Capnography & Sleep Apnea


Routine capnography monitoring for the post-anesthetic obstructive sleep apnea patient

In 2010, The American Society of Anesthesiologists (ASA) established their position that capnography monitoring should be standard practice for all patients receiving anesthesia.1 The subsequent adoption of routine capnography monitoring during management of all anesthetic patients is based on numerous studies indicating that capnography monitoring, in addition to standard pulse oximetry monitoring, improves patient care over pulse oximetry monitoring alone.2, 3 This reflects the tendency of pulse oximetry readings to indicate high oxyhemoglobin concentrations while a patient may be simultaneously bradypneic and hypoventilated. The Joint Commission has also suggested that capnography, in addition to pulse oximetry, be continuously monitored in patients that may be at risk for hypoxia and hypercarbia following sedation or the administration of narcotics.4 To improve clinical outcomes by alerting providers of potential complications or clinical deterioration more expeditiously, patients that have been identified as at-risk, particularly those patients diagnosed with obstructive sleep apnea (OSA), should be required to continue capnography monitoring throughout their peri-anesthetic course.

Capnography in the PACU

The post-anesthesia care unit (PACU) is an area where patients that have received and are recovering from anesthesia may either show signs of continued somnolence, or complain of pain requiring pharmacological intervention. Because capnography is not required and is in most cases unavailable, patients with OSA may be at-risk for respiratory compromise and further clinical deterioration.5,6 The ASA Standards of PACU Care Standard IV highlights the need to monitor patients’ oxygenation, ventilation, circulation and temperature.7 According to this standard, capnography is an essential instrument in evaluating patient status and in providing a most comprehensive clinical picture.

Despite clinical evidence and suggestions that capnography monitoring be routine in all cases, it is currently not mandatory/standard practice in conscious sedation.8 To further complicate matters, what is often performed routinely as “conscious sedation” may cross the threshold of being considered deep sedation in which an anesthesia provider should be present.9

PACU nurses’ awareness of the essential role capnography plays is critical because of the combinations of pain medications and sedatives that patients are likely to receive while they are already in recovery from being anesthetized. Because these medications are likely to have additive and potentiating effects, these patients may be at risk for hypercarbia, hypoxia, apnea, airway obstruction, among other clinical issues.

Sleep Apnea in the PACU

OSA is a diagnosis made on individuals experiencing periods of ineffective gas exchanges/cessation of breathing lasting greater than 10 seconds at varying but generally frequent intervals commonly experienced during sleep.10 Obesity is commonly a shared diagnosis in 60-90% of OSA patients as increased mass and redundant tissue commonly generates impedance for proper airflow and anatomical respiratory function.11 The patient with OSA often requires increased oxygen levels to meet their greater metabolic demands especially in times of increased demand like surgery and recovery. In patients having recently undergone anesthesia it is likely that they may still have remnant anesthetic agents in their system not yet pharmacokinetically cleared. Additionally, the OSA patient may require narcotic or benzodiazepine administration pending their PACU condition. The propensity of these agents to cause somnolence or respiratory depression is a well-known side-effect of these classes of Agent.7 Furthermore, because capnography monitoring is sensitive in detection of bradypnea prior to a drop in pulse oximetry coupled with the administration of respiratory compromising medications, patients are at significant risk without it.2 Because capnography is utilized and mandated for sedation cases in the operating room, it would only be considered sensible that such monitoring would continue throughout their perioperative course and during recovery.

The Problem

In the PACU, capnography is a useful tool in assessing airway obstruction before clinical compromise, as well as level of sedation and quality of breathing. Yet, despite these suggestions, capnography is not routinely used and many do not see to understand the complexities of interpreting capnography waveforms and values. This is evidenced by the fact that the ASA has taken the position that anesthesia utilize capnography during monitored anesthesia care (MAC) cases while other procedural sedation cases may not use it. The non-anesthesia trained providers and caregivers are at a disadvantage by not routinely using capnography for its proven early clinical detection of clinical compromise. This, in turn, places both providers and patients at risk for adverse outcomes. The implications include more appropriate utilization of sedation, improved patient recovery time, earlier detection of clinical deterioration, and a decreased risk for adverse outcomes. Furthermore, the implications for practice include not only the routine use of capnography but also education modules for RNs in the appraisal of capnography waveforms and their corresponding value analysis.

A study by Hutchison & Rodriguez revealed that patients with OSA experienced twice as many “events” than those in the control group in a capnography versus pulse oximetry study.3 ASA closed-claims analysis of data reveals that 20% of all MAC cases might have benefitted from use of capnography in detecting lack of effective gas exchange.11 This is partly the basis for the ASA now calling for the routine use of capnography in patients unless contraindicated for some reason.11 Because the PACU is considered an out-of-operating room setting, the likeliness for potential airway complications is drastically increased according to closed-claims data.6

Solving the Problem

The literature strongly advocates for the employment of capnography monitoring during anesthesia care and the evidence suggests that capnography monitoring is superior to that of routine pulse-oximetry.13 OSA patients have been identified as at-risk because of their sensitivity to airway compromise. Enhanced by the cumulative effects of anesthetics, and post-operative sedation, and anatomical predisposition, OSA patients are in need of capnography monitoring in order to prevent deleterious outcomes. When nearly 50% of closed claims cases are respiratory in nature and considered able to have been prevented, ignoring the most at-risk patient population (OSA) would be consistent with negligent practice.14 A capnography monitor remains the only mechanism to reliably assess respiratory, airway and circulatory systems simultaneously.8 Thus, capnography monitoring for the OSA patient will improve the care they receive by improving provider awareness, earlier indications of impending clinical deterioration, and reduction in post-operative poor outcome indicators.

What can be applied clinically to practice is the evidence that OSA patients should require an increased level of vigilance when being monitored during or after sedation. Additionally, the clinical observation component of the study reflects the need for confirmation assessment when alarms are triggered as was identified by Payne.15 The evidence of closed-claims data that suggests capnography could have made an impact in numerous cases in the non-operative setting has not yielded corresponding practice change. Capnography remains widely unavailable and unrequired. There is an overwhelming body of evidence which testifies to the value capnography provides as a clinical monitoring device. Multiple studies have shown capnography be accurate in various conditions and that it consistently detects clinical deterioration (respiratory depression) more expeditiously than does the standard pulse oximetry. The wealth of clinical knowledge capnography provides is not disputed in the literature. Capnography is a tool that can be best used when care providers understand the data that it provides. One of the major areas in need for improvement is in education as nurses and physicians widely understand the concept of capnography but are deficient in its content. Because of the lack of clinical use and emphasis on its employment, capnography remains an emerging clinical monitoring tool that has yet to actualize its potential. A corresponding investment in the education of staff is likely to yield the most promising results in improving patient care and making lasting evidence-based changes to practice.


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About Author

Richard R. Tennesen, CRNA, MS, BSN

Richard R. Tennesen is a certified registered nurse anesthetist at the Reading Hospital in Reading, Pa.

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