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[News] OSA Patients Benefit from Auto-Titrated CPAP Before Surgery
OSA Patients Benefit from Auto-Titrated CPAP Before Surgery

Perioperative auto-titrated continuous positive airway pressure (APAP) treatment significantly reduced apnea hypopnea index (AHI) post-op and improved oxygen saturation in patients with moderate and severe OSA, according to Canadian researchers [see below].

Investigators at the University of Toronto found that patients who received APAP for two to three nights before surgery and five nights after surgery had a better experience postoperatively. Of those who received the treatment, the median AHI was 3 events per hour on the third postoperative night, compared to 32 events per hour experienced by members of the control group, which received routine care. The APAP group also had better oxygenation in their postoperative nights.

“Since physician anesthesiologists function as perioperative physicians before, during and after surgery, it is important we help identify patients with OSA,” said Frances Chung, MBBS, professor, department of anesthesia, University of Toronto, Ontario. “In the preoperative clinic, we evaluate and educate patients regarding anesthesia. As airway experts, this is a great opportune time to treat patients for OSA.”

Fair use from:


{portions of text omitted for brevity, go here for complete study text, including charts & tables]

Perioperative Auto-titrated Continuous Positive Airway Pressure Treatment in Surgical Patients with Obstructive Sleep Apnea: A Randomized Controlled Trial


Background: Obstructive sleep apnea (OSA) may worsen postoperatively. The objective of this randomized open-label trial is to determine whether perioperative auto-titrated continuous positive airway pressure (APAP) treatment decreases postoperative apnea hypopnea index (AHI) and improves oxygenation in patients with moderate and severe OSA.
Methods: The consented patients with AHI of more than 15 events/h on preoperative polysomnography were randomized into the APAP or control group (receiving routine care). The APAP patients received APAP for 2 or 3 preoperative, and 5 postoperative nights. All patients were monitored with oximetry for 7 to 8 nights (N) and underwent polysomnography on postoperative N3. The primary outcome was AHI on the postoperative N3.
Results: One hundred seventy-seven OSA patients undergoing orthopedic and other surgeries were enrolled (APAP: 87 and control: 90). There was no difference between the two groups in baseline data. One hundred six patients (APAP: 40 and control: 66) did polysomnography on postoperative N3, and 100 patients (APAP: 39 and control: 61) completed the study. The compliance rate of APAP was 45%. The APAP usage was 2.4–4.6 h/night. In the APAP group, AHI decreased from preoperative baseline: 30.1 (22.1, 42.5) events/h (median [25th, 75th percentile]) to 3.0 (1.0, 12.5) events/h on postoperative N3 (P < 0.001), whereas, in the control group, AHI increased from 30.4 (23.2, 41.9) events/h to 31.9 (13.5, 50.2) events/h, P = 0.302. No significant change occurred in the central apnea index.

Conclusions: The trial showed the feasibility of perioperative APAP for OSA patients. Perioperative APAP treatment significantly reduced postoperative AHI and improved oxygen saturation in the patients with moderate and severe OSA.

What We Already Know about This Topic

* Continuous positive airway pressure automatically adjusted by continuous analyses of flow profiles is an effective treatment for obstructive sleep apnea, but its effectiveness and acceptance in perioperative period are unknown.

What This Article Tells Us That Is New

* In this randomized open-label clinical trial enrolling 177 patients with obstructive sleep apnea, auto-titrated continuous positive airway pressure successfully reduced the apnea hypopnea index, whereas, it remained abnormally high without the treatment

* Despite the effectiveness, only 26–48% of the patients used the continuous positive airway pressure for more than 4 h per night during the perioperative nights

OBSTRUCTIVE sleep apnea (OSA) is a common comorbidity in surgical patients.1,2 Some surgical patients with OSA may not have been diagnosed or treated before their surgery.3 OSA may have serious implications for anesthetic management, with an increased incidence of perioperative adverse events.4–7

Continuous positive airway pressure (CPAP) is the mainstay treatment for the patients with moderate and severe OSA. Utilization of CPAP in the nonsurgical OSA patients significantly decreases the frequency of apnea and hypopnea. It also reduces the number of arousals, increases oxygen saturation,8 reverses the increased incidence of hypertension in OSA patients,9 and improves daytime sleepiness10 and the quality of life.11
Postoperative CPAP treatment had been shown to decrease the incidence of postoperative complications in non-OSA patients undergoing abdominal surgeries.12,13 To date, there has been no published literature to test the feasibility and effectiveness of perioperative CPAP utilization in the surgical patients with OSA, to prevent postoperative worsening of sleep apnea and perioperative adverse events.

Auto-titrated CPAP (APAP) is a special type of CPAP. On the basis of breath-by-breath measurement of flow, APAP adjusts the delivered pressure over the course of the night to the minimal pressure necessary to maintain an unobstructed airway. Starting treatment with APAP can be as effective as CPAP treatment with polysomnography titration.14–16 The advantages of APAP include that treatment can be initiated without in-laboratory CPAP titration and the pressure applied can respond to the changes in airway resistance. These features can be very helpful for the surgical patients with suspected OSA because the time interval between the preoperative visit and the scheduled surgery is usually short. It may be difficult to assess a patient suspected of OSA and initiate CPAP treatment without delaying the scheduled surgery. Also, a pressure setting established by in-laboratory polysomnography on an outpatient setting may not be equally effective in the perioperative environment, with possible fluid shift, sedation due to narcotics and changes of body positions.

The objective of this trial is to determine if perioperative APAP treatment decreases postoperative apnea hypopnea index (AHI) and improves oxygenation in the surgical patients with moderate and severe OSA. Our hypothesis is that utilization of the perioperative APAP is an effective pathway to prevent the postoperative exacerbation of AHI and oxygen desaturation in the surgical patients with moderate and severe OSA.

Materials and Methods

Study Design

This is a prospective randomized controlled trial, which has been registered at “http://clinicaltrials.gov” (NCT01249924). Perioperative administration of APAP (S8 Auto Set II; ResMed Corp., San Diego, CA) at night is the trial intervention. The primary outcome was the AHI detected by polysomnography on the postoperative night 3 (N3). The AHI was defined as the number of apneas and hypopneas per hour of sleep. The secondary outcomes were the oxygen desaturation index and the cumulative time percentage with SpO2 less than 90% (CT90) measured from nocturnal oximetry on 3 preoperative, and 5 postoperative nights. Oxygen desaturation index was defined as the average hourly number of desaturation episodes with at least 4% desaturation and lasting at least 10 s.

Study Population

The study was carried out at the Anesthesia Departments of Toronto Western Hospital of University Health Network, and Mount Sinai Hospital in Toronto, from December 2009 to November 2011. Approvals from the Institutional Review Board of both hospitals were obtained. The approval numbers are 09-0093-B for University Health Network and 09-0037-E for Mount Sinai Hospital. The inclusion criteria of patients approached for consent in the preoperative clinics were: (1) a minimum of 3 nights of hospital stay; (2) age: more than 18 and less than 80 yr old; (3) identified as high risk of OSA or a history of OSA without CPAP treatment. The exclusion criteria of patients were: (1) unwilling or unable to give informed consent; (2) undergoing nasal, eye, head/neck surgery, intracranial, or cardiac/thoracic surgery; (3) currently undergoing treatment for sleep apnea including CPAP; (4) requiring prolonged postoperative ventilation; (5) New York Heart Association functional class III and IV; (6) valvular heart disease, dilated cardiomyopathy, implanted cardiac pacemaker, or unstable angina; (7) myocardial infarction or cardiac surgery within 3 months; (8) chronic obstructive pulmonary disease, or asthma; (9) presence of tracheostomy, facial, neck, or chest wall abnormalities; (10) abdominal aortic aneurysm surgery, chemotherapy, or immunosuppressive therapy within 3 months; (11) visiting preoperative clinic less than 3 days before surgery; and (12) requiring postoperative nasogastric tube.

APAP Usage and Compliance

Due to the dropout, 106 patients (APAP: 40 and control: 66) had polysomnography on postoperative N3, and 100 patients (APAP: 39 and control: 61) completed follow-up for postoperative N1–N5. The percentage of patients wearing APAP during all observed nights was 45% (39 of 87). The reasons for noncompliance were listed in table 3. Postoperative generalized discomfort, nausea and vomiting accounted for the majority of withdrawals, 73% in APAP group and 79% in control group.
Because not all patients were ready for APAP on preoperative N1, more patients used CPAP on preoperative N2 (table 4). Subsequently, the number of patients using APAP gradually decreased. By postoperative N5, only 45% (39 of 87) of the randomized patients were compliant with APAP.

The median usage time of APAP on all observed nights ranged from 0 to 3.8 h/night, mean from 2.4 to 4.6 h/night with 26–48% of patients using 4 h/night or more (table 4). The 95 percentile pressure ranged from 9.0 ± 3 to 10.2 ± 2 cm H2O. No significant postoperative pressure increase was observed. Although there was a slight increase in median and 95 percentile leakage on postoperative N1–4, the apnea index detected by APAP device did not increase on these nights (table 4).


o date, our study is the first randomized controlled trial to investigate the effectiveness of perioperative APAP in OSA patients undergoing surgeries. The trial showed the feasibility of the application of perioperative APAP for the surgical patients with untreated OSA. Perioperative APAP treatment effectively decreased AHI and improved postoperative oxygen saturation in the surgical patients with moderate and severe OSA. However, the overall compliance rate of APAP for the surgical patients in the perioperative setting was relatively low at 45%

CPAP is established to be the mainstay treatment for the nonsurgical patients with moderate and severe OSA. Studies show that CPAP improves both the subjective and the objective measures of sleepiness,10,23 the quality of life,11 the cognitive functions, and psychological well-being in the OSA patients.24 Long-term follow-up demonstrates that CPAP treatment significantly reduces the incidence of cardiovascular events.25

The benefit of perioperative CPAP application in the non-OSA patients may be dependent on the type of surgery. Perioperative CPAP application prevented the occurrence of postoperative pulmonary complications in the non-OSA patients undergoing abdominal surgery,12,13 but no benefit was found in cardiac surgery.26

Data on the perioperative CPAP application in the OSA patients undergoing surgeries are very limited. Reeder et al.27 reported that a patient without diagnosed OSA experienced severe postoperative respiratory obstruction during sleep and was effectively rescued by nasal CPAP. Rennotte et al.28 reported a case series of 16 patients with documented OSA. Two patients without CPAP suffered postoperative complications whereas 14 patients treated with CPAP had uneventful postoperative course. To date, our study is the first randomized controlled trial to investigate the effectiveness of perioperative CPAP in OSA patients undergoing surgeries. Our results show the practical aspect of a perioperative APAP pathway for the surgical patients with untreated OSA. APAP is effective in reducing AHI and improving oxygenation in the surgical patients with moderate and severe OSA. This finding is important to develop an evidence-based perioperative care protocol for the surgical patients with moderate and severe OSA.

In the APAP group, a higher percentage of patients received supplementary oxygen therapy on postoperative N2 and 3. The healthcare team might be more likely to prescribe oxygen therapy to the OSA patients wearing APAP. This may interfere with the interpretation of the results. Improvement in oxygen saturation may be due to the oxygen therapy, especially on the first 3 postoperative nights. However, APAP application still played a significant role in improving oxygen saturation in the APAP patients. The reason is that the APAP group had significantly less desaturation on all preoperative nights and postoperative N4 and 5, when no patients were receiving oxygen therapy. The benefit of APAP is evident because obstructive apnea index, which is not affected by the level of oxygen saturation, was significantly decreased in the APAP group. Due to the small patient number and a low incidence of postoperative complications, a larger sample is needed to test whether APAP treatment could reduce the incidence of postoperative complications.

APAP has been developed in response to the needs to cope with pressure variation in eliminating the upper airway obstruction in the different sleep stages and positions,29 and the lengthy waiting period for polysomnography and treatment.30 APAP has been shown to be as effective as standard CPAP in terms of eliminating respiratory events and improving sleepiness.31,32

Patients with undiagnosed and untreated OSA may come for surgery.3,33,34 Due to edema in the upper airway, possible fluid shift, sedation, and changes of position, the optimal pressure for eliminating sleep breathing disorders may vary after surgery. APAP may be a suitable device to deal with these challenges. Incorporating the screening tools, such as the STOP-Bang questionnaire,17,35 portable polysomnography,18 or nocturnal oximetry,21 it is possible to develop a practical pathway for identifying, diagnosing, and treating the surgical patients with undiagnosed OSA within a limited time frame. In this study, we were able to demonstrate the perioperative feasibility of APAP treatment 3 days before surgery.

One major limitation of this study is the high dropout rate and the low rate of compliance in the APAP group. Even with improved CPAP devices, compliance to CPAP is an ongoing challenge to OSA treatment in the general population. In the nonsurgical OSA patients, 5–50% of patients who were recommended CPAP may reject treatment before trying or soon after pressure titration and trial of CPAP.36 Another 12–25% of patients starting CPAP, abandon it within 3 yr.36 If adherence is defined as greater than 4 h of nightly use, 46–83% of patients with OSA have been reported to be nonadherent to treatment.37 Evidence suggests that wearing CPAP for longer than 6 h per night decreases sleepiness, improves daily functioning, and restores memory to normal levels.37 Recently we have shown that the CPAP compliant patients had a greater reduction in medication for comorbidities than the CPAP noncompliant patients.38 The severity of OSA and symptoms, the early experience and effective troubleshooting, appropriate and timely education and support, and behavioral and cost factors appear to be the main predictors of uptake and long-term compliance.36 Standard interventions, including mask optimization, heated humidification, topical nasal therapy, and sleep education followed by a change to flexible bilevel airway pressure, can improve compliance in the previously noncompliant patients.39 Cognitive behavioral therapy intervention also increases start-up and adherence of CPAP.40

There are additional factors, such as preoperative stress, anxiety and postoperative discomfort, adverse events and treatment measures (such as gastric tube), which make the acceptance and adherence to CPAP a greater challenge. In our patients, the percentage of patients wearing APAP on all observed nights was 45%. Approximately 26–48% of all the randomized patients used APAP 4 h/night or more, which is similar to 17–54% in nonsurgical patients.37 The major reason for nonadherence was postoperative pain or discomfort, nausea and vomiting (73%), followed by changing of mind (15%). If we could better control the postoperative pain or discomfort as well as nausea and vomiting, and provide stronger support and education, compliance to APAP could be improved. To incorporate CPAP into the perioperative care for OSA patents, methods to increase the compliance to CPAP need to be further explored. In this study, patients received arbitrary APAP treatment for three preoperative days before surgery. The optimal timing of the preoperative initiation of CPAP is not known and needs to be further determined.

Another limitation is that the study was not double blinded. Because we want to compare the effect of APAP treatment with routine perioperative care, sham APAP was not used in the control group. This might have introduced bias, which could be responsible for the significantly higher rate of oxygen supplementation in the APAP group on postoperative N2 and 3.

In conclusion, we demonstrate the feasibility of a perioperative APAP program for the surgical patients with moderate to severe OSA. Perioperative APAP treatment decreased postoperative AHI and improved oxygen saturation in the surgical patients with moderate and severe OSA. Perioperative compliance to APAP needs to be improved.

The above post may contain copyrighted material the use of which has not always been specifically authorized by the copyright owner. The material available is intended to advance the understanding of Sleep Apnea treatment and to advance the educational level of Sleep Apnea patients with regard to their health. Sometimes included is the full text of articles and documents rather than a simple link because outside links frequently "go bad" or change over time. This constitutes a "fair use" of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material in this post is distributed without fee or payment of any kind for research and educational purposes. If you wish to use copyrighted material from this post for purposes of your own that go beyond "fair use", you must obtain permission from the copyright owner.
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Thanks for posting that, but I have to say, to me it sounds a bit, well, self predicting, if nothing else. Since CPAP is hardly new, the effects on OSA are well known, what on earth would they have expected? To my mind, CPAP is a Gas-passer's best friend. Glad someone went to the trouble to quantify what we already knew, but also, well....duh!

The more interesting bit was the effect on subclinical patients and the various types of surgery they underwent. That would be the line I would want to pursue. Could this be an effective pro-op prep for "normals"?
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