Diagnostic utility of arterial blood gases for investigation of pulmonary embolus
Date First Published:
May 28, 2003
Last Updated:
May 19, 2005
Report by:
Margaret Maloba, Specialist Registrar (Manchester Royal Infirmary)
Search checked by:
Kerstin Hogg, Manchester Royal Infirmary
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
Embase OVID 1980-2005 week 7
Search Details:
(exp pulmonary embolism/ OR pulmonary embolus.mp.) AND (exp embolism/ OR embol$.mp. OR exp thromboembolism/ OR thromboembol$.mp.) AND (exp blood gas analysis/ OR arterial blood gas$.mp.)
Outcome:
459 papers were found of which 6 directly addressed the question
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| Improved use of Arterial Blood Gas Analysis in Suspected Pulmonary Embolism Cvitac, O 1989 USA | 78 patients with angiographically proven PE, and no cardiopulmonary disease. | Retrospective cohort | Sensitivity of hypoxaemia | 76%, | Excluded all patients with cardiopulmonary disease |
| Arterial blood Gas Analysis in the Assessment of Suspected Acute Pulmonary Embolism Stein PD 1995 USA | 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 value | pCO2=65%; pO2=68% | Recruitment bias -only those with written consent were recruited (APPX half of all suitable patients) |
| Specificity | pCO2=50%; pO2=24% | ||||
| Positive predictive value | pCO2=37%; pO2=37% | ||||
| Sensitivity | pCO2=51%; pO2=81% | ||||
| Use of the Alveolar-Arterial Oxygen Gradient in the Assessment of Acute Pulmonary Embolism Jones J S 1997 USA | 197 emergency department patients who underwent pulmonary angiography for presumed diagnosis of acute PE | Retrospective Cohort | Negative Predictive Value | pCO2>35 (61%); pO2>80 (66%) | #NAME? |
| Specificity | pCO2>35 (51%); pO2>80 (25%) | ||||
| Diagnostic value of gas exchange tests in patients with clinical suspicion of pulmonary embolism Prediletto R 1999 Italy | 773 consecutive patients with suspected PE (Part of PISAPED study) | PRCT | PE present with normal pO2 | 14% | Not all patients had gold standard (Angiogram) |
| PE present with normal pCO2 | 35% | ||||
| PE absent with normal pO2 | 13% | ||||
| PE absent with normal pCO2 | 55% | ||||
| Arterial Blood Gas Analysis and Alveolar-Arterial Oxygen Gradient in Diagnosis and Prognosis of Elderly Patients With Suspected Pulmonary Embolism Masotti L 2000 Italy | 118 patients aged over 65years who had VQ scan for suspected PE | Retrospective Cohort | Blood gases in patients with and without PE | No significant differences | #NAME? |
| Diagnostic Value of Arterial Blood Gas Measurement in Suspected Pulmonary Embolism Rodger MA 2000 Canada | 293 consecutive patients referred for imaging (VQ or Pulmonary Angiography) | Prospective Cohort | Unpaired t-test for PE/non PE | No significant differences | Not all patients got gold standard |
Author Commentary:
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.
Bottom Line:
Arterial blood gas analysis alone is of very limited diagnostic utility in suspected pulmonary embolism.
References:
- Cvitac, O. Improved use of Arterial Blood Gas Analysis in Suspected Pulmonary Embolism
- Stein PD. Arterial blood Gas Analysis in the Assessment of Suspected Acute Pulmonary Embolism
- Jones J S. Use of the Alveolar-Arterial Oxygen Gradient in the Assessment of Acute Pulmonary Embolism
- Prediletto R. Diagnostic value of gas exchange tests in patients with clinical suspicion of pulmonary embolism
- Masotti L. Arterial Blood Gas Analysis and Alveolar-Arterial Oxygen Gradient in Diagnosis and Prognosis of Elderly Patients With Suspected Pulmonary Embolism
- Rodger MA. Diagnostic Value of Arterial Blood Gas Measurement in Suspected Pulmonary Embolism