Lung Clearance Index Best Judge of Nighttime Hypoxemia, Study Suggests

Lung Clearance Index Best Judge of  Nighttime Hypoxemia, Study Suggests
5
(1)

A measure called the lung clearance index (LCI) can predict low blood oxygen levels during sleep in people with cystic fibrosis (CF) better than conventional assessments of lung function, a study suggests.

The study, “Lung clearance index evaluation in detecting nocturnal hypoxemia in cystic fibrosis patients: Toward a new diagnostic tool,” was published in the journal Respiratory Medicine.

Nocturnal hypoxemia refers to abnormally low levels of oxygen in the blood during sleep. This symptom commonly occurs in people with lung diseases like CF, and it can lead to problems including disturbed sleep, pulmonary hypertension, and heart failure. As such, there is a need to identify people who experience nocturnal hypoxemia, particularly in early stages of disease.

Finding predictors of nocturnal hypoxemia, however, has proved challenging. Blood oxygen levels during the day are not always reflective of those while asleep — people can have normal daytime oxygen levels and still experience nocturnal hypoxemia.

Moreover, measurements of lung function — mostly through forced expiratory volume (FEV), which assesses the amount of air a person can exhale in a given length of time — have been found to be poorly predictive of nighttime oxygen levels.

A team led by researchers at the University of Catania, in Italy, tested whether LCI could predict nocturnal hypoxemia.

“The Lung Clearance Index (LCI) is a measure of lung ventilation distribution obtained from a multiple-breath washout technique,” the researchers wrote.

Essentially, LCI is assessed by having a person inhale a ‘tracer gas,’ and then seeing how long it takes for that person to ‘clear’ the tracer gas from their lungs. LCI is generally measured in the number of ‘turnovers’ needed for clearance; a value above seven is typically considered outside of normal.

Researchers evaluated 31 people with stable CF (16 females, 15 males, age range 10–27, all Caucasian) who were being treated at the Cystic Fibrosis Unit of the University of Catania. All had mild to moderate disease, and underwent a battery of assessments, including LCI, FEV, and measures of oxygen levels during the day and at night.

Results showed that, in general, all participants had normal daytime oxygen levels, but mild-to-moderate nocturnal hypoxemia. This was reflected by mean SpO2 scores — a measure of oxygen saturation, the amount of oxygen in the blood based on the percentage of oxygenated hemoglobin, the oxygen-carrying molecule in red blood cells. Patients’ mean daytime SpO2 was 97%, and mean nighttime SpO2 was 93%.

There was a significant negative correlation between LCI and nighttime SpO2. That is, individuals with higher LCI values tended to have lower SpO2 (i.e., worse nocturnal hypoxemia).

The ability of LCI to predict nocturnal hypoxemia was assessed by calculating the area under the receiver operating characteristics curve (AUC) — a measure of how well a given criteria (in this case, LCI) can distinguish between groups (in this case, those with and without nocturnal hypoxemia). An AUC of 1.0 is considered a ‘perfect’ score.

Results showed that the AUC of LCI as a predictor of nocturnal hypoxemia was 0.96 (high predictive accuracy). In contrast, the AUC of FEV was 0.71 (moderate degree of accuracy).

“LCI showed a high effectiveness in predicting nocturnal hypoxemia in stable patients with CF, particularly when compared with a traditional parameter of lung function such as FEV1,” the researchers wrote.

However, “the mechanism linking changes in LCI and nocturnal desaturation remains to be cleared,” they added, noting that no standardized protocols cover the use of LCI in people with CF. Further research is needed to validate the findings of the study.

Marisa, a science writer, holds an MS in Cellular and Molecular Pathology from the University of Pittsburgh, where she studied novel genetic drivers of ovarian cancer. She specializes in cancer biology, immunology, and genetics. Marisa began working with BioNews in 2018, and has written about science and health for SelfHacked and the Genetics Society of America. She also writes/composes musicals and coaches the University of Pittsburgh fencing club.
Total Posts: 336

Patrícia holds her PhD in Medical Microbiology and Infectious Diseases from the Leiden University Medical Center in Leiden, The Netherlands. She has studied Applied Biology at Universidade do Minho and was a postdoctoral research fellow at Instituto de Medicina Molecular in Lisbon, Portugal. Her work has been focused on molecular genetic traits of infectious agents such as viruses and parasites.

×
Marisa, a science writer, holds an MS in Cellular and Molecular Pathology from the University of Pittsburgh, where she studied novel genetic drivers of ovarian cancer. She specializes in cancer biology, immunology, and genetics. Marisa began working with BioNews in 2018, and has written about science and health for SelfHacked and the Genetics Society of America. She also writes/composes musicals and coaches the University of Pittsburgh fencing club.
Latest Posts
  • NTM and urine tests
  • CF projections for 2030
  • mucus and bacteria
  • cell study for CF

How useful was this post?

Click on a star to rate it!

Average rating 5 / 5. Vote count: 1

No votes so far! Be the first to rate this post.

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post?