Development of a sleep apnea event detection method using photoplethysmography.

We studied the possibility of detection of sleep apnea or hypopnea events from photoplethysmography (PPG) wave variation patterns during sleep. In three patients with suspected sleep apnea syndrome, polysomnography (PSG) and the PPG wave were measured simultaneously during sleep. The characteristics of the PPG wave variation patterns in apnea or hypopnea events detected by PSG were investigated. It was found that pulse rate increases and pulse wave amplitude decreases during apnea or hypopnea events, and the respiratory component of heart rate variability has a tendency to decrease before the apnea or hypopnea events. Also, compared to hypopnea, the ratio of the pulse rate is higher, the reduction of the pulse amplitude is more significant, and the decrease of the degree of respiratory variation component in the apnea event is greater. We devised the apnea / hypopnea detection algorithm using these characteristics and evaluated its effectiveness.

Influence of oral appliances on craniocervical posture in obstructive sleep apnea-hypopnea syndrome patients.

PURPOSE: The existence of a relationship between head posture and mandibular function has been discussed by several authors. However, the relationship between head posture and the cervical spine in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) who are using oral appliances (OAs) remains unknown. The aim of this study was to evaluate the changes in the cervical spine associated with the use of OAs in patients with OSAHS. METHODS: Fifteen patients (4 females and 11 males; mean age, 48 years) diagnosed with OSAHS were randomly selected. An OA was fabricated individually for each patient. Two lateral cephalometric radiographs were taken while the patient was sitting awake in an upright position. The first radiograph was taken in the intercuspal position and the second was taken while the subject was wearing the OA. Analyses based on the sella-nasion (SN) line were performed in the lateral cephalogram. Comparison of craniocervical angles in patients with and without the OA was performed using Wilcoxon's signed-rank test. RESULTS: Cephalometric analysis showed that the craniocervical angles (CVT-C2V and SN-C4) with OA were higher than those without OA (P<0.05). It seems that the OA caused a significant flexion of the cranium on the upper cervical spine. A significant increase in the craniocervical angle occurred in the fourth cervical segment. CONCLUSION: The changes in forward flexion of the upper cervical spine found in this study imply that changes in the craniocervical relationship should be evaluated periodically after an OA has been inserted.

[The effectiveness of prosthodontic mandibular advancement for obstructive sleep apnea syndrome].

PURPOSE: This study investigated the hypothesis of a direct association between the shift of incisal point and the diameter of the oropharynx space, and nocturnal oximetry with and without prosthodontic mandibular advancement (PMA) which is one type of oral appliance used to treat obstructive sleep apnea syndrome (OSAS), and to indicate the effects of PMA. METHODS: A total of 19 patients with OSAS were subjected to finger pulse oximetry recording and lateral cephalometric radiography: with and without PMA. The distance of the oropharynx space (PNS-AS, SPAS, MAS, and IAS) and the shift of incisal point with PMA were measured. The oxygen desaturation index (ODI 4%) and the cumulative percentages of time spent at saturations below 90% (CT(90)) during sleeping were calculated. Spearman's rank correlation test was used to measure the relationship between the increase of the velopharyngeal space and the distance of the mandible. The ODI 4%, CT(90) and distance of the velopharyngeal space were compared for all subjects with and without PMA by Wilcoxon's linking test. RESULTS: There was a strong relationship between the increase of the lower part (IAS) and the distance of anterior shift of incisal point (r=0.61, p=0.01). ODI 4% and CT(90) significantly decreased (p<0.01) and the three liners of the oropharynx(SPAS, MAS, IAS) significantly increased with PMA (p<0.01). CONCLUSIONS: It was shown that prosthodontic mandibular advancement could reduce the ODI 4% and CT(90) value in patients with OSAS, by enlarging the oropharynx space.