Whistle and cough pressures in children with neuromuscular disorders.

RATIONALE

Expiratory muscle strength is a determinant of cough function. Maximal static expiratory pressure (PEmax) manoeuvres are widely used but are limited by patient motivation and technique. The study hypothesized that whistle mouth (PmW) and cough gastric (PgasCough) pressures might provide additional tests of expiratory muscle strength in children and young adults with neuromuscular disease (NMD).

METHODS

We retrospectively reviewed the data of lung function and respiratory muscle tests of all the patients with NMD followed in our centre between November 2001 and December 2013. PmW and PgasCough were compared to other common tests.

RESULTS

Three hundred and four respiratory evaluations were performed in 143 patients, aged 3-29 years old. Seventy-two patients had 2 to 8 evaluations. Median [interquartiles] PEmax (38 [28-54] cmH2O) did not differ significantly from PgasCough (45 [30-60] cmH2O) and both were significantly greater than PmW (30 [19-44] cmH2O). Significant good correlations were observed between all the expiratory muscle parameters. The best correlation was observed between PEmax and PmW (r = 0.812, p < 0.001). Moreover, good correlations were found between the percentage of predicted forced vital capacity and PmW (r = 0.619, p < 0.001) and PgasCough (r = 0.568, p < 0.001). Concerning the whistle test, the non-invasive measurement highly correlated with invasive measurements.

CONCLUSIONS

PmW and PgasCough are simple and valuable tests to assess expiratory muscle strength in children and young adults with NMD. These tests are particularly useful in children having difficulties to perform PEmax manoeuvre. They have the great advantage of their simplicity, but PgasCough is limited by its invasiveness.