Study objectives: Overnight polysomnography (ONP) is
the “gold standard” for the diagnosis of sleep-disordered
breathing, but it is expensive and time-consuming. Thus, daytime nap
studies have been used as screening tests. If the findings of a nap
study are normal or mildly abnormal, should ONP be performed? Do
specific abnormalities in nap studies predict abnormal findings in ONP?
To answer these questions, we conducted this study.
Design: Retrospective chart review.
Setting: Children’s hospital.
Participants:One hundred forty-three children with suspected obstructive sleep
apnea syndrome secondary to isolated adenotonsillar hypertrophy, who
had normal or mildly abnormal nap studies, and underwent ONP.
Measurements and results: We compared daytime nap and
overnight polysomnograms in 143 children (52 girls; mean [± SD]
age, 5.6 ± 3.1 years). Total sleep time was 1 h in daytime nap,
and 5.1 ± 1.3 h in ONP. The interval between the two studies was
5.9 ± 4.8 months. The findings of 59% of the nap studies were
mildly abnormal, while 66% of overnight studies were abnormal. No
individual nap study parameter (including short obstructive apneas,
hypopneas, hypoxemia, hypoventilation, snoring, paradoxical breathing,
gasping, retractions) had good sensitivity at predicting abnormal
overnight polysomnograms, but most had good specificity and positive
Conclusions: We conclude that
individual nap study parameters are not very sensitive in predicting
abnormal ONP findings. However, when nap study parameters are abnormal,
the chance of obstructive sleep apnea syndrome is