Successful treatment of obstructive sleep apnea can dramatically reduce the recurrence rate of atrial fibrillation and other arrhythmias following ablation or cardioversion. Yet many patients with a history of arrhythmia just can’t seem to use their OSA treatment. Read below to learn about one of the most critical – yet commonly missed – reasons why.
Breathing during sleep is regulated primarily by arterial CO2. When CO2 decreases below the apneic threshold, a compensatory reduction or pause in breathing occurs. This is called central sleep apnea.
Patients with a history of arrhythmia and cardiovascular conditions have a heightened ventilatory drive. They are also prone to aggressive responses to minor fluctuations in CO2. This is termed ventilatory control instability.
CPAP opens the airway and increases ventilation. In up to 50% of patients with a history of arrhythmia, this combination of increased ventilation and ventilatory control instability triggers repeated episodes of decreased breathing and attendant oxygen desaturations and sleep disruptions. This is termed treatment emergent central sleep apnea. If not recognized and managed appropriately, patient tolerance of treatment will be poor. Some may even report feelings of suffocation when CPAP drives their CO2 too low.
Unfortunately, treatment emergent central sleep apnea often goes unrecognized in the sleep center and patients are placed on inappropriate and even harmful therapy. Some will even be told to try using bilevel ventilation (“BiPAP”). This should never be used in such cases for obvious reasons – it increases tidal volume and minute ventilation, exacerbating the problem. In research settings, the approach is simple: in order to study central sleep apnea, put a patient on BiPAP until their CO2 is driven below the apneic threshold.
Please, ensure that your chosen sleep center recognizes that not all reductions in breathing are due to obstruction – particularly in patients with a history of arrhythmia. One simple hint that all too often goes unrecognized? If your patient’s breathing actually improves during REM sleep, obstruction is not the problem. OSA worsens in REM sleep due to atonia of the upper airway muscles. However, ventilatory control relaxes markedly during REM, and central sleep apnea improves.
In sum, ensure that your sleep center understands the needs of your patients and knows how to diagnose and treat them properly. The recommendation of BiPAP or failure to recognize improved breathing in REM sleep may be red flags that your patients may not be receiving evidence-based care. Needless to say, appropriate differentiation of obstructive and central sleep apnea is critical. Your patients’ recommended treatment – and treatment success – depends on it.
– Michael Mohan MD Medical Director Scottsdale
