Ventilatory Ratio at very high altitude in ARDS: A single-center longitudinal study

Richard Bautista, Hever Plati Tinta Mamani, Ademar Esteban Quisbert Quisbert

Abstract

Background

Acute Respiratory Distress Syndrome (ARDS) is characterized by shunt-related hypoxemia and increased dead space (VD). Physiologic dead space reflects the severity of lung injury and is a prognostic factor in ARDS. The Ventilatory Ratio (VR) has emerged as an alternative measure of ventilatory efficiency, being a surrogate for dead space that is easily obtained at the patient’s bedside.

Methods

Longitudinal, retrospective, cohort study. It was carried out at the Intensive Care Unit (ICU), El Alto Sur Hospital (4150 meters above sea level (m.a.s.l.), in 2021. The main objective was to determine the cut-off point on admission and fifth day of VR. The secondary outcomes were to establish mechanical ventilation and oxygenation parameters, VR on admission and fifth day stratified by survival, to evaluate the prognostic value of VR and associated factors for 90-day mortality.

Results

The area under the curve (AUC) was 0.7223 (95% CI:0.6272 – 0.8174) among the surviving patients. The cut-off point at admission was 1.495, obtaining the best AUC of VR 2.06, on day 5. For patients with VR ≤2, the median survival was 25 days and a survival rate of 49% and VR  > 2, the median survival was 18 days and a survival rate of 36.2%. Patients with VR > 2 on day 5 had a significantly lower 90-day survival compared to patients with VR ≤ 2 HR 1.52 (95% CI: 1.01-2.30; P = 0.043). VR and age were independent risk factors for mortality.

Conclusion

The value of ventilatory ratio stands out as a practical prognostic marker of ARDS at very high altitude, a value greater than 2 on day 5 and age were independently associated with higher mortality.

Keywords: Dead space, Ventilatory ratio, ARDS, Very high altitude

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