Abstract
Respiratory data can be extracted from pulse oximeter plethysmogram (pleth) traces using low pass filtering (LPF) in infants and children (Wertheim D et al. Arch Dis Child Fetal Neonatal Ed.2009;94:F301-3). Flattening of the LPF pleth trace has been observed associated with central apnoeas in infants(Wertheim D et al. Acta Paediatr.2014;103:e222-4). The study aim was to examine changes in LPF pleth traces associated with obstructive apnoeas in children. Polysomnographic data were analysed from recordings on 4 children undergoing respiratory polysomnography for suspected obstructive sleep apnoea. Signals were acquired using a Visi-3 Polysomnography system (Stowood Scientific Instruments Ltd., UK). Oximetry pleth, thoracic and abdominal Respiratory Inductance Plethysmography (RIP) bands, oxygen saturation (SpO2) and heart rate data were downloaded. Software was written in MATLAB (The MathWorks Inc., USA) to LPF the pleth signal & view with other signals. Different patterns in LPF pleth traces associated with periods of apnoea were seen. Pattern A:In 2 cases there was an increase in LPF pleth signal amplitude associated with increase in the abdominal RIP band trace, increased thoracoabdominal asynchrony and increased respiratory rate during a period of obstructive apnoea. Pattern B:In 3 recordings periods of flattening on RIP bands were associated with flattening on the LPF pleth signal as seen in central apnoeas; 1 of these recordings also included periods with pattern A. There appear to be different patterns seen on the filtered pleth traces in apnoeas which may suggest some periods were not pure obstructive apnoeas. Thus our results suggest there can be changes in the LPF pleth signal associated with obstructive apnoeas.
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