Abstract
Purpose
We analyzed site, pattern and degree of obstruction in Korean male obstructive sleep apnea syndrome (OSAS) patients by drug-induced sleep endoscopy (DISE). We also investigated possible links between BMI, AHI and DISE findings.
Materials and methods
Sixty-nine male patients underwent DISE. DISE findings were reported using our classification system in which modified ‘VOTE classification’ – obstruction type, site of obstruction, degree of obstruction and anatomical site contributing obstruction – was reported. Associations were analyzed among the results of the polysomnography, patients’ characteristics and DISE finding.
Results
Multilevel airway obstruction was found in 84.06% of patients and 15.94% had a unilevel obstruction. Among those with unilevel obstruction, 90.90% had retropalatal level obstruction and 9.10% had retrolingual level obstruction. Palate with lateral pharyngeal wall obstruction (49.28%) is the most common obstruction type of the retropalatal level and tongue with lateral pharyngeal wall (37.68%) is the most common obstruction type of the retrolingual level. Examining the relation between obstruction site according to body mass index (BMI) and severity of OSAS (apnea hypopnea index, AHI), the lateral pharyngeal wall had an increasing tendency associated with higher BMI and higher AHI. But the lateral pharyngeal wall of both levels was statistically significant associated with higher AHI.
Conclusion
The majority of the Korean male OSAS patients have multilevel obstruction and according to BMI and AHI, the DISE findings indicate that the lateral pharyngeal wall is the most important anatomical site contributing to obstruction regardless of the level at which the obstruction lies.
1
Introduction
Obstructive sleep apnea syndrome (OSAS) is a growing problem associated with excessive daytime sleepiness and an increased risk of cardiovascular and cerebrovascular complication . Continuous positive airway pressure (CPAP) therapy remains the first line medical therapy in the management of OSAS. However, long term compliance to CPAP treatment is suboptimal and many patients with OSAS seek alternative treatment, including surgical treatment .
For surgical treatment planning of snoring and OSAS, identification and determination of the site, pattern and engaging anatomical structure are important . Upper airway anatomical assessments such as CT, MRI and cephalometric measurement are often static and performed during wakefulness, which may not represent dynamic upper airway behavior during sleep. Croft and Pringle described “sleep nasoendoscopy” in 1991 as an endoscopic evaluation of the upper airway during sedation. It was developed in multiple centers throughout Europe and is now widely performed. Kezirian proposed ‘Drug induced sleep endoscopy (DISE)’, and designed the ‘VOTE classification’ that focuses on the specific structures that contribute to obstruction . Although DISE has some limitations such as a limited period of observation and multiple classification systems, it approaches the natural physiologic state of sleep more than currently available diagnostic tools. Multiple classification systems prevent the comparison of results across studies and centers. VOTE classification is a method of characterizing DISE findings focusing on its core feature, the specific structure that contributes to obstruction. This system may be an oversimplification of upper airway structure and it has some limitations for site specific surgical treatment . Although many studies for DISE were performed with Westerners, a study of Asians is rare. In some Asian countries, life patterns such as diet tend to westernization, but the way of life of Asians differs from that of westerners. We based our classification system on a modification of the VOTE system and analyzed site, pattern and degree of obstruction in Korean male OSAS patients by DISE. We also investigate possible links between BMI, AHI and DISE findings.
2
Patients and methods
2.1
General setting of study
In participants consenting for this research, Korean male patients who underwent DISE by one examiner at Busan Saint Mary’s Hospital, ENT department were enrolled. To exclude gender differences, only male patients were enrolled. Data were collected prospectively. This research protocol was reviewed and approved after deliberation by the Busan Saint Mary’s Hospital Institutional Review Board (IRB).
Before DISE, all patients received a thorough ear, nose, and throat examination and a medical history was taken. All patients underwent full night PSG (Polysomnography, WEE-1000K, Nihon Kohden, Japan), and sixty-nine patients were diagnosed by OSAS. Patients with obvious retrognathia, mandibular dysplasia, or who had undergone prior surgery of the soft palate or tongue were excluded.
2.2
Drug induced sleep endoscopy
The DISE technique is as follows. DISE was performed after application of local anesthetic spray in the nasal cavity. Sleep was induced, with patients in supine position, by intravenous administration of midazolam (0.07 mg/kg). In our study, DISE was performed under respiratory monitoring and through the help of an anesthesiologist in the operating room. Once patients were asleep, a 4 mm flexible videolaryngoscope was introduced gently through each patient’s nose. The video images of recorded DISE procedures were later evaluated by one otolaryngologist.
2.3
Classification system
We divided the pharynx into two portions: the retropalatal level (the region of posterior to the soft palate) and the retrolingual level (the region of the pharynx posterior to the vertical portion of the tongue). On this basis, we made our classification system, a modified VOTE classification. Our classification system included the following about the obstruction: site, degree, and the anatomical structure contributing the most. The retropalatal level was subdivided into the palate (antero-posterior diameter), lateral pharyngeal wall (lateral diameter), tonsil (specific structure contributing to obstruction). The retrolingual level was divided into the tongue base (antero-posterior diameter), the lateral pharyngeal wall (lateral diameter), and the epiglottis (specific structure contributing to obstruction). Degree of airway obstruction was categorized as no obstruction (0), partial obstruction (1, 50%–75%), and complete obstruction (2, > 75%) ( Table 1 ).
| Level | Degree of obstruction a | Configuration b | ||
|---|---|---|---|---|
| AP diameter | Lat. diameter | Contributing structure | ||
| Retropalatal | 0/1/2 | Palate | LPW | Tonsil |
| +/− | +/− | +/− | ||
| Retrolingual | 0/1/2 | Tongue base | LPW | Epiglottis |
| +/− | +/− | +/− | ||
a Degree of obstruction has one number for each structure: 0 = no obstruction (no vibration), 1 = partial obstruction (vibration, 50%–75%), 2 = complete obstruction (collapse,>75%).
b Dichotomous configuration noted for structures with degree of obstruction greater than 0.
2.4
Relation between BMI, AHI and DISE finding
BMI was defined as body weight(kg)/height(m) 2 . We classify patients into lower BMI group (BMI < 25) and higher BMI group (BMI ≥ 25), and compared DISE findings. The severity of OSAS is expressed in the apnea hypopnea index (AHI). Apnea was defined as a cessation of airflow for at least 10 s and hypopnea was defined as period of reduction equal to 30% airflow for at least 10 s and 4% ≥ decreased O 2 saturation. The AHI was calculated as sum of total apnea and hypopnea events. Patients who were diagnosed as having OSAS were classified into mild to moderate group (5 ≤ AHI < 30) and severe group (AHI ≥ 30). We also compared the AHI and DISE findings.
Each obstruction level and the anatomical structure contributing the most were calculated separately, with percentages expressed as a fraction of the total number of each subgroup. The sum of the percentages is greater than 100% because it is possible to have more than one most contributing anatomical structure to airway obstruction in each patient. To exclude gender differences, only male patients were included.
2.5
Statistical analysis
All statistical analyses were performed using SPSS (Statistical Package for the Social Sciences, version 17.0, SPSS, Inc., an IBM Company, Chicago, Illinois, USA). The unpaired t test was used to evaluate associations of absence or presence of various obstruction sites and its configurations with each subgroup according to the AHI and BMI. Null hypotheses of no difference were rejected if p-values were less than 0.05. Results were presented as mean and standard deviation.
2
Patients and methods
2.1
General setting of study
In participants consenting for this research, Korean male patients who underwent DISE by one examiner at Busan Saint Mary’s Hospital, ENT department were enrolled. To exclude gender differences, only male patients were enrolled. Data were collected prospectively. This research protocol was reviewed and approved after deliberation by the Busan Saint Mary’s Hospital Institutional Review Board (IRB).
Before DISE, all patients received a thorough ear, nose, and throat examination and a medical history was taken. All patients underwent full night PSG (Polysomnography, WEE-1000K, Nihon Kohden, Japan), and sixty-nine patients were diagnosed by OSAS. Patients with obvious retrognathia, mandibular dysplasia, or who had undergone prior surgery of the soft palate or tongue were excluded.
2.2
Drug induced sleep endoscopy
The DISE technique is as follows. DISE was performed after application of local anesthetic spray in the nasal cavity. Sleep was induced, with patients in supine position, by intravenous administration of midazolam (0.07 mg/kg). In our study, DISE was performed under respiratory monitoring and through the help of an anesthesiologist in the operating room. Once patients were asleep, a 4 mm flexible videolaryngoscope was introduced gently through each patient’s nose. The video images of recorded DISE procedures were later evaluated by one otolaryngologist.
2.3
Classification system
We divided the pharynx into two portions: the retropalatal level (the region of posterior to the soft palate) and the retrolingual level (the region of the pharynx posterior to the vertical portion of the tongue). On this basis, we made our classification system, a modified VOTE classification. Our classification system included the following about the obstruction: site, degree, and the anatomical structure contributing the most. The retropalatal level was subdivided into the palate (antero-posterior diameter), lateral pharyngeal wall (lateral diameter), tonsil (specific structure contributing to obstruction). The retrolingual level was divided into the tongue base (antero-posterior diameter), the lateral pharyngeal wall (lateral diameter), and the epiglottis (specific structure contributing to obstruction). Degree of airway obstruction was categorized as no obstruction (0), partial obstruction (1, 50%–75%), and complete obstruction (2, > 75%) ( Table 1 ).
| Level | Degree of obstruction a | Configuration b | ||
|---|---|---|---|---|
| AP diameter | Lat. diameter | Contributing structure | ||
| Retropalatal | 0/1/2 | Palate | LPW | Tonsil |
| +/− | +/− | +/− | ||
| Retrolingual | 0/1/2 | Tongue base | LPW | Epiglottis |
| +/− | +/− | +/− | ||
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