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BMJ Open. 2015 Mar 27;5(3):e006812. doi: 10.1136/bmjopen-2014-006812.

Assessment of PaO₂/FiO₂ for stratification of patients with moderate and severe acute respiratory distress syndrome.

Author information

1
CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Multidisciplinary Organ Dysfunction Evaluation Research Network, Research Unit, Hospital Universitario Dr Negrín, Las Palmas, Spain.
2
CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Intensive Care Unit, Hospital Universitario Río Hortega, Valladolid, Spain.
3
Intensive Care Unit, Hospital General de Ciudad Real, Ciudad Real, Spain.
4
Intensive Care Unit, Hospital Clínico Universitario de Valladolid, Valladolid, Spain.
5
Intensive Care Unit, Hospital Universitario General de León, León, Spain.
6
Intensive Care Unit, Hospital Universitario Río Hortega, Valladolid, Spain.
7
Intensive Care Unit, Complejo Hospitalario Universitario de Albacete, Albacete, Spain.
8
CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Department of Surgical Sciences, Anesthesiology & Critical Care, Hedenstierna Laboratory, Uppsala University Hospital, Uppsala, Sweden.
9
Intensive Care Unit, Hospital Virgen de la Concha, Zamora, Spain.
10
Intensive Care Unit, Hospital Virgen de la Luz, Cuenca, Spain.
11
Intensive Care Unit, Hospital Universitario La Paz, Madrid, Spain.
12
CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Critical Care Center, Corporació Sanitaria Parc Taulí, Sabadell, Spain.
13
CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Research Unit, Hospital Universitario NS de Candelaria, Tenerife, Spain.
14
Department of Respiratory Care, Massachusetts General Hospital, Boston, Massachusetts, USA Department of Anesthesiology, Harvard University, Boston, Massachusetts, USA.

Abstract

OBJECTIVES:

A recent update of the definition of acute respiratory distress syndrome (ARDS) proposed an empirical classification based on ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO₂/FiO₂) at ARDS onset. Since the proposal did not mandate PaO₂/FiO₂ calculation under standardised ventilator settings (SVS), we hypothesised that a stratification based on baseline PaO₂/FiOv would not provide accurate assessment of lung injury severity.

DESIGN:

A prospective, multicentre, observational study.

SETTING:

A network of teaching hospitals.

PARTICIPANTS:

478 patients with eligible criteria for moderate (100<PaO₂/FiO₂≤200) and severe (PaO₂/FiO₂≤100) ARDS and followed until hospital discharge.

INTERVENTIONS:

We examined physiological and ventilator parameters in association with the PaO₂/FiO₂ at ARDS onset, after 24 h of usual care and at 24 h under a SVS. At 24 h, patients were reclassified as severe, moderate, mild (200<PaO₂/FiO₂≤300) ARDS and non-ARDS (PaO₂/FiO₂>300).

PRIMARY AND SECONDARY OUTCOMES:

Group severity and hospital mortality.

RESULTS:

At ARDS onset, 173 patients had a PaO₂/FiO₂≤100 but only 38.7% met criteria for severe ARDS at 24 h under SVS. When assessed under SVS, 61.3% of patients with severe ARDS were reclassified as moderate, mild and non-ARDS, while lung severity and hospital mortality changed markedly with every PaO₂/FiO₂ category (p<0.000001). Our model of risk stratification outperformed the stratification using baseline PaO₂/FiO₂ and non-standardised PaO₂/FiO₂ at 24 h, when analysed by the predictive receiver operating characteristic (ROC) curve: area under the ROC curve for stratification at baseline was 0.583 (95% CI 0.525 to 0.636), 0.605 (95% CI 0.552 to 0.658) at 24 h without SVS and 0.693 (95% CI 0.645 to 0.742) at 24 h under SVS (p<0.000001).

CONCLUSIONS:

Our findings support the need for patient assessment under SVS at 24 h after ARDS onset to assess disease severity, and have implications for the diagnosis and management of ARDS patients.

TRIAL REGISTRATION NUMBERS:

NCT00435110 and NCT00736892.

KEYWORDS:

RESPIRATORY MEDICINE (see Thoracic Medicine)

PMID:
25818272
PMCID:
PMC4386240
DOI:
10.1136/bmjopen-2014-006812
[Indexed for MEDLINE]
Free PMC Article

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