“[W]here OSA is proving difficult to control, other [non-CPAP] approaches are required.”
Obstructive sleep apnea (OSA) is a widely prevalent problem, affecting almost 1 billion people worldwide.1 It is an established risk factor for perioperative cardiorespiratory complications and death.2–4 Much has been written about identifying the problem preoperatively, but inadequate thought has been given to perioperative treatment where significant OSA has been recognized. The accepted standard treatment for moderate to severe OSA is continuous positive airway pressure therapy delivered by nose or facemask. However, while it is highly beneficial to individual patients in controlling obstructive events, its overall population effectiveness is discounted by often inadequate compliance with it, both at home and when used in the hospital. Many patients have difficulty complying with it even when there are persuasive reasons for doing so. Hence, while it should always be considered where OSA is proving difficult to control, other approaches are required. In some cases this is to obviate the need for continuous positive airway pressure and in others as a substitute for it if the patient refuses to use it or cannot do so, for example because of facial injury. These issues provide the rationale for a study reported in this issue of Anesthesiology that considers an alternative approach to continuous positive airway pressure therapy to treat sleep disordered breathing postoperatively.5
In this study, Sakaguchi et al. examine the value of combined therapy with high-flow nasal oxygen (20 l.min-1 40% oxygen concentration) and 30-degree head-of-bed elevation to treat this problem.5 Besides the obvious effect of oxygen therapy in enhancing oxygenation, the authors demonstrate that application of either of the therapy components results in a small reduction in the number of partial or complete obstructive events recorded, with these effects additive when they are combined. While the strategy provides incomplete control of OSA, these findings certainly make a case for considering it where continuous positive airway pressure therapy is unsuitable or refused by the patient.
The effects described by Sakaguchi et al. have a biologically plausible basis and have been previously investigated in other contexts. Apart from augmenting oxygenation, high-flow oxygen therapy generates up to several cm H2O of positive airway pressure within the upper airway, helping pneumatically splint it.6 Upper-body elevation increases dimensions of the upper airway and decreases its collapsibility through alleviation of gravitational effects on its structures, reduction in the rostral fluid shifts that occur with recumbency, and an increase in functional residual capacity with associated caudal displacement of the diaphragm, which helps increase longitudinal traction on the upper airway.7 While these effects have been previously described, the combined use of high-flow oxygen and upper-body elevation in the perioperative setting has not. Sakaguchi et al. address this knowledge gap adroitly, and in so doing help draw attention both to these therapeutic options and, more generally, to the case for non–continuous positive airway pressure alternatives for postoperative OSA management.5
Apart from the approaches described by Sakaguchi et al., these other non–continuous positive airway pressure options deserve exploration for perioperative use. They include other forms of positional therapy besides upper body elevation; oral appliances to produce mandibular advancement (jaw thrust); oropharyngeal and nasopharyngeal airway devices; and, in very limited circumstances, such as with some forms of major upper airway surgery, temporary tracheostomy. Drug considerations are also important, including care with use of drugs with sedative potential in these patients. As yet, specific drug treatments for OSA remain a distant prospect, as do other easy ways of activating dilatory upper airway musculature noninvasively.
Besides upper body elevation, other positional strategies for OSA treatment include lateral positioning of the patient, rather than supine. OSA severity is reduced by at least 50% in the lateral relative to the supine posture in approximately 60% of OSA patients. Indeed, in 20% of OSA patients, it is present only when sleeping supine.8 Neck position is another positional influence on OSA severity, with neck flexion increasing propensity to obstruction and extension reducing it.9
Oral appliances that are designed to advance the mandible—produce jaw thrust—are in widespread use for OSA treatment, and many consider them first-line treatment for snoring and milder forms of OSA.10 The most effective of these are made-to-measure, adjustable appliances where construction is individualized based on dental impressions taken from the patient, followed by careful titration of the degree of mandibular advancement to effect. However, the perioperative setting is not the place for slowly implemented therapies, and there are an increasing number of off-the-shelf alternatives available for home use that may prove useful perioperatively, even in patients previously naïve to them. This is a proposition that deserves further investigation.
Oropharyngeal and nasopharyngeal airway devices are time-honored methods of controlling upper airway obstruction. However, they are likely to have limited applicability in the perioperative management of upper airway obstruction beyond the postanesthetic care unit because of discomfort with their use and, in the case of oropharyngeal devices, easy displacement. Nevertheless, they may be useful at least as a stopgap measure while other OSA treatment strategies are implemented, such as withdrawal of sedatives where these are in use. Furthermore, nasopharyngeal stenting devices have been used, with some success, to address sleep-related velopharyngeal obstruction, the primary site of obstruction in the majority of OSA cases.11 Again, this is another continuous positive airway pressure alternative that deserves further consideration.
Tracheostomy is a drastic measure to treat OSA that, while highly effective, has very rarely been used for this application since the advent of continuous positive airway pressure therapy. However, there remain limited indications for its (usually temporary) use, such as in cases of severe postoperative edema or other airway obstruction after major upper airway surgery.
Caution with use of opioid, hypnotic, and sedating drugs is an important OSA management principle. These drugs are commonly used perioperatively, and OSA management guidelines recommend minimizing this, asking that thought be given to analgesic alternatives such as multimodal analgesic therapy or, where applicable, regional analgesic techniques, together with use of readily reversible anesthetic techniques.12 It follows that where these drugs are in use perioperatively and OSA-related problems develop, their withdrawal should be considered along with alternative ways to address analgesic requirements.
Specific drug therapy for OSA remains a distant prospect. The notion of a drug that activates upper airway muscles in a sleeping individual to a similar degree to that observed during wakefulness is attractive, but to date, efforts to achieve this have been unrewarding. Other ways of activating upper airway dilator muscles during sleep, such as with an implanted hypoglossal nerve stimulator, have a place in OSA treatment,13 and it is possible that transcutaneous stimulatory techniques may evolve to a point where they become a readily applicable way of achieving this in the perioperative setting.
As Sakaguchi et al. imply, in all of this, it must be remembered that continuous positive airway pressure and other positive airway pressure therapies, such as bilevel ventilatory support where there is concurrent hypoventilation, remain an accepted standard in terms of capacity to control OSA and should always be considered where difficult-to-control OSA is evident. They can be made to work consistently in closely supervised circumstances, such as high-dependency units, if attending staff are well trained in their application and motivated to apply them.
The author is not supported by, nor maintains any financial interest in, any commercial activity that may be associated with the topic of this article.