Polysonographic changes in obese patients with indication of bariatric surgery

ABSTRACT Introduction: obstructive Sleep Apnea Syndrome (OSAS) is a serious confition that compromises the quality of life and survival of patients. Its main risk fator in adults is obesity and the gold standard test for diagnosis is polysomnography (PSG), mainly through the apneia-hypopnea index (AHI). Objective: to analyze the sleep pattern of obese patients with indication for bariatric surgery, determining the main polisomnographic parameters compromised by obesity. Methods: This work is a cross-sectional study with analysis of polysomnography perfomed in patients with obesity in the peroperative period of bariatric surgery at a clinic in Vitória da Conquista/BA during 2017. The Epi Info 7 platform was used for analysis of the data. Results: 58 polysomnographic reports were analyzed, with 56,9% morbdly obese and 43,1% non-morbid. The prevalence of OSAS was 70,68% and de AHI ranged from zero to 84,6 with a mean of 19,47±22,89 e/h. morbidly obese, compared to “non-morbid”, had a longer saturation time below 80% and 90% (0,4±0,93 vs. 0,12±0,45 e 4,87±7,38 vs. 1,36±2,87 respectively; p-value=0,02 in both), worse index respiratory disorders ((29,24±25,36 vs. 16,88±16,21; p-value=0,02), higher AHI (24,71±25,68 vs. 12,56±16,67; p-value=0,02), higher hypopnea index values (16,41±17,10 vs. 6,99±8,52; p-value=0,006) and lower minimum saturation (78,24±9,80 vs. 85,24±6,33; p-value=0,004). Conclusions: the high prevalence of OSAS found confirms its indication in the preoperative period of bariatric surgery. The main respiratory event involved in most individuals with OSAS was the hypopnea index.


INTRODUCTION
T he Obstructive Sleep Apnea and Hypopnea Syndrome (OSAHS) is a sleep-related respiratory disorder characterized by upper airway obstruction that results in a cycle of hypoxemia, increased work of breathing, and frequent micro-arousals 1 .As obesity represents a very prevalent and reversible risk factor for OSAHS in adults 2 , its global increase directly impacts the syndrome rates 3 .There is a predominance in obese and middleaged individuals, reaching more than 40%, substantially higher than the prevalences of 2% in women and 4% in men in the general population 4,5 .Along with systemic arterial hypertension (SAH), OSAHS is one of the most prevalent comorbidities of obese patients in the preoperative period of bariatric surgery 6,7 .
Although the pathophysiological mechanism is not yet fully elucidated, it is accepted that the adipose tissue in the neck compresses and narrows the upper airway lumen, inducing it to collapse, causing a drop in oxyhemoglobin saturation, an increase in adrenergic discharge, and its consequent clinical manifestations, which are better analyzed through polysomnography [8][9][10] .
OSAHS is related to several morbidities, such as SAH, acute myocardial infarction, stroke, traffic accidents, among others, and is therefore considered a public health problem 11 .It chronically alters the sensitivity of the peripheral chemoreflex, causes cardiovascular dysfunction and metabolic dysregulation associated with varied symptoms, mainly daytime sleepiness, nocturnal awakening, and nocturnal suffocation, especially in the long term 12,13 .Even so, most patients with the syndrome are asymptomatic, which does not mean a milder disease 13 .
The standard exam for OSAHS diagnosis is type 1 polysomnography (PSG) and currently most bariatric surgery programs have PSG as a routine preoperative assessment 14 .In general, the syndrome reaches its incidence peak around the sixth decade of life, but in individuals with a relevant BMI increase, this peak moves to the fifth decade 2 .The objective of this work is to identify the polysomnographic alterations found in obese patients in the preoperative period of bariatric surgery.

METHOD
This is a cross-sectional study with analysis of polysomnographies performed in obese patients in a clinic located in Vitória da Conquista, state of Bahia (BA), Brazil.
We selected all 58 patients who underwent the examination in a sleep medicine facility in the preoperative evaluation of bariatric surgery during 2017, in Vitória da Conquista/BA.We analyzed the results using the Epi Info Movements Index (PLM), Respiratory Disturbances Index (RDI), Apnea-Hypopnea Index (AHI), Apnea Index (AI), Hypoapnea Index (HI), average saturation (AVSAT), minimum saturation (MINSAT), time with blood oxygen saturation below 90% (SAT <90%) and time with blood oxygen saturation below 80% (SAT <80%).
We divided patients according to BMI in morbidly obese (grade 3) and non-morbidly obese (grades 2 and 1).As for age, we considered two groups, one with patients aged 39 years or less and another containing patients aged 40 years or more.Finally, regarding AHI, we divided the patients twice, both into two groups: the first had groups of patients classified as "normal and mild" versus "moderate and severe", and the other considered "non-apneic" versus "apneic" patients.It   The group of "morbidly obese" showed worsening of polysomnographic parameters when compared to the group of "non-morbidly obese" in the SAT <80% (p=0.02),SAT <90% (p=0.02),RDI (p=0.02),HI (p=0.006),AHI (p=0.02), and MINSAT (p=0.004), as shown in Table 2.
As for the AHI divided in "Moderate and severe" versus "Normal and mild" with other polysomnographic variables, we observed a worse apnea-hypopnea index in patients with higher weight (p=0.007) and BMI (p=0.03), in addition to being related to worse MINSAT (p<0.00001) and AVSAT (p<0.00001), as shown in Table 4.
When analyzing "apneic" versus "non-apneic" individuals, the AHI showed statistical significance with sex and age group.While females corresponded to 17 "non-apneic" patients and 32 "apneic", the male group had all the subjects classified as "apneic" (p=0.03).
Among individuals under 40 years of age, 20 were in the "apneic" group and 13 in the "non-apneic" one.In patients aged 40 years or more, the values were 21 and four, respectively (p=0.04) (Table 5).
The occurrence of sleep apnea was influenced by age, so that the "non-apneic" group had a mean age of 32.29±7.17years versus 40.60±9.39years in the "apneic" group (p=0.001).Finally, analyzing the    15 , also failed to prove the impact of obesity on these variables.
We observed that middle-aged patients have worse indexes of AROUI, RDI, AHI and HI regardless of obesity, since there was no statistically significant relationship between obesity degrees and age group.Sleep quality is multifactorial, and obesity is not necessarily the main factor involved.However, when present, obesity can worsen and hinder the treatment of several other diseases that share the same risk factors and clinical characteristics, such as metabolic syndrome and atrial fibrillation 18 .
The relationship between OSAHS and obesity was mainly observed through the increase in hypopneas to the detriment of other variations of sleep-related respiratory disorders, being the main variable found.

DISCUSSION
Grade 3 obese patients had more severe AHI values than the ones with grades 1 and 2, showing a direct relationship between the increase in BMI and AHI worsening.
When comparing these values with the prevalence of this syndrome in the normal population, an alarming increase can be seen 4 .The study by Tangerina et al. 15 diverged from the results herein presented in that the average ages of patients affected by OSAHS vs. the non-affected ones were 44.6±10.2 and 53.1±9.1 years, respectively.However, the authors of the study believe that, among the variables involved in OSAHS, age is the least influential if the average is within the values considered as middle age (between 40 and 55 years).
The proportions found regarding AHI agreed with the findings of Weingarten et al. 16 , who classified 22.45% as non-apneic, 30.99% with mild apnea, 15.93% The studied sample differed from the epidemiology described in the literature regarding sex, as it is a procedure sought mainly by the female population, in up to 70% 19 .AHI was directly related to weight and Fernandes Polysonographic changes in obese patients with indication of bariatric surgery not just BMI, which can be explained by most of the population studied being female and also having higher rates of obesity.
The discrepancy between the number of patients according to sex may have affected the results and, thus, disagrees with the literature.This effect may have been increased by the population of men studied, all of whom have some degree of OSAHS, and a greater proportion is over 40 years of age.Men sought surgery with a later and worse OSAHS condition, since the search for medical service tends to be delayed, generally when the weight interferes significantly with daily activities 20 .
Furthermore, women are also motivated by individual aesthetic issues and even by external interference imposed by the society they belong to, leading them to seek surgical intervention earlier 21,22 .Even so, a very similar proportion between sexes was observed by Modena et al. 2 in the preoperative period of bariatric surgery, confirming that the population profile in surgery clinics may differ from the general population.
The relationship of OSAHS with age group and sex allows to infer that when the average age is lower or very close to the beginning of the middle age, BMI can be an important and relevant criterion for the development of the syndrome.This association with male sex has been described in other studies and may be due to the distribution of the adipose tissue of obese men, more common in the vicinity of the upper airways, causing worsening of ventilatory mechanics 5,[23][24][25] .
Classically, OSAHS can be treated with continuous positive airway pressure (CPAP), although with low adherence 4 .Researches have evaluated the impact of CPAP and respiratory physiotherapy on pulmonary mechanics in the pre-and postoperative period of bariatric surgery, with positive results 26,27 , which can therefore serve as an adjuvant in the treatment of the syndrome.Some limitations can be reported in the present study, such as the discrepancy in the number of patients between sexes, the lack of association between the OSAHS degree and the difficulty of clinical control of comorbidities, and, most importantly, the nonperformance of control PSG after weight reduction to compare it with the previous result.Studies with a larger number of patients and based on sample calculations can overcome some of the imperfections and be more reliable.

R E S U M O R E S U M O
the recommendations of the American Academy of Sleep Medicine (AASM) regarding polysomnographic criteria, which classify OSAHS taking into account the apnea/hypopnea index (AHI), which reflects the number of apneas and hypopneas per hour of sleep.The condition is considered mild when the AHI is between 5 and 15, moderate when between 15 and 30, and severe when greater than 30.Values below 5 are considered normal.The variables studied were age, sex, weight, body mass index (BMI), height, total sleep time (TST), sleep latency (LATENCY), REM sleep latency (REMLAT), sleep efficacy (SE), non-REM sleep time 1 (NREM1), non-REM sleep time 2 (NREM2), non-REM sleep time 3 (NREM3), REM sleep time (REM), time wake after sleep onset (WASO), Arousals Index (AROUI), Periodic Limb

Fernandes
Polysonographic changes in obese patients with indication of bariatric surgery Continuous weight gain can further compromise the quality of life and sleep, including the worsening of respiratory disorders, which can interfere with other clinical conditions, worsening prognosis, morbidity, and mortality.The main respiratory event involved in most individuals with OSAHS was the hypopnea index.

Table 3 .
Analysis of the variables AROUI, RDI, AHI and HI according to age group.

Table 6 .
comparison of the distribution of apnea degrees between the sample of each study.

Table 5 .
Normal patients versus those affected by OSAHS according to gender and age group.
to obese ones without separating them by degrees.Other authors, such as Tangerina, et al.