Matt Harmon

142 Chapter seven The median FIO 2 fraction was 0.35 (0.30-0.45). In patients with a supranormal arterial oxygen content (> 13.3 kPa), 48% were ventilated with an FiO 2 ≥ 0.4. Mechanical ventilation settings in hypoxemic vs. normoxemic patients As a surrogate marker of pulmonary complications, hypoxemic patients (P/F ratio < 200 mmHg) were compared to normoxemic patients (P/F ratio ≥ 200 mmHg) (supplemental table 2). PEEP was significantly higher in hypoxemic patients compared to normoxemic patients as was Pplat driving pressure V T and respiratory rate. Static compliance was lower in hypoxemic patients compared to normoxemic patients (34.3 (27.2-41.4) vs. 38.7 (32.8-48.4), p = 0.002). Mechanical ventilation settings during TTM in survivors vs. non- survivors at 28-days Baseline differences are given in table 1. V T , PEEP, Pplat and driving pressure did not differ between groups (table 2). Static compliance of the respiratory system was significantly lower while respiratory rate was significantly higher in non- survivors compared to survivors. Figure 2 shows the distribution of ventilation parameters plotted against V T and PaO 2 levels. The distribution for survivors and non-survivors at 28-days was largely the same. Figure 3 shows the relationship between mortality and ventilation settings using Loess regression curves. Mortality appears to be higher when driving pressures are above 20 cmH 2 O and when plateau pressures are above 25 cmH 2 O. Also, mortality is higher in patients with P/F ratios below 200 and in patients with low compliance. Of interest, high tidal volumes were not apparently related to mortality. Mechanical ventilation factors were included in a multivariable logistic regression model with a priori selected variables for disease severity and medical history to assess which factors were independently associated with mortality. In this analysis, with the exception of high respiratory rate, ventilator parameters were not associated with 28-day mortality (supplemental table 1).