CPF was measured using the Mini–Wright Peak Flow Meter from Clement Clarke International Ltd., portable, made of plastic material. It was used in order to assess the strength and speed exerted by the expiration in liters per minute (L/min). During the period in which we used our mechanical tool we did not realize any damage of the instrument. The testing was done in sitting position in a chair with no armrest. Subjects were seated and asked to perform a voluntary cough. The volunteers performed a maximal inspiration, followed by a quick, short and explosive expiration on the peak flow meter. The difference from the peak expiratory flow is the higher glottis pressure and the higher resistance induced by the closed glottis, which characterizes a forced cough. Three measures were carried out and we considered the average of three results for each individual.