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Diagnostic utility of arterial blood gases for investigation of pulmonary embolus

Three Part Question

In [patients with clinical diagnosis of pulmonary embolus] do [arterial blood gases] aid in [making a definite diagnosis]?

Clinical Scenario

A 28 year old woman presents with acute suspected pulmonary embolus (PE). You wonder whether normal arterial blood gases are sufficient to rule out pulmonary embolus.

Search Strategy

Medline OVID1966- 2005 Feb week 1
Embase OVID 1980-2005 week 7
(exp pulmonary embolism/ OR pulmonary AND (exp embolism/ OR embol$.mp. OR exp thromboembolism/ OR thromboembol$.mp.) AND (exp blood gas analysis/ OR arterial blood gas$.mp.)

Search Outcome

459 papers were found of which 6 directly addressed the question

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Cvitanic et al
78 patients with angiographically proven PE, and no cardiopulmonary disease.Retrospective cohortSensitivity of hypoxaemia76%,Excluded all patients with cardiopulmonary disease
Stein PD
768 patients age>18, with clinical diagnosis of PE (Part of Prospective Investigation Of Pulmonary Embolism Diagnosis - PIOPED study)Prospective Randomized Control trial (PRCT)Negative predictive valuepCO2=65%; pO2=68%Recruitment bias -only those with written consent were recruited (APPX half of all suitable patients)
SpecificitypCO2=50%; pO2=24%
Positive predictive valuepCO2=37%; pO2=37%
SensitivitypCO2=51%; pO2=81%
Jones S
197 emergency department patients who underwent pulmonary angiography for presumed diagnosis of acute PERetrospective CohortNegative Predictive ValuepCO2>35 (61%); pO2>80 (66%)-Seriously ill patients possibly excluded because they were on oxygen -Selection bias as only patients with angiography were recruited
SpecificitypCO2>35 (51%); pO2>80 (25%)
Prediletto R
773 consecutive patients with suspected PE (Part of PISAPED study)PRCTPE present with normal pO214%Not all patients had gold standard (Angiogram)
PE present with normal pCO235%
PE absent with normal pO213%
PE absent with normal pCO255%
Masotti L
118 patients aged over 65years who had VQ scan for suspected PERetrospective CohortBlood gases in patients with and without PENo significant differences-No gold standard -Minimal data and statistics given
Rodger MA
293 consecutive patients referred for imaging (VQ or Pulmonary Angiography)Prospective CohortUnpaired t-test for PE/non PENo significant differencesNot all patients got gold standard


Pulmonary angiography, the gold standard diagnostic tool in Pulmonary Embolism,has an unacceptibly high mortality and morbidity rate. It cannot presently be used routinely in clinical practice. A reliable, cost effective, non invasive test if identified would be of great use.

Clinical Bottom Line

Arterial blood gas analysis alone is of very limited diagnostic utility in suspected pulmonary embolism.


  1. Cvitac, O Improved use of Arterial Blood Gas Analysis in Suspected Pulmonary Embolism Chest 1989;95:48-51
  2. Stein PD Arterial blood Gas Analysis in the Assessment of Suspected Acute Pulmonary Embolism Chest 1996;109:78-81
  3. Jones J S Use of the Alveolar-Arterial Oxygen Gradient in the Assessment of Acute Pulmonary Embolism American Journal of Emergency Medicine July 1998; 16:333-337
  4. Prediletto R Diagnostic value of gas exchange tests in patients with clinical suspicion of pulmonary embolism Critical Care 1999; 3:111-116
  5. Masotti L Arterial Blood Gas Analysis and Alveolar-Arterial Oxygen Gradient in Diagnosis and Prognosis of Elderly Patients With Suspected Pulmonary Embolism Journal of Gerontology 2000; 55A:M761-M764
  6. Rodger MA Diagnostic Value of Arterial Blood Gas Measurement in Suspected Pulmonary Embolism American Journal of Respiratory and Critical Care Medicine 2000; 162: 2105-2108