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 angile (PA) technique and compared to normal values (0–24°) 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 < 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° ± 39°; range 28°–168°) compared to the normal controls (P < 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.