial

BACKGROUND

Spinal Muscular Atrophy (SMA) is characterized by progressive and predominantly proximal and axial muscle atrophy and weakness. Respiratory muscle weakness results in impaired cough with recurrent respiratory tract infections, nocturnal hypoventilation, and may ultimately lead to fatal respiratory failure in the most severely affected patients. Treatment strategies to either slow down the decline or improve respiratory muscle function are wanting.

OBJECTIVE

The aim of this study is to assess the feasibility and efficacy of respiratory muscle training (RMT) in patients with SMA and respiratory muscle weakness.

METHODS

The effect of RMT in patients with SMA, aged ≥ 8 years with respiratory muscle weakness (maximum inspiratory mouth pressure [PImax] ≤ 80 Centimeters of Water Column [cmH2O]), will be investigated with a single blinded randomized sham-controlled trial consisting of a 4-month training period followed by an 8-month open label extension phase.

INTERVENTION

The RMT program will consist of a home-based, individualized training program involving 30-breathing cycles through an inspiratory and expiratory muscle training device. Patients will be instructed to perform 10 training sessions over 5-7 days per week. In the active training group, the inspiratory and expiratory threshold will be adjusted to perceived exertion (measured on a Borg scale). The sham-control group will initially receive RMT at the same frequency but against a constant, non-therapeutic resistance. After four months the sham-control group will undergo the same intervention as the active training group (i.e., delayed intervention). Individual adherence to the RMT protocol will be reviewed every two weeks by telephone/video call with a physiotherapist.

MAIN STUDY PARAMETERS/ENDPOINTS

We hypothesize that the RMT program will be feasible (good adherence and good acceptability) and improve inspiratory muscle strength (primary outcome measure) and expiratory muscle strength (key secondary outcome measure) as well as lung function, patient reported breathing difficulties, respiratory infections, and health related quality of life (additional secondary outcome measures, respectively) in patients with SMA.

DISCUSSION

RMT is expected to have positive effects on respiratory muscle strength in patients with SMA. Integrating RMT with recently introduced genetic therapies for SMA may improve respiratory muscle strength in this patient population.

TRIAL REGISTRATION

Retrospectively registered at clinicaltrial.gov: NCT05632666.

Effect of Threshold Inspiratory Muscle Training on Functional Fitness and Respiratory Muscle Strength Compared to Incentive Spirometry in Children and Adolescents With Obesity: A Randomized Controlled Trial

BACKGROUND

To determine the effect of threshold inspiratory muscle training (IMT) on functional fitness and respiratory muscle strength (RMS) compared to incentive spirometry (IS) in children/adolescents with obesity.

METHODS

A total of 60 obese children/adolescents aged 8-15 years were randomized into the threshold IMT group (n = 20), the IS group (n = 20), or the control group (n = 20). The IMT group performed 30 inspiratory breaths with the intensity set at 40% of baseline maximal inspiratory pressure (MIP) twice daily for 8 weeks; the IS group performed 30 breaths with sustained maximum inspiration twice daily for 8 weeks; and, the control group was assigned no training device for 8 weeks. Six-min walk test (6-MWT), RMS, and spirometry were compared between baseline and 8 weeks.

RESULTS

Six-MWT distance (528.5 ± 36.2 vs. 561.5 ± 35.2 m, p = 0.002) and MIP (121.2 ± 26.8 vs. 135.3 ± 32.1%Predicted, p = 0.03) were significantly improved after 8 weeks of IMT training. There was no significant difference in any evaluated pulmonary function parameters between baseline and 8 weeks in the IS or control groups; however, 6-MWT distance demonstrated a trend toward significant improvement in the IS group (526.9 ± 59.1 vs.549.0 ± 50.6 m, p = 0.10). No significant difference among groups was found for any variable relative to change from baseline to post-training.

CONCLUSION

Eight weeks of threshold IMT training significantly improved both inspiratory muscle strength (MIP) and functional fitness (6-MWT) in children/adolescents with obesity. Eight weeks of IS training yielded a trend toward significantly improved functional fitness.

The effects of inspiratory muscle training in adults with muscular dystrophy

Background/Aims Patients with muscular dystrophy usually have impaired lung function and respiratory muscle strength, leading to pneumonia and respiratory failure, which are significant causes of morbidity and mortality. Inspiratory muscle training might be a safe adjunct treatment to increase the strength and endurance of weakened respiratory muscles. The researchers have developed a new protocol for inspiratory muscle training and evaluated its effect on inspiratory muscle strength and coughing capacity.

Methods A total of 12 participants diagnosed with muscle dystrophy and decreased maximal inspiratory pressure (<60 cmH2O) participated in this prospective study. Training was individually tailored, starting with low resistance levels and progressing according to tolerance and symptoms. The primary outcome measure was maximal inspiratory pressure. Secondary outcomes were maximal expiratory pressure, peak cough flow and the feasibility of the intervention.

Results There were two participants who did not complete the study, and three were lost to follow-up; therefore, only seven patients finished the intervention. In these patients, the authors found a statistically significant improvement in the maximal inspiratory pressure (P=0.018) and peak cough flow (P=0.046) after 3 months of training. There was also an improvement in the maximal expiratory pressure, although this was not statistically significant (P=0.176). Median compliance to training was 99% (94.5–100).

Conclusions This intervention led to statistically significant improvements in inspiratory muscles strength and coughing capacity in patients with muscular dystrophy. The results were significantly positive and contribute to the evidence in support of this underused, yet possibly beneficial, treatment, although larger randomised controlled trials are required to verify this.