Lung sound analysis may help assess treatment efficacy, predict asthma attacks in children
A recently developed technology for analysing lung sound (ic700) may be able to assess efficacy of inhaled corticosteroid therapy and predict asthma attacks in children, as demonstrated by a study from Japan.
“The ic700 [which uses the index of the chest wall and sound intensity, both at 700 Hz] enables the evaluation of airflow limitation in asymptomatic asthmatic children with airway narrowing … [it] represents a new and easy procedure for the noninvasive monitoring of childhood asthma,” said the researchers.
Participants were 70 children with asthma, aged 9 months to 15 years (mean age 6.4 years, 58.6 percent male, mean ic700 score 1.8), who had not received continuous inhaled corticosteroid and/or leukotriene receptor antagonists and who presented as outpatients at the Minami Wakayama Medical Center in Tanabe, Japan.
Lung sound recording (carried out for ≥20 seconds with a sound sensor placed at the upper right anterior of the chest) was conducted in the asymptomatic phase before and at 1, 2, 4, 6, and 8 weeks following inhaled corticosteroid treatment initiation. Asthma control was assessed at 10 weeks after treatment and ic700 scores at 4, 6, and 8 weeks were compared with symptoms or attacks occurring in the following 2 weeks. Participants were divided into an uncontrolled and well-controlled group.
Participants experienced a significant improvement in mean ic700 scores after 8 weeks of treatment, with a mean 1.7 dB before treatment and 0.2 dB at 8 weeks post-treatment for participants aged over 6 years and 1.9 dB before treatment and -0.5 dB at 8 weeks post-treatment for participants under 6 years (p<0.001 for both age groups). [Respirology 2017;doi:10.1111/resp.13109]
The ic700 cut-off value for predicting asthma attacks in 2 weeks was evident in all children at 4, 6, and 8 weeks after treatment initiation with area under the curve values of 0.90, 0.92, and 0.86, respectively, and a high degree of sensitivity, specificity, and positive and negative predictive values at each time frame (94, 77, 60, and 98 percent, respectively, at week 4; 83, 89, 88, and 83 percent, respectively, at week 6; and 84, 82, 79, and 86 percent, respectively, at week 8; all p<0.001).
Exhaled nitric oxide levels, Asthma Control Test (ACT), and Child-ACT scores did not differ between patients in the well-controlled and uncontrolled groups at 4, 6, and 8 weeks post-treatment.
“The ic700 represents the change in intensity of inspiratory lung sounds in a rather asymptomatic state,” said the researchers.
“When the intermediate-frequency components of lung sounds are transferred to the chest wall, the ic700 increases, implying that there is asthmatic airway dysfunction even when children are asymptomatic. We assume that the change in lung sounds with mild flow limitation is caused by airway wall thickening and mild airway narrowing in the small airways,” they said.
The researchers highlighted that issues such as the impact of individual differences on nonparoxysmal lung sounds and determining the most suitable index for young children need to be addressed before this technology can be incorporated into routine clinical practice.