Hyperoxaemia and hypoxaemia are associated with harm in patients with ARDS

BMC Pulmonary Medicine

Table 4 Univariable and multivariable analysis for hospital mortality

Predictor	Univariable analysis		Multivariable analysis
Predictor	Odds ratio [95% CI]	p-value	Odds ratio [95% CI]	p-value
Age (years)	1.05 [1.03, 1.08]	< 0.001	1.05 [1.03, 1.08]	< 0.001
Male	1.02 [0.57, 1.85]	0.95
APACHE II	1.04 [0.99, 1.09]	0.12
Non-respiratory SOFA score	1.12 [1.03, 1.22]	0.007	1.11 [1.00, 1.23]	0.05
Admission source
Emergency	0.85 [0.46, 1.61]	0.62
Elective	1.41 [0.39, 4.84]	0.58
Medical	0.96 [0.54, 1.70]	0.89
Surgical	1.48 [0.82, 2.68]	0.19
ARDS severity^a
Moderate	0.79 [0.42, 1.47]	0.46
Severe	0.57 [0.23, 1.32]	0.20
ARDS risk factor
Trauma	0.58 [0.25, 1.25]	0.18
Pneumonia	1.26 [0.68, 2.39]	0.46
Non-pulmonary sepsis	1.62 [0.78, 3.37]	0.19
Baseline ventilation parameters
Tidal volume (ml/kg PBW)	1.03 [0.88, 1.20]	0.71
PEEP (cmH₂O)	0.87 [0.77, 0.97]	0.01	0.86 [0.75, 0.98]	0.03
Mean airway pressure (cmH₂O)	0.95 [0.89, 1.00]	0.15
Lactate (mmol/L)	1.17 [1.00, 1.37]	0.05	1.13 [0.93, 1.39]	0.21
Vasopressor use	1.70 [0.95, 3.08]	0.08
Adjunctive therapies
Neuromuscular blockade	0.52 [0.27, 0.98]	0.05
Nitric oxide	1.12 [0.46, 2.61]	0.79
Prone positioning	0.92 [0.27, 2.76]	0.88
Highest PaO₂ (kPa/mmHg)
Quadratic term	1.00 [1.00, 1.00]	0.09
Linear term	0.88 [0.76, 1.01]	0.09
Highest FiO2	1.00 [0.91, 1.09]	0.96
Highest P/F ratio	0.98 [0.96, 1.00]	0.10
Average time-weighted PaO₂ (kPa/mmHg)
Quadratic term	1.07 [1.01, 1.14]	0.03	1.09 [1.02, 1.18]	0.02
Linear term	0.17 [0.04, 0.73	0.02	0.11 [0.01, 0.63]	0.02

Average time-weighted PaO₂ was obtained by calculating the value between consecutive time points prior to multiplying this value by the period of time between these points. The sum of these time-weighted values was then divided by the total time of mechanical ventilation (up to 7 days from onset of ARDS) within the timepoints of interest
APACHE II, Acute physiology and chronic health evaluation II; SOFA, Sequential organ failure assessment score; PaO₂, partial pressure of arterial oxygen; FiO₂, Fraction of inspired oxygen; P/F ratio, partial pressure of arterial oxygen to fraction of inspired oxygen ratio; PBW, predicted body weight; PEEP, Positive end-expiratory pressure
^aThe reference category for the comparison was Mild

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