Sleeping children with Prader-Willi syndrome (PWS) and severe obstruction of the upper airways — those between the nose and the larynx — go without sufficient breathing for longer periods when their apnea is worse, compared to children without the disease but with the same levels of obstruction, a study reports.
The findings were reported in the journal Archives of Disease in Childhood, in a study titled “Hypoventilation disproportionate to OSAS severity in children with Prader-Willi syndrome.”
Obstructive sleep apnea syndrome (OSAS) is the most common type of apnea (cessation of breathing), and is known to affect 80 percent of children with PWS. Abnormal respiratory control, obesity, and malformation of the adenoid and tonsil glands (important tissues for the immune system found in the mouth) are among the causes of OSAS in these children.
Longer periods of insufficient breathing (hypoventilation) raise blood levels of carbon dioxide (hypercapnia).
Researchers in the United Kingdom and Greece tested the hypothesis that children with PWS and OSAS experience hypercapnia for a longer period of total sleep time than non-syndromic children with similar levels of airway obstruction, measured with the obstructive apnea-hypopnea index (OAHI).
The study, involving London’s Great Ormond Street Hospital and the Royal Brompton Hospital, included children with and without PWS and known to snore who were of similar age, body mass index (BMI) and OAHI. There were 48 children with PWS (median age, 2.3 years) and 92 without it (median age, 2.2 years).
They were analyzed on percentage of total sleep time in hypercapnia (carbon dioxide levels over 50 millimeters of Hg). Severity of OSAS was measured by the number of apnea events per hour during sleep: fewer than one, between one and five, and more than five.
Results showed that the groups did not differ in the percentage of total sleep time in hypercapnia. However, researchers found a link between PWS and OSAS severity, and the duration of hypoventilation.
PWS patients with “moderate to severe” apnea spent a longer time in a hypercapnic state throughout their total sleep time — meaning, these children experienced higher percentages of hypercapnia, compared to the control group, when their apnea symptoms worsened. Specifically, researchers reported the percentage of hypercapnia among PWS children with OSAS to be 0.2% in the group with fewer than one apnea episode per hour during sleep, 1% in the group with one to five episodes, and 33% in those with more than five apnea episodes per hour.
They concluded that “children with PWS and moderate to severe OSAS tend to hypoventilate and thus to become hypercapnic for longer periods of their sleep compared with typically developing children with similar frequency of obstructive events.”
Researchers also emphasized that “pediatricians caring for patients with PWS should be alerted by the presence of symptoms and signs indicative of deteriorating obstructive [sleep-disordered breathing] and consult a sleep center.”