Infant weight gain linked to better lung function in those with cystic fibrosis

Infants with cystic fibrosis who gain weight more quickly than their peers also have better lung function, say researchers at Lucile Packard Children's Hospital.

The findings suggest that physicians and parents should redouble their efforts to keep very young children with the condition well-nourished. It also reinforces previous research indicating that lung damage begins very early in life even in children with few or no symptoms of the disorder.

'Freedom from respiratory symptoms and gaining weight steadily are important to infants this age,' said pediatric pulmonary scholar Christin Kuo, MD. 'Infants with cystic fibrosis often have trouble with both.' Kuo presented her research at the annual meeting of the Pediatric Academic Societies that was held on May 3 in Hawaii.

A link between nutrition and pulmonary function has been well-established in adults with cystic fibrosis, but until now it's not been proven in infants who may not yet show outward signs of the disorder. Precisely how nutrition could affect pulmonary function remains to be determined.

Although cystic fibrosis is known primarily as a lung disease, the disorder also affects the digestive system and interferes with proper food digestion and absorption. In fact, before the advent of routine prenatal and newborn screening for the disorder, the first sign that a child might be affected was a lack of bowel movements within 48 hours of birth, unusual-looking or unusual-smelling bowel movements, or failure to grow at a normal pace. The resulting caloric deficit for infants can make staying healthy even more difficult.

'Children with cystic fibrosis expend a lot of calories just breathing,' said Kuo, 'and, because they suffer from frequent lung infections, they're probably not eating really well either.' In addition to encouraging affected children to eat plenty of food, physicians use enzymes, vitamins and nutritional supplements to keep them well-nourished.

Kuo and her colleagues at Packard Children's Center for Excellence in Pulmonary Medicine and Cystic Fibrosis analyzed data from 27 infants with cystic fibrosis between the ages of 2.5 to 40 months. Fourteen patients were clinically symptomatic with either respiratory distress or malabsorption. When they compared the infants' daily weight gain over an average interval of six months with the results of lung function tests performed during the same intervals, the researchers found that those who grew more rapidly retained less air in their lungs using a technique that measures lung function in infants.

The phenomenon of retention, known as 'air trapping,' is an important measure of lung health. Although no one expels all the air in their lungs with each breath, abnormally high or low levels of trapping are signs of pulmonary problems. Retaining excess amounts of air in the lungs, perhaps due to inflammation in the tiniest airways of the lung, reduces the volume of fresh air that can be inhaled in the next breath and lowers breathing efficiency.

Kuo's research confirms an association between nutritional status and lung health even in young infants with cystic fibrosis and suggests one way to possibly slow the progress of the disorder.

'We may need to intensify our nutritional rehabilitation of these children,' said Kuo, who is expanding her studies to include a larger number of infants and a variety of novel lung function tests. 'It would enhance our ability to care for these infants if we have an accurate and readily available pulmonary function test for this age group to track the progress of this disorder,' she said. 'There's room for a lot more research in this area.'

Kuo's colleagues at Packard Children's include Jacqueline Zirbes, RN; Carol Conrad, MD; David Cornfield, MD; and Carlos Milla, MD.