System Based Approach
Respiratory Noises: How Useful are They Clinically?

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Although clinicians place considerable weight on the identification of the various forms of noisy breathing, there are serious questions regarding both the accuracy (validity) and the reliability (repeatability) of these noises. To avoid diagnostic errors, clinicians need to consider the whole constellation of symptoms and signs, and not focus on the specific “type” of noise. Given the high error rate with “parent-reported wheeze” there is a need to reexamine the extensive literature on the epidemiology of wheeze in infants and young children, because parent-reported wheeze is unconfirmed by a clinician. It is obvious we need more high-quality research evidence to derive better evidence on the clinical utility of these noises, and their natural history.

Section snippets

Wheeze

Wheeze is a high-pitched, continuous musical noise, often associated with prolonged expiration. While predominantly heard in the expiratory phase, wheeze can occur throughout the respiratory cycle. Basic respiratory physiology tells us that wheeze emanates from the intrathoracic airways, and can be produced by pathology either in the large, central airways, or the small, peripheral airways. The intensity of the wheeze is a poor indicator of the severity of the obstruction. Indeed, if the

Prevalence of noisy breathing

Although wheeze is well studied, there are few observational studies of infants addressing the question of “how common are all forms of noisy breathing?” To answer this question Thornton and colleagues13 studied a birth cohort of almost 300 randomly chosen, normal-term infants in Cambridge, England. This cohort was followed longitudinally from birth to 6 months. Mothers were interviewed at home about any concerns they had regarding their infant's health. In addition, mothers were questioned in

What do parents understand by wheeze?

This question was addressed in a hospital-based observational study of older children.21 A total of 139 children (aged 4 months to 15 years, median 2.5 years) were assessed in the emergency department (ED) to measure the agreement between clinician and parent report on the noise. There was a less than 50% agreement between a clinician's finding wheeze and parents' report of wheeze. That is, in children presenting to ED with wheeze (or asthma), where the doctor finds wheeze, 39% of the parents

Validation of respiratory questionnaire to measure wheeze

A study from Brazil attempted to validate a questionnaire on wheeze in infancy.22 In this study of young children presenting to the ED with an acute respiratory illness, parents answered a questionnaire on wheezing (adapted from the International Study of Wheezing in Infants).22 A total of 209 infants aged 12 to 15 months were assessed. Fifty-six of these were reported to be currently wheezing and this was confirmed in 43. A further 153 parents reported “no current wheeze” and this absence of

Comparing the severity of parent-reported wheeze with clinician-confirmed wheeze

One observational study measured the lung function of children with “confirmed” (by clinicians) with “unconfirmed” (parent-reported) wheeze.23 This study was part of a large UK birth cohort (n = 1000) and describes a subgroup of 454 children followed to the age of 3 years. A total of 186 (41%) of these children had “parent-reported wheeze,” and in 130 (29%) the wheeze was “confirmed” by a clinician. Specific airway resistance (sRaw) was measured at the age of 3 by plethysmography. The major

Utility of videos as a “gold standard”

An observational study from the United Kingdom investigated the terminology used by parents to describe noisy breathing in infants younger than 18 months of age.7 The parents of approximately 100 infants with noisy breathing were interviewed. These infants were from three separate populations: hospital inpatients (n = 44), hospital outpatients (n = 19), and a community sample (n = 29). Almost half the parents used the term “wheeze” (or whistle/musical sound) to describe noisy breathing

Natural history/prognosis of noisy breathing

An important question is whether early respiratory noises predict subsequent wheeze. The study by Turner and colleagues28 described the natural history of the full range of these early respiratory noises. This observational study was part of a large Scottish birth cohort of approximately 2000 infants. A respiratory questionnaire (modified ISAAC questionnaire) was administered at the age of 2 and 5 years. The key findings were the following: children with a “whistle” at age 2 were more likely to

Do parents and children agree on symptoms of wheeze?

In an attempt to validate parent-reported exercise wheeze in older children (age 6 to 18 years), 97 children were assessed in summer camps in California.31 Both criterion validity and construct validity were assessed by comparing reported symptoms on exercise with measured lung function following an exercise provocation test. Parents completed a telephone survey of their child's symptoms with exercise. As expected, parents generally report fewer exercise-related symptoms of wheeze than their

Acoustic analysis

Adult studies have highlighted problems with both accuracy (validity) and reliability (or repeatability) of respiratory signs using a stethoscope.32, 33, 34 Given the increased difficulty of examining young, uncooperative children, the assumption is that errors will be substantially greater in pediatric practice. In an attempt to improve the utility of respiratory noises, computerized acoustic analysis has been evaluated. Most studies have been in adults and the published data in children are

Utility of tracheal sound recordings

Several groups have used tracheal sound recordings in children, particularly to explore this method as a more sensitive indicator of wheeze in bronchial provocation testing of very young children. Godfrey and colleagues36, 37 used nebulized AMP challenge in 80 preschool children and found detection of wheeze acoustically to be a more sensitive way of detecting airway obstruction than the stethoscope (PC wheeze), thus enabling the challenge to be ceased earlier (and safer). Pediatric studies

Use of video questionnaires to identify stridor

Video questionnaire has been used to identify upper airway abnormalities.42 A group of 43 preschoolers (range 3 to 58 months, median 17 months) with noisy breathing were studied via fiberoptic bronchoscopy. Thirty (70%) had wheeze as their main symptom, 19 were clinician confirmed, whereas the other 11 had only parent-reported wheeze. Parents were shown previously validated video clips of wheeze, stridor, and other airway noises. Ten of the 30 parents who initially reported wheeze identified

Summary

A number of conclusions can be drawn from the research evidence on noisy breathing (Box 1). It is clear that there are major problems with both the accurate (valid) and reliable (reproducible) identification of “respiratory noises.” This is particularly so when the noise is “parent reported,” and not confirmed by a clinician.

Clearly, clinicians must exercise great care when diagnosing specific types of noisy breathing to ensure it is not incorrectly labeled. An error in recognition will result

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