Impact of altitude-adjusted hypoxia on the Pulmonary Embolism Rule-out Criteria



      The Pulmonary Embolism Rule-out Criteria (PERC) defines hypoxia as an oxygen saturation (O2 sat) < 95%. Utilizing this threshold for hypoxia at a significant elevation above sea level may lead to an inflated number of PERC-positive patients and unnecessary testing. The aim of this study was to determine the effect of an altitude-adjusted O2 sat on PERC's sensitivity and the potential impact on testing rates.


      At the University of Utah Emergency Department (ED) (elevation: 4980 ft/1518 m), we prospectively enrolled a convenience sample of patients presenting with chest pain and/or shortness of breath. We calculated PERC utilizing triage vital signs and baseline clinical variables and noted the diagnosis of acute PE during the ED visit. We adjusted the PERC O2 sat threshold to <90% to account for altitude to determine the potential impact on outcomes and decision tool performance.


      Of 3024 study patients, 1.9% received the diagnosis of an acute PE in the ED, resulting in a sensitivity of 96.6% for the traditional PERC (95% CI: 88.1%–99.6%). Utilizing a definition of hypoxia of <90%, the sensitivity of the altitude-adjusted PERC rule was 94.8% (95% CI: 85.6%–98.9%). Assuming that imaging would not have been pursued for PERC-negative patients, the altitude-adjusted PERC rule would have reduced the overall rate of advanced imaging by 2.7% (95% CI: 1.8%–4.1%).


      Adjusting the PERC O2 sat threshold for altitude may result in decreased rates of advanced imaging for PE without a substantial change in the sensitivity of the PERC rule.
      To read this article in full you will need to make a payment
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to The American Journal of Emergency Medicine
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Kline J.A.
        • Mitchell A.M.
        • Kabrhel C.
        • Richman P.B.
        • Courtney D.M.
        Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism.
        J Thromb Haemost. 2004 Aug; 2: 1247-1255
        • Kline J.A.
        • Courtney D.M.
        • Kabrhel C.
        • Moore C.L.
        • Smithline H.A.
        • Plewa M.C.
        • et al.
        Prospective multicenter evaluation of the pulmonary embolism rule-out criteria.
        J Thromb Haemost. 2008 May; 6: 772-780
        • Fesmire F.M.
        • Brown M.D.
        • Espinosa J.A.
        • Shih R.D.
        • Silvers S.M.
        • Wolf S.J.
        • et al.
        American College of Emergency Physicians. Critical issues in the evaluation and management of adult patients presenting to the emergency department with suspected pulmonary embolism.
        Ann Emerg Med. 2011 Jun; 57: 628-652
        • Hackett P.H.
        • Roach R.C.
        High-altitude medicine.
        in: Auerbach P.S. Wilderness medicine: management of wilderness and environmental emergencies. Mosby, St. Louis, MO1995: 1-37
        • Goldberg S.
        • Buhbut E.
        • Mimouni F.B.
        • Joseph L.
        • Picard E.
        Effect of moderate elevation above sea level on blood oxygen saturation in healthy young adults.
        Respiration. 2012; 84: 207-211
        • Rojas-Camayo J.
        • Mejia C.R.
        • Callacondo D.
        • Dawson J.A.
        • Posso M.
        • Galvan C.A.
        • et al.
        Reference values for oxygen saturation from sea level to the highest human habitation in the Andes in acclimatised persons.
        Thorax. 2017 Oct 20; ([Epub ahead of print, pii: thoraxjnl-2017-210598])
      1. Accessed February 6, 2018.

        • Wolf S.J.
        • Mccubbin T.R.
        • Nordenholz K.E.
        • Naviaux N.W.
        • Haukoos J.S.
        Assessment of the pulmonary embolism rule-out criteria rule for evaluation of suspected pulmonary embolism in the emergency department.
        Am J Emerg Med. 2008 Feb; 26: 181-185
        • Morris A.H.
        • Kanner R.E.
        • Crapo R.O.
        • Gardner R.M.
        Clinical pulmonary function testing: a manual of laboratory procedures.
        2nd ed. Intermountain Thoracic Society, Salt Lake City, UT1984 ([tables 5–6])
        • van Belle A.
        • Büller H.R.
        • Huisman M.V.
        • Huisman P.M.
        • Kaasjager K.
        • Kamphuisen P.W.
        • et al.
        Christopher Study Investigators. Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography.
        JAMA. 2006 Jan 11; 295: 172-179
        • Severinghaus J.W.
        Simple, accurate equations for human blood O2 dissociation computations.
        J Appl Physiol Respir Environ Exerc Physiol. 1979 Mar; 46: 599-602
        • Kabrhel C.
        • Matts C.
        • Mcnamara M.
        • Katz J.
        • Ptak T.
        A highly sensitive ELISA D-dimer increases testing but not diagnosis of pulmonary embolism.
        Acad Emerg Med. 2006 May; 13: 519-524
        • Theunissen J.
        • Scholing C.
        • van Hasselt W.E.
        • van der Maten J.
        • Ter Avest E.
        A retrospective analysis of the combined use of PERC rule and Wells score to exclude pulmonary embolism in the Emergency Department.
        Emerg Med J. 2016 Oct; 33: 696-701
        • Penaloza A.
        • Verschuren F.
        • Dambrine S.
        • Zech F.
        • Thys F.
        • Roy P.M.
        Performance of the Pulmonary Embolism Rule-out Criteria (the PERC rule) combined with low clinical probability in high prevalence population.
        Thromb Res. 2012 May; 129: e189-e193
        • Hugli O.
        • Righini M.
        • Le Gal G.
        • Roy P.M.
        • Sanchez O.
        • Verschuren F.
        • et al.
        The pulmonary embolism rule-out criteria (PERC) rule does not safely exclude pulmonary embolism.
        J Thromb Haemost. 2011 Feb; 9: 300-304
        • Kline J.A.
        • Shapiro N.I.
        • Jones A.E.
        • Hernandez J.
        • Hogg M.M.
        • Troyer J.
        • et al.
        Outcomes and radiation exposure of emergency department patients with chest pain and shortness of breath and ultralow pretest probability: a multicenter study.
        Ann Emerg Med. 2014 Mar; 63: 281-288
        • Woo J.K.
        • Chiu R.Y.
        • Thakur Y.
        • Mayo J.R.
        Risk-benefit analysis of pulmonary CT angiography in patients with suspected pulmonary embolus.
        AJR Am J Roentgenol. 2012 Jun; 198: 1332-1339
        • Buchanan I.
        • Teeples T.
        • Carlson M.
        • Steenblik J.
        • Bledsoe J.
        • Madsen T.
        Pulmonary embolism testing among emergency department patients who are pulmonary embolism rule-out criteria negative.
        Acad Emerg Med. 2017 Nov; 24: 1369-1376