Response to “Advancing mechanistic interpretation of diaphragmatic interventions in children with cerebral palsy”

Dear Editor,

We thank the authors for their thoughtful and constructive comments on our recently published randomized controlled trial. ¹ We appreciate their interest in our work and their recognition of the clinical relevance and feasibility of the intervention. Their remarks provide a valuable opportunity to further clarify the interpretation of our findings and to elaborate on several methodological and mechanistic aspects of the study within the context of pediatric neurorehabilitation.

We agree that the interpretation of improvements in respiratory muscle strength and chest expansion should be considered within the broader framework of neuro-respiratory motor control. Repeated motor tasks have been shown to enhance muscle activation through increased motor unit recruitment and improved coordination via central nervous system pathways. ² In this context, the observed increases in maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) may reflect neuromuscular adaptations associated with skill-based breathing practice rather than solely structural changes in pulmonary mechanics. Manual diaphragmatic relaxation may contribute to improved diaphragm and lower thoracic mobility, while diaphragmatic breathing exercises may facilitate better synergy and coordination between respiratory muscles during inhalation and exhalation. Together, these neuromuscular and biomechanical mechanisms may help explain the increased inspiratory and expiratory pressures observed in the intervention group. We also agree that the absence of objective assessment of breathing patterns, such as respiratory rate, tidal volume, or diaphragmatic activation, may limit the ability to distinguish specific diaphragmatic effects from potential accessory muscle compensation. Future studies incorporating detailed respiratory pattern analysis may further clarify the physiological mechanisms underlying diaphragmatic interventions in children with cerebral palsy.

Direct physiological assessment methods, such as diaphragmatic ultrasonography, could provide more specific information regarding diaphragmatic structure and excursion following intervention. However, MIP/MEP measurements and chest expansion assessments remain clinically feasible and standardized outcome measures that have been accepted in contemporary respiratory rehabilitation randomized controlled trials involving children with cerebral palsy.^3–6 In the present study, respiratory muscle testing was performed in accordance with ATS/ERS recommendations. ⁷ In addition, chest expansion was evaluated not only at the axillary level but also at epigastric and subcostal regions, which may more closely reflect lower thoracic and diaphragmatic mobility. We believe that the use of clinically applicable assessment tools is particularly important in pediatric rehabilitation settings, where accessibility and applicability to routine clinical practice remain highly relevant. Nevertheless, future studies incorporating ultrasonographic evaluation may further clarify the structural and functional mechanisms underlying diaphragmatic interventions in children with cerebral palsy.

Physiological respiratory improvements may not necessarily translate directly into measurable functional gains without task-specific integration into postural and motor activities. In the present study, Gross Motor Function Measure (GMFM-B) scores were included as a secondary outcome measure to explore the potential functional reflection of respiratory improvements, given the known contribution of the diaphragm to trunk control and postural stability. However, the intervention itself was not specifically designed as a task-oriented sitting or trunk training program. In this context, future studies combining respiratory interventions with task-specific trunk and postural rehabilitation approaches may help further clarify the relationship between respiratory and functional motor outcomes in children with cerebral palsy.

We acknowledge that the relatively small sample size may increase susceptibility to effect size inflation and limit reproducibility. However, the study was designed as a preliminary randomized controlled trial, and effect sizes were reported to support interpretation of clinical relevance alongside statistical significance. Non-parametric analyses were preferred in consideration of the sample size and data distribution characteristics. Dose-response relationships and intervention adherence are also important considerations for future pediatric respiratory rehabilitation research; however, evaluation of dose-response effects was not among the primary aims of the present study. We also support the emphasis on maintaining clear CONSORT-based reporting standards in small clinical trials.

In conclusion, we are pleased by the interest shown in our study and by the opportunity to further highlight the potential role of respiratory rehabilitation in children with cerebral palsy. We hope that increasing attention to this area will encourage future studies investigating both the physiological and functional effects of diaphragmatic interventions using more comprehensive and integrated approaches. We believe that improving awareness of respiratory involvement in cerebral palsy and expanding clinically applicable intervention strategies remain important goals within pediatric rehabilitation research and practice.