Hemogasanalysis Point of Care (EPOC) in Pre-Hospital: The Importance of An Early Diagnosis of Silent Hypoxemia in a Context of Scarce Health-Care Resources.
Authors: Montemerani Sara , Urbanelli Asia , Cini Silvia , Sbrana Giovanni , Tori Thomas , Mandò Massimo , Iannelli Giovanni , Schiraldi Fernando 
Published: August 2021

Abstract
IntroductionArterial blood gas (ABG) is a useful diagnostic test in the emergency setting. Thanks to the evolution of miniaturized technologies, it was possible to produce a Point of Care ABG analyzer that extended the use of blood gas analysis even in an out-of-hospital context. In the beginning of 2020, the Emergency Medical Service (EMS) of USL Toscana Sud-Est introduced a Point of Care ABG analyzer to characterize respiratory failure in pre-hospital. The onset of SARS-CoV-2 pandemic made the testing ground much more challenging. However, this situation highlighted the potential utility of the hand-held ABG analyzer for a better identification of silent hypoxemia in SARS-CoV-2 patients in pre-hospital setting.MethodsPrimary endpointEarly identification of cases of silent hypoxemia in pre-hospital setting. In our retrospective observational analysis, we want to understand how many patients with silent hypoxemia the hand-held analyzer detect respect the standard measure of peripherical oxygen saturation (SpO2) at rest with pulse oximeter or respect the 6 minutes walking test.Design and settingWe performed a retrospective descriptive analysis of 48 consecutive SARS-CoV-2 patients who activated the territorial Emergency Medical Service of Arezzo (USL Toscana Sud-Est). We included patients between October and November 2020. Age < 18 and pregnancy were considered exclusion criteria. After the telephone triage, the operations center sent the ALS ambulance with a team made up of a physician and a nurse who performed a clinical evaluation of the patient and an arterial blood gas analysis directly at home. Arterial blood was collected from the patient's radial or brachial artery. ALS team directly visualized the result of the exam on EPOC.ResultsA total of 48 SARS-CoV-2 patients were collected, 28 men and 20 women, respectively. Nineteen of the total amounts of 48 SARS-CoV-2 patients had silent hypoxemia identified with the hospital ABG analyzer (gold standard). They didn’t refer dyspnea or didn’t show increased work of breathing during clinical evaluation. These patients had an arterial blood gas oxygen tension (PaO2) of less than 60 mmHg. EPOC identified 20 cases of silent hypoxemia instead of the 19 identified with the hospital blood gas analyzer (Sensibility 100%, Specificity 97%, VPP 95%, VPN 100% with 95% CI). The pulse oximeter detected 21 cases of silent hypoxemia (Sensibility 100%, Specificity 94%, VPP 89%, VPN 100% with 95% CI). The 6 minutes walking test detected only 11 of the 19 cases of silent hypoxemia because the test was aborted in 5 cases, and it was not performed in other 3 cases.ConclusionFrom this first descriptive analysis, we conclude that hand-held blood gas analyzer is useful in the early identification of silent hypoxemia in COVID-19 patients. The EPOC system is a handheld and wireless solution that provides accurate results in less than one minute after sample introduction at the patient’s side. The portability of this point-of-care tool make it potentially useful in pre-hospital clinical practice.