Introduction
The nature and management of the noisy breathing infant and preschool
child is always a challenge for the paediatrician and general physician.
In clinical practice the evaluation of respiratory sounds is based on
parental history, describing noises heard at a distance and on doctors’
physical qualification of auscultatory findings. Although different lung
sounds are well defined1, the evaluation by parents
and even by physicians can be problematic. Parents and caregivers use a
variety of rather descriptive terms to report respiratory sounds that
could often be misleading. They use a variety of terms for the same
sound and the same terms for different sounds.2-4Parental misinterpreting is well known especially in infants and young
children with overuse of the term “wheeze”, describing many different
respiratory sounds.3,5,6 An observational study by
Elphick et al. demonstrated that “rattle” in infants younger than 18
months is often labelled by parents as “wheeze”.6
Respiratory noises can be considered as clinical features of certain
conditions with underlying aetiologies consisting of pathologically
distinct processes and different treatment options. Therefore, confusion
in terminology must be avoided, and accurate and correct description of
breath sounds is important. While early wheeze has become a predictor of
subsequent persistent asthma7-9, other lung sounds
could be a marker for different disease entities, not related to asthma.
While the “wheezy infant” is seen as a distinct clinical entity, the
“rattling infant” is not, perhaps wrongly. Infants who mainly
“rattle”, were less likely to wheeze at older age and more likely to
outgrow their noisy breathing.5,10
Rattles are believed to be caused by excessive airway secretions, often
in combination with a viral infection, which move during normal airflow
within the central airways. On occasion rattling disappears after
coughing and clearing of airway secretions.11 Clinical
guidelines on the treatment of rattling infants and young children are
lacking and only few studies focus on this topic. The need for treatment
should depend on the presence of subjective discomfort to avoid needless
medication. Wheezes on the other hand, are most commonly associated with
airway obstruction due to various mechanisms, e.g., bronchoconstriction,
airway wall oedema, intraluminal obstruction (e.g., foreign body or
mass), external compression, or dynamic airway
collapse.11
Differentiating the heterogeneous group of noisy breathing infants is
important to further delineate the most appropriate approach, given that
they have different aetiologies, natural histories and different
responses to therapy.5 An early differential diagnosis
by the use of non-invasive or minimally invasive techniques is of high
importance for a “precision medicine” approach preventing under- and
overtreatment. Exhaled breath analysis has potential to improve noisy
breathing diagnosis. Volatile organic compounds (VOCs) in exhaled breath
can be valuable biomarkers that reflect metabolic processes. This study
aims to investigate the clinical potential of exhaled volatile
biomarkers in the differentiation of noisy breathing infants. The
current manuscript examined whether the severity of rattling could be
estimated from the exhaled breath profile.