Page 455 - Cardiac Nursing

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C HAPTER 1 9 / Exercise Testing 431
by the patient’s request to stop. The reason for stopping the test
should be carefully recorded because the symptoms or signs RECOVERY PERIOD
manifested by exercise often relate to the mechanism of impair-
ment. Determining the endpoint of an exercise test can be prob- Some debate exists as to whether the postexercise recovery period
lematic. It requires integration of objective physiologic data and should be an active or passive process. This decision should be
termination criteria with subjective judgment based on clinical made on the basis of the purpose of the exercise test. If the test is
experience. Some patients may be unable or unwilling to exer- performedfor diagnostic purposes, then it appears to be of value
cise to an adequate level. In patients with suspected coronary to place the patient in the supine position immediately after stop-
disease, a symptom-limited, maximal test is usually more diag- ping exercise. The increase in venous return to the heart observed
nostic. Thus, patients should be instructed to exercise to the in the supine position results in increases in ventricular volume,
point at which they can no longer continue because of fatigue, wall stress, and, consequently, myocardial oxygen demand. Several
dyspnea, or other symptoms. They should be informed that the studies have shown that ST-segment abnormalities are enhanced
test will be terminated if abnormal responses are observed by the in the supine position and that an active recovery may attenuate
operators. Although patients should be encouraged to exercise as the magnitude of these changes. 4,73 Once thought to be false-
long as possible, they should not be pushed beyond their capacity positive responses, ST-segment changes 2 to 4 minutes into
and any request to stop the test should be honored. Inability to recovery are now known to be particularly important for the de-
fully monitor the patient’s responses because of technical difficul- tection of ischemia. Patients with symptom-limiting angina or
ties should result in immediate termination of the test. Most prob- dyspnea may become more uncomfortable in the supine position
lems can be avoided by having an experienced physician, nurse, or and should recover in a seated upright or semirecumbent position.
exercise physiologist standing next to the patient, measuring blood If the test is performedfor nondiagnostic purposes such as for a
pressure and assessing patient appearance during the test. The ex- fitness evaluation in a healthy or athletic person, then an active re-
ercise technician should operate the recorder and treadmill, take covery may be safer and more comfortable.
appropriate tracings, enter data on a form, and alert the physician Typically, an active recovery period consists of walking on the
to any abnormalities that may appear on the monitor. treadmill at a speed of 1.5 to 2.0 mph or continuing to pedal the
Although many efforts have been made to objectify maximal cycle ergometer slowly at a work rate ranging from 0 to 25 W. An
effort, such as age-predicted maximal heart rate, a plateau in oxy- active recovery decreases the risk of hypotension and may mini-
gen uptake, exceeding the ventilatory threshold, or a respiratory mize the risk of dysrhythmias secondary to elevated cate-
exchange ratio greater than unity, all have considerable measure- cholamines in the postexercise period. Standing recovery should
ment error and intersubject variability. 50,68–71 This variability oc- be avoided because of potential complications associated with ve-
curs regardless of the population tested. The 95% confidence lim- nous pooling. Regardless of the method of recovery, patients
its for maximal heart rate based on age, for example, range should be monitored for at least 6 to 8 minutes into the postexer-
considerably (see Fig. 19-3); therefore, this endpoint is maximal cise period. Blood pressure, the electrocardiogram, and symptoms
17
for some and submaximal for others. The classic index of a per- should be monitored and recorded at 2-minute intervals for the
son’s cardiopulmonary limits, a plateau in oxygen uptake, is not duration of the recovery period. The recovery period should be ex-
observed in many patients, is poorly reproducible, and has been tended as long as necessary to resolve symptoms or abnormal he-
confused by the many different criteria applied. 68–71 Although modynamic or electrocardiographic responses. After completion
subjective, the Borg Perceived Exertion Scale is helpful for assess- of the recovery portion of the test, patients should be given
ing exercise effort 72 (Display 19-5). Good judgment on the part posttest instructions that include avoidance of long, hot showers
of the physician remains the most effective criterion for terminat- or baths. In addition, patients should be told they may experience
ing exercise. fatigue and muscle soreness and to avoid any heavy exertion that
day. Any pain or discomfort during the day after the test should
be reported to their physician immediately.
DISPLAY 19-5 Borg Rating of Perceived
Exertion Scale
6 ASSESSING TEST ACCURACY
7 Very, very light
8
9 Very light All diagnostic tests misclassify patients a certain percentage of the
10 time. In the context of the exercise test, this is not a trivial issue,
11 Fairly light because people who are inaccurately identified as havingdisease
12 may be subjected unnecessarily to additional, more invasive, and
13 Somewhat hard costly procedures. When the test is performedproperly, it com-
14 monly serves the very important purpose of screening those who
15 Hard should or should not undergo these additional procedures. How-
16 ever, a patient with significant CAD who is incorrectly classified
17 Very hard
18 as normal may not receive appropriate medical therapy. How ac-
19 Very, very hard curately the exercise test distinguishes people withdisease from
20 those without disease depends on the population tested, the defi-
nition of disease, and the criteria used for an abnormal test.
The most common terms used to describe test accuracy are
From Borg, G. A. V. (1985). An introduction to Borg’s RPE scale. Ithaca, NY: Movement
Publications. sensitivity and specificity. Sensitivity is the percentage of times a