High risk of patient self-inflicted lung injury in COVID-19 with frequently encountered spontaneous breathing patterns: a computational modelling study

Weaver, Liam; Das, Anup; Saffaran, Sina; Yehya, Nadir; Scott, Timothy E.; Chikhani, Marc; Laffey, John G.; Hardman, Jonathan G.; Camporota, Luigi; Bates, Declan G.

Abstract

Background: There is ongoing controversy regarding the potential for increased respiratory effort to generate patient self-inflicted lung injury (P-SILI) in spontaneously breathing patients with COVID-19 acute hypoxaemic respiratory failure. However, direct clinical evidence linking increased inspiratory effort to lung injury is scarce. We adapted a computational simulator of cardiopulmonary pathophysiology to quantify the mechanical forces that could lead to P-SILI at different levels of respiratory effort. In accordance with recent data, the simulator parameters were manually adjusted to generate a population of 10 patients that recapitulate clinical features exhibited by certain COVID-19 patients, i.e. severe hypoxaemia combined with relatively well-preserved lung mechanics, being treated with supplemental oxygen.

Results: Simulations were conducted at tidal volumes (VT) and respiratory rates (RR) of 7 ml/kg and 14 breaths/min (representing normal respiratory effort) and at VT/RR of 7/20, 7/30, 10/14, 10/20 and 10/30 ml/kg / breaths/min. While oxygenation improved with higher respiratory efforts, significant increases in multiple indicators of the potential for lung injury were observed at all higher VT/RR combinations tested. Pleural pressure swing increased from 12.0±0.3 cmH 2 O at baseline to 33.8±0.4 cmH 2 O at VT/RR of 7 ml/kg/30 breaths/min and to 46.2±0.5 cmH 2 O at 10 ml/kg/30 breaths/min. Transpulmonary pressure swing increased from 4.7±0.1 cmH 2 O at baseline to 17.9±0.3 cmH 2 O at VT/RR of 7 ml/kg/30 breaths/min and to 24.2±0.3 cmH 2 O at 10 ml/kg/30 breaths/min. Total lung strain increased from 0.29±0.006 at baseline to 0.65±0.016 at 10 ml/kg/30 breaths/min. Mechanical power increased from 1.6±0.1 J/min at baseline to 12.9±0.2 J/min at VT/RR of 7 ml/kg/30 breaths/min, and to 24.9±0.3 J/min at 10 ml/kg/30 breaths/min. Driving pressure increased from 7.7±0.2 cmH 2 O at baseline to 19.6±0.2 cmH 2 O at VT/RR of 7 ml/kg/30 breaths/min, and to 26.9±0.3 cmH 2 O at 10 ml/kg/30 breaths/min.

Conclusions: Our results suggest that the forces generated by increased inspiratory effort commonly seen in COVID-19 acute hypoxaemic respiratory failure are comparable with those that have been associated with ventilator-induced lung injury during mechanical ventilation. Respiratory efforts in these patients should be carefully monitored and controlled to minimise the risk of lung injury.

• Journal Article Type: Article
• Acceptance Date: Jul 6, 2021
• Online Publication Date: Jul 13, 2021
• Publication Date: Dec 1, 2021
• Deposit Date: Jul 7, 2021
• Publicly Available Date: Jul 7, 2021
• Journal: Annals of Intensive Care
• Electronic ISSN: 2110-5820
• Publisher: Springer Science and Business Media LLC
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Issue: 1
• Article Number: 109
• DOI: https://doi.org/10.1186/s13613-021-00904-7
• Keywords: Critical Care and Intensive Care Medicine
• Public URL: https://nottingham-repository.worktribe.com/output/5760477
• Publisher URL: https://annalsofintensivecare.springeropen.com/articles/10.1186/s13613-021-00904-7
• Additional Information: Received: 24 March 2021; Accepted: 6 July 2021; First Online: 13 July 2021; : ; : Not applicable.; : Not applicable.; : The authors declare that they have no competing interests.