Respiratory disease reduces the ability to perform exercise. Dynamic exercise that involves large muscle groups produces increases in metabolic O₂ consumption (O₂) and CO₂ production (CO₂). This increase in metabolic demand leads to stresses on other mechanisms taking part in O₂ and CO₂ transport. Exercise testing measures the functional reserves of these mechanisms by testing under load. Analysis of ventilatory and cardiovascular disorders includes procedures that measure respiratory outcomes, blood gas values, and cardiovascular responses during exercise. Ventilation and gas exchange are altered during exercise in healthy persons; however, specific abnormalities are noted in the presence of cardiovascular or respiratory impairment. Exercise tests are valuable for assessing the severity and type of impairment in existing or undiagnosed conditions.

The normal response to graded exercise is an increase in ventilation and cardiac output such that alveolar and arterial gases (i.e., O₂ and CO₂) are maintained at optimal levels to meet metabolic demands. A cardiopulmonary exercise test (CPET) is the measurement of the patient’s ventilatory and alveolar–arterial gas responses during exercise. No significant or abnormal changes in the electrocardiographic complex, blood pressure, airflow patterns during inspiration and expiration, arterial blood gases (ABGs) and chemistry, or hemodynamic pressures should occur. Exercise testing is done to evaluate fitness, functional capacity, and other limiting factors in persons with obstructive or restrictive diseases. The efficiency of the cardiopulmonary system may be altered during exercise; CPET assesses ventilation, gas exchange, and cardiovascular function during increased demands. Dyspnea on exertion due to cardiovascular causes can be differentiated from that due to respiratory causes. Precise information about mechanisms that influence O₂ and CO₂ transport during exercise can be obtained by using a staged approach.

A CPET can detect or exclude many conditions even though the response may be nonspecific. For example, if the patient complains of severe shortness of breath despite a normal exercise response, a psychogenic cause is likely. However, a few conditions exhibit diagnostic responses—for example, exercise-induced asthma or myocardial ischemia. These tests can also reveal the degree of impairment in conditions affecting the respiratory and circulatory systems and may uncover unsuspected abnormalities (Table 14.2).

Most clinical problems can be assessed during the simple procedures included in stage 1 (see Procedure section for description) that should be done before more complex tests. Abnormal results indicate that more precise information is required through stage 2 protocols. If stage 3 protocols are implemented, arterial blood analysis is necessary. In 75% of cases, stage 1 is sufficient. Oxygen titration can be done during graded exercise to determine the oxygen needs for improving exercise tolerance and increasing functional capacity.

1. Stage 1:

   1. Place ECG electrodes on the patient’s chest and connect to ECG machine.

   2. Position a facemask on the patient to monitor oxygen intake and carbon dioxide output.

   3. Place a blood pressure cuff and pulse oximeter appropriately.

   4. Record blood pressure readings, ECG analysis, and ventilation during incremental cycle ergometry or treadmill walking.

   5. Take measurements at the end of each minute. Remember that the test continues until maximal allowed symptoms occur (i.e., to a symptom-limited maximum). Measure O₂ uptake (O₂) and CO₂ output (CO₂) if possible.

   6. Alert the patient that total examination time is approximately 30 minutes.

2. Stage 2:

   1. In this stage, more complex analytic methods are required.

   2. Have exercise build to a steady state, usually 3–5 minutes for each workload.

   3. In addition to stage 1 measurements, determine mixed venous CO₂ tension by means of rebreathing techniques.

3. Stage 3:

   1. In this stage, blood gas sampling and analysis are required.

   2. Insert an indwelling catheter into the brachial or radial artery.

   3. In addition to stage 2 tests, determine measurements for cardiac output, alveolar ventilation, ratio of dead space to tidal volume (VD/VT), alveolar-to-arterial O₂ tension difference (A-aDO₂), venous admixture ratio, and blood lactate concentrations.

4. See Chapter 1 guidelines for intratest care.

Altered values may reveal:

1. Cardiac arrhythmias or ischemia

2. Degree of functional impairment caused by obstructive or restrictive ventilatory 
disease

3. Hypoventilation

4. Workload level at which metabolic acidosis (lactic acidosis) occurs

Pretest Patient Care

1. Explain the purpose and procedure for exercise stress testing and assess for contraindications, interfering factors, and ability to follow verbal instructions.

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

1. The exercise tolerance of any person is affected by the degree of impairment related to:

   1. Mechanical factors

   2. Ventilatory efficiency

   3. Gas exchange factors

   4. Cardiac status

   5. Physical condition

   6. Sensitivity of the respiratory control mechanism

2. Obese persons have a higher-than-normal oxygen consumption at any given work rate, even though muscular and work efficiency values are normal.

Normal

• Increase in ventilation, heart rate, and blood pressure appropriate to the level of exercise

• No abnormal changes in the ECG (no arrhythmias), ABGs, or hemodynamic pressures