Abstract: A peak flow meter has an element (4) displaceable along a hollow body (2) by the exhalation of a subject, and means for indicating the maximum displacement of that element as a measure of peak flow. Pre-set markers (20) are located at selected positions to indicate selected displacement values. The markers are in the form of elements that are snap-fitted onto the meter body at chosen positions and they have a toothed interengagement (12,28) with the body as they snap-fit into place.

Abstract: A peak flow meter has a body forming a chamber along which a piston can be moved against the force of a spring by a subject exhaling through an inlet into the chamber. A slot runs along a side of the chamber to allow the air to escape and a pointer is movable along the slot by the piston to indicate its maximum displacement. A deflector at the chamber inlet concentrates the flow through the chamber towards the side at which the slot is located. By the use of such a deflector it is possible to measure reliably relatively small peak exhalation rates.

Abstract: A Friedmann analyser wtih an arrangement of fixed and rotatable shutters for displaying different patterns of light spots to a subject has a screen for displaying to the operator each light spot pattern selected by illumination of a series of light-emitting elements at fixed positions over the screen area. The light-emitting elements are actuated by a fixed array of infra-red emitting and receiving elements that direct radiation onto a binary-coded reflective pattern displaceable with the rotatable shutter and sense the radiation reflected by said pattern so that with the displacement of the shutter different reflected code signals are sensed associated with respective shutter light patterns displayed to the subject.