Obstructive sleep apnea (OSA) affects millions of people in our society. More than 1 million people were treated for this disorder in 2006, and its prevalence may exceed 10% of the adult population. It is also estimated that over 80% of patients with OSA undergoing sedation for surgery are undiagnosed,2 presenting a large number of potential patients who are risk of injury or death. OSA is not only a prevalent disorder, but is also associated with significant health risks and costs to society.3
Untreated OSA incurs increased risks of hypertension, coronary-artery disease, atherosclerotic disease, stroke, congestive heart failure, and arrhythmias over time, much as untreated diabetes or hypercholesterolemia inexorably leads to worsening of cardiovascular health.4 Under the usual circumstances, OSA does not typically lead to an untimely respiratory death at home; it leads to untimely cardiovascular events. In contrast, accidental deaths and injuries due to OSA are not so time dependent. They are more circumstance dependent. For example, the untreated sleepiness of OSA increases the risk of motor vehicle accident by 2.6-6.3 times,6 but the person must be driving to suffer this consequence.
Ironically, the health care setting during the perioperative period or during sedation or analgesia is one in which OSA patients have an increased risk of adverse events. This type of safety risk (predictable and potentially reducible) is an excellent target for efforts to improve patient safety. Respiratory therapists may play a key role in improving the safety of hospitalized patients with OSA.
The perioperative or acute care context provides an increased challenge to the poorly controlled upper airway of patients with OSA. Anesthesia, analgesia, and sedative agents all worsen respiratory control and upper-airway muscle tone, leading to worsening of OSA. Due to the unstable nature of the upper airway, OSA patients undergoing sedation and postoperative pain management can be at higher risk for respiratory and cardiovascular complications than other patients.
OSA is most often treated effectively using positive airway pressure (PAP) after an attended polysomnogram. While a useful treatment is available, the effort to improve patient safety has three main problems. First, many (if not most) patients with OSA have not yet been diagnosed, so their treatment settings have not been determined.1 OSA has not been systematically sought as an important part of the medical history, and PAP therapy, even for patients who rely on it at home, is not often prescribed in the hospital setting.7 Second, patients with OSA require management strategies that reduce the risk of accidental respiratory failure, delirium, and cardiac arrhythmia. These strategies will probably involve PAP during sleep or periods of sedation and careful monitoring. Third, not all patients can easily use PAP when acutely ill, sedated, or dealing with other perioperative issues. This is particularly true of PAP-naive patients. They may require particularly close monitoring until sleep and respiratory parameters more closely approximate baseline values. Systematic screening to identify patients at risk or with OSA, routine attention to the unique respiratory problems of these patients in the acute care setting, and aggressive but appropriate monitoring of candidates to further mitigate risk are needed.
The Joint Commission (formerly JCAHO) recently invited the medical community to comment publicly on screening and managing OSA patients undergoing sedation.8 The comments are currently under review and will probably be used to develop new guidelines to assist the Joint Commission in the accreditation process. The pertinent goal noted in the document is to reduce the risk of postoperative complications for patients with OSA (goal 17). The requirement for goal 17 is that the organization screen for OSA prior to surgical procedures involving the use of centrally acting anesthetic and/or analgesic agents. The rationale for the requirement is that OSA places patients at increased risk for postoperative respiratory complications after receiving a centrally acting anesthetic and/or analgesic agent. It is estimated that 80% to 90% of patients with OSA are undiagnosed. By screening patients for OSA, organizations will reduce the occurrence of perioperative respiratory complications in at-risk patients.
There are four implementation expectations: anesthesia evaluation includes screening patients who may be at risk for OSA; the anesthesia plan of care takes account of identified risk factors; the organization develops an OSA protocol based on recommendations from identified best practices; and the organization’s OSA protocol is applied to the anesthesia care of both known OSA patients and those patients identified as at risk by the screening process.
Screening and Identification
The most important step in improving the safety of patients with OSA is identifying who they are. As awareness of OSA increases in the public and the medical community, so does the number of patients being diagnosed and treated. Recent data from a report issued by the US Department of Health and Human Services showed that sleep-study volume increased 175% from 2000 to 2005. Despite this impressive increase in testing, many estimates suggest that the majority of patients with OSA are not diagnosed.
Screening must be used to identify these patients. Several screening methods have been suggested and are being tested. The American Society of Anesthesiologists and the Anesthesia Patient Safety Foundation issued a statement on screening for OSA and postoperative management of OSA in 2006.9 While the optimal screening system has not emerged, nearly any currently published screening system is better than none. Most are simple questionnaires or measures that produce coarse estimates of OSA risk, and may be implemented cheaply.10 Essentially, patients must be asked about their OSA; if they do not have a diagnosis of OSA, their risk for OSA must be assessed systematically. The major obstacles to screening implementation are cultural and logistical.
As obesity in perioperative patients increases, so do the challenges facing the anesthesiologist. Often, the obese patient presents without a preoperative evaluation for OSA, so decisions must be made by the attending anesthesiologist based on a brief clinical assessment and a verbal history from the patient and, if available, their sleep partner. When OSA is suspected, the mitigation of risk involves the judicious choice of anesthetic technique, as well as recognition of the potential respiratory side effects of commonly used medications.
Institution of a formal OSA protocol is probably the most useful tool in the safe delivery of perioperative care. Memorial Health System, Colorado Springs, Colo, successfully implemented such a risk-management protocol, which has served to educate and instruct all who are involved in caring for OSA patients.6 Such a protocol must involve input from patients, preoperative-screening staff, anesthesiologists, postanesthesia care unit (PACU) personnel, respiratory therapists, pulmonologists, and staff from the sleep-disorder center. The protocol must not end when the patient is discharged. Following up with the appropriate health care provider is mandatory to treat the patient for OSA, as well as the associated morbidities. It is important to note that the learning and acceptance curves for patients are steep, and the person implementing an OSA protocol must be aware of the need for complete support from the medical and nursing administrations.
After 5 years of clinical experience with the Memorial Health System OSA Protocol, a revision to the outpatient arm of the algorithm was completed (see figure below). A revision of the inpatient OSA protocol is currently under way.
|Figure: Memorial Health System’s OSA Protocol Orders|
If there is suspicion of OSA, the anesthesiologist has several tools available to minimize risk and ensure adequate pain control. Peripheral nerve blocks can reduce adverse effects and, in appropriate patients, often remove the need for opiate pain medications entirely. When not contraindicated, nonsteroidal anti-inflammatory drugs can be used preemptively; continuous-flow cold therapy, elevation, distraction, patient education, and music therapy are all useful adjuncts in minimizing opiate need.7
The report and transfer of care from the anesthesiologist to the PACU nurse are critical components of care. The report from the anesthesiologist should include a reasonable assessment of risk5 for OSA so that the PACU nurse can watch for adverse events. The PACU nursing assessment is potentially a useful tool for recognizing and monitoring the OSA patient. Because the nurse-to-patient ratio in the PACU is generally 1:1 or 1:2 and care occurs during the critical period of waking from anesthesia, there is an excellent opportunity for a properly trained PACU nurse to assess signs and symptoms of OSA. The respiratory therapy department’s involvement should begin early in the perioperative process. The report and transfer of care from the PACU nurse to the floor nurse and respiratory therapist are vital elemenst of this process.
OSA Management in Acute Care
Application of PAP is an important aspect of OSA management in hospitalized or acutely ill patients. A common problem, however, is one of education in the respiratory department. Sleep centers typically care for OSA patients and determine their needs for PAP devices, masks and other interfaces, and humidifiers. The general knowledge of the sleep center needs to be shared with the respiratory care department in the medical center. Many RTs take care of critically ill patients who need airway management and require full or partial ventilatory support provided via endotracheal tube (or, in the case of noninvasive positive-pressure ventilation, a full-face or nasal mask). OSA patients also need postoperative airway management, but with a different approach and an understanding of their condition.
Many patients undergoing surgery may already be on PAP or bilevel therapy at home. If so, they should be encouraged to bring their PAP devices to the hospital, along with their masks and humidifiers. Depending on the length of surgery and on pain-management issues, they should be closely monitored for problems, even when using their own devices at the settings used at home. Pain medications and sleep deprivation can call for adjustments to therapy pressures or modes.8,9 Patients exhibiting central apneas after surgery may need bilevel systems set with backup respiratory rates. In our experience, mask fit and comfort, pressure sensitivity, aerophagia, and claustrophobic response to full-face or ill-chosen masks are important problems in patient compliance in the acute care setting. Many hospitals are not adequately equipped with a range of comfortable interfaces, and patients (especially the PAP naive) require considerable attention, coaching, and frequent equipment adjustment to foster success.
Providing oxygen without PAP to OSA patients can be dangerous because it can offset hypoxia and prolong apneas, leading to increased hypercapnia and worsening the hemodynamic consequences of apnea. Oxygen can be used with PAP to improve oxygenation, but it should not be considered as a treatment for an unstable airway or for obstructive or central apneas. One recent study>8 showed that application of PAP plus oxygen in postoperative patients (with or without OSA) improved outcomes, compared with oxygen alone.
The application, adaptation, and modification of PAP require closer monitoring than usually occurs on most general hospital wards. Enhanced RT coverage may be aided by advanced physiologic monitoring to improve patient safety. Noninvasive respiratory monitoring has many clinical advantages over invasive monitoring. It entails less cost to the patient, both financially and physiologically.
Impedance involves passing an electric current through the patient’s chest to measure the change in impedance as chest volume changes. This may identify apneic pauses. Inductance, or respiratory inductive plethysmography, measures changes in the cross-sectional areas of the rib cage and abdomen. These are translated into lung-volume estimates, and the absence of a breath may be easily identified.
In thermistry, a thermocouple sensor detects changes in temperature at the mouth and/or nose. Expired air heats the sensor; inspired air cools it. These devices may detect impaired airflow due to apnea/hypopnea. Volumetric monitoring measures tidal volume and respiratory rate using a mask and pneumotachometer; apneas and hypopneas may be identified early.
Pulse oximeters are ubiquitous in respiratory care. They are not optimal identifiers of apnea/hypopnea, however, particularly in patients using supplemental oxygen. Pulse oximetry alone should not be relied on as an indicator of adequate airway patency or airflow; it provides only an estimate of blood oxygen saturation.
End-tidal capnography (ETco2) measures carbon dioxide in exhaled breath. Many variables influence the ETco2 result; while ETco2 monitoring is a valuable adjunct in the operating room, it is not as reliable in open circuits or in complicated critical care or acute-illness settings. Moisture in sidestream breath can corrupt values, and the heat and weight of the sensors can cause unplanned extubation. Transcutaneous continuous carbon dioxide monitoring may sidestep these issues, and may prove a good indicator of hypoventilation. This technology is developing and is just entering clinical use.
Most medical centers have multiple monitoring solutions available; in critical care areas, the use of monitoring systems is standard practice. When the OSA patient is placed in an area with minimal monitoring and a high patient-to-caregiver ratio, however, there tend to be problems, particularly in the early morning hours. This seems to be when patients are most vulnerable to apnea. The extension of physiologic monitoring and the improvement of provider-to-patient ratios are probably necessary.
Pay Now or Pay Later
The major impediments to the improvement of patient safety, apart from some notable gaps in knowledge, are inertia and cost. Screening for OSA entails organizational change, but not much cash outlay. Provision of PAP devices is not very expensive, though proper training and staffing can be costly. Because of the fiscal challenges that hospitals face, patients are moved out of high-cost, well-monitored, well-staffed areas while they are still critically ill. As a result, standing guard over their vital signs as they recuperate on the general floor or a step-down unit is more crucial than ever. Comprehensive patient monitoring is not cheap, but neither is hypoxemia that goes unrecognized. Financially, this is a pay-now-or-pay-later situation. Over the past 5 years, numerous lawsuits have related to treated and untreated OSA patients who had complications after surgery.11 Several of these suits have resulted in multimillion-dollar settlements, so low-cost OSA screening may be prudent management for any medical center.
In addition to the possible legal, public-relations, and human costs associated with adverse events, there is reason to believe that untreated OSA, even in the absence of catastrophic events, is costly. One study11 showed that untreated OSA patients had longer hospital stays and increased major complications following total hip arthroplasty. Hypoxemia can cause myocardial ischemia, compromised wound healing, decreased resistance to infection, impaired cerebral function, short-term memory loss, and sundown syndrome (confusion at night), often making a patient combative, prolonging hospital stays, and driving up costs.
The risks to patients with OSA might not abate immediately after they leave the hospital. Patients cannot achieve proper rest or rapid–eye-movement (REM) sleep in the hospital due to pain, medications, noise, and other factors.12,13 When patients do resume normal REM sleep, typically 3 to 5 days after surgery, they can experience prolonged apneas associated with spikes in blood pressure and other unwanted symptoms.14 The implication is that patients identified as having OSA in the hospital and successfully started on PAP therapy need appropriate follow-up plans at discharge.
Our health care system can do a better job of identifying patients with OSA and managing their care to prevent accidents, both in the hospital and upon discharge. The RT, as an expert in observing and managing pathological changes in respiration, plays a key role. To deal with the problem effectively, however, the entire health system must align itself with this effort.
Ron F. Richard is senior vice president of strategic marketing for the Americas, ResMed Corp, Poway, Calif; Timothy I. Morgenthaler, MD, is assistant professor of medicine at the Mayo Clinic College of Medicine, and consultant in the Division of Pulmonary and Critical Care Medicine and the Mayo Clinic Sleep Disorders Center in Rochester, Minn; Carla Lickteig, BSN, RN, CPAN, is PACU nurse clinician, Memorial Health System, Colorado Springs, Colo; C. Bryan Carr, MD, is anesthesiologist at Memorial Hospital, Colorado Springs. For further information, contact [email protected]
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