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Three Part Question

[Can we reliably diagnose] [Pulmonary embolism] based on the [Arterial blood gas analysis]?

Clinical Scenario

A 35 yrs old girl comes to the Emergency department with acute shortness of breath for last 6 hrs. The working diagnosis of pulmonary embolism is made. The D dimer was sent but will take 2-3 hrs for the results to be available. You wonder if arterial blood gas analysis can be used to diagnose the PE.

Search Strategy

Embase 1974 to March 25
and
Ovid medline 1946 to march week 4 2015
The following keywords were used; Pulmonary embol* OR PE or Thromboembolism or Pulmonary infarct, Partial pressure oxygen OR pO2, Sens* Spec* Accur* Diag*

Search Outcome

Combined = 200 results.
Then only using dates 2000 to Current = 97.
Only 7 articles were relevant to our question.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Rodger, Carrier et al December 2000 America	246 patients	Prospective cohort study. 293 consecutive patients referred for imaging to investigate suspected PE were approached to participate in a trial over 30 months. ABG and other clinical data was gathered. Undertaken in Ottawa - similar demographic population to the UK.	Patients classified into 'PE' or 'no PE'	212/246	Single centre study, patients with suspected PE referred to a centre for VQ scan (high prevalence and will effect PPV and NPV) No power calculation. Excluded patients not counted in the final results, no CI or P values mentioned, 34 unclassified patients ? potential diagnosis of PE but no pulmonary angiography performed (physician decision). Excluded from the data analysis. 20 ABGs were not performed on room air (135 were)
			Diagnosis of PE	49/246
			Classified patients that had ABG	155/212
			Unclassified	34/246
			ABG data alone or in combination with other clinical data are not useful in the assessment of suspected PE.
Schneider R.F., Ntimba F.D., Hourizadeh A., Schwartz J.B., Eber C.D., Patnana M., Goldfarb R. April 2002 America	54 patients age range 28-91	Retrospective analysis at a 1,368 bed teaching hospital between June 1997 and December 1999, identified 54 patients with 'Massive PE' (>50% vascular occlusion).	PaO2 <60mmHg	28 patients (71%) of those that had ABG performed	Small sample size. ABGs were only performed in an even smaller no. of pts (39).
			ABG performed	39/54 patients
Metafratzi Z.M., Vassiliou M.P., Maglaras G.C., Katzioti F.G., Constantopoulos S.H., Katsaraki A., E Jan 2006 Greece	Retrospective study of 122 patients.	Helical CT pulmonary angiography was performed in 78 patients who were suspected of having acute pulmonary embolism and selected as being free of underlying cardiopulmonary disease. 34 patients were diagnosed with PE. The severity was assessed by the pulmonary artery obstruction index, which was then correlated with the arterial partial pressure of oxygen (Pao(2)). The pO2 was significantly low p=0.024 in patients with PE. The strongest correlation was observed between the PaO2/FiO2 ratio and mortality (P = .003).	pO2	Signifcantly lower in patients with PE (p=0.024)	Small sample size 122 patients. Retrospective study.
Duszansk A., Kukulski T. et al 2011	158 patients	pO2 difference 68mm of hg in survivors vs 62 in non survivors was statistically not significant (p 019). pO2 as an independent risk factor for hospital mortality was not significant predictor			Small sample size, single centre Doesn’t specify how was the sample taken Under what conditions?

Comment(s)

There isn’t any level 1 or 2 evidence available. Only level 3 evidence is available in the literature.

Clinical Bottom Line

Pulmonary embolism cannot be diagnosed based on the arterial blood gas analysis alone.

References

1. MARC A. RODGER, MARC CARRIER, GWYNNE N. JONES, PASTEUR RASULI, FRANÇOIS RAYMOND, HELENE DJUNAEDI, and PHILIP S. WELLS Diagnostic Value of Arterial Blood Gas Measurement in Suspected Pulmonary Embolism American Journal of Respiratory and Critical Care Medicine . Volume 162, Issue 6, December 2000
2. Masotti L., Ceccarelli E., Cappelli R., Barabesi L., Forconi S. Arterial Blood Gas Analysis and Alveolar-Arterial Oxygen Gradient in Diagnosis and Prognosis of Elderly Patients With Suspected Pulmonary Embolism Journal of Gerontology: MEDICAL SCIENCES 55 (12) (pp M761-M764), 2000.
3. Schneider R.F., Ntimba F.D., Hourizadeh A., Schwartz J.B., Eber C.D., Patnana M., Goldfarb R. Massive pulmonary embolism: A comparison of radiological and clinical characteristics and outcomes. Emergency Radiology 9 (2) (pp 79-81), 2002
4. Metafratzi Z.M., Vassiliou M.P., Maglaras G.C., Katzioti F.G., Constantopoulos S.H., Katsaraki A., Efremidis S.C. Acute pulmonary embolism: Correlation of CT pulmonary artery obstruction index with blood gas values. American Journal of Roentgenology 2006 Jan;186(1):213-9.
5. Paul D. Stein, Afzal Beemath, Fadi Matta, John G. Weg, Roger D. Yusen, Charles A. Hales, Russell D. Hull, Kenneth V. Leeper Jr., H Dirk Sostman,V Clinical Characteristics of Patients with Acute Pulmonary Embolism: Data from PIOPED II Am J Med October 2007; 120(10): 871–879
6. Shafiq I., Siddique N., Chauhan Investigating suspected pulmonary embolism as outpatient: The Portsmouth experience. British Thoracic Society Winter Meeting 2010
7. Duszansk A., Kukulski T. et al Predictors of in-hospital mortality in patients with acute pulmonary embolism. European Journal of Echocardiography. 2011