Auto-titration of CPAP is an essential tool for diagnosing and treating obstructive sleep apnea.

 John A. Wolfe, RRT

Diagnosing and treating obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) is both an art and a science. Once the nature of a patient’s OSA has been established (central, peripheral, or mixed), clinicians face the challenge of selecting the ideal interface and the optimal level of CPAP. An amazing (and some might say bizarre) array of masks and headgear have been developed in an attempt to address the unique facial anomalies that are infinitely variable from one patient to the next. Just as each patient has unique facial features, the pharyngeal anatomy is slightly different from one individual to the next. In addition, their soft tissue may transform slightly as they adjust from one position to another. Not surprisingly, this creates a challenge when selecting the correct level of CPAP. There is no magic number that applies to all patients, and the amount of CPAP required to maintain a patent airway for any patient may actually change from one minute to the next. For example, higher pressures are generally needed in the supine position and during rapid eye movement (REM) sleep.1

Auto-titration of constant positive airway pressure (APAP) offers an important tool to optimize treatment, increase efficacy, and enhance patient compliance. APAP devices effectively normalize sleep while delivering a mean pressure typically 37% lower than fixed pressure therapy.2 While insufficient pressure can not provide effective therapy, too much pressure can increase discomfort and pressure-related side effects, ultimately contributing to patient noncompliance.

A summary of peer-reviewed articles conducted by a task force appointed by the American Academy of Sleep Medicine endorses the technology saying, “APAP can be used to treat many patients with OSA (auto-adjusting) or to identify an effective optimal fixed level of continuous positive airway pressure (CPAP) for treatment (auto-titration).”3 In the diagnostic setting, auto-adjusting can make determining the appropriate prescription levels easier and, in some cases, more precise. For many patients, both the patient’s sleep apnea diagnosis and an appropriate CPAP level can be determined in one visit. It saves both time and money compared to spending a night in the laboratory to determine OSA and another to determine optimal CPAP. At home, APAP can be a useful tool in the quest to optimize patient treatment and compliance.

Because it is responsive to changes in the patient’s pressure requirements, APAP can be used to titrate pressure settings and may be more effective for patients with significant medical comorbidities. Mark Petrun, MD, medical director of the sleep laboratory for Northern Colorado Pulmonary Associates, Fort Collins, Colo, says, “It fills an important niche for people who we cannot titrate in the sleep lab,” either because they can not settle into sleep at the laboratory or have difficulty going there, or because their insurance (or lack of insurance) may limit their options. He emphasizes that in some cases a patient’s optimal pressure can not be determined in a single night. In addition, it can be an important alternative for patients who are struggling to maintain compliance with traditional CPAP.

There is conflicting evidence as to whether APAP is more effective in the treatment of OSA than traditional CPAP. Although there is considerable evidence that “APAP reduced the apnea plus hypopnea index to acceptable levels (AHI <10/hour) in greater than 80% to 95% of OSA patients studied,”3 the previously mentioned task force noted that sufficient direct comparisons between CPAP, APAP, and placebo are lacking. Importantly, many patients notice a difference and prefer APAP therapy.

How it Works
APAP devices operate on one of two principles:

1. Devices that use “flow limitation” analysis titrate the patient’s pressure based on a continuous analysis of breathing patterns (flow) and adjust pressures using a multilevel algorithm to determine the optimal CPAP level. By making subtle changes in pressure and effectively assessing the impact of those changes, the machine can continually search for the best possible pressure level for the individual. Secondary algorithms assess and address leaks and variable breathing patterns. Snoring, apnea, hypopnea, and leaks all have a telltale signature the auto-titration mechanism can recognize. Once it detects one of these situations, it raises the pressure gradually to maintain normal breathing.

2. Devices that use an acoustic-based algorithm analyze vibrations from the pharyngeal wall to determine the appropriate pressure. In effect, they react to snoring and adjust the pressure up or down in reaction to the patient’s needs. They can also change the pressure within a specific breath if a problem is detected. If solely dependent on vibration, these devices may not work in nonsnorers or patients who have undergone upper-airway surgery.3

“No studies have systematically compared the efficacy of one APAP technology with another,”3 and devices using different technology may not produce the same results in a given patient.

A Patient’s Perspective
Dick Goodman used a fixed CPAP system for 9 years, and was generally satisfied with the setup. About a month ago, he agreed to replace his old equipment after discussions with his home care clinician and physician. They had all agreed there was some room for improvement and he decided to try out an APAP system. Because he had been having some problems with a stuffy nose, and consequently kept opening his mouth, they also switched from a nasal mask to a face mask that covered both his nose and mouth. He was already using a humidifier. He was at first reticent to try the face mask, thinking it would be uncomfortable. “I didn’t think I would like [the mask], but I adjusted to it really quick,” the patient says.

He was pleased with the auto-titration feature as well. “It’s quieter and more compact than my old unit,” he says. He also noted that it does not seem to blow as hard. “If I’m stopped up, I thought [the machine] should be blowing harder,” he says, but that was decidedly not the case. “It doesn’t seem to have the [same] pressure the other one did—it doesn’t blow as hard,” he says, adding that the quality of his sleep was as good as or better than ever. “Overall, I’m very pleased,” he adds.

Surprisingly, the lower noise level was not a benefit to him and actually created a problem for his wife, who had grown accustomed to sleeping with the “white noise” drone of the old unit. “So we still run [the old unit] at night,” he chuckles, “because my wife sleeps better with it running.”

OSA continues to be widely undiagnosed and untreated. Once it is diagnosed, the benefits of CPAP in the treatment of OSA are well documented and unimpeachable. It has long been recognized as the most effective treatment for patients with moderate to severe OSA.4-6 Treating OSA with CPAP is considerably more challenging and time-consuming than treating a condition with pharmaceutical drugs. Patient education, clinical assessment, support during treatment (especially during the initiation phase), and continuous follow-up are important cornerstones to successful CPAP treatment. Because the mean pressure is often lower than the optimal fixed CPAP pressure, APAP can increase comfort and compliance for some patients. Every patient’s experience is different, bu
t it may be hypothesized that APAP will be most effective in those who experience the biggest difference between CPAP and APAP levels.

APAP is not a “magic bullet,” but rather an important tool that may be underutilized. A manager of a nationally affiliated home medical equipment company said that while physicians are generally aware of the benefits of APAP, they frequently need to be reminded to consider it. He said, “When we report back to them that the patient is having difficulty adjusting to their CPAP and we suggest trying APAP, they often ask me, ‘Why didn’t I think of that in the first place?’”

John A. Wolfe, RRT, is a contributing writer for Sleep Review.

1. Oksenberg A, Silverberg DS, Arons E, Radwan H. The sleep supine position has a major effect on optimal nasal continuous positive airway pressure: relationship with rapid eye movements and non-rapid eye movements sleep, body mass index, respiratory disturbance index, and age. Chest. 1999;116:1000-1006.
2. Teschler H, Berthon-Jones M. Intelligent CPAP system: clinical experience. Thorax. 1998;53(suppl 3):S49-S54.
3. Berry R, Parish J, Hartse K. The use of auto-titrating continuous positive airway pressure for treatment of adult obstructive sleep apnea: an American Academy of Sleep Medicine Review. Sleep. 2002;25:148-173.
4. Loube DI, Gay PC, Strohl KP, Pack AI, White DP, Collop NA. Indications for positive airway pressure treatment for adult obstructive sleep apnea patients: a consensus statement. Chest.1999;115: 863-866.
5. Sullivan CE, Issa FG, Berthon-Jones M, Eves L. Reversal of obstructive sleep apnea by continuous positive airway pressure applied through the nares. Lancet. 1981;1:862-865.
6. ATS Statement. Indications and standards of use of nasal continuous positive airway pressure (CPAP) in sleep apnea syndromes. Am J Respir Crit Care Med. 1994;150:1738-1745.