ATS Pulmonary Function Laboratory Manual

ATS Pulmonary Function Laboratory Management & Procedure Manual | 3rd Edition

The second approach requires that the exercise be stopped when desaturation is observed and the patient allowed to rest (seated or standing). The O 2 flow rate is increased, and after 5 to 10 minutes to allow equilibration, the exer- cise is restarted. This approach may require several exercise sessions and O 2 flow-rate changes to achieve the desired information. It is to be noted that measuring O 2 saturation immediately after exercise is not acceptable. In hypox- emic patients O 2 saturation generally increases rapidly after the cessation of exercise. Indications and Contraindications The indications and contraindications for performing the exercise test for the assessment of desaturation are pro- vided in Tables 17.1 and 17.2, respectively. Table 17.1 Indications for Performing an Exercise Test for the Assessment of Desaturation • Assess and quantify the adequacy of Sa O 2 at rest and during exercise in patients who are clinically suspected of de- saturation (e.g., dyspnea on exertion, pulmonary disease, decreased carbon monoxide diffusing capacity [Dl CO ], decreased Pa O 2 at rest). • Titrate or adjust supplemental O 2 to treat hypoxemia or desaturation during activity. • Assess preoperatively for lung resection or transplant. • Assess the degree of impairment for medico-legal disability evaluation (e.g., pneumoconiosis, or asbestosis). • Ensure that oxygenation is maintained during anesthesia or operative procedures.

Table 17.2

Contraindications for Performing an Exercise Test for the Assessment of Desaturation

Absolute contraindications

• Unstable angina • Uncontrolled systemic hypertension • Recent systemic or pulmonary embolism

Relative contraindications

• For adults, a resting diastolic blood pressure >110 mmHg or resting systolic blood pressure >200 mm Hg (1). • If Sp O 2 <85% with patient breathing room air, do not perform a room-air assessment. • If a resting room air arterial blood gas (ABG) analysis results in any of the following: ○ pH <7.30 or >7.50 ○ Pa CO 2 >50 mm Hg and with pH <7.30 ○ Pa O 2 <55 mm Hg at sea level* ○ Sa O 2 <87%* ○ Carboxyhemoglobin (COHb) >8% ○ Methemoglobin (METHb) >5% ○ Total hemoglobin (tHb) <8 • Unstable (fluctuating) pulse oximetry reading or the oximeter does not display quality signal indicators as described in the manufacturers manual • Sustained tachydardia (e.g., in adults, a resting heart rate greater than 120 beats/minute after 10 minutes) • Non-compliant patient or one not capable of performing the test because of weakness, pain, fever, dyspnea, lack of coordination, or psychosis. • Recent (within the previous 4 weeks) myocardial infarction (MI) is a relative contraindi- cation. However, the test may be indicated in MI patients with coexisting lung disease to ascertain the need for supplemental O 2 during ambulation.

*If values are less than the listed values, perform the exercise test with supplemental O 2 .

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