Fig. 1. The trends of temperature-corrected arterial blood gas values (PCO₂, base deficit, pH) and lactate during CO₂ administration.

Each symbol represents one patient. Baseline values (0-point) correspond to the last measured value prior to the start of CO₂ inhalation. The last data point on the graphs correspond to values measured after the offset of CO₂ administration. The x-axis displays the time in hours since the start of CO₂ inhalation. a PCO₂ trends for each patient during the study. Patients spent 95.1% of time (range: 44.6–98.5%) in the desired PCO₂ range (40–60 mm Hg) during the 5% CO₂ administration, calculated by linear interpolation between the blood gas measurements. All PCO₂ values were >40 mm Hg, the lower value of the target range. b pH trends for each patient during the study. A repeated-measures linear mixed-effect model predicted that pH remained stable over time during the CO₂ administration. Baseline value, time in hours since the beginning of inhalation, and Thompson encephalopathy score were considered to have fixed effects. c Base deficit trends for each patient during the study. The same model predicted that base deficit decreased by 0.61 mmol/L per hour throughout the CO₂ inhalation period. d Lactate trends for each patient during the study. The same model predicted that lactate levels decreased by 0.55 mmol/L per hour throughout the CO₂ inhalation period.