Three components of obstructive sleep apnea/hypopnea syndrome.

The aims of this study were to calculate the apnea-hypopnea index (AHI), which represented as the number of apnea-hypopnea occurrences per hour, the 4% oxygen desaturation index (ODI4) and the breathing-related arousal index (B-ArI) in polysomnographic studies of obstructive sleep apnea/hypopnea syndrome (OSAHS) patients and to investigate whether there was any relationship between each pair of scoring schemes. Thirty-four cases of OSAHS were studied. Total OSAHS patients were subdivided into those with a high AHI (> 25), and those with a low AHI (< 25). The correlation between each pair of scoring schemes for OSAHS with a high AHI showed high value. The correlation between AHI and ODI4 for OSAHS with a low AHI was 0.18 and that between AHI and B-ArI showed a weak correlation of 0.59, while that between ODI4 and B-ArI was only -0.078. Our results mean that oxygen desaturation and arousal occur separately in mild or moderate OSAHS patients, even though they are diagnosed with the same level of OSAHS by means of AHI. Breathing-related arousal without oxygen desaturation often occurs in mild or moderate OSAHS patients. We previously reported that AHI does not accurately reflect the severity of the increase in negativity of esophageal pressure manifested as respiratory efforts. We consider that the comprehension and assessment of OSAHS can be improved by the systematic differentiations among the three components: oxygen desaturation, arousals and respiratory efforts.