British Journal of Anaesthesia 2021 Jan; 126(1): 48–55. doi: 10.1016/j.bja.2020.09.042
Weiss TT, Cerda F, Brady Scott J et al.
- COVID-19 causes acute respiratory distress syndrome (ARDS) in approx. 20% hospitalized patients.
- ARDS – High mortality (35%-46%)
- Prone positioning recommended by Surviving Sepsis Campaign COVID subcommittee
- Pre-COVID shown to improve Pa02/Fi02 ratio, reduce 28-day mortality
- Initial proning shown to improve oxygenation in intubated/non-intubated COVID patients
- Lack of reports on physiological effects of repeat proning and association with mortality and length of hospital
- ” To investigate the effect of prone positioning for patients with COVID-19 ARDS that required invasive ventilation”
- Single centre retrospective cohort study, Chicago, USA
- March 18th-31st 2020
- Adult ICU patients, confirmed COVID (PCR swab), requiring invasive ventilation and prone positioning
- Intubated and proned outside of hospital
- Reintubated and proned on their second intubation in hospital
- Prone positioning protocol: Video + Checklist, MDT lead by resp therapist
- Proning Criteria:
- PaO2/FiO2 ratio of <20 with PEEP 10 cm H20
- FiO2 >0.6
- Prone maintained for 16hrs
- Proning terminated when Pa02/Fi02 remained >20 when supine or ECMO or palliative care required.
- Lung protective ventilation (TV 6ml/kg, Pplateau , High PEEP/Low Fi02 tables)
- ECMO considered if lung protective ventilation could not be maintained with proning, paralysis, inhaled pulmonary dilators.
- Data collected from notes and ABG results for first 3 proning sessions
- Subject demographics laboratory results and co-morbidities collected
- Pre and post prone parameters collected:
- Ventilator settings
- Ventilatory ratio (MVxPaCO2/IBWx100x37.5)
- Correlates with VD/VT (pulmonary dead space fraction) an independent predictor of mortality in ARDS: higher related to worse outcomes
- Outcomes collected; each patient followed up until hospital discharge
- Oxygenation, assessed by Pa02/Fi02 ratio, before and after initial prone
- Positive response defined as increase in Pa02/Fi02 ratio 20%
- Serial Pa02/Fi02 ratio after repeated proning – compared between subjects discharged vs required ECMO or died
- Haemodynamic and Ventilatory parameters on repeat proning
- 50 subjects, 8 excluded, 42 eligible
- 25 subjects required proning on at least 3 occasions
- Total of 31/42 (76%) survived to discharge, avg 21.5-day ICU admission
- 5 – ECMO, 11- Died
- Primary outcome:
- Pa02/Fi02 ratio improved from 17.9 to 28.2 within 81 mins for 36 subjects (P<0.01)
- Pa02/Fi02 ratio improved 20% in 72% (26/36) subjects
- Improvements persisted on returning to supine
- Secondary outcomes:
- Subjects who were discharged from hospital were more likely to have an improvement in Pa02/Fi02 ratio 20% on second and third proning session, compared to those who died or required ECMO.
- Ventilatory parameter and CV parameters remained relatively static on prone positioning
- In this study P/F ratio improvement >20% after first proning showed no differences between treatment success and failure group
- Did show survivors responded to second and third proning in contrast to little or no response in those who died or needed EMCO
- 28-day ICU mortality 21.4% (similar to PROSEVA trail)
- May help in decision making RE: ECMO
- In subjects who responded to proning, no difference in compliance compared to treatment failure group
- Small, single centre study
- Retrospective – non RCT (difficult in pandemic)
- No CT imaging to assess lung parenchyma for those who didn’t respond to proning
- Ventilatory ratio used as a surrogate assessment of dead space
- Absence of some ABG results (put down to immediate need for prone positioning and increased staff workload) leading to 36 of 42 included patients being analysed.
- Could this introduce bias? Immediacy of proning need linked to acuity of patient?
- Patients with COVID ARDS frequently responded to initial proning with improved oxygenation
- Subsequent proning in subject who survived to discharge was associated with greater improvements in oxygenation
- May guide decision making RE: escalation to ECMO
- Supports practice of prone positioning in COVID ARDS
Summary by Dr C Cregg. Journal Club Meeting 11 March 2021.
(Photo: Marco Mantovani/Getty Images)