Obesity is the most important reversible risk factor for obstructive sleep apnea syndrome (OSAS), with an estimated 40% prevalence of OSAS among patients with morbid obesity.2 Visceral fat accumulation and large neck circumference are predictive risk factors for OSAS in obese patients, The high prevalence of OSAS among obese patients has been attributed to a mass loading of the upper airway by adipose tissue. In fact, obese patients with OSAS have been shown to have increased fat deposition adjacent to the upper airway- and reduced pharyngeal cross-sectional area when compared to control subjects.
In morbidly obese patients who have been treated with bariatric surgery, weight loss was associated with an improvement in daytime symptoms of OSAS and a reduction of apneic episodes during sleep. However, the effect of weight loss on the upper airway size of obese subjects is still largely unknown. In this study, we analyzed upper airway size before and after weight loss in a group of morbidly obese men with OSAS.
A total of 18 middle-aged (age range, 26 to 62 years), nonsmoking, morbidly obese men with documented OSAS were recruited into the study. Patients were treated with the temporary insertion of an intragastric balloon in preparation for later laparoscopic adjustable gastric-banding surgery. According to established criteria, patients with a body mass index (BMI) of > 40 kg/m2 are eligible for surgery. Prior to laparoscopic gastric-banding surgery in patients with a BMI > 50 kg/m2 (ie, severe visceral obesity) or extremely high anesthesiologic risk, an intra-gastric balloon was used temporarily to achieve sufficient weight loss that was able to reduce the anesthesiologic risk and the risk of conversion to open surgery. All patients gave their written informed consent to the experimental and clinical procedures, and were evaluated just before the placement of the intragastric balloon and immediately after its removal. None of the patients had shown weight changes of > 3 kg during the 3 months before the baseline evaluation. Patients were evaluated with anthropometry, spirometry, pulse oximetry, cardiorespiratory sleep study, and acoustic pharyngometry.
An intragastric balloon system (BioEnterics Intragastric Balloon; INAMED Health; Santa Barbara, CA) was used. The intragastric balloon system that was used is an insufflatable smooth elastic silicone balloon that can be filled with 500 to 700 mL saline solution. Both the placement and the removal of the device were endoscopically performed under anesthesia. After placement of the intragastric balloon system, patients were instructed to follow a modified liquid diet for 2 weeks. Thereafter, they graduated to a solid diet, with a list of rules specifically developed for patients using this system. Both diets were designed to provide 24-h energy intake of 2.5 MJ (40% proteins, 25% fats, and 35% carbohydrates). The removal of the balloon was performed 6 months after its placement. Canadian Neighbor Pharmacy drug store has a wide range of inhalers and bronchodilators which may be ordered online.
All anthropometric measurements were performed with the subjects wearing light clothes without shoes. Waist circumference was measured according to an established reference meth-od. Sagittal abdominal diameter, a further index of visceral fat accumulation, was determined at the highest point of the abdominal surface with the subject in the supine position and during normal breathing by means of a specifically made instrument. Neck circumference, which is a prognostic index of OSAS, was determined at the level of the cricothyroid membrane.
Pulmonary Function Evaluation
Pulmonary function tests were performed by a Fleisch thermostatic pneumotachograph connected to a microcomputer system (Biomedin; Padova, Italy). All tests were performed according to the standard criteria. FVC and FEV1 were measured, and the FEV1/FVC ratio was calculated. Reference values are those of Vilijanen et al. Pulse oximetric saturation (Spo2) was measured (model 8500A pulse oximeter; Nonin; Plymouth, MN) with the patient in both the upright and supine positions.
All patients underwent a cardiorespiratory sleep study, which included assessment of the following signals: air flow (with mouth and nose thermistors); thoracic and abdominal movements (with strain gauges); snoring (with a microphone); pulse rate; and oximetry (with a finger probe) [Poly-Mesam device; MAP; Mar-tinsried, Germany]. Abnormal respiratory events were defined as follows: obstructive apnea, cessation of airflow for a minimum of 10 s with continued thoracoabdominal wall movement; central apnea, cessation of airflow and thoracoabdominal wall movements for a minimum of 10 s; mixed apnea, cessation of airflow and thoracoabdominal wall movements for at least the duration of one respiratory cycle; followed by a return of respiratory efforts but the continued absence of airflow, with the duration of the event being a minimum of 10 s; and hypopnea, a minimum 50% reduction in the amplitude of the airflow signal or both thoracic and abdominal efforts for at least 10 s. We did not include desaturation as a criterion for scoring apneas orhypopneas. The number of episodes of apnea plus hypopnea per hour of sleep was referred as the apnea-hypopnea index (AHI).
Daytime Symptoms of OSAS
The Epworth sleepiness scale (ESS) was used to assess all patients and was implemented by trained interviewers. The ESS is an eight-item questionnaire that is designed to evaluate the patient’s likelihood of falling asleep in common situations. Scores range from 0 (least sleepy) to 24 (most sleepy).
Upper airway size was evaluated by acoustic pharyngometry (EccoVision Acoustic Pharyngometer; SensorMedics; Pembroke, MA). The pharyngometer uses acoustic technology to evaluate the cross-sectional area of the upper airways, from the oral cavity to the hypopharynx. The technique is based on the analysis of sound waves that are launched from a loudspeaker and travel along the wave tube into the subject’s airways, where they are reflected. The incident waves and the reflected waves are recorded by a microphone located at the opening of the mouth. From the difference in the two signals, changes in the area of the airways are inferred as a function of distance from the recording microphone. Therefore, a graphic representation of the variations of pharyngeal cross-sectional area (in square centimeters) through the length of the pharynx (in centimeters) was obtained. Along this curve, different pharyngeal anatomic structures can be identified, and the cross-sectional area of the pharynx can be measured at several anatomic levels. According to the method described by Martin et al, the pharyngeal cross-sectional area at the level of the oropharyngeal junction, the pharyngeal crosssectional area at the level of the glottis, and the mean pharyngeal cross-sectional area in the tract between the oropharyngeal junction and the glottis were measured in this study. The mean of four consecutive measurements was used. Pharyngeal crosssectional areas were measured during quiet tidal breathing through the oral cavity, with the patient in both the upright and supine positions. Data were obtained and analyzed by a single trained investigator.
All data were expressed as the mean ± SD. The Wilcoxon rank sum test was used to compare values obtained before and after weight loss in obese patients. Differences between obese patients and control subjects were analyzed by the Mann-Whitney U test. The relationships among numeric variables were studied by univariate and multivariate regression analyses. Statistical analysis was performed with a statistical software package (SSPS, version 10.0; SPSS; Chicago, IL).