Complex sleep apnea: the hedgehog and the fox

The prevalence and polysomnographic characteristics of treatment-emergent central sleep apnea with obstructive sleep apnea

PURPOSE

To investigate the prevalence of treatment-emergent central sleep apnea (TECSA) in individuals with obstructive sleep apnea syndrome (OSAS) during continuous positive airway pressure (CPAP) titration and assess their polysomnographic characteristics.

METHODS

A total of 116 patients with OSAS who underwent full-night CPAP titration at the Sleep Laboratory of Adana City Research and Education Hospital from September 2017 to January 2018 were recruited for the study. The patients' polysomnographic data related to respiratory events and sleep stages were reviewed in a retrospective manner.

RESULTS

While on CPAP titration, 20 of the 116 patients developed central sleep apnea (CSA). The prevalence of TECSA in the patients with OSAS was 17.2%, being separately determined as 16.3% and 2.2% for the male and female patients, respectively. In the baseline PSG, the groups did not statistically significantly differ in relation to the apnea hypopnea index (AHI), central apnea index (CAI), arousal index (AI), or oxygen desaturation index (ODI). However, the TECSA group had a significantly higher mean oxygen saturation value compared to the non-TECSA group (p = 0.01). The total AHI, CAI, and AI values of the TECSA group were significantly higher during the whole CPAP titration compared to the non-TECSA group. No significant difference was observed in the comparison of the two groups in relation to the titration pressure and ODI.

CONCLUSION

TECSA is a phenomenon that can occur with obstructive sleep apnea treatment and mostly regress spontaneously following appropriate CPAP treatment. TECSA is observed at different rates of prevalence. In this study, the prevalence of TECSA was higher than previously reported.

Complex sleep apnea syndrome

Complex sleep apnea is the term used to describe a form of sleep disordered breathing in which repeated central apneas (>5/hour) persist or emerge when obstructive events are extinguished with positive airway pressure (PAP) and for which there is not a clear cause for the central apneas such as narcotics or systolic heart failure. The driving forces in the pathophysiology are felt to be ventilator instability associated oscillation in PaCO2 arterial partial pressure of Carbon Dioxide, continuous cositive airway pressure (CPAP) related increased CO2 carbon dioxide elimination, and activation of airway and pulmonary stretch receptors triggering these central apneas. The prevalence ranges from 0.56% to 18% with no clear predictive characteristics as compared to simple obstructive sleep apnea. Prognosis is similar to obstructive sleep apnea. The central apnea component in most patients on followup using CPAP therap, has resolved. For those with continued central apneas on simple CPAP therapy, other treatment options include bilevel PAP, adaptive servoventilation, permissive flow limitation and/or drugs.

Treatment of complex sleep apnea syndrome

Complex sleep apnea syndrome (CompSAS) describes the coexistence or appearance and persistence of central apneas or hypopneas in patients with obstructive sleep apnea upon successful restoration of airway patency. We review data on treatment of CompSAS with CPAP, bilevel positive airway pressure, and adaptive servoventilation and discuss evidence for the addition of medications (analgesics, hypnotics, acetazolamide) and gases (oxygen, CO2) to positive airway pressure therapy. Future research should focus on defining outcomes in patients with CompSAS and allow for more accurate tailoring of therapy to the pathophysiology present in the individual patient.

Characteristics of Japanese patients with complex sleep apnea syndrome: a retrospective comparison with obstructive sleep apnea syndrome

OBJECTIVE

The prevalence of complex sleep apnea syndrome (CompSAS) among Asian patients with obstructive sleep apnea syndrome (OSAS) has not yet been reported. Distinguishing CompSAS from pure OSAS is difficult using only diagnostic polysomnography (PSG). We examined the prevalence of CompSAS in Japanese patients with OSAS and the possibility to distinguish CompSAS from pure OSAS by analyzing the severity of respiratory events based on either sleep body position or sleep stage using a diagnostic PSG.

PATIENTS AND METHODS

A retrospective chart review of 297 consecutive Japanese patients who were 15 years of age or older with a primary diagnosis of OSAS who were referred for CPAP titration (AHI> or =20 events/hr).

RESULTS

Seventeen patients (5.7%) out of the 297 patients who had an obstructive apnea hypopnea index (AHI) of 20 or higher showed adverse increases in central apnea index (CAI) by the treatment with CPAP whereas obstructive apnea index (OAI) and mixed apnea index (MAI) were significantly decreased. In the results, the AHI on the PSG for CPAP titration reached only approximately half of the values on the diagnostic PSG. In these CompSAS patients, both the total CAI and the CAI in the supine position during NREM sleep on the diagnostic PSG were significantly higher than those in the OSAS group. The sleep body position did not so strongly affect the AHI, OAI and MAI in the CompSAS group. Multiple, stepwise, and logistic regression analyses revealed that the CAI in the supine position during NREM (p=0.026) was a significant variable to distinguish CompSAS from OSAS statistically although the variables were within the normal range.

CONCLUSION

The prevalence of CompSAS in Japanese OSAS patients may be lower when compared with Caucasian patients. The increase of CAI in the supine position during NREM sleep on diagnostic PSG may be a characteristic feature in CompSAS.