No effect of oral high frequency oscillation combined with forced expiration manoeuvres on tracheobronchial clearance in chronic bronchitis
M van Hengstum, J Festen, C Beurskens, M Hankel, W van den Broek, F Corstens
European Respiratory Journal 1990 3: 14-18; DOI: 10.1183/09031936.93.03010014