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BACKGROUND: Manually-assisted coughing and mechanical insufflation-exsufflation (MI-E) are commonly used in patients with Duchenne muscular dystrophy (DMD). Few studies have compared cough peak flow (CPF) with manually-assisted coughing to other methods, such as MI-E + manually-assisted coughing. In addition, few studies have reported the reliability of the measured CPF values. This study aimed to compare CPF with different cough-assistance methods and to examine the reliability of CPF data. METHODS: The study included 12 subjects with DMD (mean age, 34 ± 8 y). CPF, CPF + manually-assisted coughing (assisted CPF), maximum insufflation capacity (MIC) + CPF (MIC-CPF), MIC + manually-assisted coughing (MIC+assisted CPF), MI-E (MI-E--CPF), and MI-E + assisted CPF were measured. A spirometer was used to compare CPF measurements obtained with each of the cough-assist techniques. The reliability of the measured CPF values was analyzed using Bland-Altman analysis. RESULTS: CPF was 59 ± 34 L/min, assisted CPF was 113 ± 32 L/min, MIC-CPF was 170 ± 30 L/min, MIC+assisted CPF was 224 ± 62 L/min, MI-E--CPF was 199 ± 40 L/min, and MI-E + assisted CPF was 240 ± 38 L/min. A fixed and proportional bias was found in the CPF measurements made with the peak flow meter and the spirometer. The average 95% CI in the difference between peak flow meter, MI-E, and CPF obtained using the spirometer were -7.45 to -1.95 and -1.45 to 4.95, respectively. Test for correlation was r = 0.54 (P < .001) for CPF (peak flow meter) and CPF (spirometer) and r = 0.17 (P = .17) in CPF (MI-E) and CPF (spirometer), respectively. CONCLUSION: MI-E + assisted CPF was the highest. The CPF measured with the peak flow meter suggested underestimation. [ABSTRACT FROM AUTHOR]