THE RELATIONSHIP BETWEEN DISEASE SEVERITY AND PREDICTORS OF DIFFICULT INTUBATION IN PATIENTS WITH OBSTRUCTIVE SLEEP APNEA SYNDROME

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1 Acta Medica Mediterranea, 2015, 31: 67 THE RELATIONSHIP BETWEEN DISEASE SEVERITY AND PREDICTORS OF DIFFICULT INTUBATION IN PATIENTS WITH OBSTRUCTIVE SLEEP APNEA SYNDROME BUKET CAGLA OZBAKIS AKKURT 1, SIBEL DOGRU 2, ONUR KOYUNCU 1, ISIL DAVARCI 1, SEBAHAT GENC 2 1 Mustafa Kemal University Faculty of Medicine Department of Anesthesiology - 2 Mustafa Kemal University Faculty of Medicine Department of Pulmonary Diseases ABSTRACT Objectives: The objective of our study was to identify clinical and polysomnographic predictors of difficult intubation, through the correlation between commonly used measurements to predict difficult intubation. Methods: Consecutive patients diagnosed with moderate or severe obstructive sleep apnea syndrome (OSAS) using polysomnography (PSG), and sex and age matched normal controls were included in the study. The patient group was divided into two subgroups as mild/moderate and severe desease groups. Body mass index (BMI), neck circumference (NC), abdominal circumference (AC), Epworth Sleepiness Scale (ESS) score, Apnea/Hypopnea Index (AHI), Arousal Index (AI) were recorded. Predictive tests for difficult intubation were recorded for each subject. Records were compared between all groups. Results: Forty OSAS patients and 39 control subjects were enrolled in the study. Class III-IV Modified Mallampati Test (MMT) score was found in 37 (%92,5) OSAS patients, while in 10 (25.6 %) of the control subjects. There was statistically significant difference between two groups in terms of NC, AC, interincissor distance (IID). There was a significant inverse correlation between sternomental distance (SMD) and AHI in patients with OSAS. Conclusion: AHI is a reliable predictor of difficult intubation in patients with OSAS and is correlated with the sternomental distance. Key words: Difficult intubation, OSAS, sternomental distance, mallampati. Received June 18, 2014; Accepted October 02, 2014 Introduction Obstructive sleep apnea syndrome (OSAS) is a common pathology in which patients develop repetitive pharengeal airway closure during sleep (1). It is increasingly recognized as an independent risk factor for cardiac, neurologic, and perioperative morbidities (2). It has been shown that reduction in mandibular body length, inferiorly positioned hyoid bone, and retroposition of the maxilla can be seen in patients with OSAS. Difficult or failed endotracheal intubations are one of the leading causes of anaesthesia-related morbidity and mortality in these patient groups. The incidence of difficult endotracheal intubation has been reported to be 3.2% and has been attributed to the abnormalities of the face or the upper airway which are seen in OSAS patients (3). Unrecognized OSAS can cause perioperative complications including exaggerated respiratory depression from anesthetics and analgesics, increased postoperative reintubation, cardiac dysrhythmia, and longer hospital stay. Therefore, the American Society of Anesthesiologists recommends early identification and appropriate preparation for perioperative management of patients with suspected OSAS (4). The objective of our study was to identify clinical and polysomnographic predictors of difficult intubation, through the correlation between commonly used measurements to predict difficult intubation.

2 68 Buket Cagla Ozbakis Akkurt, Sibel Dogru et Al Materials and methods Seventy-nine patients were enrolled to the study. The Local Ethics Commitee approved the study protocol and all subjects signed an informed consent form for their participation. Consecutive patients diagnosed with moderate or severe OSAS using polysomnography (PSG), and sex and age matched normal controls were included in the study. Subjects who have OSAS symptoms were excluded from control group. Symptoms and disease history, body mass index (BMI), neck circumference (NC), abdominal circumference (AC), Epworth Sleepiness Scale (ESS) score, Apnea/Hypopnea Index (AHI), Arousal Index (AI), Oxygen Desaturation Index (ODI), Minimum Oxygen Saturation (MOS), mean Oxygen Saturation (MeOS), Apnea duration, Hypopnea duration and duration of desaturation were recorded. PSG was performed using Compumedics E Series 44 channel polysomnograph, Profusion PSG3 Software (Abbotsford, VIC, Australia). Electroencephalography (EEG), electrooculography (EOG), submental electromyography (EMG), electrocardiography (ECG), finger pulse oxymetry, thoracic and abdominal movements, body position, and bilateral anterior tibial EMG were recorded. An oronasal thermistor and nasal canula were used to detect apnea and hypopneas. All signals were digitized and stored on a personal computer. Scoring was performed according to the recommendations of Rechtschaffen and Kales and the American Academy of Sleep Medicine (AASM) rules (5). ESS is a subjective scale of sleepiness and has been translated into several languages (1) where the patient grades his excessive daytime sleepiness (EDS). In this scale,the individual is asked to rate on a scale of 0 to 3 the chance of dozing in 8 specific situations, Total score of 10 or higher is considered the patient has EDS. AHI was defined as the number of apneas and hypopneas per hour. AI is defined as the number of arousals per hour. We performed the predictors of difficult intubation as reported in our previous study on rheumatoid arthritis and predictors of difficult intubation (6). Modified mallampati test (MMT), thyromental distance (TMD), sternomental distance (SMD), inter-incisor distance (IID) and atlanto-occipital joint extension measurements were used to predict difficult intubation. MMT was performed with the patient in the sitting position, head in a neutral position, the mouth wide open and tongue protruding to its maximum. Classification was assigned according to the extend the base of tongue is able to mask the visibility of pharyngeal structures into four classes (Class I-IV). TMD was defined as the distance from the mentum to the thyroid notch with the patient s neck fully extended. Alignment of these two axes is difficult if the TMD is <3 finger breadths or <6 cm in adults; cm is less difficult, while >6.5 cm is normal. The SMD was measured as the distance from the suprasternal notch to the mentum with the head fully extended and the mouth closed. A value of less than 12 cm has been found to predict a difficult intubation. The IID was measured as the distance between upper and lower incisors. Normal is 4.6 cm or more, while <3.8 cm predicts a difficult airway. Atlantoocipital angles were measured to determine the extension of the joint. After the patient was asked to hold the head erect, facing directly to the front; they were asked to extend the head maximally. Then the angle traversed by the occlusal surface of upper teeth (AOA 1 ) was measured using a goniometer. Any reduction in extension was expressed in grades: Grade I: >35, Grade II: 22-34, Grade III: 12-21, Grade IV: <12. In order to measure the second angle; the patient was asked to lie in the supine position with no pillow under the head and to extend the head maximally. Then the angle between the mouth corner-tragus line and the horizontal line was measured (AOA2). When the angle is <80 difficult intubation is expected. Data were analyzed using SPSS version 13.0 for Windows software (SPSS Inc; Chicago, Illinois). Differences in categorical variables were evaluated using a chi-square test for independence. Student s t test and Mann Whitney U test were used to compare mean values between two group. Correlation analyses were performed using the pearson test. A p value <0.05 was considered statistically significant. All results are expressed as means ± SD or percent. Results Seventy nine patients including 40 OSAS patients and 39 control subjects participated in our

3 The relationship between disease severity and predictors of difficult intubation in patients study. There was no significant diffirence between patient and control groups in terms of age and gender ( p>0.05). Mean BMIs were ± 7.18, and ± 4.87 in OSAS patients and control group respectively, and were significantly different (p<0.001). The incidence of witnessed apnea, snoring, EDS and hypertension was significantly higher in OSAS patients than control group (p<0.001). There was no diffirence between two groups regarding cardiovascular diseases and diabetes mellitus (Table 1). OSAS Group (n=40) Control Group (n=39) Age (yr) ± ± 7.08 >0.05 Gender (M/F) 35/5 35/4 >0.05 BMI*(kg/m 2 ) ± ± 4.87 <0.001 Class III-IV MMT score was found in 37 (92.5%) OSAS patients, while in 10 (25.6%) of the control subjects (p <0.001). There was statistically significant difference between two groups in terms of NC, AC, IID and AOA1 (p<0.001, p<0.001, p= 0.028, p=0.004, respectively) (Table 2). When OSAS patients were divided into two groups (mild to moderate, and severe), a significant difference was found in terms of AC, SMD and AOA 2 (p= 0.017, p<0.001, p=0.006, p=0.014, respectively) (Table 3). MMT* Mild and Moderate OSAS (n=12) Severe OSAS (n=28) Witnessed apnea 37 (92.5%) 0 <0.001 Snoring 40 (100%) 16 (41%) <0.001 EDS**[n(%)] 27 (67.5%) 13 (32.5%) <0.001 Classes I and II[n (%)] 0 3 (10.7%) Classes III and IV[n (%)] 12 (100%) 25 (89.3%) >0.05 Hipertention 14 (35%) 1 (2.6%) <0.001 Cardiovascular Diseases 3 (7.5%) 0 >0.05 Diabetes Mellitus 4 (10%) 1 (2.6%) >0.05 Table 1: Recorded measurements of patients in control and patient group. *BMI= body mass index.**eds=exessive day-time sleepiness. Neck circumference ± ± 3.65 > ± ± <0.001 Sterno-mental distance ± ± OSAS Group (n=40) Control Group (n=39) Tiro-mental distance 9.29 ± ± 1.43 >0.05 MMT* İnter-incisor distance 5.20 ± ± 0.59 >0.05 Classes I and II [n (%)] 3 (7.5%) 29 (74.4%) <0.001 AOA 1 ** >0.05 Classes III and IV[n (%)] 37 (92.5%) 10 (25.6%) Neck circumference ± ± 3.33 < ± ± <0.001 Sterno-mental distance ± ± 2.23 >0.05 Tiro-mental distance 9.1 ± ± 0.96 >0.05ǃ İnter-incisor distance 5.08 ± ± AOA 1 ** Classes I and II [n (%)] 18 (45%) 30 (76.9%) Classes III and IV[n (%)] 22 (55%) 9 (23.1%) AOA 2 *** 78.3 ± ± 11.8 >0.05 Table 2: Measurement of neck circumference, abdominal circumference, interincissor distance and AOA 1 between groups. *MMT=modified mallampati test.**aoa1 =atlanto-occipitale angle 1.***AOA 2 =atlanto-occipitale angle 2.! Mann Whitney- U test was used. Classes I and II[n (%)] 6 (50%) 12 (42.9%) Classes III and IV[n (%)] 6 (50%) 16 (57.1%) AOA 2 *** ± ± Table 3: Recorded measurements between mild/modarete and severe OSAS patients. *MMT=modified mallampati test.**aoa 1 =atlanto-occipitale angel 1.***AOA 2 =atlanto-occipitale angel 2. There was a significant inverse correlation between SMD and AHI in patients with OSAS (r=0.44) (Fig 1). AC was inversely correlated with AHI too. But this correlation was not statistically significant (r=0,36) (Table 4).

4 70 Buket Cagla Ozbakis Akkurt, Sibel Dogru et Al Fig. 1: Sternomental distance. Discussion Apne/Hypopnea Index In the present study we compared predictors of difficult intubation in OSAS patients with control group and found that predictors of difficult intubation such as MMT, NC, AC, IID and atlantoocipital angle are significantly different in OSAS patients when compared with normal control group. We also found that the AHI was significantly correlated with decreased SMD. Various studies have been run on OSAS patients to define the relationship between the disease and difficult intubation (7-13). Results of these studies have been controversial. Most authors have stated that OSAS was a risk factor for difficult intubation whereas others have reported that it was not a risk factor for difficult intubation (14). Neligan et al has investigated if morbid obesity, obstructive sleep apnea and neck circumference were independent risk factors for difficult tracheal intubation. They stated that there was no relationship between the Age Age - r 0.24 p 0.13 r 0.610* 0.36** p SMD Abdominal Circumference r 0,44** ** p Table 4: Correlation between AHI and SMD. - presence and severity of OSAS, BMI, or NC and difficulty of intubation or laryngoscopy grade. Only a Mallampati score of 3 or 4 or male gender predicted difficult intubation. In a retrospective study; Kim et al investigated preoperative predictors of difficult intubation in patients with OSAS and found that the prevalence of difficult intubation was higher in the OSAS group than in the control group and that the occurrence of difficult intubation can be predicted using AHI (7). In our study we compared the predictors between the OSAS and control groups and also between the mild /moderate and severe OSAS groups. The BMI was significantly higher in the OSAS group so we suggested that this difference could effect the results and that the difficult intubation could not only be attributed to OSAS. But we also compared the difference between the mild/moderate and severe OSAS groups. The BMI was similar between the OSAS patients so its effect on results were excluded. We found that AHI was significantly correlated with SMD. SMD decreased significantly as the AHI increased. In morbid obese patients it has been shown that problematic intubation was associated with TMD, increasing NC, BMI, and a Mallampati score of > or = 3 (15). Thus comparing NC, and TMD in groups with significantly different BMI may reflect some misunderstood results. However mallampati score has been shown to be an independent risk factor for difficult intubation in OSAS patients (9). In our study we also found that 92.5% of the patients with OSAS were MMT class III and IV whereas only 25.6 % of the control group were so. As we mentioned above; the significant difference in NC and AC may be affected from the difference in the BMI. In our study the TMD was similar between all groups. The AHI has been identified as an independent risk factor for difficult intubation in patients with OSAS (6,10,16). Siyam et al. reported that intubation was more difficult in OSAS patients than in controls (8). However, they did not find a significant correlation between AHI and difficult intubation in OSAS patients. On the other hand Kim et al. has compared the AHI in failed intubation patients and successfull intubation patients with OSAS and found that there was a significant relationship between AHI and difficult intubation (7). Their explanation for this relation was that mallampati score and AHI may share the same anatomical characteristics.

5 The relationship between disease severity and predictors of difficult intubation in patients But in our study we divided the OSAS patients into two groups as severe and mild/moderate based on the AHI. We also searched if there was any correlation between other predictors of difficult intubation and AHI. We found a significant reverse correlation between AHI and SMD. So we suggested that the effect of AHI on difficult intubation could attributed to this correlation between AHI and SMD. In their study, Kim et al. Found that AHI was significantly correlated with BMI. Similarly Friedman et al also have reported that the MMI and BMI were correlated with severe AHI and difficult intubation (10). But in our study BMI was not statistically different in mild/moderate and severe OSAS patients, while AHI was significantly higher in the severe group. Mean BMI in OSAS patients was 34,61± 7,18 and they were in obese classification. In our study we also compared the atlantooccipital angles between groups. We found that the AOA1 was significantly higher in the control group when compared to OSAS patients. However when we compared the OSAS patients; the AOA2 angle was significantly higher in the mild/moderate group but we did not find a correlation between the AHI and these angles. Yet; we could not find a correlation between AHI and atlantoocipital angles. In conclusion we suggest that AHI is a reliable predictor of difficult intubation in patients with OSAS and is correlated with the SMD. References 1) Schwab RJ, Remmers JE, KunaST. Anatomy and physiology of upper airway obstruction. In: Kryger MH,Roth T, Dement WC, eds. Principles and practice of sleep medicine. St. Luis, Missouri: Elsevier Inc 2011: ) Park JG, Ramar K, Olson EJ. Updates on definition, consequences, and management of obstructive sleep apnea. Mayo Clin Proc. 2011; 86(6): ) Lee SJ, Lee JM, Kim TS, Park YG. The relationship between the predictors of obstructive sleep apnea and difficult intubation. Korean J Anesthesiol 2011; 60(3): ) Park JG, Ramar K, Olson EJ. Updates on definition, consequences, and management of obstructive sleep apnea. Mayo Clin Proc. 2011; 86(6): ) Iber C, Ancoli-Israel S, Chesson A, Quan S; for the American Academy of Sleep Medicine. The AASM manual for the scoring of sleep and associated events: rules, terminology and technical specifications. 1st ed. Westchester, IL: American Academy of Sleep Medicine; ) Akkurt BC, Guler H, Inanoglu K, Turhanoglu AD, Turhanoglu S, Asfuroglu Z. Disease activity in rheumatoid arthritis as a predictor of difficult intubation? European Journal of Anaesthesiology. 2008; 25: ) Kim JA1, Lee JJ. Preoperative predictors of difficult intubation in patients with obstructive sleep apnea syndrome. 8) Siyam MA, Benhamou D. Difficult endotracheal intubation in patients with sleep apnea syndrome. Anesth Analg Oct; 95(4): ) Lam, B; Ryan, F; Ip, MSM; Lam, WK Mallampati score is a good and independent predictive factor for obstructive sleep apnoea (OSA) The 5 th Medical Research Conference, Hong Kong,China, January 2000, 22 n. Supp 2, ) Friedman M, Tanyeri H, La Rosa M, et al Clinical pre dictors of obstructive sleep apnea Laryngoscope : ) Benumof JL. Obstructive sleep apnea in the adult obese patient: implications for airway management. Anesthesiol Clin North America Dec; 20(4): Review. 12) Connolly LA Anesthetic management of obstructive sleep apnea patients. J Clin Anesth 1991; 3: ) Hillman DR, Loadsman JA, Platt PR, Eastwood PR Obstructive sleep apnoea and anaesthesia. Sleep Med Rev 2004; 8: ) Neligan PJ1, Porter S, Max B, Malhotra G, Greenblatt EP, Ochroch EA. Obstructive sleep apnea is not a risk factor for difficult intubation in morbidly obese patients. Anesth Analg Oct;109(4): doi: /ane.0b013e3181b12a0c. 15) Gonzalez H1, Minville V, Delanoue K, Mazerolles M, Concina D, Fourcade O. The importance of increased neck circumference to intubation difficulties in obese patients. Anesth Analg Apr; 106(4): ) Hiremath AS, Hillman DR, James AL, Noffsinger WJ, Platt PR, Singer SL Relationship between difficult tracheal intubation and obstructive sleep apnoea. Br J Anaesth May; 80(5): Correspoding author BUKET CAGLA OZBAKIS AKKURT Mustafa Kemal University Faculty of Medicine Department of Anesthesiology Antakya/ Hatay (Turkey)