I have patients who complain of difficulty tolerating the forced air generated by their CPAP therapy. What solutions do you recommend?
A patient’s complaint about pressurized air must always be clarified as either an inspiratory or expiratory problem. The problem is rare on inspiration because pressurized air is travelling inward or the same direction as the inspiratory phase of breathing; thus, it is also rare that a patient will complain about intolerance for both phases of respiration. Most complaints are directed at expiration, which produces the phenomenon of “expiratory pressure intolerance” (EPI) among PAP users.
EPI most commonly indicates both the subjective sensation of discomfort and the objective finding of irregularities on the expiratory limb of the airflow curve. We recently published a paper in Journal of Sleep Disorders: Treatment and Care (http://www.scitechnol.com/2325-9639/2325-9639-2-107.php) suggesting that the mechanical effect of fighting against pressurized air flowing inward during expiratory flow outward may be a precursor to iatrogenic central apneas and ultimately the diagnosis of complex sleep apnea. Unfortunately, most sleep technologists are not trained to observe these subtle findings on the expiratory limb of the airflow curve, and most sleep doctors may also be unaware of this phenomenon, perhaps believing this issue is strictly subjective.
The lack of awareness about EPI contributes to the widely held belief that most patients adapt to fixed CPAP over time and that central apneas observed on first titrations resolve over time as well. As research suggests, complex sleep apnea allegedly does not persist or develop in a large majority of CPAP users. In contrast, our experience with more than a thousand 2nd opinion cases indicates virtually all CPAP users presenting with suboptimal responses show EPI on their initial 2nd opinion titrations. Many of these patients never adapted to CPAP; they continued to suffer until expiratory relief was provided, which is why our sleep center virtually ceased prescribing CPAP devices in 2005 and only recommends BPAP, ABPAP, ASV, or IVAPS units.
Complicating the EPI factor is AASM mandated policy to eliminate upper airway resistance or RERAs on the inspiratory curve, a policy we strongly favor and implement at our center. EPI and RERAs are tightly linked, because higher pressures must round the inspiratory air flow curve (i.e. normalize airflow by eliminating RERAs), yet higher pressure creates more EPI in susceptible patients. This juxtaposition reinforces the value of dual pressure systems; and the auto-adjusting features in some of these devices further improve the capacity to normalize the airflow curve on inspiration without causing or aggravating expiratory pressure intolerance. However, it cannot be repeated often enough that the sleep tech in the lab must titrate the patient manually even though the device is set for auto mode. Regrettably, the use of home trials of auto devices does not in our experience resolve RERAs. As smart as the auto-adjusting algorithm might be, a sleep tech with a trained eye to spot subtle RERAs shows a more consistent ability to normalize the airflow signal and inhibit EPI, the combination of which yields optimal objective results and eliminates patient complaints about pressure intolerance.