The Relationship Between Anthropometric Measures, Blood Gases, and Lung Function in Morbidly Obese White Subjects

Abstract

BackgroundObesity may cause adverse effects on the respiratory system. The main purpose of this study was to investigate how various measures of obesity are related to arterial blood gases and pulmonary function.MethodsThis is a cross-sectional study of consecutive morbidly obese patients with normal lung function. Blood gas samples were taken from the radial artery after 5 min of rest with subjects sitting upright. Lung function measurements included dynamic spirometry, static lung volumes, and gas diffusing capacity.ResultsThe 149 patients (77% women) had a mean (SD) age of 43 years (11 years) and BMI of 45.0 kg/m2 (6.3 kg/m2). The mean expiratory reserve volume (ERV) was less than half (49%) of predicted value, whilst most other lung function values were within predicted range. Forty-two patients had an abnormally low pO2 value (<10.7 kPa [80 mmHg]), while eight patients had a high pCO2 value (>6.0 kPa [45 mmHg]). All anthropometric measures correlated significantly with decreasing pO2 and increasing pCO2 (all P values < 0.05). BMI, neck circumference (NC), and waist circumference (WC) were negatively correlated with ERV (r = −0.25, −0.19, −0.21, respectively, all P values < 0.05). Multiple linear regression showed that BMI, WC, and NC were significantly associated with pO2 after adjustments for age, gender, and pack-years (all P values < 0.001). The models explained 34–36% of the variations in pO2. BMI, NC, and WC were also significantly associated with pCO2 (all P values < 0.05).There was no significant association between waist-to-hip ratio and blood gases (both P values > 0.27).ConclusionsBoth central and overall obesity were associated with unfavorable blood gases and low ERV.

Pulmonary function and blood gases after gastric bypass and lifestyle intervention: a comparative study

“…Low ERV has been associated with decreased compliance and small airway closure resulting in impairment of gas exchange , and we have previously shown that ERV is positively associated with pO 2 and negatively associated with pCO 2 . Moreover, low ERV and high IC may also lead to an increased contribution of highly ventilated and poorly perfused lung units, resulting in ventilation/perfusion mismatch .…”

“…Dynamic and static lung volumes, gas diffusing capacity and arterial blood gases were measured. Compared with lifestyle intervention, surgery resulted in a significantly greater increase in forced vital capacity (mean [95% confidence interval] between-group difference, 7 [4][5][6][7][8][9][10]%), forced expiratory volume in 1 s (7 [5][6][7][8][9]%), total lung capacity (5 [1][2][3][4][5][6][7][8]%), vital capacity (7 [4-9]%), functional residual capacity (18 [12][13][14][15][16][17][18][19][20][21][22][23][24]%), expiratory reserve volume (48 [30-66]%) and partial pressure of oxygen in arterial blood (0.5 [0.0-1.0] kPa). These associations either disappeared or diminished after adjusting for weight loss.…”

“…On the contrary, elevated inspiratory capacity (IC) probably reflects the relative preservation of TLC in the presence of decreased FRC (8). Moreover, in morbidly obese subjects with normal lung function, several measures of obesity are associated with low arterial oxygenation, arterial carbon dioxide retention and low ERV (9).…”

Adiposity markers and lung function in smokers: a cross-sectional study in a Mediterranean population

“…However, other factors such as body weight can exert an influence on lung function [3]. Specifically, excess weight has a negative impact on the respiratory system due to its effect on gas exchange, respiratory mechanics, muscular endurance and breath control [4, 5]. No consensus exists about the physiopathological mechanisms by which excess weight leads to respiratory complications, although it seems that these include mechanical impact on the diaphragm (impeding descent into the abdominal cavity) or on the chest wall (changes in compliance, the work of breathing and elastic recoil) [6].…”

Effect of Alveolar Recruitment on Oxygenation and Carbon Dioxide Elimination During Laparoscopic Bariatric Surgery and Comparison With Pressure Controlled and Volume Controlled Ventilation

“…7 Pneumoperitoneum and systemic resorption of CO2 associated with laparoscopic surgery may further impact oxygenation in the obese. Reduction in arterial oxygenation during anaesthesia has been seen to be greater in obese compared with lean patients and this is directly related to the increase in BMI.…”