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 Table of Contents  
ORIGINAL RESEARCH REPORT
Year : 2022  |  Volume : 19  |  Issue : 4  |  Page : 119-122

Analysis of spirometric variables with increasing body mass index in normal and overweight healthy individuals


1 Department of Physiology, Panimalar Medical College Hospital & Research Institute, Poonamallee, Chennai, Tamil Nadu, India
2 Crescent School of Pharmacy, B.S. Abdur Rahman Crescent Institute of Science and Technology, Vandalur, Chennai, Tamil Nadu, India

Date of Submission24-May-2022
Date of Acceptance14-Oct-2022
Date of Web Publication09-Nov-2022

Correspondence Address:
Dr. Ilham Jaleel
Panimalar Medical College Hospital and Research Institute, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcls.jcls_41_22

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  Abstract 


Background: The relationship between the parameters of body mass index (BMI) and lung function has been established by numerous studies done earlier. Those studies have been done mainly on obese individuals, but only a very few studies have been done in people with normal BMI or overweight group. Our aim is to analyze the various spirometric variables, namely forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), forced expiratory flow (FEF 25%–75%), and peak expiratory flow rate (PEFR), with respect to increase in the BMI in otherwise normal healthy subjects. Methods: The present study design is a randomized experimental parallel-group study. Sixty individuals who were otherwise healthy without any respiratory illness were selected for this study. Their anthropometric measurements were taken. Based on WHO classification, the subjects were grouped as follows: Group I with a BMI of 18.5–24.9 as a normal weight group and Group II with a BMI of 25–29.9 as the overweight group. Using Medispiror, the spirometric variables were determined. Analysis of spirometric variables, namely FEV1, FVC, FEF 25%–75%, and PEFR, were all done using the appropriate statistical method. Results: The results showed that there was a significant decrease in all spirometric variables except PEFR with an increase in BMI. However, the decrease in FVC was relatively more than the decrease in FEV1. Conclusion: This study can be concluded that there is a significant decrease in spirometric variables, namely FEV1, FVC, and FEF 25%–75%, as the BMI increases even in normal individuals who are not obese.

Keywords: Body mass index, forced expiratory flow 25%–75%, forced expiratory volume in 1 s, forced vital capacity, peak expiratory flow rate


How to cite this article:
Jaleel I, Ahamed HN. Analysis of spirometric variables with increasing body mass index in normal and overweight healthy individuals. J Clin Sci 2022;19:119-22

How to cite this URL:
Jaleel I, Ahamed HN. Analysis of spirometric variables with increasing body mass index in normal and overweight healthy individuals. J Clin Sci [serial online] 2022 [cited 2022 Nov 30];19:119-22. Available from: https://www.jcsjournal.org/text.asp?2022/19/4/119/360619




  Introduction Top


It is well known that the respiratory well-being of an individual is affected by obesity. The reason is an increase in the consumption of oxygen and increased carbon dioxide production. Stiffening of the respiratory system can occur leading to an increase in the mechanical work required for breathing.[1],[2] The increase in body mass leading to alteration in the airway function has caused concerns about whether the mechanical effects of increasing body mass index (BMI) contribute to airway remodeling mechanics of the respiratory system that could induce subclinical airway dysfunction. Numerous studies have been done previously demonstrating the opposite relationship between increasing BMI and lung volumes.[3] A number of studies that have been done, state that an increase in body weight, especially obesity, can cause a decrease in lung volume.[4],[5],[6],[7],[8] In obese people, increased work of breathing leads to breathlessness and wheezing.[9] There can be a direct effect of obesity on airway caliber, lung volume, or respiratory muscle strength.[10],[11] In obesity, reduction in functional residual capacity (FRC) is more significant. This is because FRC becomes similar to residual volume (RV) in morbid obese conditions. However, changes in total lung capacity (TLC) and RV are small and TLC is usually maintained in normal and obese individuals.[4] In addition to the above findings, few studies have reported that FRC and expiratory reserve volume can decrease with increasing BMIs.[12],[13],[14],[15],[16] With increasing BMI, spirometric variables such as forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) tend to decrease, however, they tend to be within the normal range.[17],[18] Spirometric variables, namely FVC, FEV1, and forced expiratory flow rate (FEF) 25%–75%, tend to decrease with extreme obesity.[19] There is numerous literature that concludes that expiratory flow decreases in association with an increase in body weight. Numerous studies have reported the changes in spirometric variables in obesity. However, only a few studies have been done on people with BMI in the normal range and overweight. The present work aims to study the effects of increasing BMI on lung function among individuals having the normal range of BMI and overweight BMI. This will help us to understand the detrimental effects of increasing BMI even before an individual becomes obese.


  Methods Top


The participants

The participants of 60 females aged between 18 and 40 were recruited from a community-based population living in Pallavaram, Chennai, Tamil Nadu, India. They were explained about the study and written consent was obtained. A questionnaire was given to them. It included questions regarding their personal habits such as smoking, whether they were asthmatics with or without treatment, and sociodemographic data which would influence the spirometric variables.

The inclusion criteria are the participants who were free from any respiratory illness and comorbid conditions such as hypertension and diabetes. Smokers were excluded from the study. Data were collected on various anthropometric measures including height and weight. A clinical stadiometer was used to measure height in bare or stocking feet. Bodyweight was measured with a calibrated precision scale. The study was approved by the institutional human ethical committee (IHEC#: 935/SBMC/IHEC/2012–104), Sree Balaji Medical College and Hospital, Chennai.

Calculation of body mass index

BMI was calculated by dividing the weight in kilograms by the square of the height in meters (Kg/m2).

Measurement of spirometric variables

Spirometry was done using a computerized spirometer (“Medspiror” Helios 401–RMS recorder and medicare system, Chandigarh, India). The Medspiror RMS recorder is calibrated before the beginning of the spirometry test as per the manufacturer's instructions. The reliability and validity of Medspiror Helios 401 RMS are high as confirmed by the 95% confidence interval when the parameters were repeated for three times. Age, sex, weight, the height of the subject, and the ambient temperature were recorded and fed into the spirometer. The subject was given instruction to take a deep breath and blow into the mouthpiece in a sitting position quickly and forcefully as possible. FEV1, FVC, FEF 25%–75%, and peak expiratory flow rate (PEFR) were measured. The best of the three maneuvers was selected for analysis. The predicted values for the variables were also used in the analysis.

Grouping of participants

The study participants were divided into two groups based on their BMI. Group I with a BMI of 18.5–24.9 is termed as normal weight women (n = 22) and Group II with a BMI of 25–29.9 is termed as overweight women (n = 25). Thirteen participants were excluded from the study.

Statistical analysis

Statistical analysis was performed using GraphPad Prism 4.0. The data of all the variables were expressed in mean ± standard error of the mean, an unpaired t-test with Welch's correction was performed. The result was considered statistically significant if P = < 0.05.


  Results Top


Variation of forced expiratory volume in 1 s and forced expiratory volume in 1 s Predicted %

[Figure 1]a and [Figure 1]b represents the variation of FEV1 and FEV1 PRED% in two different BMI range groups. The mean value of FEV1 for normal and overweight group was found to be 1.85 ± 0.16 vs. 1.34 ± 0.07; t (2.792) =28.36 (P < 0.01) and FEV1 for normal and overweight was found to be 79.27 ± 5.34 vs. 66.84 ± 2.80; t (2.06) =32.02 (P < 0.05), respectively. Both the parameters decreased significantly in the overweight group as compared to the normal weight group.
Figure 1: (a) Shows the variation of FEV1 in individuals in the normal and overweight category. **Represents P < 0.01, overweight versus normal weight. (b) Shows the variation of FEV1 PRED % in individuals in the normal and overweight category. *Represents P < 0.05, overweight versus normal weight category. FEV1: Forced Expiratory Volume in 1s

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Variation of forced vital capacity and forced vital capacity PRED %

[Figure 2]a and [Figure 2]b represents the variation of FVC L and FVC %. The mean value of FVC for normal and overweight group was found to be 2.23 ± 0.20 vs. 1.44 ± 0.07; t (3.427) =26.65 (P < 0.01) and FVC PRED% for normal and overweight was found to be 79.41 ± 5.10 vs. 66.5 ± 2.88; t (2.20) =33.41 (P < 0.05), respectively. Both the parameters significantly decreased in the overweight group as compared to the normal weight group.
Figure 2: (a) Shows the variation of FVC in individuals in the normal and overweight category. ** Represents P < 0.01, overweight versus normal weight. (b) Shows the variation of FVC PRED % in individuals in the normal and overweight category. * Represents P < 0.05, overweight versus normal weight category. FVC: Forced Vital Capacity

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  Variation of forced expiratory flow 25%–75% and forced expiratory flow 25–75 PRED% Top


[Figure 3]a and [Figure 3]b represents the variation of FEF (25%–75%) and FEF 25–75% PRED%. The mean value of FEF 25–75% for normal and overweight group was found to be 2.29 ± 0.25 vs. 1.67 ± 0.14; t (2.1.2) =33.36 (P < 0.05) and FEV1% PRED% for normal and overweight was found to be 63.18 ± 5.34 vs. 49.6 ± 2.90; t (2.23) =32.76; (P < 0.05), respectively. Both the parameters are significantly decreased in the overweight group as compared with the normal weight group.
Figure 3: (a) The variation of FEF 25-75 in individuals in the normal and overweight category. *Represents P < 0.05, overweight versus normal weight. (b) Shows the variation of FEF 25-75 PRED % in individuals in the normal and overweight category. *Represents P < 0.05, overweight versus normal weight category. FEF: Forced Expiratory Flow

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Variation of peak expiratory flow rate and peak expiratory flow rate PRED%

[Figure 4]a and [Figure 4]b represents the effect of normal weight and overweight on PEFR and PEFR PRED%. The mean value of for normal and overweight group was found to be 4.63 ± 0.35 vs. 4.30 ± 0.26; t (0.749) =39.58; P = NS) and PEFR PRED% for normal and overweight was found to be 73 ± 5.532 vs. 72.6 ± 2.84; t (0.096) =31.62; P = NS), respectively. Both the parameters are decreased in the overweight group as compared with the normal weight group but they are not statistically significant. There were significant differences in the spirometric variables FEV1, FVC, and FEF 25–75%, though the values remained within the normal range. However, the difference in PEFR was not significant between the two groups.
Figure 4: (a) The variation of PEFR in individuals in the normal and overweight category. (b) Shows the variation of PEFR PRED % in individuals in the normal and overweight category. PEFR: Peak Expiratory Flow Rate

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  Discussion Top


Obesity is becoming a major health issue nowadays. An increase in body weight has its own impact in clinical medicine, especially in pulmonary medicine, due to its effect on lung volumes. Recent studies show that an increase in body weight is associated with symptoms such as breathlessness and wheezing. However, these studies suggest that the respiratory mechanics are affected rather than the airflow obstruction.[7],[19] Hence, it is very important to know the relation between increasing BMI and lung function tests.

It is well known from previous studies that spirometric variables such as FEV1 and FVC decrease with increasing BMI. However, the variation in FEV1 and FVC is small. In healthy obese children and adults, the variation is within the normal range.[17],[18] Even in morbidly obese individuals, the FEV1/FVC ratio is well preserved or increased. This shows that both parameters are affected to the same extent. Hence, it can be understood that obesity has an impact on lung volume rather than an airway obstruction. It is well known that an increase in body weight affects the function of the respiratory system, which depends on the interaction of the lungs with the chest wall and muscles. Truncal obesity causes a reduction in chest wall compliance and thereby affecting respiration. It is evident from our data that there is a decline in FVC as the BMI increases even in the normal to the overweight category. This data clearly indicates that a decline in lung function begins even before a person becomes prone to overweight. The reason for the same being the rise in the intra-abdominal pressure with increasing BMI, having a mechanical effect on the diaphragm.[9] The variation in PEFR is not significant between the two groups. Age has been found to be an important factor rather than BMI in determining the PEFR in healthy individuals. The previous study has shown that age and height as predictors of PEFR and the association of higher BMI with lower PEFR are seen in children.[20]


  Conclusion Top


Our study has given us the information that there is significant variation in the spirometric variables, namely FEV1, FVC, and FEF 25%–75%, with relation to BMI even in normal, overweight, or obese individuals and the decline in FVC is more when compared to FEV1. This may be helpful for clinicians to avoid over-diagnosing obstructive airway disease in persons who are overweight and obese.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Bhardwaj P, Poonam K, Jha K, Bano M. Short communication effects of age and body mass index on peak expiratory flow rate in Indian population. Indian J Physiol Pharmacol 2014;58:166-9.  Back to cited text no. 19
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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