How usable is CPAP?  A recent study outlines the sorry reality[1]:

…Epidemiological data show that on average 25% of OSA patients do not accept CPAP treatment and, of those who undertake the therapy, only 30-60% can be considered adherent [8]. An acceptable adherence to therapy is usually considered a minimum of 4 hours/night for at least 70% of the nights of therapy [9]…

So bottom line, between 78% and 55% of people find CPAP unusable.

Most people find CPAP unusable.

After looking at many studies regarding what they call “compliance” or “adherence” the numbers above look to me to be what I have read elsewhere. Yes I really do believe that it could be as low as 22% of people being able to use CPAP long term!!

So why on earth do so many find CPAP unusable?! I think some hints are seen in the business portion of a recent study[2]:

…Measurements and Main Results: Pathophysiologic traits varied substantially among participants. A total of 36% of patients with OSA had minimal genioglossus muscle responsiveness during sleep, 37% had a low arousal threshold, and 36% had high loop gain. A total of 28% had multiple nonanatomic features. … A three-point scale for weighting the relative contribution of the traits is proposed. It suggests that nonanatomic features play an important role in 56% of patients with OSA…

CPAP can help to lessen the effects of airway collapse from anatomic causes. But nonanatomic causes are involved some 56% of the time. Most of the time.

The noise, vibration, and discomfort of CPAP use are not likely to help with “arousal threshold” issues. Indeed one would think they may well exacerbate them. I believe they do with me.

High “loop gain” (ventilatory control loop gain) is exactly what leads to hypocapnic central apnea. Breath too much, loose too much carbon dioxide going below the “apneic threshold” and a central apnea you will have.

As I first started reading about finding the hypocapnic apneic threshold (AT) they appeared to simply be raising CPAP pressures to invoke the central apnea. In today’s research dealing with determining the AT[3] they tend to use timed pulses of pressure to increase breathing volume.

What I find is that very simply the higher my CPAP pressure is the more I have a tendency to experience unstable breathing and “clear airway apneas” (likely hypocapnic central apneas). CPAP pressure does indeed seem to be a “plus” factor regarding respiratory control loop gain.

So CPAP pressure tends to exacerbate the “control loop gain” issues.

Another thing is that control loop gain and likely arousal threshold are not stable parameters. When I experienced traumatic stress I actually found myself hyperventilating to the point of aura during the daytime. The anniversary of the traumatic event, getting used to a new outside temperature (hot or cold), and even too much exercise – all of these I have tracked to being associated with the development of unstable breathing (loop gain problems) in my nightly CPAP data.

I track my CPAP data regularly and so can and do respond to problems as they crop up. But the normal procedure is to set things up and let them be.

It is no wonder to me that most people find CPAP unusable.

[1] Usefulness of reinforcing interventions on continuous positive airway pressure compliance

Lo Bue et al. BMC Pulmonary Medicine 2014, 14:78

http://www.biomedcentral.com/1471-2466/14/78

[2] Danny J. Eckert, David P. White, Amy S. Jordan, Atul Malhotra, and Andrew Wellman “Defining Phenotypic Causes of Obstructive Sleep Apnea. Identification of Novel Therapeutic Targets”, American Journal of Respiratory and Critical Care Medicine, Vol. 188, No. 8 (2013), pp. 996-1004.

doi: 10.1164/rccm.201303-0448OC link: http://www.atsjournals.org/doi/abs/10.1164/rccm.201303-0448OC#.U_06LdZx0xB

[3] X. S. Zhou , J. A. Rowley , F. Demirovic , M. P. Diamond , M. S. Badr

Effect of testosterone on the apneic threshold in women during NREM sleep

Journal of Applied Physiology Published 1 January 2003 Vol. 94 no. 1, 101-107 DOI: 10.1152/japplphysiol.00264.2002

[8] Catcheside PG: Predictors of continuous positive airway pressure adherence.

F1000 Med Rep 2010, 2:70. doi:10.3410/M2-70.

[9] Weaver TE, Grunstein RR: Adherence to continuous positive airway pressure therapy the challenge to effective treatment.

Proc Am Thorac Soc 2008, 5:173–178.

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