Mixed apnea has the polysomnographic characteristics of central and obstructive apnea in the same event (Figure 21.1). Mixed apnea is usually central-obstructive. Obstructive-central apnea is very rare, except as terminal events.
The type of apnea does not have a strong correlation with the cause of the apnea nor with the location of the pathology. Neonates with myasthenia gravis may have central apnea if the diaphragmatic involvement predominates, or obstructive apnea if upper airway muscle involvement predominates. The apnea type offers a window to the pathophysiology of the apnea that, when analyzed in conjunction with other clinical and laboratory findings, contributes to the differentiation between neurological and nonneurological causes of apnea and among the different possible sites of neurological involvement.