prognostic role of aa do2 in acute pulmonary embolism

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  • 1. Prognostic Role of Alveolar-arterial Oxygen Pressure Difference (AaDO2) in Acute Pulmonary Embolism Hsu Jen Te

2. Background

  • This study investigated the utility of alveolar-arterial oxygen pressure difference (AaDO2) in predicting short-term prognosis of acute pulmonary embolism (PE).

3. Introduction

  • Acute pulmonary embolism (PE) has high incidence and mortality rates
  • The International Cooperative Embolism Registry of 2454 patients reported a high 90-day all-cause mortality rate of 17.4%

4. ICOPER: Mortality 11.4%at 2week & 17.4 at 3 months 5. Acute Pulmonary Embolism

  • Low PaO2
  • Low PaCO2
  • High AaDO2

6. Four processes cause arterial hypoxaemia due to inefficient pulmonarygas exchange :

  • ventilationperfusion ( V / Q ) mismatch
  • Hypoventilation
  • diffusion limitation
  • true shunt.

7. ABG analysis have proved disappointing as diagnostic modalities

  • normal values for alveolar-arterial oxygen gradient do not exclude acute PE
  • hypoxemia discriminates poorly between those with and without acute PE.
  • absence of such abnormal values of arterial blood gas analysis, alone or in combination, do not exclude PE.

8. Paper reviews

  • AaDO2 has a linear correlation to actual perfusion defect
  • a sensitive indicator suggestive of resolved emboli

9. Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study

  • a linear correlation existed between AaDO2 andPE severity
  • pulmonary artery mean pressure ,
  • the number ofmismatched perfusiondefects

10. Our interests

  • The possibility of different gradients of AaDO2 or other artery blood gas analyses can be utilized to predict prognosis of acute PE

11. Methods and Materials CMRGP 650031 12. Study Sample

  • This study retrospectively identified 114 consecutive patients hospitalized at Chang Gung Memorial Hospital (CGMH), Taiwan, between May 2001 and July 2003 with acute PE.

13. Including criteria

  • spiral computed tomography (CT) or
  • high probability ventilation and perfusion lung scan
  • first arterial blood gas analysis under room air(FIO2=0.21) 1 year.

21. Statistical analysis

  • The students t-test for comparing continuous variables
  • the proportion test for categorical variables
  • Receiver operating characteristic(ROC) analyses were applied to determine the high-sensitivity AaDO2 and a/APO2 cutoff value
  • Multivariate Cox regression analyses were employed to estimate the cumulative probability of primary and composite endpoints

22. Results

  • Total 114 patients
  • Only 1 patient had an AaDO2< 20 mmHg.
  • The other 113 patients had abnormal AaDO2 values (AaDO2> 20 mmHg).

23. Table 1. Clinical characteristics, echocardiographic parameters, and cardiac troponin I inPE survivors and patients who died at 30 days. 24. Table 2. Clinical characteristics, echocardiographic parameters, and cardiac troponin I in the 30-day composite-event free group vs. the 30-day composite event group 25. 30-day mortality & composite event rate

  • All-cause 30-day mortality was17.5%.
  • The 30-day composite event rate was26.3%.

26. Parameters influences primary end point

  • Cancer
  • Hypotension
  • Thrombocytopenia
  • low PaCO2 level
  • elevated Troponin I level.

27. Additive parameters influences secondary end point

  • diabetes mellitus (DM)
  • AaDO2 level
  • a/APO2 level
  • renal insufficiency
  • right ventricular dilatation (RVD).

28. The analytical findings have not been published

  • Statistical analysis demonstrated that incidence ofthrombocytopenia andrenal insufficiencywere significantly different between 30-day composite endpoint group and 30-day composite event-free group; this analytical finding has not been published.

29. Incidence of thrombocytopenia

  • The odds ratio for 30-day mortality was4.49(95% CI=1.8610.87).
  • The odds ratio for 30-day composite endpoint was2.96(95% CI=1.446.11).

30. Figure 1. ROC curves for variable artery blood gas analysis. 31. Figure 2. ROC curves for AaDO2 and a/APO2-R

  • The area for a/A PO2 =0.650
  • The area for AaDO2
  • =0.657

32. The optimal cut-off value for AaDO2 was 53mmHg.

  • The incidence of AaDO253mmHg also showed a significant difference between those two groups(primary end points)
  • the positive predictive value for 30-day death was25%;the negative predictive value was as high as92%
  • for the secondary endpoint, the positive predictive value of a/APO2 was39%,and negative predictive value was83%.

33. A prognostic cut-off value of a/APO2 ratio was 0.49

  • the positive predictive value for primary end-point was26.5%,and negative predictive value was89%.

34. Figure 3. Survival curves at 1 year, based on a cut-off values of AaDO253mmHg vs. AaDO2