Correlation of alveolar–arterial gradient with Computed Tomography Pulmonary Artery Obstruction index in acute Pulmonary Embolism

SUMMARY Objektive: The purpose of our study was to investigate the relationship between the pulmonary artery obstruction index (PAOI) assessed with helical computed tomography (CT) and impairment in blood gases in patients with acute pulmonary embolism (PE). Method: This retrospective study design was carried out in the Tertiary Training and Research Hospital Emergency Clinic over a 6-month period with patients in whom PE was detected. The Alveolar–arterial (A-a) oxygen gradient for oxygen was calculated according to the formula 150 – 1.25 (PaCO2 – PaO2), and the PAOI for each patient was measured with the Qanadli score at the mediastinal window using chest CT angiography (CTA). Results: There were 113 patients included in the study; their mean age was 61.40 (±16.082) years and 51.4% of the patients were female. The mean Alveolar–arterial (A-a) oxygen gradient value was 65.13(±18.78) in massive embolism group. The mean PAOI was determined as 34.027 (min:7.5, max:83.7). The relationship between the radiologically measured PAOI and the Alveolar–arterial (A-a) oxygen gradient were compared, and an increase in the index was detected as the Alveolar–arterial (A-a) oxygen gradient level increased;this difference was found to be statistically significant (r=0.400; p<0.001). Conclusions: This retrospective observational study found a weak but positive correlation between the PAOI and the Alveolar–arterial (A-a) oxygen gradient. Our study showed that consideration of the Alveolar–arterial (A-a) oxygen gradient increases the sensitivity of blood gas analysis in documented pulmonary embolism.All data showed that the Alveolar–arterial (A-a) oxygen gradient values may be clinically beneficial, as such testing is easy to perform and cost-effective.Moreover, it can be performed at the bedside to detect which patients should be treated with thrombolytics. Keywords : Pulmonary Embolism, Arterial–Alveolar Gradient, Pulmonary Artery Obstruction Index OZET Amac: Calismamizin amaci akut pulmoner emboli saptanan hastalarda helikal bilgisayarli tomografi ile hesaplanan pulmoner arter obstruksiyon indeksinin (PAOI) kan gazi parametrelerinden alveolar-arterial oksijen gradienti ile iliskisinin arastirilmasidir. Yontem: Bu retrospektif calismaya 3. Basamak egitim arastirma hastanesi acil tip klinigine 6 aylik donemde basvuran ve pulmoner emboli tespit edilen hastalar dahil edildi. Alveolar-arterial oksijen gradient ‘’150-1,25(PaCO2-Pa02)’’ formulu ile hesaplandi. Bulgular: Calismaya 113 hasta dahil edildi. Hastalarin yas ortalamasi 61.40 (±16,082) ve %51.4’ u bayandi. Alveolar-arterial oksijen gradient ortalamasi masif emboli grubunda 65,13 (±18,78) saptandi. PAOI ortalamasi 34,027 (min:7,5 max:83,7) idi. PAOI ile alveolar-arterial oksijen gradienti arasindaki iliski karsilastirildiginda alveolar-arterial oksijen gradienti yukseldikce pulmoner arter obstruksiyon indeksinin arttigi ve bu iliskinin istatistiksel olarak anlamli oldugu goruldu (r=0,400 p<0,001). Sonuc: Bu retrospektif gozlemsel calismada PAOI ile alveolar-arterial gradient arasinda zayif ancak pozitif bir korelasyon saptandi. Calismamiz pulmoner emboli saptanan hastalarda kan gazi analizinde P(A-a) O2 gradientinin sensitivitesinin arttigini gosterdi. Butun datalar alveolar-arterial oksijen gradientin kolay uygulanabilinir, dusuk maliyetli ve faydali olabilecegini gostermektedir. Dahasi yatak basi uygulamada trombolitik tedavi planlanan hastalarda tanisal alternatif bir secenek olarak kullanilabilir. Anahtar sozcukler: Pulmoner Emboli, Alveolar-arterial gradient, Pulmoner Arter Obstruksiyon indeksi