(3) Rubber tubes. One tube connects the bladder and handbulb. Air that is
forced out of the handbulb travels through the tube and enters the bladder. A second
tube connects the bladder and the gauge.
(4) Release valve. The release valve (screw) is a device for releasing air
from the bladder. It is located between the handbulb and the tubing. One hand can
operate both the handbulb and the release valve easily. The valve is controlled by a
screw. When tightened, no air escapes. When unscrewed fully, the air escapes rapidly.
(Note: The screw does not separate from the apparatus. "Unscrewed fully" means the
screw is turned so that air will escape as fast as possible.) The screw can also be
turned to any position between completely closed and full release. In this way, you can
let air escape from the bladder as quickly or as slowly as you wish.
(5) Gauge. The gauge measures the air pressure in the bladder. There are
two types of gauges--the mercury gauge and the aneroid gauge.
(a) Mercury. The mercury gauge has a column of mercury in a glass
tube. The column of mercury measures the air pressure in the bladder. The higher the
pressure of air in the bladder, the higher the column of mercury. The height of the
column of mercury is determined using a scale to the side of the tube containing the
mercury. Usually there is a scale on each side of the glass tube in order to make it
easier to read the height of the column. As air is released from the bladder, the air
pressure drops and the column of mercury becomes shorter.
(b) Aneroid. The aneroid gauge is circular and has a dial. The greater
the air pressure in the bladder, the farther the needle on the dial rotates. A scale on the
dial is equivalent to the scale of the mercury gauge. Both scales measure the force of
air pressure in the bladder in terms of mm Hg. As the air pressure is released, the
needle moves in a counter-clockwise direction. The gauge will normally be designed so
that it can be attached to the bladder. This frees the person taking the blood pressure
from having to hold the gauge in one of his hands.
b. Stethoscope. The stethoscope is an instrument used for listening to sounds
produced within the body. A stethoscope consists of a diaphragm, metal and rubber
tubing, and earpieces (figure 5-3).
(1) Diaphragm. The diaphragm is normally a flat metal disk that is placed
on the body area being examined. The diaphragm will pick up sounds produced within
the body such as the heartbeat and breathing sounds. Sometimes a bell-shaped
listening device is used instead of a flat disk. Some stethoscopes have combination
(both flat disk and bell) listening devices.
(2) Tubing. The hollow and metal tubes transmit the sounds from the
diaphragm to the earpieces. The rubber tubing provides flexibility.