Value of arterial blood gas analysis in patients with acute dyspnea: an observational study

Introduction: The diagnostic and prognostic value of arterial blood gas analysis (ABGA) parameters in unselected patients presenting with acute dyspnea to the Emergency Department (ED) is largely unknown. Methods: We performed a post-hoc analysis of two different prospective studies to investigate the diagnostic and prognostic value of ABGA parameters in patients presenting to the ED with acute dyspnea. Results: We enrolled 530 patients (median age 74 years). ABGA parameters were neither useful to distinguish between patients with pulmonary disorders and other causes of dyspnea nor to identify specific disorders responsible for dyspnea. Only in patients with hyperventilation from anxiety disorder, the diagnostic accuracy of pH and hypoxemia rendered valuable with an area under the receiver operating characteristics curve (AUC) of 0.86. Patients in the lowest pH tertile more often required admission to intensive care unit (28% vs 12% in the first tertile, P < 0.001) and had higher in-hospital (14% vs 5%, P = 0.003) and 30-day mortality (17% vs 7%, P = 0.002). Cumulative mortality rate was higher in the first (37%), than in the second (28%), and the third tertile (23%, P = 0.005) during 12 months follow-up. pH at presentation was an independent predictor of 12-month mortality in multivariable Cox proportional hazard analysis both for patients with pulmonary (P = 0.043) and non-pulmonary disorders (P = 0.038). Conclusions: ABGA parameters provide limited diagnostic value in patients with acute dyspnea, but pH is an independent predictor of 12 months mortality.