For chronic obstructive pulmonary disease (COPD) or emphysema patients, maintaining a healthy body weight is an important aspect of disease management. That is because obesity can often lead to a worsening of symptoms, as well as a decrease in both exercise tolerance and quality of life. In addition, obesity been recognized for having a significant effect on respiratory function in both healthy and diseased lungs.
This relationship was further explored by Dr. Stephen Littleton, attending physician in the division of Pulmonary, Critical Care, and Sleep Medicine at Cook County Hospital in Chicago and assistant professor of medicine at Rush University Medical Center, in the January 2012 issue of Respirology. The study, “Impact of obesity on respiratory function,” examined the respiratory function of both obese and average patients, making special note of breathing patterns, respiratory mechanisms, and lung volumes.
What Dr. Littleton found was that “obese patients tend to have higher respiratory rates and lower tidal volumes (the volume of gas inhaled and exhaled during one respiratory cycle),” wherein the respiratory rate increases to compensate for depressed tidal volumes. However, lung volume – particularly expiratory reserve volume (ERV), or the maximum volume of air that can be expelled from the lungs after normal expiration – is the most consistently affected respiratory function in these patients.
In addition, increased BMI has also been found to result in the reduction of pulmonary function in the following tests:
- · Forced expiratory volume in one second (FEV1)
- · Forced vital capacity (FVC)
- · Total lung capacity
- · Functional residual capacity
- · Expiratory reserve volume
Yet, weight loss can be an effective means to improving these symptoms.
“Perhaps one of the best ways of studying the effects of obesity on pulmonary function is to study the same group of patients before and after weight loss, [with]each patient acting as their own control,” said Dr. Littleton. “It seems that most of the changes associated with obesity are reversed after significant weight loss, and are therefore likely to be caused by obesity itself.”