Jenkins 2014.

Study characteristics
Methods	Study design: RCT comparing IBS to sham intervention* Study grouping: cross‐over 'Rescue' vs maintenance therapy: both inpatients and outpatients were included, no differentiation made between rescue and maintenance therapy. Ethics: no information available regarding ethical review provided for the RCT. For the second, non‐randomised study, approval by the University of Manitoba's Research Ethics Board was reported. Written informed consent was obtained from all caregivers, and assent was obtained from participants where applicable.
Participants	Baseline characteristics No separate data were provided for the first period of cross‐over; therefore, aggregated data are provided for all participants, who underwent all interventions. Sample size, n: 23 Age in years, mean: 11 (range 3–19) Gender (male/female), n: 17/6 Diagnosis, n: NMD disorders: DMD 8; SMA 1; facio‐scapulo‐humeral muscular dystrophy 1; congenital fibre type disproportion (myopathy) 1; BMD 1; limb girdle muscular dystrophy 1; Charcot‐Marie‐Tooth Type 1 disease 1. 9 children with other CNS disorders were also included, without separation of results: seizure disorder 1, cerebral palsy 2, spinal cord injury 1, Rett syndrome 1, encephalomalacia 1, hypoxic brain injury 1, Batten disease 1, and Cri‐du‐Chat syndrome  1. Bodyweight in kg, mean: 43.8 (range 12–80) Cognitively aware and able to communicate, n: 15 Scoliosis, n: 12 Spinal fusion surgery, n: 7 Ambulatory, n: 5 NIPPV at night, n: 7 Inclusion criteria Aged > 1 year Diagnosed with NMD Admitted to Winnipeg Children's hospital and required chest physiotherapy for airway clearance or attended the Muscular Dystrophy Clinic at the Rehabilitation Centre for Children or Children's Hospital Physiotherapy (outpatient follow‐up) Exclusion criteria None indicated Pretreatment No separate group data reported
Interventions	Intervention characteristics IBS Position: those in hospital were studied in different positions (depending on their ability to sit). Sitting position was preferred. All patients attending outpatient facilities were assessed in the sitting position. For the IBS manoeuvre, participants indicated when they felt that maximum stacking was reached. Duration: 15 s Technique description: 3 involuntary stacking interventions (IBS) were applied to each participant, using a resuscitator bag, mask interface, and a unidirectional valve. IBS was randomly interspersed with sham treatment (same intervention but without a 1‐way valve). Prior to, and after each series of interventions, the mask was applied to each participant and 30 s of flow and pressure data were recorded. Repetitions: 3 Sham Position: those in hospital were studied in different positions (depending on their ability to sit). Sitting position was preferred. All the patients attending outpatient facilities were assessed in the sitting position. Duration: 15 s Technique description: 3 sham interventions were applied to each participant (using a resuscitation bag and mask without a valve); randomly interspersed with IBS manoeuvres. Prior to, and after each series of interventions, the mask was applied to the participant and 30 s of flow and pressure data were recorded. Repetitions: 3
Outcomes	Separate first‐period data were not presented, precluding analysis. Tidal volume Outcome type: continuous Unit of measure: mL Fully reported Respiratory rate Outcome type: continuous Unit of measure: breaths/min Fully reported SaO2 Outcome type: continuous Unit of measure: % Fully reported Adverse events: not reported
Identification	Funding source: Children's Hospital Foundation of Manitoba and Health Sciences Centre Foundation, Winnipeg, Mannitoba, Canada Conflict of interest: funding source declared and unlikely to constitute a conflict of interest. Country: Canada Setting: Winnipeg Children's Hospital for inpatients; Muscular Dystrophy Clinic at The Rehabilitation Centre for Children or Children's Hospital Physiotherapy for outpatient follow‐up Comments: some participants were unable to communicate verbally or follow instructions (due to age and cognition level). This study formed the basis of the Masters thesis by HML Jenkins. First author name: Heather ML Jenkins Institution: Department of Physiotherapy Services, Winnipeg Children's Hospital Email: hjenkins@hsc.mb.ca Address: Department of Physiotherapy Services, Winnipeg Children's hospital, CH246‐840 Sherbrook Street, Winnipeg, Manitoba, Canada R2A 1S1
Notes	Attempts to contact corresponding author for first‐period data were unsuccessful. *This paper also reported on a second study, which was a "comparative study" of voluntary and supported, compared to IBS in 6 children and adolescents with DMD. Although the order of voluntary and IBS was randomised, all received supported breathstacking as the final intervention. Therefore, this study was an observational, non‐randomised study, which did not qualify for inclusion in this review. Only data for the randomised cross‐over trial are therefore presented.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "This initial study of IBS followed a randomized cross over design. Inpatient subjects were assigned by blocked order randomization to two streams, either receiving the intervention or the sham in the morning and the reverse in the afternoon of the same day." Quote: "randomized cross over design." Quote: "assigned by blocked order randomization to two streams," Quote: "For each participant the sequence of interventions was randomized." Comment: randomised cross‐over trial; however, no indication was given as to how randomisation was achieved.
Allocation concealment (selection bias)	Unclear risk	Comment: unclear how allocation concealment was maintained. No information was provided.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "The sham trial was done to rule out the possible effects of the placement of a mask on the child’s face and of the effect of dead space ventilation during the 1 min of recording time." Comment: unclear if blinding was successfully achieved. Both IBS and sham were performed in the same way except for the presence or absence of a valve. Unclear if the masks looked identical, with a sham valve, or whether the valve was simply not added to the mask circuit for the sham intervention. It is likely that the intervention would have "felt" different, and in that way could have unblinded participants. Some participants were not cognitively aware/could not communicate.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: insufficient information to allow judgement. Not stated if the assessments were performed by the physiotherapists performing the interventions/sham or if they were performed by an independent assessor. If the assessor was present during the stacking manoeuvres to take the measurements, they would have been aware of the intervention (allocation).
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Twenty‐four children and adolescents participated in the study of IBS. Data from one patient were excluded due to a face mask leak. Twenty‐three children, 15 inpatients and 8 outpatients, were included in the final analysis." Comment: it was mentioned that 1 participant's results were excluded due to a facial mask leak, and this was considered unlikely to have introduced bias. Data of 4 participants who could not breathstack were described in the text (e.g. all had a tidal volume lower than the dead space of the mask).
Selective reporting (reporting bias)	Low risk	Comment: all outcome measures described in the methods section were reported.
Other bias	High risk	Comment: the following factors placed the study at high risk for other bias. Short‐term cross‐over study design, with unknown carry‐over effect. A short‐term cross‐over design may not be appropriate to NMD, a condition that requires long‐term follow‐up. The heterogeneity of neurological and neuromuscular conditions (including cerebral palsy, spinal cord injury, progressive muscular dystrophy, etc.) decreases the generalisability of the results, owing to differences in underlying pathology, upper motor and lower motor neuron involvement, progression of conditions, etc. The mean of 3 trials was used for analysis, but the authors did not specify if there was a limitation on the variation between the 3 trials and the mean could, therefore, present skewed results if there a large variance/outliers were present. Oral control/bulbar involvement may have influenced results, and this was not well considered. No washout period was mentioned. Learning effect with different procedures/interventions could have introduced bias, and was not accounted for. Unclear whether the groups were similar at the start of the study. Separate data were not available for the 2 periods of the study. Only pooled data per intervention were available and data could, therefore, not be used for meta‐analysis. Unclear whether groups were treated similarly throughout the study, as no information was available.