key: cord-0870485-4njab0i3
authors: Arina, Pietro; Baso, Beatrice; Moro, Valeria; Patel, Hemani; Ambler, Gareth
title: Discriminating between CPAP success and failure in COVID-19 patients with severe respiratory failure
date: 2020-11-16
journal: Intensive Care Med
DOI: 10.1007/s00134-020-06304-y
sha: 13061fcc0014fcfe51f0f8863d2bb6970246ce4e
doc_id: 870485
cord_uid: 4njab0i3

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Of 108 within-hospital admissions, 93 (86%) received CPAP as initial respiratory failure management (median[IQR] PaO 2 /FiO 2 ratio 13 [10-18] kPa) (Supplementary Fig. 1 ). Thirty-two (34%) were adjudged CPAP successes and 61 (66%) failures (14 deaths (23%) with CPAP as the ceiling of treatment, 47 (77%) requiring invasive ventilation of whom 26 died). Demographics and ICU admission values of respiratory rate, inspired oxygen concentration (FiO 2 ) and PaO 2 /FiO 2 ratio were similar between groups (Supplementary data). Admission values of C-reactive protein (CRP) (p < 0.0001), N Terminal-pro-B-type natriuretic peptide (NT-proBNP) (p < 0.001), troponin-T (p < 0.001) and d-dimers (p < 0.05) were significantly higher in CPAP failure patients (Fig. 1 ). Other organ support was only required for CPAP failure patients receiving invasive ventilation (46 vasopressors, 28 renal replacement therapy), but none for CPAP successes. At 6 h post-CPAP the PaO 2 /FiO 2 ratio rose by 76.7% (37.9 to 99.8%) in CPAP success patients but only by 38.1% (−24.4 to 100.5) in the failure group (p = 0.015).

For outcome prediction (CPAP failure), sixteen potential predictor physiological or biochemical variables were assessed. Details are provided in the Supplementary Index. In brief, separate univariable logistic regression models were fitted for each predictor, with p values < 0.05 determining variables entered into a multivariable logistic regression model. Failure of CPAP to avert death or invasive mechanical ventilation was associated with increased blood levels of thrombo-inflammatory and cardiac injury/dysfunction biomarkers on ICU admission. This may reflect an increased incidence of pulmonary thrombi either identifiable on imaging or multiple microthrombi, with subsequent right heart strain. The much-increased requirement for vasopressor and renal support in invasively ventilated patients reflects disease severity, but a significant iatrogenic contribution from high airway pressures, heavy sedation and hypovolaemia cannot be excluded. The high positive predictive value using elevated CRP and NT-proBNP may identify patients likely to fail CPAP. If validated, this could be gainfully used in management pathways and to stratify patients for intervention studies.

The online version of this article (https ://doi.org/10.1007/s0013 4-020-06304 -y) contains supplementary material, which is available to authorized users. 

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The UCL Critical Care COVID-19 Research Group members involved in this research comprised: Petra Voegele: Intensive Care Unit, University College London Hospitals NHS Foundation Trust, London UK; Nishkantha Arulkumaran: Intensive Care Unit, University College London Hospitals NHS Foundation

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Accepted: 16 October 2020