The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts

COMPARISON OF PULSE OXIMETRY UTILIZING A FOREHEAD PROBE VERSUS FINGER PROBE IN PATIENTS WITH LUNG DYSFUNCTION UNDERGOING SIMPLE STEP EXERCISE

Carl D. Mottram1, Rhonda Baumberger1, Kelly Sapan1, Mark Shafer1, Michael Stoffels1, Alan Zeccardi1, Paul Scanlon1



Background: Pulse oximetry is used for the assessment of oxygen saturation (SpO2) and gas exchange during exercise testing. However, reliability of arterial saturation data continues to be an issue. Assessment of the quality of the signal is critical to interpretation of the data. Two major sources of poor quality are lack of signal secondary to low perfusion and motion artifact. This is especially a problem during exercise testing. Both entities can cause either a false positive (desaturation when none is present) or a false negative (missed hypoxemia) errors, although false positive errors tend to be more common. Recently manufacturers have developed forehead sensors that try to address these sources of noise. Hypothesis: The forehead probe because of its central location can detect desaturation faster and more accurately than a finger probe that is peripherally located during a standardized step exercise test used to screen for exercise induced desaturation.

Methods:
46 subjects referred to the pulmonary function lab for a complete pulmonary function test (PFT) were included in the study. Inclusion criteria was a DLCO <50%, which would predispose the subjects to having exercise induced desaturation. As a component of a PFT our laboratory performs a standardized timed step test to screen for exercise induced desaturation. Two Nellcor N-600 pulse oximeters, one unit with a standard reusable finger probe and the other with the Max-Fast forehead probe will be placed on the subject according to manufacturer's instructions. Correct placement and signal strength will be assessed prior to starting exercise. Resting saturation and heart rate will then be recorded. The subject will then be instructed to step to a cadence of 15 steps per minute on a 9 inch step for 3 minutes or until volitional termination. At termination of exercise SpO2 and heart rate was recorded.

Results:
Table 1

Conclusion:
In patients performing a submaximal exercise test, although there was a statistical difference between the finger probe and forehead probe, the results were not clinically significant. However there did appear to be a systematic bias with the forehead probe reading higher than the finger probe both at rest and with exercise. As an addition finding, 61% of the subjects with a DLCO <50% showed desaturation during exercise using this simple testing modality (desaturation = change ≤ or value of <93%).