Respiratory dysfunction is the major cause of morbidity and mortality in patients with spinal muscular atrophy (SMA). Air stacking is a clearance airway technique frequently used but its effects on cardiac autonomic function in patients with spinal muscle atrophy is not clear.

Objective: To evaluate the acute effect of air stacking and posture on cardiac autonomic function in patients with spinal muscular atrophy types II and III.

Methods: Patients with spinal muscle atrophy type II and III will be recruited. Electrocardiogram signals will be recorded for analyses of heart rate variability during air stacking in supine and sitting position.

Background: Respiratory dysfunction is the major cause of morbidity and mortality in patients with spinal muscular atrophy. Air stacking is a clearance airway technique frequently used but its effects on cardiac autonomic function in patients with spinal muscle atrophy is not clear.

Objective: To evaluate the acute effect of air stacking and posture on cardiac autonomic function in patients with spinal muscular atrophy types II and III.

Methods: Patients with spinal muscle atrophy type II and III will be recruited. Electrocardiogram signals will be recorded for analyses of heart rate variability during air stacking in supine and sitting position. Data will collected before, during and after air stacking and will be compared using Anova Repeated Measures or Kruskal-Wallis Anova on Ranks, followed by Tukey test. The relationship between heart rate variability indexes and age will be evaluated by Pearson correlation. Significant level will be set at 5%.

Inclusion Criteria:

• diagnosis of SMA types II and III,
• absence of acute respiratory disease in the last two weeks,
• agreement to participate in the study,
• according written informed consent and
• at least 5 years old.

Exclusion Criteria:

• respiratory disease in the last two weeks