Estimated dead space fraction and the ventilatory ratio are associated with mortality in early ARDS

Luis Morales-Quinteros; Marcus J Schultz; Josep Bringué; Carolyn S Calfee; Marta Camprubí; Olaf L Cremer; Janneke Horn; Tom van der Poll; Pratik Sinha; Antonio Artigas; Lieuwe D Bos; MARS Consortium

doi:10.1186/s13613-019-0601-0

Estimated dead space fraction and the ventilatory ratio are associated with mortality in early ARDS

Ann Intensive Care. 2019 Nov 21;9(1):128. doi: 10.1186/s13613-019-0601-0.

Authors

Luis Morales-Quinteros¹, Marcus J Schultz^{2

3

4}, Josep Bringué^{5

6}, Carolyn S Calfee^{7

8

9}, Marta Camprubí⁵, Olaf L Cremer¹⁰, Janneke Horn², Tom van der Poll^{11

12}, Pratik Sinha^{7

8}, Antonio Artigas^{13

5

6}, Lieuwe D Bos^{2

3

14}; MARS Consortium

Affiliations

¹ Intensive Care Unit, Hospital Universitari Sagrat Cor, Grupo Quironsalud, Carrer de Viladomat, 288, 08029, Barcelona, Spain. luchomq2077@gmail.com.
² Department of Intensive Care, Academic Medical Center, Amsterdam, The Netherlands.
³ Laboratory of Experimental Intensive Care and Anesthesiology, Academic Medical Center, Amsterdam, The Netherlands.
⁴ Mahidol Oxford Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
⁵ Critical Care Center, ParcTaulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, Sabadell, Spain.
⁶ CIBER Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain.
⁷ Department of Medicine, Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, University of California, San Francisco, San Francisco, CA, USA.
⁸ Department of Anesthesia, University of California, San Francisco, San Francisco, CA, USA.
⁹ Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA.
¹⁰ Department of Intensive Care Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
¹¹ Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
¹² Division of Infectious Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
¹³ Intensive Care Unit, Hospital Universitari Sagrat Cor, Grupo Quironsalud, Carrer de Viladomat, 288, 08029, Barcelona, Spain.
¹⁴ Department of Respiratory Medicine, Academic Medical Center, Amsterdam, The Netherlands.

Abstract

Background: Indirect indices for measuring impaired ventilation, such as the estimated dead space fraction and the ventilatory ratio, have been shown to be independently associated with an increased risk of mortality. This study aimed to compare various methods for dead space estimation and the ventilatory ratio in patients with acute respiratory distress syndrome (ARDS) and to determine their independent values for predicting death at day 30. The present study is a post hoc analysis of a prospective observational cohort study of ICUs of two tertiary care hospitals in the Netherlands.

Results: Individual patient data from 940 ARDS patients were analyzed. Estimated dead space fraction and the ventilatory ratio at days 1 and 2 were significantly higher among non-survivors (p < 0.01). Dead space fraction calculation using the estimate from physiological variables [V_D/V_{T phys}] and the ventilatory ratio at day 2 showed independent association with mortality at 30 days (odds ratio 1.28 [95% CI 1.02-1.61], p < 0.03 and 1.20 [95% CI, 1.01-1.40], p < 0.03, respectively); whereas, the Harris-Benedict [V_D/V_{T HB}] and Penn State [V_D/V_{T PS}] estimations were not associated with mortality. The predicted validity of the estimated dead space fraction and the ventilatory ratio improved the baseline model based on PEEP, PaO₂/FiO₂, driving pressure and compliance of the respiratory system at day 2 (AUROCC 0.72 vs. 0.69, p < 0.05).

Conclusions: Estimated methods for dead space calculation and the ventilatory ratio during the early course of ARDS are associated with mortality at day 30 and add statistically significant but limited improvement in the predictive accuracy to indices of oxygenation and respiratory system mechanics at the second day of mechanical ventilation.

Keywords: ARDS; Acute respiratory distress syndrome; Dead space; Intensive care unit; Mortality; Prediction; Prognostication; Respiratory dead space; Ventilatory ratio.