Patent ID: 6626846
Filing Date: 2003-09-30
Classification: A61B

Abstract:
A meter for measuring the ventilatory capacity of a subject, the meter having: a chamber formed by a wall with an axial direction defined by an inner surface of said wall, said chamber having an exit slot in said wall; a piston within said chamber being displaceable axially against a resilient bias by blowing air into said chamber, and means for recording a maximum displacement of said piston, said piston having a transverse dimension perpendicular to said axial direction, said exit slot being adapted for the escape of the air from said chamber as said slot is increasingly opened by the displacement of said piston against said bias, there being a bounded region of a sliding contact between said piston and said inner surface of said wall of at any one position of said piston, said bounded region being separated axially by a distance not less than about 25% of the transverse dimension of said piston, said sliding contact guiding displacement of said piston and preventing tilting of said piston.