Lung function assessment by electrical impedance tomography among obese patients

Obesity is a growing problem worldwide. It is well reported that obesity is associated with various degrees of respiratory function compromise, which could be contributed by mechanical factors as well as co-morbid diseases such as asthma. While spirometry is the gold standard for lung function measurement, it does have the drawback of only being able to measure the global function of the lungs and is uncomfortable for those with difficulty using a large degree of effort. A prospective cross-sectional study was conducted in Queen Mary Hospital, Hong Kong to recruit Chinese obese and non-obese subjects, to compare and correlate the lung function parameters measured by electrical impedance tomography (EIT) and spirometry. Obesity was diagnosed based on the local definition of body mass index of 25 kg/m² or above, using the cut-off value for Asian population. A total of 42 obese subjects and 35 non-obese subjects were included in this study. The spirometric values (Litres) measured by spirometry and EIT demonstrated good correlation among obese and non-obese subjects, with Pearson correlation coefficient of 0.705 and 0.673 for FEV₁ among obese and non-obese subjects, p-value < 0.01. The Pearson correlation coefficients were 0.568 and 0.541 for FVC among obese and non-obese subjects respectively, p-value < 0.01. EIT technology has comparable performance in lung function measurement among obese and non-obese subjects. It can suggest that EIT is a potential tool for lung function measurement in obese subjects as in non-obese subjects.