Additionally, nocturnal PtcCO 2 level was found to increase independently of the severity of the obstructive sleep apnea (OSA) due to respiratory muscle hypotonicity among children with Down syndrome 10. A study where PSG, transcutaneous CO 2 (PtcCO 2), and end-tidal CO 2 (PetCO 2) levels were compared in 609 patients, mean PtcCO 2 was found above 50 mmHg in 11.9% of 318 patients who had an apnea-hypopnea index (AHI) below 59. However, there has been no consensus yet on a validated definition of nocturnal hypoventilation (NH) in children. Therefore, CO 2 measurements have been recommended as a marker of airway obstruction and quantitative measurement of alveolar hypoventilation in all children 7, 8. Thus, screening tests are needed to diagnose SDB before the development of signs of daytime hypercapnia among children with neuromuscular weakness.Īlthough in the literature PSG is considered the gold standard test for diagnosing and classifying SDB and determining its severity, there is an ongoing debate as to whether or not routine monitoring of the CO 2 level is performed in most sleep laboratories. Furthermore, daytime respiratory function tests do not reliably identify patients with SDB in the absence of hypercapnia 5, 6. As there is no large-scale studies, the incidence varies by different study centers, children’s age range, NMD type, the diagnostic method used, and even differing criteria used in the diagnostic methods.Īs symptoms and signs alone are not sufficiently reliable for diagnosing sleep-disordered breathing (SDB) and as polysomnography (PSG) has limited practicality and availability, various researchers have thought various alternative diurnal and nocturnal screening tests to predict SDB. In children with NMD, the prevalence of sleep-disordered breathing (SDB) disorders (hypoventilation, hypoxemia, central or obstructive apnea-hypopnea) was reported as high as 30-70% 3, 4. Neuromuscular weakness will worsen nocturnal respiratory problems in sleep, and thus will lead to hypercapnia and hypoxemia that frequently emerge at night before daytime ventilation disorders become evident 2. In sleep, however, they become vulnerable to hypoventilation and hypercarbia associated with shallow ventilation and reduced tonus of upper respiratory tract and intercostal muscles. Patients can avoid hypoxemia and hypercarbia via controlled hyperventilation when awake. In this group of patients, respiratory system muscles are also affected in addition to skeletal muscles. Patients with neuromuscular disease (NMD) will not only experience parenchymal lung diseases such as recurrent pneumonia and atelectasis but also nocturnal sleep-disordered breathing disorders as their respiratory muscle weakness progresses 1.
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