ATS Pulmonary Function Laboratory Manual

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

5.2. Dyshemoglobins: COHb falsely elevates Sp O 2 lengths, and at high levels tends to force the Sp O 2 reading towards a value of 85% (9, 13, 14, 16–18). 5.3. Intravascular dyes, including methylene blue, indigo carmine, and indocyanine green have been reported to lower Sp O 2 measurements (8, 9). 5.4. Exposure of measuring probe to ambient light during measurement (8, 9, 12, 14, 17). 5.5. Low perfusion states, from vasoconstriction or hypothermia (8, 9, 14, 16, 17, 19, 32). 5.6. Nail polish, mood-type nail polish, or acrylic nail coverings can alter oximetry readings when a finger probe is used; black or brown nail polish significantly lower readings (20). Tattoos can also be a source of error and the probe should be located where tattoos do not exist. It is recommended that any nail polish be routinely removed before finger probes are used for pulse oximetry (8, 9, 21). 5.7. Inability to detect saturations below 83% with the same degree of accuracy and precision as at higher saturations (8, 9, 22, 23). 5.8. Inability to quantify the degree of hyperoxemia present (9, 24). 5.9. Hyper-bilirubinemia has been shown NOT to affect the accuracy of Sp O 2 readings (25–27). 5.10. Skin pigmentation can be a source of error, but this has not been consistently proven (8, 9, 13). 5.11. Venous pulsations: venous blood volume can also pulsate in some settings, producing erroneously low Sp O 2 readings and an inaccurate PR (28, 29). 6. To validate pulse-oximeter readings, direct measurement of Sa O 2 may be made on a CO-oximeter. The cor- relation of Sp O 2 to Sa O 2 should be done simultaneously with initial testing of the patient, then periodically re-evaluated if the patient’s clinical status has changed (9, 13, 16, 17, 22, 30). 7. A normal Sp O 2 in the presence of an elevated inspired O 2 concentration provides little or no information on the adequacy of patient ventilation. Pulse oximetry alone should not be relied upon as the sole monitor for patient status in situations such as bronchoscopy, intubation, or cardiac arrest (31). References 1. American Association for Respiratory Care Clinical Practice Guideline. Exercise testing for evalua- tion of hypoxemia and/or desaturation. 2001 Revision and Update. Respir Care 2001;46:514–522. 2. Dempsey JA, Wagner PD. Exercise-induced arterial hypoxemia. J Appl Physiol (1985) 1999;87: 1997–2006. 3. Swerts PM, Mostert R, Wouters EFM. Comparison of corridor and treadmill walking in patients with severe chronic obstructive pulmonary disease. Phys Ther 1990;70:439–442. 4. Perloff D, Grim C, Flack J, Frohlich ED, Hill M, McDonald M, Morgenstern BZ. Human blood pres- sure determination by sphygmomanometry. Circulation 1993;88:2460–2470. 5. Borg GAV. Perceived exertion as an indicator of somatic stress. Scand J Rehabil Med 1970;2:92–98. PubMed 6. Borg GAV. Psychophysical bases of perceived exertion. Med Sci Sports Exerc 1982;14:377–381. PubMed 7. Hess DR. Monitoring in Respiratory Care. NBRC Horizons 1993;19:1–2. 8. CLSI. Pulse Oximetry; Approved Guideline 2005. CLSI Document HS3-A: Volume 25, No. 5 (ISBN 1-56238-562-3. Wayne, PA: Clinical and Laboratory Standards Institute. 9. Welch JP, DeCesare MS, Hess D. Pulse oximetry: instrumentation and clinical applications. Respir Care 1990;35:584–601. 10. Escourrou PJ, Delaperche MF, Visseaux A. Reliability of pulse oximetry during exercise in pulmo- nary patients. Chest 1990;97:635–638. values; MetHb absorbs light at both oximeter wave-

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