At least 3-4 children in every class suffer from lung diseases such as asthma, sickle cell disease or cystic fibrosis, and lung diseases are the most common cause of long term illness in children. Understanding how the lungs work and develop during childhood is important for the diagnosis and management of these conditions.
One way to understand how the lungs work is by doing some breathing tests. Breathing tests are now available even for very young children, but we need to know what to expect in a healthy child before we can detect if lung disease is present in those with breathing difficulties.
We know that some factors affect how lungs grow, such as height, age and sex:
During childhood, lung function increases with age and height. The graph above shows values of Forced Expired Volume in 0.5 second (The amount of air which can be forcibly exhaled from the lungs in the first 0.5s after taking the deepest breath possible) in 622 healthy children from 0-9 years of age. It demonstrates that height (and age) is a major determinant of lung growth.
The graph above shows how lung function changes throughout life. During childhood lung function increases rapidly until 20-25 years of age. Up until puberty, lung function is similar in boys and girls of the same height and age, however as children go through puberty, chest growth is more rapid in boys and subsequently men on average have larger lungs than women of the same age and height.
As shown above, the lungs grow rapidly during childhood so ‘expected values’ are usually based on height. However, this does not take ethnicity into account.
It has been shown previously that lung function (vital capacity) in healthy black soldiers was 6 to 12% lower than in white European soldiers.
The differences are thought to be due to differences in body physique and proportions.
Therefore, the relative contribution of body shape, size and composition needs to be investigated further in order to understand the underlying basis for the ethnic differences observed.
Our team has recently developed improved ‘lung growth charts’ for white European children, but these are not suitable for children from other ethnic groups, in whom respiratory diseases are very common. We therefore need to study lots of healthy children of all ethnicities, so that we can treat all children equally. In this study we investigated the relationship between body size and composition and lung growth in healthy children of all ethnicities (SLIC study). This has improved our understanding of how the lungs change as children grow and how to interpret the lung function results of children with lung disease irrespective of ethnic origin.