Respiratory rate is an inadequate parameter of ventilation in non-intubated sedation

Abstract

We compared the respiratory rate (RR) and transcutaneous carbon dioxide pressure (${\text{Pt}}{{\text{c}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}$) during intravenous sedation (IVS), to determine whether RR is a useful parameter for monitoring ventilation. This was a prospective cohort study. The study sample comprised dental patients who received IVS via propofol or midazolam administration at Nippon Dental University Hospital. We simultaneously measured RR (through capnography), ${\text{Pt}}{{\text{c}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}$ (using the ${\text{Pt}}{{\text{c}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}$ monitor), and percutaneous oxygen saturation (SpO₂). RR was the predictor and the outcome variable was ${\text{Pt}}{{\text{c}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}$. Data were analyzed by Dunnett’s test and Pearson’s correlation coefficient. P < 0.05 was considered statistically significant. The study sample consisted of 15 patients. No significant changes were identified in the RR and SpO₂ measurements over time. However, ${\text{Pt}}{{\text{c}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}$ values obtained from 20 to 40 min after induction of sedation were significantly higher than baseline values (P < 0.05). A correlation was found between RR and ${\text{Pt}}{{\text{c}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}$ (P < 0.05), but the correlation coefficient was low (r = 0.22), indicating a weak correlation between these two factors. The results of this study suggest that RR is an inadequate parameter for monitoring ventilation during IVS; however, ${\text{Pt}}{{\text{c}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}$ may be useful for monitoring.