The Effects of Nitrous Oxide-Oxygen Inhalation Sedation on Autonomic Response to Dental Scaling in Patients with Severe Motor and Intellectual Disabilities

Abstract : There is no information available regarding the physiological effects of nitrous oxide (N2O)-oxygen inhalation sedation for patients with severe motor and intellectual disabilities (SMID) and healthy adults (HA). To evaluate this, we assessed autonomic functions with heart rate (HR) variability during dental treatment under N2O-oxygen inhalation sedation. Nine SMID patients and 9 HA patients were randomly assigned to inhale 0%, 30% or 40% of N2O on each treatment day. HR (ECG) and respiration rate (piezo band) were measured in the supine position after resting for 5 min as a baseline, followed by 5-min N2O-oxygen inhalation, infiltration anesthesia (IA), and dental scaling (DS). The high frequency (0.15-0.4 Hz : HF) component of HR was defined as a parasympathetic nerve activity and the ratio of the low frequency (0.04-0.15 Hz : LF) component to HF (LF/HF) was defined as a cardiac sympathetic nerve activity. Sedations inducing increases in HF and decreases in LF/HF were considered effective. In HA patients, HR was lower during 5-min N2O inhalation and IA compared to baseline. In SMID patients, it was lower during 5-min N2O inhalation, but similar during IA, and higher during DS compared to baseline. HF increased after 5-min N2O inhalation until IA in both HA and SMID patients. This change in HF was remarkable at 30% N2O in HA patients, and 40% N2O in SMID patients. LF/HF was lower during 5-min N2O inhalation and IA compared to baseline only in SMID patients, especially at 40% N2O. These results suggest that N2O-oxygen inhalation with relatively higher concentration is effective even in patients with severe motor and intellectual disabilities, and the dental stress is alleviated by using N2O-oxygen inhalation for them.