Rib cage to abdominal asynchrony in children undergoing polygraphic sleep studies

We assessed rib cage (RC) to abdominal (AB) asynchrony in 110 children, aged 1 to 50 months who underwent diagnostic daytime polygraphic sleep studies (PSG), and correlated the results. RC-AB asynchrony was calculated by the phase angle (PA) technique and compared to normal values (0-24 degrees) derived from a separate group of 45 control children, matched for age and weight. Eighty-two of the 110 patients had PSG as part of their evaluation for obstructive sleep apnea. There was a high association between the phase angles and the PSG results (P less than 0.01; Fisher's exact test). PSG was abnormal in 38/82 patients (46%) and the phase angle was increased in 51/82 (62%) (mean +/- SD, 68 degrees +/- 39 degrees; range 28 degrees - 168 degrees) compared to the normal controls (P less than 0.001). Fourteen of the 110 patients had bronchopulmonary dysplasia; of these, PSG and PA results agreed in six normal and seven abnormal studies and disagreed in only one (P = 0.002). Six of 110 patients had Down's syndrome; 5 of 6 had increased RC-AB asynchrony, compared to 3 of 6 who had abnormal PSG. Eight of 110 patients were evaluated for central apnea and hypoventilation; PA was abnormal in 4 of 8, who also had abnormal PSG and in 1 with normal PSG. We conclude that RC-AB measurement by the PA technique may be an important adjunct to the evaluation of breathing disorders during sleep in small children and it may be a good screening test for small children who need PSG.