Physical Exam

Oxygen Saturation

also known as Pulse oximetry

🎬

Video coming September 2026

How to Perform

Place a pulse oximeter probe on a well-perfused site (typically a fingertip, an earlobe, or a toe), aligning the light source and detector across the tissue and ensuring the nail is free of dark polish. Allow the reading to stabilize, confirm that the displayed pulse rate matches the patient's palpated pulse and that the signal is adequate as indicated by a smooth and regular waveform, then record the oxygen saturation (SpO2).

How to Interpret

Cardiac Tamponade

Oximetry paradoxus ratio 1.2 or above

Rule in

Minimally helpfulDerived CI

Rule out

—

Evidence:Limited

Hepatopulmonary Syndrome

Oxygen saturation <96% in chronic liver disease

Rule in

Minimally helpfulDerived CI

Rule out

Not helpfulDerived CI

Evidence:Limited

Pneumonia

Hypoxemia (SpO2 <95% on room air)

Rule in

Somewhat helpful

Rule out

Not helpful

Evidence:Strong

References

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Hartert TV, Wheeler AP, Sheller JR. Use of pulse oximetry to recognize severity of airflow obstruction in obstructive airway disease: correlation with pulsus paradoxus. Chest. 1999;115(2):475-481. PMID: 10027449.
Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost. 2004;2(8):1247-55. PMID: 15304025. Kline JA, Courtney DM, Kabrhel C, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost. 2008;6(5):772-80. PMID: 18318689. Singh B, Mommer SK, Erwin PJ, Mascarenhas SS, Parsaik AK. Pulmonary embolism rule-out criteria (PERC) in pulmonary embolism — revisited: a systematic review and meta-analysis. Emerg Med J. 2013;30(9):701-6. PMID: 23038695. Wells PS, Anderson DR, Rodger M, et al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism. Thromb Haemost. 2000;83(3):416-20. PMID: 10744147. Le Gal G, Righini M, Roy PM, et al. Prediction of pulmonary embolism in the emergency department: the revised Geneva score. Ann Intern Med. 2006;144(3):165-71. PMID: 16461960.
Wang CS, FitzGerald JM, Schulzer M, Mak E, Ayas NT. Does this dyspneic patient in the emergency department have congestive heart failure? JAMA. 2005;294(15):1944-1956. doi:10.1001/jama.294.15.1944. PMID: 16234501. Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure. Circulation. 2022;145(18):e895-e1032. PMID: 35363499. Nieminen MS, Bohm M, Cowie MR, et al. Executive summary of the guidelines on the diagnosis and treatment of acute heart failure. Eur Heart J. 2005;26(4):384-416. PMID: 15681577.
Keahey L, Bulloch B, Becker AB, Pollack CV Jr, Clark S, Camargo CA Jr; Multicenter Asthma Research Collaboration (MARC) Investigators. Initial oxygen saturation as a predictor of admission in children presenting to the emergency department with acute asthma. Ann Emerg Med. 2002 Sep;40(3):300-307. doi:10.1067/mem.2002.126813. PMID: 12192354.
Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention (2024 Report). Available at https://ginasthma.org. National Asthma Education and Prevention Program. Expert Panel Report 3 (EPR-3): Guidelines for the Diagnosis and Management of Asthma. NIH Publication 07-4051; 2007. Cloutier MM, Baptist AP, Blake KV, et al. 2020 Focused Updates to the Asthma Management Guidelines. J Allergy Clin Immunol. 2020;146(6):1217-1270. doi:10.1016/j.jaci.2020.10.003. PMID: 33280709.
American College of Surgeons Committee on Trauma. Advanced Trauma Life Support: Student Course Manual. 10th ed. American College of Surgeons; 2018. Roberts DJ, Leigh-Smith S, Faris PD, et al. Clinical presentation of patients with tension pneumothorax: a systematic review. Ann Surg. 2015;261(6):1068-78. doi:10.1097/SLA.0000000000001073. PMID: 25563887. Inaba K, Branco BC, Eckstein M, et al. Optimal positioning for emergent needle thoracostomy. J Trauma. 2011;71(5):1099-103. PMID: 22071914.
Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):801-810. doi:10.1001/jama.2016.0287. PMID: 26903338. PMC: PMC4968574. Seymour CW, Liu VX, Iwashyna TJ, et al. Assessment of Clinical Criteria for Sepsis. JAMA. 2016;315(8):762-774. PMID: 26903335. Evans L, Rhodes A, Alhazzani W, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2021. Crit Care Med. 2021;49(11):e1063-e1143. doi:10.1097/CCM.0000000000005337. PMID: 34605781. Vincent JL, Moreno R, Takala J, et al. The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. On behalf of the Working Group on Sepsis-Related Problems of the European Society of Intensive Care Medicine. Intensive Care Med. 1996;22(7):707-10. PMID: 8844239.
Phua SL, Hawke FE, Chuter VH, Tehan PE. Sensitivity and Specificity of Pulse Oximetry for Identification of Peripheral Artery Disease: A Systematic Review. J Cardiovasc Nurs. 2025;40(2):E65-E71 (published online 2023). doi:10.1097/JCN.0000000000001030. PMID 37787731.
Pilatis ND, Jacobs LE, Rekpattanapipat P, et al. Clinical predictors of pulmonary hypertension in patients undergoing liver transplant evaluation. Liver Transpl. 2000;6(1):85-91. doi:10.1002/lt.500060116. PMID: 10648583.
Goldhill DR, McNarry AF, Mandersloot G, McGinley A. A physiologically-based early warning score for ward patients: the association between score and outcome. Anaesthesia. 2005;60(6):547-553. doi:10.1111/j.1365-2044.2005.04186.x. PMID: 15918825.
Forde KA, Fallon MB, Krowka MJ, Sprys M, Goldberg DS, Krok KL, Patel M, Lin G, Oh JK, Mottram CD, Scanlon PD, Kawut SM; Pulmonary Vascular Complications of Liver Disease 2 Study Group. Pulse oximetry is insensitive for detection of hepatopulmonary syndrome in patients evaluated for liver transplantation. Hepatology. 2019;69(1):270-281. PMID: 30070715. PMC6652183.
Doukky R, Improvola G, Shih MJ, et al. Usefulness of oximetry paradoxus to diagnose cardiac tamponade. Am J Cardiol. 2019;123(3):498-506. doi:10.1016/j.amjcard.2018.10.031. PMID: 30477799.
Cloutier MM, Baptist AP, Blake KV, et al. 2020 focused updates to the asthma management guidelines. J Allergy Clin Immunol. 2020;146(6):1217-1270. PMID: 33280709.
Doukky R, Improvola G, Shih MJ, et al. Usefulness of oximetry paradoxus to diagnose cardiac tamponade. Am J Cardiol. 2019;123(3):498-506. PMID: 30477799.
Forde KA, Fallon MB, Krowka MJ, et al. Pulse oximetry is insensitive for detection of hepatopulmonary syndrome in patients evaluated for liver transplantation. Hepatology. 2019;69(1):270-281. PMID: 30070715.
Global Initiative for Asthma. Global strategy for asthma management and prevention, 2024 report. Global Initiative for Asthma; 2024.
Goldhill DR, McNarry AF, Mandersloot G, McGinley A. A physiologically-based early warning score for ward patients: the association between score and outcome. Anaesthesia. 2005;60(6):547-553. PMID: 15918825.
Keahey L, Bulloch B, Becker AB, Pollack CV Jr, Clark S, Camargo CA Jr; Multicenter Asthma Research Collaboration (MARC) Investigators. Initial oxygen saturation as a predictor of admission in children presenting to the emergency department with acute asthma. Ann Emerg Med. 2002;40(3):300-307. PMID: 12192354.
Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost. 2004;2(8):1247-1255. PMID: 15304025.
Phua SL, Hawke FE, Chuter VH, Tehan PE. Sensitivity and specificity of pulse oximetry for identification of peripheral artery disease: a systematic review. J Cardiovasc Nurs. 2025;40(2):E65-E71. PMID: 37787731.
Pilatis ND, Jacobs LE, Rekpattanapipat P, et al. Clinical predictors of pulmonary hypertension in patients undergoing liver transplant evaluation. Liver Transpl. 2000;6(1):85-91. PMID: 10648583.
Roberts DJ, Leigh-Smith S, Faris PD, et al. Clinical presentation of patients with tension pneumothorax: a systematic review. Ann Surg. 2015;261(6):1068-1078. PMID: 25563887.
Seymour CW, Liu VX, Iwashyna TJ, et al. Assessment of clinical criteria for sepsis. JAMA. 2016;315(8):762-774. PMID: 26903335.
Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):801-810. PMID: 26903338.
Wang CS, FitzGerald JM, Schulzer M, Mak E, Ayas NT. Does this dyspneic patient in the emergency department have congestive heart failure? JAMA. 2005;294(15):1944-1956. PMID: 16234501.