Effect of short-term ketogenic diet on end-tidal carbon dioxide.

Background & Aims: Previous studies have shown that end-tidal carbon dioxide (EtCO) is lower with the presence of supraphysiological ketones as in the case of chronic ketogenic diet (KD) and diabetic ketoacidosis (DKA). This study aimed to determine changes in EtCO upon short term KD.

Methods: Healthy subjects were screened not to have conditions that exerts abnormal EtCO nor contraindicated for KD. Subjects underwent seven days of KD while the EtCO2 and blood ketone (beta-hydroxybutyrate; β-OHB) parameters were sampled at day zero (t0) and seven (t7) of ketosis respectively. Statistically, the t-test and Pearson's coefficient were conducted to determine the changes and correlation of both parameters.

Results: 12 subjects completed the study. The mean score ± standard deviation (SD) for EtCO were 35.08 ± 3.53 and 35.67 ± 3.31 mm Hg for t0 and t7 respectively. The mean score ±SD for β-OHB were 0.07 ± 0.08 and 0.87 ± 0.84 mmol/L for t0 and t7 respectively. There was no significant difference of EtCO between the period of study (p > 0.05) but the β-OHB increased during t7 (p < 0.05). There was also no correlation between the parameters.

Conclusions: These findings suggest that EtCO may not be utilized to determine short term nutritional ketosis.