Hypertonic saline helps to lessen airway wall thickness in children

Automated way of measuring airway structure supports CF treatment

Steve Bryson, PhD avatar

by Steve Bryson, PhD |

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One year of treatment with hypertonic saline, inhaled twice daily, reduced the thickness of the airway walls in children with cystic fibrosis (CF), according to an analysis of clinical trial data.

Researchers used an automated method to assess changes in lung structure captured on CT scans, and supported this method in measuring treatment efficacy in clinical trials and therapy regimens.

The study, “Automatic bronchus and artery analysis on chest computed tomography to evaluate the effect of inhaled hypertonic saline in children aged 3-6 years with cystic fibrosis in a randomized clinical trial,” was published in the Journal of Cystic Fibrosis.

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Inhaled hypertonic saline helps to clear sticky mucus of CF from lungs

Hypertonic saline is a concentrated solution of sodium chloride (common salt) that, when inhaled, helps clear the thick and sticky mucus that marks CF from the lungs. Studies suggest that hypertonic saline can improve patients’ lung function and lower their number of exacerbations, a sudden worsening of lung symptoms.

A Phase 2/3 study called SHIP-CT (NCT02950883) tested an inhaled 7% hypertonic saline against 0.9% isotonic saline (normal salt levels) in preschool children twice daily for 48 weeks (almost one year). Chest CT scans before and after treatment in children ages 3 to 6 found lung damage significantly less likely with hypertonic saline.

Using CT scans from SHIP-CT, researchers applied an automated method — not yet validated when the trial’s data was analyzed — to more objectively assess changes in airway structure in response to hypertonic saline treatment.

The team specifically measured bronchial widening or bronchial wall thickening using the broncho-arterial (BA) ratio, the diameter of a bronchial airway divided by the diameter of its accompanying artery. A BA value of 1 indicates healthy lungs.

CT scans from 115 CF patients were included in this study, covering 113 pretreatment (baseline) and 102 scans at 48 weeks of treatment. In the trial, 60 children were given isotonic saline and 55 received hypertonic saline.

Significantly less bronchial wall thickening seen with hypertonic saline use

At 48 weeks, bronchial wall thickening was significantly lower in the hypertonic saline group compared with the isotonic saline group, as assessed by the ratio of the bronchial wall thickness and arterial diameter. Similar results were seen when the bronchial wall area was divided by the bronchial outer area, a measure of bronchial wall thickening independent of artery diameter changes.

After adjustments, the mean bronchial wall thickness divided by the artery diameter was 0.171 in the isotonic saline group and 0.160 in the hypertonic saline group, with a mean difference of 0.011.

According to the researchers, this finding demonstrated that CF children with hypertonic saline had a 6% thinner bronchial wall at 48 weeks compared with those given isotonic saline.

“A reduction in bronchial wall thickening can reflect both more effective clearance of mucus and/or reduction of inflammatory thickening,” they wrote.

No significant difference in bronchial widening was seen after 48 weeks of treatment, as assessed by both the outer and inner diameter of a bronchial airway divided by adjacent arterial diameter.

Overall, bronchial wall thickening was present in 64% to 75% of BA measurements, and bronchial widening in 28% and 40%. The right upper lobe of the lung was the most affected, data showed.

Weak correlations were found between changes in bronchial wall thickness and lung function, as indicated by the lung clearance index (LCI), which measures how long a tracer gas can be cleared from the lungs.

“The automatic BA-analysis is able to detect and measure a large number of BA-pairs on chest CTs in children … who participated in the SHIP-CT study,” the researchers concluded. “The automatic analysis of BA-dimensions allows for objective and sensitive detection of bronchial wall thickening and bronchial widening.”