Study	Reason for exclusion
Bianchi 2014	Incorrect study design: prospective observational study.
Kang 2000	Incorrect study design: observational study design.
Silva 2012	Incorrect patient population: mechanically ventilated people diagnosed with head trauma, stroke, congestive heart failure, and ventilator‐associated pneumonia. No participants with NMD.
Toussaint 2003	Incorrect intervention: intrapulmonary percussive ventilation, which is a peripheral airway clearance technique and not a cough augmentation technique.
Toussaint 2009	Incorrect study design: prospective cross‐sectional observational study.
Winck 2004	Incorrect study design: prospective observational study.

NMD: neuromuscular disease.