The symptoms of CSA are similar to those of OSA (figure 19). While excessive weight and snoring are significant features of OSA, they may not be so prominent in CSA (Naughton & Bradley, 1998).
Full polysomnography (PSG) with oesophageal pressure measurement is the gold standard for diagnosing CSA (Randerath et al., 2017). In routine practice, different surrogates of respiration and respiratory effort are used (figure 20).
As we have already discussed, specific PSG patterns can be associated with different clinical entities and they should therefore be described precisely to enable identification of the underlying and often overlapping causes (Baillieul et al., 2019). Separating central from obstructive hypopneas is very challenging when abnormal respiratory events are measured in a sleep study, but this is both crucial and necessary for the diagnosis of CSA.
The International Classification of Sleep Disorders – Third Edition (ICSD-3) specifies that CSA is classified as at least 10 central apneas and hypopneas per hour of sleep together with frequent arousals and fragmented sleep (Sateia et al., 2014).
CSA can be identified by the following criteria during PSG if there is a combination of:
In contrast to an obstructive event, the classification of an apnea as central is based on there being no ventilatory effort during the event (Berry et al., 2012).
Hypopneas are identified by a combination of:
Central hypopneas are characterised by a temporary reduction in ventilatory effort during sleep (Berry et al., 2012).
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