Recognition, anticipation, and planning for a potential difficult airway are key issues in safe perioperative management. Studies from the United Kingdom1 and United States2 show that failed perioperative airway management remains a significant problem resulting in brain damage or death. Over the last decade, major airway societies3–5 have published guidelines for assessment and management of the difficult airway; however, there is little information in these guidelines specifically pertaining to obstructive sleep apnea (OSA).
With the increasing prevalence of obesity, the prevalence of OSA is also rising; it ranges from 9% to 25% in the general adult population, with 25% of men and 10% of women estimated to have OSA.6 Patients with OSA and difficult airway share certain anatomic, morphologic, and physiologic features7: (1) obesity and OSA increases the volume of soft tissue surrounding the pharyngeal airway, (2) greater visceral fat reduces lung volume and thus increases the propensity for pharyngeal wall collapse, and (3) neural compensation is depressed during sleep and anesthesia. These problems are compounded, where present, by narrow skeletal confines, such as with retrognathia.
A systematic review by Singh et al8 showed that ultrasound airway parameters, including tongue base thickness and retroglossal diameter, are correlated to the severity of OSA. Thus, OSA patients have features of an anatomically difficult airway due to a crowded collapsible pharyngeal space, compounded by physiological problems related to lower functional residual capacity and increased oxygen consumption, both leading to faster oxygen desaturation.9 Another recent meta-analysis demonstrated that patients with OSA, compared to patients without OSA, have a 3–4 times higher risk of difficult intubation, difficult mask ventilation, or both.6 Conversely, 66% of patients with difficult intubation have been shown to be diagnosed later to have OSA.10 The recent Society of Anesthesia and Sleep Medicine guideline on intraoperative management of patients with OSA provides a valuable overview of perioperative airway management.11
The purposes of this review are (1) to evaluate the evidence for the association between OSA and difficult airway, and (2) to discuss optimal airway management of an OSA patient undergoing either nonairway or upper airway surgery.
THE ASSOCIATION OF OSA AND DIFFICULT AIRWAY
The association between difficult intubation and OSA was first studied formally by Hiremath et al.12 In this study, patients with difficult intubation were at increased risk of OSA, where apnea-hypopnea index (AHI) was found to be higher in the difficult intubation group versus the control group (AHI 28.4 events/h versus AHI 5.9 events/h, P < .02).12
Siyam and Benhamou13 conducted a retrospective case-control study and demonstrated that the occurrence of difficult intubation was 8-fold higher in OSA patients compared to patients with no OSA (21.9% vs 2.6%; P < .05). Another retrospective study by Kim and Lee14 indicated that the occurrence of difficult intubation might be predicted using the AHI, because the severity of the OSA was significantly associated with a higher incidence of difficult intubation in patients undergoing uvulopalatopharyngoplasty. For patients with AHI <40 events/h, the incidence of difficult intubation was 3.3%; for AHI 40–70 events/h, 19.3%; and AHI >70 events/h, 27.6%.14
Two large database observational studies by Kheterpal et al15,16 assessed the incidence of difficult airway in patients with OSA. In the first, a multivariate analysis showed that a history of OSA was an independent risk factor for combined difficult mask ventilation and difficult intubation.15 In 700 patients with OSA, the occurrence of difficult mask ventilation was 4-fold higher (OSA versus no OSA: 8% vs 2%; odds ratio [OR]: 3.96; confidence interval [CI], 2.9-5.3) and the occurrence of combined difficult mask ventilation and difficult intubation was 5-fold higher in OSA patients compared to non-OSA patients (OSA versus no OSA: 2.5% vs 0.5%; OR: 5.44; 95% CI, 3.2-9.2).15 The second study, conducted in 2013, was a large multicenter observational study.16 Of 25,661 OSA patients, the occurrence of combined difficult mask ventilation and difficult laryngoscopy was 3-fold higher in OSA compared to non-OSA patients (OSA versus no OSA: 1% vs 0.3%; OR: 3.7; 95% CI, 3.1-4.3). It has been postulated that reduced oropharyngeal space and/or the presence of increased soft tissue within it, as with a large tongue, are causal attributes for OSA and the difficult airway. A prospective observational study by De Jong et al17 compared the incidence of difficult intubations in OSA patients in the intensive care unit and in operating theater settings. It was found that in patients with OSA, the incidence of difficult intubation was 3 times higher in the intensive care unit than in the operating theater. Of 63 patients with OSA in the ICU, 24 patients (38%) had difficult intubation; and of 213 OSA patients in the operating theater, 28 patients (13%) had difficult intubation.17 This suggested that intubation conditions in the ICU were less favorable compared to the operating theater and more attention to OSA and the difficult airway has been paid in the latter circumstance.17
In the systematic review and meta-analysis by Nagappa et al,6 the occurrence of the difficult airway was compared between patients with OSA and those without a prior OSA diagnosis undergoing surgical procedures. Of 72,888 patients, difficult mask ventilation was 3-fold higher in the OSA compared to non-OSA patients (OSA versus non-OSA: 4.48% vs 1.11%: pooled OR 3.39; 95% CI, 2.74-4.18). Similarly, in patients with OSA, the odds for difficult intubation were increased by 3-fold compared to patients without OSA (OSA versus non-OSA: 13.5% vs 2.5%; pooled OR 3.46; 95% CI, 2.32-5.16). For combined difficult mask ventilation and difficult intubation, OSA patients had a 4-fold higher incidence than non-OSA patients (OSA versus non-OSA: 1.11% vs 0.3%: pooled OR 4.12; 95% CI, 2.93-5.79). Even though there was a higher risk of difficult airway in patients with OSA, there was no significant difference in the incidence of supraglottic airway failure rates between the groups.6
The available evidence on this topic comprises small prospective studies, case-control studies, and large database studies, with the final estimates consistently indicating an increased risk of difficult airway in patients with OSA. Because it is difficult to conduct a sufficiently powered randomized controlled trial to investigate the association between difficult airway and OSA, the quality of evidence on the association between the OSA and difficult airway was considered as moderate.11 In 2018, the Society of Anesthesia and Sleep Medicine recommended that known or suspected OSA should be considered as a risk factor for difficult intubation, difficult mask ventilation, or a combination of both.11 Adequate preparations and difficult airway management precautions should be undertaken in OSA patients.
PATIENTS WITH OSA AND SURGERY
Patients with OSA presenting for surgery can broadly fall into 2 main groups: (1) those that are scheduled for OSA-related upper airway surgery or (2) those scheduled for other surgeries unrelated to OSA. Examples of the former would include pharyngoplasty, palate surgery, tonsillectomy, epiglottis surgery, maxillofacial surgery, hyoid bone surgery, and upper airway stimulation, or a combination of these.18 While non-OSA procedures in patients with OSA are broad-ranging, they are commonly found in surgical specialties that deal with obesity-related issues, such as bariatric procedures, joint arthroplasty, and liposuction surgery.
The preoperative assessment of the patient with OSA should involve the evaluation and optimization of concomitant comorbidities. These may comprise treatment-resistant hypertension, diabetes, heart failure, ischemic heart disease, metabolic syndrome, obesity, hypoventilation syndrome, and pulmonary hypertension, to name a few.19–21 The American Society of Anesthesiologists, the American Academy of Sleep Medicine, the Society of Anesthesia and Sleep Medicine, the Canadian Anesthesiologists’ Society, and others have developed clinical practice guidelines for the perioperative management of patients with OSA, with the goal of reducing perioperative complications.19,21–24 A leading concern for the anesthesiologists is in managing the difficult airway in these patients with OSA. The eventual anesthesia modality is determined by anatomy, comorbidities, surgical requirements, opinions of the care team and, where flexibility exists, patient preference.
PREDICTING THE DIFFICULT AIRWAY IN PATIENTS WITH OSA
Quantitative meta-analysis evidence has demonstrated that patients with a known diagnosis of OSA have a 3- to 4-fold increased risk of either tracheal intubation and/or mask ventilation (Table).6,11 Patients suspected of and previously diagnosed with OSA have a higher incidence of difficult airway because characteristics of a difficult airway share common morphological features with patients with OSA—a reduced skeletal structure (cervico-maxillomandibular enclosure) and/or increased oropharyngeal soft tissue. This combination results in a pharyngeal-anatomical imbalance.7 Features associated with OSA (eg, increase in neck circumference, short thyromental distance, large tongue, snoring) are also known predictors for the difficult airway.16
Perioperative Airway Strategies for Patients With OSA
|Specific predictors of the difficult airway
||Suspected OSA with STOP-Bang ≥3/8
Diagnosis of OSA associated with a 3- to 4-fold increased risk of either tracheal intubation and/or mask ventilation
Apnea-hypopnea index ≥40/h
Upper airway OSA-related surgeries
|Awake tracheal intubation where there is a known difficult airway or evidence of multiple predictors of a difficult airway
||Judicious sedation by a separate independent anesthesiologist
Effective topicalization (lidocaine <9 mg/kg lean body weight)
Supplemental oxygen (eg, high-flow nasal oxygen)
Awake flexible bronchoscopy, videolaryngoscopy, or combined technique
|Considerations for asleep intubation
||Availability of skilled assistance
Onsite portable storage units/difficult airway cart
Consider apneic oxygenation techniques (eg, nasal cannula 15 L·min−1 insufflation and high-flow nasal oxygen)
Head elevated laryngoscopy position for obese patients
Guidance from difficult airway algorithms
Two-handed mask ventilation technique
Consider immediate reversal of deep rocuronium paralysis with sugammadex (16 mg/kg) in the cannot-intubate-cannot-oxygenate scenario
|General principles for airway management
||Minimizing postsurgery respiratory depression and airway obstruction via use of short-acting general anesthetic agents and multimodal analgesia techniques
Avoid opioids and gabapentinoids if possible
Mitigate gastroesophageal reflux disease and aspiration risk (rapid sequence induction and intubation, cricoid pressure, proton pump inhibitors, and H2-receptor antagonists)
|Emergence and extubation
||Anticipate potential difficult extubation
Awake extubation (patient cooperative and fully conscious)
Extubate in a nonsupine position (semiupright)
Extubation guidelines (remifentanil infusion, airway exchange catheters)
Caution in concurrent upper airway surgery
Monitored care (oxygenation and ventilation) for patients at higher risk
Positive airway pressure device recommenced postoperatively
Abbreviations: OSA, obstructive sleep apnea; STOP-Bang, Snoring, Tiredness, Observed apnea, high blood Pressure, Body mass index, Age, Neck circumference, and Gender.
A commonly used bedside screening test for OSA is the STOP-Bang (Snoring, Tiredness, Observed apnea, high blood Pressure, Body mass index, Age, Neck circumference, and Gender) questionnaire,25 which consists of an 8-point dichotomous assessment where a score of ≥3 places a patient at risk of OSA. Higher STOP-Bang scores of ≥3 correlated with difficult airway prediction in obese patients,26 and may be a useful tool to predict difficulty in intubation.27 In addition, front of neck access would be expected to be difficult if the OSA patient has a large neck circumference.
A retrospective review of the legal literature over a 20-year period (1991–2010) in patients suspected or known to have OSA undergoing surgical procedures revealed that severe complications (death and hypoxic brain injury) were because of the difficult airway.28 More than one-third were from otorhinolaryngology and OSA-related operations.28 It would be prudent, therefore, to regard OSA-related upper airway surgeries as a predictor for the difficult airway. Drug-induced sleep endoscopy is a commonly used method used by otorhinolaryngologists in the evaluation of upper airway obstruction for patients with OSA.29 These images and recordings may be a useful adjunct in characterizing the pattern of upper airway obstruction, visualization of supraglottic structures, assessing intraluminal anatomy, and thereby anticipating difficulties in airway management.
Obviating the Need for Airway Manipulation
In some situations, airway management issues may be circumvented, favoring the safe conduct of surgery. Various options involving nonmanipulation of the upper airway for intraoperative anesthesia should be considered, such as regional anesthesia techniques and judicious use of minimal and moderate sedation. There is a moderate level of evidence to favor the use of regional anesthesia in patients with OSA.11 From retrospective studies, intraoperative neuraxial anesthesia was found to be associated with a lower incidence of major complications (eg, requirement for mechanical ventilation, intensive care services, postoperative pulmonary complications) compared to when general anesthesia was administered in joint arthroplasty patients.30,31 Certain anxiolytic agents may have a safer profile with less respiratory depression and upper airway obstruction effects, as well as better maintenance of airway patency. These include ketamine and dexmedetomidine,11,32,33 and should be titrated as required utilizing lower doses. Conversely, patients with OSA may be at increased risk of desaturation and other adverse respiratory events from the use of intravenous propofol and benzodiazepine for sedation.11,21 Continuous oxygenation and ventilation monitoring are recommended during procedural sedation in patients with OSA.22
In the situation where general anesthesia is necessary or preferable due to surgical considerations and where there is a known difficult airway, evidence of multiple predictors of a difficult airway or risk of rapid desaturation, an awake tracheal intubation (ATI) technique may be favored. The Difficult Airway Society published airway management guidelines for ATI in 2020.34 If performed correctly, the ATI technique confers an element of safety because airway patency is maintained and the patient is breathing spontaneously. The intubationist would therefore be able to manage the airway in an unhurried manner.
Supplemental oxygen (high-flow or low-flow nasal oxygen) and administration of effective topicalization (lidocaine maximum dose of <9 mg/kg lean body weight) are recommended.34 Sedation should not be a substitute for ineffective airway topicalization with minimal sedation administered judiciously, preferably by an independent anesthesiologist (Table). Remifentanil and dexmedetomidine are viable options due to lower oversedation risk.35 ATI using either flexible bronchoscopy, or videolaryngoscopy, or as a combined technique are feasible options with comparable success rate.36 Current evidence does not support any particular videolaryngoscope as having an advantage; familiarity with the device would be a more important consideration.34
Adequate preparation for difficult airway in a patient suspected or diagnosed with OSA is the prerequisite to successful airway management—with the availability of skilled assistance, onsite difficult airway cart, and supplemental oxygen administration.3 Preoxygenation should be strictly observed to delay the onset of hypoxia, targeted to an end-tidal oxygen fraction of 0.87–0.90.4 Apneic oxygenation techniques (eg, nasal cannula 15 L·min−1 insufflation) have been found from randomized trials and meta-analysis to be useful in increasing the safe apnea period and reducing hypoxemia in obese patients and emergency intubations, respectively (Table).37–39 Other useful difficult airway techniques include adopting the head-elevated laryngoscopy position (alignment of ear and sternal notch) for patients with OSA who have concurrent obesity. This serves a 2-fold purpose of increasing the functional residual capacity during preoxygenation and improving the laryngoscopic view.40
The airway manager and the assisting team should be familiar with difficult airway algorithms.3,4 The benefits of videolaryngoscopy include improved visualization of the larynx and increased intubation success.3 These advantages may make using videolaryngoscope-assisted intubation from the outset a reasonable airway management option. Videolaryngoscopes and supraglottic airway devices may be useful in failed initial intubation attempts and rescue ventilation.4 The latter may be used as a conduit for intubation. If videolaryngoscopy fails, consideration should be given for hybrid techniques, such as (1) videolaryngoscopy and flexible bronchoscopic intubation and (2) supraglottic airway device and flexible bronchoscopic intubation. Some of the newer second-generation supraglottic airway devices are purpose-made to permit the direct passage of a sufficiently sized adult endotracheal tube with flexible bronchoscopic guidance, such as the LMA Protector™a, or Ambu AuraGain™. These are preferred to utilizing an intermediate exchange catheter (eg, LMA Unique™b, LMA ProSeal™c).
Two-hand facemask ventilation techniques may be necessary in the difficult mask ventilation situation, where the thenar eminence grip has been found to be superior compared to the conventional E-C clamp grip.41 In a cannot-intubate-cannot-oxygenate scenario with deep paralysis by rocuronium, high-dose sugammadex (16 mg/kg) has been shown to bring about the reversal of paralysis within 3 minutes of administration.42 In situations where reversal of paralysis is unsuccessful in averting the cannot-intubate-cannot-oxygenate scenario, timely surgical or front-of-neck access should be performed. The Difficult Airway Society suggests the scalpel-bougie technique4; yet, which front-of-neck access technique to use would be dependent on the availability of equipment, training, and familiarity. For patients with concomitant obesity and OSA, a cutdown may be required.4
Other General Principles and Considerations
The anesthesia technique used should aim toward minimizing respiratory depression and upper airway obstruction postsurgery by avoiding carry-over sedation. With this goal in mind, short-acting intravenous-cum-inhalational agents and multimodal analgesia may be used, including but not restricted to utilization of remifentanil infusions, desflurane, dexmedetomidine, ketamine, acetaminophen, nonsteroidal anti-inflammatory drugs, dexamethasone, intravenous lidocaine, and peripheral nerve blocks.11,18,19 Opioids and gabapentinoids should be administered sparingly and with caution because these may cause airway obstruction, suppress arousal responses, and depress respiratory drive (Table).11,22,43,44
Gastroesophageal reflux disease (GERD) has been found to be associated with OSA.45 If GERD is suspected to be present, preanesthesia administration of gastric acid–reducing agents (H2-receptor antagonists, proton pump inhibitors), rapid sequence induction, and induction with cricoid pressure may be considered to mitigate the risk of aspiration.19
Emergence From Anesthesia and Extubation
A corollary for OSA patients with difficult initial airway management is an anticipated difficult extubation course. This is especially so if the patient has concurrent obesity and risks of pulmonary aspiration of gastric contents. Other red flags would be difficult mask ventilation and/or tracheal intubation at induction. To avoid postextubation airway obstruction, particular attention should be given for extubation, with verification of neuromuscular blockade reversal (with a quantitative train-of-four monitor) and performance in a semiupright position with the patient cooperative and fully conscious.19,22 The Difficult Airway Society has promulgated guidelines on dealing with such situations, where awake extubation on remifentanil infusions, insertion of airway exchange catheters, and transition to supraglottic airway–guided extubation may be utilized (Table).46
OSA patients who have undergone upper airway surgery are particularly at risk of postextubation complications because of bleeding, edema, or anatomical distortion associated with the procedure on the background of a difficult airway. According to a consensus publication on the care of patients with OSA undergoing upper airway surgery, both OSA and upper airway surgery are risk factors for difficult extubation, and postextubation monitoring is recommended.18 In some cases, such as after base-of-tongue intervention and invasive lower pharyngeal airway surgery, there is an established increased risk of bleeding, edema, and airway obstruction.18
Patients at higher risk of postoperative airway complications should be monitored for oxygenation and ventilation for a longer period in the postanesthesia care unit and, subsequently, a high acuity area, with the accessibility of expeditious intervention.19,22 These would comprise patients with severe OSA, uncontrolled comorbidities, nonadherence to perioperative positive airway pressure therapy, particular types of surgery (eg, upper gastrointestinal, thoracic, upper airway surgeries), and the need for higher dose postoperative intravenous opioids for analgesia.19,22 Patient’s own positive airway pressure therapy should be recommenced at previously prescribed settings during sleep as soon as deemed feasible.19,21,22
OSA is the most common sleep-related breathing disorder, and the difficult airway is perhaps the anesthesiologists’ quintessential concern. OSA and the difficult airway share certain similar anatomical, morphological, and physiological features. Individual studies and systematic reviews of retrospective, case-control and large database studies have shown a consistent association between patients with OSA and the difficult airway; OSA patients have a 3- to 4-fold higher risk of difficult intubation, difficult mask ventilation, or a combination of both. For future research, OSA-specific large prospective studies with reduced vulnerability of bias are suggested to confirm and quantify the association between this common sleep disorder and the difficult airway.
Nevertheless, current knowledge strongly suggests that anticipation and proactive perioperative management of the difficult airway should be undertaken in these airway-at-risk patients with OSA. Prudent intraoperative management comprises the use of regional anesthesia where possible, considering an awake intubation technique where there is the presence of notable difficult airway predictors and risk of rapid desaturation following induction of general anesthesia. Familiarity with difficult airway algorithms, cautious extubation, and appropriate postoperative monitoring of patients with OSA are necessary to mitigate perioperative risks.
Name: Edwin Seet, MBBS, MMed, FAMS.
Contribution: This author helped conceive, structure, search evidence, and write the manuscript for this review article.
Name: Mahesh Nagappa, MD.
Contribution: This author helped conceive, structure, search evidence, and write the manuscript for this review article.
Name: David T. Wong, MD, FRCPC.
Contribution: This author helped conceive, structure, search evidence, and write the manuscript for this review article.
This manuscript was handled by: Toby N. Weingarten, MD.
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