Ranges of blood gas parameters for all breath-holds. Initial (< 1 min), Final and Recovery (2 – 3 min) blood gas values compared across all breath-holds. Different letters in the superscript denote significant differences in that parameter between the three time periods. Values are reported as mean ± SE. Venous blood parameters represented in the table are partial pressure of oxygen (pO2), partial pressure of carbon dioxide (pCO2), saturation of haemoglobin (sO2), oxygen content (O2ct), total circulating haemoglobin (tHb), haematocrit (Hct), and pH. Differences were assessed using a linear mixed effect model with seal ID as a random effect. Differences in least square means were assessed using a Tukey’s test following a significant difference between periods.