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Assessing ventilatory control stability in children with and without an elevated central apnoea index
Author(s) -
Harman Katherine,
Weichard Aidan J.,
Davey Margot J.,
Horne Rosemary S.C.,
Nixon Gillian M.,
Edwards Bradley A.
Publication year - 2020
Publication title -
respirology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 85
eISSN - 1440-1843
pISSN - 1323-7799
DOI - 10.1111/resp.13606
Subject(s) - medicine , interquartile range , hypoxic ventilatory response , ventilation (architecture) , anesthesia , hypoxia (environmental) , cardiology , respiratory system , oxygen , mechanical engineering , chemistry , organic chemistry , engineering
Background and objective Frequent central apnoeas are sometimes observed in healthy children; however; the pathophysiology of an elevated central apnoea index (CAI) is poorly understood. A raised CAI may indicate underlying ventilatory control instability (i.e. elevated loop gain, LG) or a depressed ventilatory drive. This pilot study aimed to compare LG in otherwise healthy children with an elevated CAI to healthy controls. Methods Polysomnographic recordings from children (age > 6 months) without obstructive sleep apnoea and with a CAI > 5 events/h ( n = 13) were compared with age and gender‐matched controls with a CAI < 5 events/h ( n = 13). Spontaneous sighs were identified during non‐rapid eye movement (NREM) sleep, and breath–breath measurements of ventilation were derived from the nasal pressure signal. A standard model of ventilatory control (gain, time constant and delay) was used to calculate LG by transforming ventilatory fluctuations seen in response to a sigh into a ventilatory‐drive signal that best matches observed ventilation. Results The high CAI group had an elevated LG (median = 0.36 (interquartile range, IQR = 0.35–0.53) vs 0.28 (0.23–0.36); P ≤ 0.01). There was no difference in either the time constant ( P = 0.63) or delay ( P = 0.29) between groups. Elevated LG observed in the high CAI group remained after accounting for degree of hypoxia (average oxygen saturation (SpO 2 ) during each analysable window) experienced (0.40 (0.30–0.53) vs 0.25 (0.23–0.37); P = 0.04). Conclusion An elevated CAI in otherwise healthy children is associated with a raised LG compared to matched controls with a low CAI, irrespective of level of hypoxia. This relative ventilatory instability helps explain the high CAI and may ultimately be able to help guide diagnosis and management in patients with high CAI.