The final study population accounted for 378 patients: 290 (77%) were acidotic on admission (acidotic group), while 88 were www.selleckchem.com/products/brefeldin-a.html controls. Baseline characteristics and the CPAP setting of the acidotic group and controls are summarized in Table Table11.Table 1Baseline characteristics on admission and before continuous positive airway pressure treatmentThe mean �� standard deviation duration of CPAP treatment was 318 �� 485 minutes and 262 �� 198 minutes in the acidotic group and controls, respectively (P = 0.289). The mean �� standard deviation FiO2 during CPAP was 48 �� 11% and 47 �� 9% in the acidotic group and in controls, respectively (P = 0.219). The mean �� standard deviation PEEP during CPAP was 8.1 �� 1.7 cmH2O and 7.9 �� 1.4 cmH2O in the acidotic group and in controls, respectively (P = 0.

229).A total of 28 patients (9.7%) in the acidotic group and eight patients (9.1%) among controls experienced a clinical failure (odds ratio = 1.069; 95% confidence interval = 0.469 to 2.438; P = 0.875) (see Table Table2).2). Acidemia on admission did not affect clinical failure after adjustment for age, history of acute myocardial infarction, hypocapnia, normotension and PaO2/FiO2 ratio in a multivariable logistic regression model (P = 0.205).Table 2Clinical endpoints of the study population, according to presence or absence of acidemia on admissionThe crude proportion of clinical failure in the study population is presented in Figure Figure1,1, split by pH value on admission. The 95% confidence interval of the controls group included the point estimate and most of the confidence intervals of the other groups.

Figure Figure22 shows the time course of the mean arterial pH in the study population. Survival analysis indicates that, among acidotic patients, the time at which 50% of patients reached the 7.35 threshold was 173 minutes (95% confidence interval = 153 to 193) (see Figure Figure33).Figure 1Clinical failure rate of the study population by pH value on admission. The 95% confidence intervals of the control group are depicted with dashed horizontal lines.Figure 2Time course of pH during continuous positive airways pressure treatment. The time course of mean arterial blood pH during continuous positive airways pressure treatment in the acidotic group and in controls. Adjusted for age and sex; missing data replaced …Figure 3Survival analysis of time to pH ��7.

350 among acidotic patients. Dotted lines indicate the time at which 50% of the sample reached the threshold pH (173 minutes).Respiratory, metabolic and mixed acidotic populationsAmong the 290 acidotic patients, 13 could not be further classified. Among the other 277 patients, 122 (44%) showed a respiratory acidosis, 89 (32%) Batimastat a metabolic acidosis, and 66 (24%) a mixed acidosis on admission.