Is Partial pressure of oxygen (pO2) a good predictor to diagnose Pulmonary Embolism?
Date First Published:
August 24, 2015
Last Updated:
September 21, 2016
Report by:
Pippa Johnstone, Foundation Year 2 doctor (University Hospitals Birmingham)
Search checked by:
Dr M Majeed, University Hospitals Birmingham
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
and
Ovid medline 1946 to march week 4 2015
Search Details:
The following keywords were used; Pulmonary embol* OR PE or Thromboembolism or Pulmonary infarct, Partial pressure oxygen OR pO2, Sens* Spec* Accur* Diag*
Outcome:
Combined = 200 results.
Then only using dates 2000 to Current = 97.
Only 7 articles were relevant to our question.
Then only using dates 2000 to Current = 97.
Only 7 articles were relevant to our question.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| Diagnostic Value of Arterial Blood Gas Measurement in Suspected Pulmonary Embolism MARC A. RODGER, MARC CARRIER, GWYNNE N. JONES, PASTEUR RASULI, FRANÇOIS RAYMOND, HELENE DJUNAEDI, and PHILIP S. WELLS Dec-00 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. | |||||
| Arterial Blood Gas Analysis and Alveolar-Arterial Oxygen Gradient in Diagnosis and Prognosis of Elderly Patients With Suspected Pulmonary Embolism Masotti L., Ceccarelli E., Cappelli R., Barabesi L., Forconi S. Mar-00 Italy | Patients >65 years old |
Retrospective observational study over 6 years. Compared the data of 75 patients with a high probability of PE on lung scan (according to PIOPED criteria) (confirmed PE group) with the data of 43 patients with a normal lung scan. Defined normal values as pO2 >75 mm Hg Found significantly lower mean values of pO2 and SO2 in the confirmed PE group. Hypoxemia and increased alveolar-arterial oxygen gradient have a high sensitivity and low specificity in the diagnosis of PE in elderly. Advantages: All ABGs taken on room air and within 12 hours of admission. Detailed description of methods including how blood samples were taken. |
Retrospective single centre study. Patient group limited to >65 years old. Didn’t mention how many had underlying lung disease, 12 hrs is a wide time frame for the ABGs and how long the patient had been on or off the oxygen? |
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| Massive pulmonary embolism: A comparison of radiological and clinical characteristics and outcomes. Schneider R.F., Ntimba F.D., Hourizadeh A., Schwartz J.B., Eber C.D., Patnana M., Goldfarb R. Apr-02 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 | ||||
| Acute pulmonary embolism: Correlation of CT pulmonary artery obstruction index with blood gas values. Metafratzi Z.M., Vassiliou M.P., Maglaras G.C., Katzioti F.G., Constantopoulos S.H., Katsaraki A., Efremidis S.C. Jan-06 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. |
| Clinical Characteristics of Patients with Acute Pulmonary Embolism: Data from PIOPED II 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 Oct-07 America | Prospective cohort. Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). |
Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). The partial pressure of oxygen in arterial blood (PaO2) while breathing room air was measured in 122 patients. Among all patients with pulmonary embolism (192), the PaO2 while breathing room air was 80 mm Hg or higher in 32%. Acute pulmonary embolism cannot be excluded on the basis of a normal PaO2. |
Certain amount of selection bias: the patients that were enrolled in the clinical trial were those with sufficient characteristics to alert clinicians to the potential diagnosis and therefore inclusion to trial. This in itself may have missed PEs that presented with normal clinical values, potentially such as with normal pO2. Only 122/824 (total participants) had ABGs, demonstrating selection bias. |
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| Investigating suspected pulmonary embolism as outpatient: The Portsmouth experience. Shafiq I., Siddique N., Chauhan 2010 UK | During 6 month period from November 2007 to April 2008, random selection of 92 patients of the 176 outpatients that were investigated for suspected PE. Retrospective review of their clinical notes. |
Method: Random selection The only significant differences in clinical or physiological parameters between groups was PO2, which was significantly lower in the group with PE (p 0.032) (12/91 diagnosed with PE) |
Small sample - 92 pts Only used pts investigated for suspected PE as an outpatient (based on clinical criteria of stability) |
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| Predictors of in-hospital mortality in patients with acute pulmonary embolism. 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? |
Author Commentary:
There isn’t any level 1 or 2 evidence available. Only level 3 evidence is available in the literature.
Bottom Line:
Pulmonary embolism cannot be diagnosed based on the arterial blood gas analysis alone.
References:
- 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
- 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
- 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.
- 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.
- 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
- Shafiq I., Siddique N., Chauhan. Investigating suspected pulmonary embolism as outpatient: The Portsmouth experience.
- Duszansk A., Kukulski T. et al. Predictors of in-hospital mortality in patients with acute pulmonary embolism.