Have you ever heard of newborn screening? Basically, newborn screening is a public health service which can identify potential hormone-related, genetic, or metabolic conditions. Since early identification is so crucial to early treatment and better outcomes, newborn screening is incredibly important. According to Cystic Fibrosis News Today, testing functional residual capacity (FRC) during newborn screening could help identify newborns with cystic fibrosis (CF). While FRC has been used before to detect CF, there is limited data in terms of FRC and newborn screening, so doctors sought to make this connection clearer. Check out the full study results published in Pediatric Pulmonology.

Functional Residual Capacity (FRC)

So what exactly is FRC? As described by Erin Hopkins and Sandeep Sharma, FRC is: 

the volume remaining in the lungs after a normal, passive exhalation [which] in a normal individual…is about 3L. The FRC also represents the point of the breathing cycle where the lung tissue elastic recoil and chest wall outward expansion are balanced and equal.

Currently, despite its importance, evaluating lung function in newborns can be difficult. This is because many current tactics require radiation exposure and sedation. Thus, researchers from the Indiana University School of Medicine began wondering how FRC could be used to achieve this goal. 

To begin, researchers evaluated data from 45 children. Data was collected either retrospectively or prospectively. Altogether, patients had undergone lung function tests – such as FRC, forced vital capacity (FVC), or forced expiratory flow (FEF) –  during hospitalization, clinical trials, or study testing. Findings show:

• While some patient scores were within the “norm,” a lower FVC score highlighted poor or progressively worsening lung function.
• When evaluating the FRC score, researchers determined that children with CF sometimes had hyperinflated lungs. In fact, 44% of patients within this study had hyperinflation.
  • Hyperinflation occurs when air becomes trapped in the lungs, preventing adequate airflow throughout the body. Learn more about lung hyperinflation.
• A cut-off value of 36 breaths per minute indicated lung hyperinflation. Identifying this also correlated with FRC. 

Ultimately, the researchers determined that measuring respiratory rates could be a clinical marker of CF. However, they found that evaluating FRC is a sensitive, accurate, and noninvasive way to identify hyperinflated lungs and CF. 

Cystic Fibrosis (CF)

Caused by CFTR gene mutations, cystic fibrosis (CF) is characterized by progressively worsening respiratory and digestive system damage. Because CF is inherited in an autosomal recessive pattern, patients must receive one defective gene from each parent. As CFTR mutations impact salt movement, patients with CF have thick, sticky mucus which builds up throughout the body. When this mucus collects, it can trap bacteria and clog airways, causing a host of other issues. In addition to lung damage, CF mucus also prevents digestive enzymes from doing their job, causing nutrient absorption difficulties. Symptoms include:

• Intestinal blockage (in newborns)
• Salty skin
• Persistent coughing or wheezing
• Foul-smelling, greasy stools
• Constipation
• Infertility (male)
• Exercise intolerance
• Shortness of breath
• Nasal inflammation
• Poor weight gain
• Frequent lung infections
• Rectal prolapse
• Respiratory failure