Abstract: An apparatus for measuring peak expiratory flow of a human patient and an incentive spirometer has a housing having a passageway and a mouthpiece connected to the passageway. An elongated slender rod extends through the passageway and has a sliding member a predetermined size slideably mounted thereon adapted to slide on the rod when a patient exhales into the mouthpiece through the passageway. A magnet is attached to the slideable member for sliding therewith to hold the slideable member in position at the maximum position the slideable is raised on the slender rod. The passageway may be tapered in a reverse cone shape making the sliding member more difficult to raise as it moves up the passageway so that patients can lift the slideable member, while most patients cannot lift the member all the way to the top of the passageway.

Abstract: A drainage control valve apparatus utilizes a pressure relief valve for opening upon a predetermined fluid pressure being applied thereto and a liquid column is used for holding the pressure relief valve open by the weight of the liquid column escaping past the pressure relief valve to apply a negative pressure to the back of a pressure relief valve element. A small opening or a check valve releases the suction column when drainage is complete to allow the pressure relief valve to close. The pressure relief valve may be a spring biased valve and may be adjusted by varying the compression on the spring. The unit may be attached to a patient's leg with a strap. A method of draining a bladder is provided having the steps of opening a pressure relief valve under bladder pressure in a catheter, holding the pressure relief valve open with the suction of a column of liquid formed by the liquid passing the opened pressure relief valve and releasing the pressure relief valve when drainage is substantially complete.