Respiratory Muscle Strength Correlated with Abdominal Circum- ference in Obese Individuals in Pre-Bariatric Surgery

Background: The presence of alterations in respiratory mechanics of obese population, cause acceleration in the breathing pattern, making it of low amplitude and causing an increase in the work. The measures of Maximal Inspiratory Pressure (MIP) and Maximal Expiratory Pressure (MEP) can be used to quantify the strength of respiratory muscles. Objective: To evaluate the relationship of increased abdominal circumference with respiratory muscle strength in obese patients in pre-operative bariatric surgery by comparing the values with the values predicted by the equation of Costa et al. Methods: This study involved 154 patients. All belonging to the group of patients attended the clinic Life Worth in process of pre-operative bariatric surgery. Were Measured Inspiratory Pressures and Maximal Expiratory Pressure (MIP and MEP) by manometer. Result: the average age of 37.7 ± 10.3 years, with a mean BMI of 41.5 ± 4.6, showing the average circumference of 123.4 ± 12.2 cm. Showing a correlation of MIP and MEP with the CA to p<0.05. Conclusion: Both genders, do not present a correlation of muscular strength with abdominal circumference.


Introduction
In recent years, obesity is one of the main problems of public health [1,2] Being a disease not transmissible and chronic, with an increase in adipose tissue, which is frequently related to health risks [3][4][5][6] Obesity is defined by a Body Mass Index (BMI) according to the classification of the World Health Organization (WHO) [1] is divided into: the top of the weight -overweight (BMI 25-29.9kg/ m2) and obesity (BMI 30-34.9kg/m2) grade II (BMI 35-39.9kg/ m2) level III (BMI > 40 kg/m2) [2,[7][8][9][10] There are various factors that interfere with the respiratory mechanics of obese [11] the fat stored in the abdominal cavity (Gynoid) restricts the scalability and reduces lung volumes [11,12]. There is a general concept that complacency total respiratory is reduced by the impairment chest and lung, being the component chest the more important. A reduction in the compliance of the chest wall is attributed to fat around the ribs and chest [13]. The presence of alterations in respiratory mechanics of this population cause acceleration in the breathing pattern, making it of low amplitude and provoking an increase in work [11,14] The strength of respiratory muscles can be evaluated directly by means of static as the maximal respiratory pressures, using the manuvacuômentro. The measures of Maximal Inspiratory Pressure (MIP) and Maximal Expiratory Pressure (MEP) can be used to quantify respiratory muscle strength in healthy individuals of different ages [15] MIP is a measure of inspiratory muscle strength, while the MEP measures the strength of the abdominal muscles and intercostal [16] Due to the inefficacy of respiratory muscles, muscle strength and endurance may be reduced [7,17] The values of MIP and MEP are dependent not only on the strength of respiratory muscles, but also changes in lung volume in which they are incurred the measures and the corresponding pressure value of the elastic recoil of the respiratory system [15,18] The values of MIP and MEP measurements are compared with the values predicted by the equations of Costa [19].
According to Arora [20] the weight has an influence on the maximal respiratory pressures and may be related to muscle mass, therefore changes in weight could affect the mass of the diaphragm, influencing the respiratory muscle performance. Due and efficiency of combating obesity bariatric surgery has been considered the most effective method of treatment [8,21]. The objective of this study was to correlate the increase in Waist Circumference (WC) with respiratory muscle strength in obese patients in preoperative bariatric surgery, comparing the values with the values predicted by the equation of Costa [19].

Methodology
It is a study not randomized, with cross-sectional design, not controlled, experimental, mixed and aggregated. The study included 154 patients (36 men and 118 woman), with ages between 17 and 69 years. All who participated in the study, were patients who seek the Vida Vale clinic for bariatric surgery, accompanied by a multidisciplinary team specialized in the digestive system team specialized in Digestive system (Especializados em Moléstia do Aparelho Digestivo-EMAD). Included patients who had a Body Mass Index (BMI) = 35 kg/m2, with no current dependence on illicit drugs and alcoholism and presenting cognitive conditions for understanding simple orders. All volunteers were instructed on how to study procedures, in accordance with the requirements of Resolution 466/12 of the National Health Council. The study was approved by the research ethics in humans with the opinion number 1458166 and the participants investigated signed the informed consent form. The preoperative evaluation included clinical history, physical examination and measurements of respiratory muscle strength. The measures were obtained with the patient in the sitting position, using a manometer NS 120-SR of the mark Instrumentation Industries®, where the patient was instructed to put a stop nose and attaching his mouth in a disposable mouthpiece. For the measurement of MIP, individuals have expired in the filler until the residual volume and, subsequently, will generate a maximal inspiratory effort against an airway occlusion. For the MEP, individuals have inspired the nozzle up to Total Lung Capacity (TLC), and then a maximum effort against expiratory an airway occlusion during this last measure, individuals held with the hands the muscles of the perioral face to prevent leakage and accumulation of air in the lateral region of the oral cavity. To this end, three measurements were performed and the biggest result was recorded in the record of each volunteer.
The anthropometric assessment, patients remained in orthostatic position, without shoes. The body mass index was obtained by a digital scale (Welmy; Santa Bárbara D'Oeste -SP, Brazil), with a maximum capacity of 300 kg. Height was measured by a stadiometer of own scales and the calculation of the BMI was calculated using the equation: body mass index (kg)/estatura² (m) [22] The abdominal circumference was measured with the patient standing in front of the examiner, using a tape measure in centimeters, flexible and inelastic, directly on the skin, without compressing the tissue, located between the ribs and the iliac crest. Using the cut-off point of 94-102 cm for mens and 80-88 cm for woman [23][24][25][26]. The data were analyzed by SPSS software v.20 (IBM SPSS Statistics). The normality of the data was tested by means of the Shapiro-Wilk test, which proved to be parametric and therefore, have been demonstrated in mean and standard deviation. We calculated the simple frequency between men and woman. The comparison between men and woman for the variables studied was performed using the Student's t-test for independent samples. The correlations were performed through Pearson's correlation test. It was established the value of statistical significance at p < 0.05. Table 1 shows the basic characteristics of the 154 patients involved and evaluated in this study for bariatric surgery, with an average age of 37.7 ± 10.3 years (17 to 69 years). The mean BMI was 41.5 ± 4.6 (35 to 57), with 56.49% of patients presenting degree III obesity. In relation to waist circumference, 100% of the volunteers are above the established by the society in accordance with the genres (94-102 cm for men and 80-88 cm for woman). Among men and woman, the mean waist circumference was 123.4 ± 12.2 cm (99 to 163 cm).

Men (n=36)
Woman ( The illustration shows the distribution of patients according to the classification of BMI. The mean body mass index was of 41,5Kg/m² with a range of 35 to 57,5 kg/m², being the most prevalent among woman obesity III with 50.42% and 77.14% also have obesity grade III (Figure 1). The (Figures 2,3).   demonstrates the maximum pressures carried out, comparing with the pressures predicted, according to sex. With inspiratory muscle strength in woman of 120.1 ± 37.3% of predicted, expiration 60.6 ± 18% of predicted; among men inspiratory muscle strength 52.2 ± 19.5% of predicted and expiratory 58.5 ± 17.6% of predicted. The values of MIP and MEP measured and predicted the volunteers are shown in Table. Presenting as mean MIP of 73.7 ± 23.8 cm H2O (20 to 120 cm H2O), MEP of 61.0 ± 18.2 cm H2O (20 to 120 cm H2O). There was no correlation of MIP and MEP with the CA (p<0.05) (

Discussion
One of the goals of the preoperative evaluation, in patients who are candidates for bariatric surgery, is to identify if there are reductions in the volumes, strength and abilities due to the increase in weight, as described in the literature [27] obesity may alter re-spiratory mechanics, lung volumes, airway resistance and respiratory muscles [28] In this study, the muscle strength and maximal expiratory pressure of patients are reduced when compared to normal values. A study [29] was conducted to evaluate the muscle strength respiratory function in morbidly obese patients by means of pressure manometry. At the end of the study, concluded that overweight and obesity have significant injury in the ventilatory pressures maximal inspiratory pressure and maximal expiratory pressure, because they might interfere in the movement of the diaphragm and chest wall excursion [29] As seen in our study, the pressures are reduced, except the inspiratory muscles of woman, showing above normal values. Magnani and Caetano [30] evaluated the circumference and the respiratory pressures of 99 obese individuals aged between 20 and 64 years and found that obesity does not interfere with the pressure generated by muscles breathing, even in obese patients with the distribution of body fat more superior, shown by the waist/hip ratio. In another study [31] with 103 obese women (57 obese and 46 healthy), concluded that obese woman has a higher respiratory muscle strength when compared to healthy. The variables of the bioimpedance and obesity had a direct relationship with the respiratory muscle strength. The variables of waist circumference and waist-hip/ did not influence the strength under obese. In harmony with our findings, the increase in circumference has no relation with the force.
The increase in respiratory muscle strength in patients can be explained by an adaptation to chronic overload that accompanies obesity, shown by the largest amount of fibers of type II and a small amount of fibers of type I [32] and this is a possible explanation for the inspiratory muscle strength of woman being higher than the predicted value. Second Forti [33] obese woman morbid showed higher inspiratory muscle strength than eutrophic, and seem to have similarity in the behavior of the force of the expiratory muscles, however these findings are inconclusive. Complementing that of the three equations used to reference value, The Harik-Khan seems to be more appropriate to calculate the values MIP for obese vicious. Although some studies [27,29] show that the lung capacity and forces are reduced in the morbid obese patient, others have shown that morbidly obese patients when compared to normal patients, do not present a significant difference in lung function. There is a general concept that complacency total respiratory is reduced by the impairment chest [28] however, the literature shows a large discrepancy on the subject and on standardization of reference values.
The proposal of the study was to verify if the abdominal circumference has an influence on the forces of respiratory muscle of obese patients. Considering the data obtained with the evaluation, it was possible to compare the influence of BMI on the strength respiratory, noting a negative correlation between waist circumference and the MIP and MEP in patients, even those with a decrease of force, calculated by the equations proposed by Costa [19].

Conclusion
The men evaluated presented respiratory muscle strength less than the predicted, since the obese patients, only maximal expiratory pressure were reduced. Both sexes show no correlation of muscular strength with abdominal circumference.