Sunitha Palanidurai1, Jason Phua2,3,4, Yiong Huak Chan5, Amartya Mukhopadhyay2,3,4,6. 1. Intensive Care Unit, Alexandra Hospital, National University Health System, 378 Alexandra Road, Singapore, 159964, Singapore. palanisunitha@gmail.com. 2. FAST and Chronic Programmes, Alexandra Hospital, National University Health System, Singapore, Singapore. 3. Division of Respiratory & Critical Care Medicine, Department of Medicine, National University Hospital, National University Health System, Singapore, Singapore. 4. Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. 5. Biostatistics Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. 6. Medical Affairs, Alexandra Hospital, Singapore, Singapore.
Abstract
BACKGROUND: The current Berlin definition of acute respiratory distress syndrome (ARDS) uses the PaO2/FiO2 (P/F) ratio to classify severity. However, for the same P/F ratio, a patient on a higher positive end-expiratory pressure (PEEP) may have more severe lung injury than one on a lower PEEP. OBJECTIVES: We designed a new formula, the P/FP ratio, incorporating PEEP into the P/F ratio and multiplying with a correction factor of 10 [(PaO2*10)/(FiO2*PEEP)], to evaluate if it better predicts hospital mortality compared to the P/F ratio post-intubation and to assess the resultant changes in severity classification of ARDS. METHODS: We categorized patients from a dataset of seven ARDS network trials using the thresholds of ≤ 100 (severe), 101-200 (moderate), and 201-300 (mild) for both P/F (mmHg) and P/FP (mmHg/cmH2O) ratios and evaluated hospital mortality using areas under the receiver operating characteristic curves (AUC). RESULTS: Out of 3,442 patients, 1,057 (30.7%) died. The AUC for mortality was higher for the P/FP ratio than the P/F ratio for PEEP levels > 5 cmH2O: 0.710 (95% CI 0.691-0.730) versus 0.659 (95% CI 0.637-0.681), P < 0.001. Improved AUC was seen with increasing PEEP levels; for PEEP ≥ 18 cmH2O: 0.963 (95% CI 0.947-0.978) versus 0.828 (95% CI 0.765-0.891), P < 0.001. When the P/FP ratio was used instead of the P/F ratio, 12.5% and 15% of patients with moderate and mild ARDS, respectively, were moved to more severe categories, while 13.9% and 33.6% of patients with severe and moderate ARDS, respectively, were moved to milder categories. The median PEEP and FiO2 were 14 cmH2O and 0.70 for patients reclassified to severe ARDS, and 5 cmH2O and 0.40 for patients reclassified to mild ARDS. CONCLUSIONS: The multifactorial P/FP ratio has a greater predictive validity for hospital mortality in ARDS than the P/F ratio. Changes in severity classification with the P/FP ratio reflect both true illness severity and the applied PEEP strategy. TRIAL REGISTRATION: ClinialTrials.gov-NCT03946150.
BACKGROUND: The current Berlin definition of acute respiratory distress syndrome (ARDS) uses the PaO2/FiO2 (P/F) ratio to classify severity. However, for the same P/F ratio, a patient on a higher positive end-expiratory pressure (PEEP) may have more severe lung injury than one on a lower PEEP. OBJECTIVES: We designed a new formula, the P/FP ratio, incorporating PEEP into the P/F ratio and multiplying with a correction factor of 10 [(PaO2*10)/(FiO2*PEEP)], to evaluate if it better predicts hospital mortality compared to the P/F ratio post-intubation and to assess the resultant changes in severity classification of ARDS. METHODS: We categorized patients from a dataset of seven ARDS network trials using the thresholds of ≤ 100 (severe), 101-200 (moderate), and 201-300 (mild) for both P/F (mmHg) and P/FP (mmHg/cmH2O) ratios and evaluated hospital mortality using areas under the receiver operating characteristic curves (AUC). RESULTS: Out of 3,442 patients, 1,057 (30.7%) died. The AUC for mortality was higher for the P/FP ratio than the P/F ratio for PEEP levels > 5 cmH2O: 0.710 (95% CI 0.691-0.730) versus 0.659 (95% CI 0.637-0.681), P < 0.001. Improved AUC was seen with increasing PEEP levels; for PEEP ≥ 18 cmH2O: 0.963 (95% CI 0.947-0.978) versus 0.828 (95% CI 0.765-0.891), P < 0.001. When the P/FP ratio was used instead of the P/F ratio, 12.5% and 15% of patients with moderate and mild ARDS, respectively, were moved to more severe categories, while 13.9% and 33.6% of patients with severe and moderate ARDS, respectively, were moved to milder categories. The median PEEP and FiO2 were 14 cmH2O and 0.70 for patients reclassified to severe ARDS, and 5 cmH2O and 0.40 for patients reclassified to mild ARDS. CONCLUSIONS: The multifactorial P/FP ratio has a greater predictive validity for hospital mortality in ARDS than the P/F ratio. Changes in severity classification with the P/FP ratio reflect both true illness severity and the applied PEEP strategy. TRIAL REGISTRATION: ClinialTrials.gov-NCT03946150.
Authors: V Marco Ranieri; Gordon D Rubenfeld; B Taylor Thompson; Niall D Ferguson; Ellen Caldwell; Eddy Fan; Luigi Camporota; Arthur S Slutsky Journal: JAMA Date: 2012-06-20 Impact factor: 56.272