AJA Asian Journal of Anesthesiology

Advancing, Capability, Improving lives

Research Paper
Volume 57, Issue 4, Pages 117-124
Atul Anand Ambekar 1 , Shalini G. Saksena 2 , Jitendra S. Bapat 2 , Manju T. Butani 2
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Abstract

Objective

Obstructive sleep apnoea hypopnoea syndrome associated with obesity poses major perioperative airway challenge. Drug-induced sleep endoscopy (DISE), is a real-time upper airway flexible fiberoptic nasoendoscopy in awake and sedation/anaesthesia-induced sleep. The aim of current study was to assess the correlation of bedside airway screening tests with level of obstruction during DISE.

Methods

Study was performed in endoscopy suite. Parameters calculated in 40 study group patients were Berlin questionnaire responses, Apnea hypopnea index (AHI), interincisor distance, Mallampati classification (MPC), neck circumference (NC), thyromental distance (TMD), NC/TMD ratio, sternomental distance (SMD), upper lip bite test, lateral cephalometry derived gonial angle and mentohyoid distance (MHD), Muller’s manoeuvre during awake nasoendoscopy, and Croft–Pringle grade of airway obstruction during DISE and effect of jaw thrust.

Result

All patients were American Society of Anesthesiologists physical status 1 and 2 with AHI > 30. Positive responses to Berlin questionnaire, body mass index, and AHI increased with increasing grade of DISE. DISE grades 1–5 were observed in 0% (0), 5% (2), 37.5% (15), 27.5% (11), and 30% (12) patients respectively. Muller’s manoeuvre showed lateral wall collapse in 40% (16) patients and concentric collapse in 40% (16) patients. Airway patency improved with jaw thrust in 60% (24) patients. Significant association of DISE was found with MPC (p = 0.028), TMD (p = 0.003), MHD (p = 0.008), and NC/TMD ratio (p = 0.002), effect of Muller’s manoeuvre (p =0.002), and effect of jaw thrust (p = 0.000).

Conclusion

Bedside screening tests MPC, TMD, NC/TMD ratio, and MHD correlate significantly with level of obstruction during DISE.

Keywords

obesity, airway obstruction, sleep apnea, polysomnography, cephalometry, sleep endoscopy


Introduction

Identification of airway obstruction and difficult mask ventilation is extremely important for an anesthesiologist. There is no single test which can reliably predict this, also there is no standardization with respect to a set of screening tests to reliably predict this.1 Difficult and impossible mask ventilation can be related to a difficult intubation.2 A combination of bedside screening tests is used, but most of them aim to identify difficult intubation.

Routine clinical assessment includes Berlin questionnaire (i.e., Appendix), body mass index (BMI), neck circumference (NC), Mallampati classification (MPC), thyromental distance (TMD), NC to TMD ratio, and sternomental distance (SMD). Polysomnography means conducting a sleep study and calculating the apnoea-hypopnea index (AHI). Lateral cephalometry means performing a lateral X-ray of the neck with soft tissue exposure and calculating the mentohyoid distance (MHD) and mandibular slope angle.

Obstructive sleep apnea hypopnea syndrome (OSAHS) is caused by collapse of the oropharynx during sleep which can occur at multiple levels of the upper airway.3 OSAHS patients pose a major airway challenge for mask ventilation, intubation, and extubation. In the present study, after confirmation of diagnosis with history and polysomnography, patients underwent drug-induced sleep endoscopy (DISE) which can identify the anatomical area of airway obstruction in awake and sedation/anesthesia induced sleep in real time.4-6

As most bedside screening tests were aimed at identifying difficult intubation and no screening tests were available to predict difficult ventilation or level of airway obstruction, the aim of current study was to assess the correlation of bedside screening tests with level of obstruction during DISE.

Methods

Institutional ethics committee approval was taken (Approval code: 814-14-SHS*[MRC]). It was a single institutional prospective observational study performed in the endoscopy suite.

Patient Population

Forty patients with complaint of snoring who came to the ear, nose and throat (ENT) department was the study population. March 2014 to August 2015 (18 months) was the time frame to address the study. Previously, DISE has not been used for patient assessment in any study, hence no parent study was found, and convenience based sampling technique for deriving the study population was suggested by the statistician. Convenience based sampling technique was used considering the study duration and number of patients attending the ENT outpatient department with complaints of snoring and further consenting to DISE. Inclusion criteria were males and females above the age of 15 years, presenting with symptoms of sleep disordered breathing like snoring, choking episodes at night, increased daytime somnolence, morning tiredness, BMI ≥ 25, and AHI score ≥ 5 on polysomnography. Exclusion criteria were patients with history of severe chronic obstructive pulmonary disease, any upper airway mass, pregnant females, and history of allergy to midazolam or propofol.

Bedside Screening Tests

A detailed history of the patient was obtained using the Berlin questionnaire. Routine investigations in the form of complete blood count, chest X-ray, electrocardiogram, liver function tests, renal function tests, fasting blood sugar, post prandial blood sugar and serum electrolytes were performed. Clinical airway assessment in the form of BMI calculated as weight in kilograms divided by the square of height in meters, NC measured at the level of cricothyroid membrane in centimeters, TMD measured in centimeters from upper border of thyroid cartilage up to the mentum with neck in full extension, NC to TMD ratio, SMD calculated in centimeters from sternal notch up to the mentum with neck in full extension, mouth opening calculated in observer’s finger breadths, upper lip bite test observed as the ability to protrude the lower incisors beyond the upper incisors and MPC carried out with the patient sitting, opening their mouth, and protruding the tongue maximally, producing a score of 1–4, depending on anatomical structures seen was performed. Lateral cephalometry (i.e., lateral neck X-ray) with the neck extended was obtained, MHD and mandibular slope angle was measured radiographically (Fig. 1). AHI was calculated using polysomnography which is categorized as Mild: 5–15, Moderate: 15–30, and Severe: > 30.

Figure 1.
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Fig. 1. Lateral neck X-ray (cephalometry) depicting mandibular slope angle (R-A-B) and mentohyoid distance (M-H).

R: mandibular ramus; A: angle of mandible; B: body of mandible; M: mentum; H: hyoid bone.

Awake Endoscopy and Drug-Induced Sleep Endoscopy

Informed consent of the patients was taken. All patients were kept fasting overnight. Video recorded awake nasoendoscopy with fibreoptic nasopharyngoscope was performed initially after decongesting the nose with xylometazoline (0.1%) solution to assess the upper airway (Video 1, available at https://doi.org/10.6859/aja.201912_57(4).0002). Effect of Muller’s manoeuvre was examined and recorded (Fig. 2A and B). Muller’s manoeuvre is the manoeuvre wherein the patient is asked to perform forceful inspiration (sniff) against a closed glottis and the wall of the pharynx that collapses during this manoeuvre is observed. DISE was then performed. A peripheral intravenous (IV) line was secured with 22 G cannula, all monitors were attached in the form of heart rate, blood pressure, electrocardiogram, plethysmograph (SpO2), end-tidal CO2, and bispectral index. Each patient was then administered IV Midazolam in the dose of 0.03– 0.05 mg/kg as a slow bolus. IV propofol was then administered in a dose of 0.50–2.00 mg/kg to achieve a level of sedation approximating natural sleep. Sedation level was monitored using Bispectral index monitor (BIS) to maintain a score of 50–70 to ascertain an adequate anaesthesia depth. When the patient was asleep and actively snoring with BIS between 50–70, a video recorded fibreoptic nasopharyngoscope was used to assess the upper airway (Video 1, available at https://doi.org/10.6859/aja.201912_57(4).0002). Croft–Pringle grade of obstruction was recorded:

(1) Grade 1: Simple palatal level snoring

(2) Grade 2: Single palatal level obstruction

(3) Grade 3: Palatal level obstruction with intermittent oropharyngeal involvement

(4) Grade 4: Sustained multi-segment involvement

(5) Grade 5: Tongue base level obstruction (Fig. 2C)

Video 1.
Figure 2.
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Fig. 2. (A) depicts collapse of the lateral oropharyngeal walls, (B) depicts collapse of antero-posterior walls during Muller’s maneuver in awake nasoendoscopy, and (C) depicts collapse of tongue base during drug-induced sleep endoscopy.

A: anterior oropharyngeal wall; L: lateral oropharyngeal wall; P: posterior oropharyngeal wall; E: epiglottis; B: tongue base.

Effect of jaw thrust was examined and recorded. Jaw thrust was performed by lifting both the angles of the mandible and whether the obstruction was relieved was observed using the fiberoptic nasopharyngoscope. Post procedure patients were observed in post-anaesthesia care unit.

Statistical Analysis

Mean values of quantitative parameters were correlated with the DISE grades, and the general trend was observed. Significance of association of individual qualitative parameters (i.e., those parameters with a dichotomous response and those with grades of severity) with the DISE grade was derived using the Fisher’s exact test of significance 2-sided, which included--Berlin questionnaire response, comorbidities, mouth opening, effect of Muller’s manoeuvre, effect of jaw thrust, modified MPC and upper lip bite test. Significance of association of individual quantitative parameters (i.e., those parameters having a numerical value) with the DISE grade was derived using the one-way analysis of variance (ANOVA) test, which included--BMI, NC, TMD, NC to TMD ratio (NC/TMD ratio), SMD, AHI, mandibular slope angle, MHD, and maximum desaturation. Computer software SPSS version 20.0 (IBM Corp., Armonk, NY, USA) was used.

Results

Forty patients satisfying all the criteria were recruited over a period of 18 months and the observations were recorded (Tables 1 and 2). The following parameters changed in the same direction as the grade of severity of DISE–BMI, TMD, SMD, MHD, AHI, and maximum desaturation.

Table 1. Patient demographics and compiled observations of clinical airway tests
Table 1.
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Table 1. Patient demographics and compiled observations of clinical airway tests (continued)
Table 1.
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Table 2. Drug induced sleep endoscopy observations
Table 2.
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Significant association was found between TMD (p = 0.003), NC/TMD ratio (p = 0.002), and MHD (p = 0.008) with DISE using the one-way ANOVA test (Table 3).

Table 3. Statistical association of all parameters with drug-induced sleep endoscopy
Table 3.
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Significant association was found between MPC (p = 0.028), effect of Muller’s maneuver (p = 0.002), and effect of jaw thrust (p = 0.000) with the DISE findings using the Fisher’s exact test of significance 2-sided (Table 3).

Discussion

OSAHS is a growing worldwide problem. These patients present at the hospital for surgical procedures at a higher rate than is their prevalence in the general population. It has been reported in the medical literature that obstructive sleep apnoea (OSA) is associated with difficult mask ventilation, difficult endotracheal intubation and a higher than normal incidence of postoperative respiratory complications. The incidence of difficult intubation for general surgery in nonobese patients is estimated to be 2.2% and for obese patients it is 15.5%, whereas for obstetric surgeries it is 3.3–7.9% in non-obese patients and 35.0% in obese patients.7 It is thus imperative that the anesthesia provider be prepared to safely accomplish their anesthetic and recovery.

Maintenance of an upper airway patency is essential for normal respiratory function. It is one of the primary objectives of an anesthesiologist. The maintenance of a patent upper airway depends primarily on pharyngeal structures. OSAHS is caused by repetitive partial or complete obstruction of the upper airway, characterized by episodes of breathing cessation during sleep, which lasts for 10 or more seconds.

A large number of patients with OSAHS are undiagnosed when they present for surgery and anesthesia. There are a set of investigations which confirm the diagnosis of OSAHS, amongst which polysomnography is the gold standard. Polysomnography determines the AHI and classifies the severity of the disease.8-10 This investigation may not be feasible in many instances; therefore, various questionnaires have been developed to identify this condition. The earliest questionnaire developed was the Berlin questionnaire.11 Later, the STOP questionnaire was introduced and subsequently the STOP-BANG questionnaire was developed.12

For airway assessment in the general population and suspected OSA patients there are standard param- eters namely interincisor distance, upper lip bite test, modified MPC, TMD, SMD, and these tests have been verified to have high sensitivity and specificity when used in combination.13

DISE is a dynamic parameter introduced in the last 20 years which can provide real time demonstration of the anatomical region of airway collapse and can be recorded. It is being used primarily to determine the type of corrective airway surgery the patient requires. This investigation was recently introduced at our institute. DISE requires the administration of monitored sedation to produce sleep, snoring, hypopnea and apnea following which the airway is assessed using a flexible fiberoptic nasoendoscope.

Therefore, the present observational study was designed to assess the correlation between the bedside screening tests with level of airway obstruction during DISE.

Significant association was observed between MPC, TMD, NC/TMD ratio, MHD, and DISE. As individual tests MPC, TMD, NC/TMD ratio are proven predictors of difficult intubation in obese patients.14-16 Kim et al. has demonstrated that the ratio of NC to TMD was a better indicator than other standard tests for predicting difficult intubation.14 Cagla Ozbakis Akkurt et al. has demonstrated that in patients of OSAHS, AHI and SMD also become important predictors of difficult intubation.17

Preoperative awake endoscopy has been recommended by Rosenblatt et al.,18 but it has the drawback of not being able to identify anatomical airway structures which collapse due to sedation and/or anesthesia. Visualization of actual collapse of palate, lateral pharyngeal wall, tongue base/epiglottis and multi-level collapse is possible only during DISE. This will help to identify patients where bag-mask ventilation would be difficult or near impossible (DISE grades 4 and 5). The patients who benefitted from jaw thrust would probably be effectively ventilated using an oropharyngeal airway. Study by Rosenblatt et al.18 has described the advantage of preoperative awake endoscopy. The implication of current study is that the clinicians may predict the possibility of airway obstruction or difficult mask ventilation using these bedside screening tests whenever sedation is provided.

Though the present study has been able to demonstrate significant association between a few airway assessment parameters, namely modified MPC, TMD, NC/TMD ratio, MHD, Muller’s maneuver during awake endoscopy, and DISE findings, this study has limitations. The actual airway management namely bag mask ventilation and intubation was not a part of this study. This would have validated the correlation of DISE with the difficulty encountered during bag mask ventilation and intubation. The patients who underwent drug induced sleep nasoendoscopy did not necessarily require corrective airway surgery. They were offered mandibular advancement devices or continuous positive airway pressure devices to improve their airway patency. Hence, data of difficult ventilation/intubation could not be collected. Another limitation of this study is that the bedside screening tests were correlated with DISE findings as a whole, and not with high-grade obstruction and low-grade obstruction on DISE separately, due to the small sample size of 40.

The present study and its findings can be used to plan the anesthetic management for OSAHS patients coming for any surgical intervention. In future, we plan to subject OSAHS patients coming for any surgical intervention to preoperative DISE in addition to the standard airway tests. This will help to validate the utility of DISE as a preoperative predictive test for difficult airway.

From the present study, we conclude that, among the airway assessment parameters, modified MPC, TMD, NC/TMD ratio, and cephalometric MHD have significant association with DISE findings. Muller’s manoeuvre showed the possible sites of airway collapse during awake nasoendoscopy which had significant association with the DISE findings in OSAHS patients.Improvement of airway patency with jaw thrust manoeuvre during DISE was identified and had significant association. Performing DISE will identify the actual anatomical sites of airway obstruction. Bedside clinical airway assessment parameters, lateral cephalometry, and awake & DISE may help to identify OSAHS patients with a potentially difficult airway at risk of obstruction and difficult mask ventilation during sedation and anaesthesia and to improve patient safety in OSAHS patients.

Acknowledgments

The authors thank that Dr. Milind Kirtane, MS ENT, Consultant ENT surgeon, P. D. Hinduja National Hospital, Mumbai.


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