Page 248 - Cardiac Nursing

LWBK340-c10_p211-244.qxd 30/06/2009 10:46 AM Page 224 Aptara

224 PA R T III / Assessment of Heart Disease

descent. Consistently large a waves are seen in tricuspid stenosis,
pulmonary hypertension, and right ventricular failure. Cannon a Table 10-3 ■ ACCEPTABLE BLADDER DIMENSIONS
waves are seen in patients with atrioventricular dissociation as the (IN CM) FOR ARMS OF DIFFERENT SIZES *
3
right atrium contracts against the closed tricuspid valve. The a Bladder Bladder Arm Circumference
wave is absent in atrial fibrillation because of the absence of coor- Cuff Width (cm) Length (cm) Range at Midpoint (cm)
dinated atrial contraction. Elevated v waves and rapid y descents
suggest tricuspid regurgitation or increased intravascular volume. Newborn 3 6 6
Blunting of the y descent suggests impaired atrial emptying in Infant 5 15 6–15 † †
early ventricular diastole, such as occurs in tricuspid stenosis, peri- Child 10 8 21 16–21
22–26
24
Small adult
cardial disease, or cardiac tamponade. Adult 13 30 27–34
Large adult 16 38 35–44
Adult thigh 20 42 45–52
Blood Pressure
* There is some overlapping of the recommended range for arm circumferences to limit
Systemic arterial blood pressure can be measured indirectly or di-
the number of cuffs; it is recommended that the larger cuff be used when available.
rectly. Indirect measurement of blood pressure is most common † To approximate the bladder width:arm circumference ratio of 0.40 more closely in in-
and is described in this section. Direct measurement of blood fants and children, additional cuffs are available.
From Perloff, D., Grim, C., Flack, J., et al. (2001). Human blood pressure determination
pressure, an invasive technique requiring placement of an arterial
by sphygmomanometry. Dallas, TX: American Heart Association.
catheter, may be necessary in certain conditions, such as clinical
shock. Direct measurement of blood pressure is discussed in
Chapter 21. accuracy of measurement, should be approximately twice that of
Blood pressure should be measured at each health encounter. width, or 80% of the limb circumference. Inflatable bladders and
The auscultatory method of measurement with a properly cali- cuffs are available in various sizes. Table 10-3 summarizes recom-
brated and validated instrument should be used. Patients should mended bladder dimensions for blood pressure cuffs. It is impor-
be seated quietly in a chair, with feet on the floor and arm sup- tant to remember that cuff size is determined by patient size, not
ported for at least 5 minutes before measurement. 20 patient age. 22
Evaluate the patient’s current blood pressure. If it differs
greatly from the usual, immediate intervention may be required. Manometers. There are two types of manometers: mercury
Normal blood pressure in people 18 years of age or older is de- and aneroid. Mercury manometers, which are the most reliable, can
fined as less than 120/80 mm Hg, and prehypertension is defined be mounted either on a portable stand or on the wall above the bed
as systolic pressure of 120 to 139 mm Hg or diastolic pressure of or table. A reservoir of mercury (Hg) is attached to the bottom of
80 to 90 mm Hg. Patients with prehypertension are at increased the manometer, which is calibrated in millimeters (mm). In re-
risk for progression to hypertension. 20 Hypertension is defined as sponse to pressure exerted on the bulb, mercury rises vertically in
systolic blood pressure of 140 mm Hg or greater, diastolic blood the manometer. As pressure is released from the bag, the column of
pressure of 90 mm Hg or greater, or taking antihypertensive med- mercury falls, and blood pressure can be measured in millimeters
ication. 20 (See Chapter 35 for treatment of hypertension.) In of mercury. It is important that the meniscus of the mercury be at
western societies, blood pressure tends to increase with increasing eye level when the blood pressure is measured. The blood pressure
age. This increase is not biologic, and there is clear evidence that reading should be taken at the top of the meniscus. If the wall
lowering blood pressure in older adults reduces the risk of stroke, mounting is too high or the portable stand too low, errors in blood
cardiac disease, and all-cause mortality. 21 The higher the blood pressure determinations will be made.
pressure, the greater the increase in the heart’s work and oxygen In response to efforts by the Environmental Protection Agency
consumption. Blood pressures less than 90/60 mm Hg may de- to reduce potential mercury spills and exposure, many clinical fa-
crease blood and oxygen delivery to an already compromised my- cilities are using aneroid gauges or electronic monitoring devices,
ocardium. Taking into account symptoms of myocardial ischemia To date mercury manometers remain the gold standard. Accurate
and adequacy of cerebral and peripheral perfusion may enable the measurement of blood pressure with non-mercury instruments re-
examiner to judge more accurately the clinical significance of quires sufficient standards of validation and stringent programs of
blood pressure changes in the cardiac patient. calibration. 23
Aneroid manometers have round gauges calibrated in millimeters
Sphygmomanometer of mercury, or torr (1 torr 1 mm Hg), and affixed to the blood
pressure cuff. Advantages of the aneroid manometer are that it is
Blood pressure is measured indirectly using a sphygmomanometer
easily seen, is conveniently portable, and, with the cuff, composes
(inflatable bladder inside a pressure cuff, a manometer, and an in-
one unit. Unfortunately, the calibration of the dial frequently be-
flation system) and stethoscope. Stethoscopes are described later
comes inaccurate. It is important before each use to check that the
in this chapter.
indicator needle is pointing to the zero mark on the dial. If the nee-
Bladder and Cuff. The inflatable bladder fits inside a nondis- dle is either below or above this mark, the blood pressure reading
tensible covering, termed the cuff. Size and placement of the blad- will be incorrect and the scale may no longer be linear.
der (rather than the cuff ) are crucial in obtaining accurate blood Calibration of an aneroid manometer is performed using a
pressure measurements. The bladder width should be 40% of the mercury manometer as the reference manometer (Fig. 10-10). 22
circumference of the limb (usually the arm) to be used. Bladders The mercury manometer must be functioning correctly to obtain
that are too narrow for the size of the limb reflect a falsely elevated reliable results. Aneroid manometers should be recalibrated by
blood pressure, whereas bladders that are too wide reflect an erro- qualified personnel at least yearly or whenever the needle does not
neously low blood pressure. Bladder length, which also affects point to zero.