Wheeze detection as a measure of bronchial challenge in young children with cough-variant asthma and with classic asthma

A breath sound analysis in children with cough variant asthma

BACKGROUND

Cough variant asthma (CVA) is characterized by a chronic cough and bronchial hyperresponsiveness without confirmation of wheezing. Using a breath sound analyzer, we evaluate the characteristics of breath sound in children with CVA.

METHODS

Nine children with CVA (median age, 7.0 years) participated. The existence of breath sounds was confirmed by sound spectrogram. Breath sound parameters, the frequency limiting 50% and 99% of the power spectrum (F₅₀ and F₉₉), the roll-off from 600 to 1200 Hz (Slope) and spectrum curve indices, the ratio of the third and fourth area to the total area of the power spectrum (P₃/P_T and P₄/P_T) and the ratio of power and frequency at 50% and 75% of the highest frequency of the power spectrum (RPF₇₅ and RPF₅₀) were calculated before and after β₂ agonist inhalation. A spirogram and/or forced oscillation technique were performed in all subjects.

RESULTS

On a sound spectrogram, wheezing was confirmed in seven of nine patients. All wheezing on the image was polyphonic, and they almost disappeared after β₂ agonist inhalation. An analysis of the breath sound spectrum showed that P_T, P₃/P_T, P₄/P_T, RPF₅₀ and RPF₇₅ were significantly increased after β₂ agonist inhalation.

CONCLUSIONS

Children with CVA showed a high rate of inaudible wheezing that disappeared after β₂ agonist inhalation. Changes in the spectrum curve indices also indicated the bronchial reversibility. These results may suggest the characteristics of CVA in children.

The highs and lows of wheezing: A review of the most popular adventitious lung sound

Wheezing is the most widely reported adventitious lung sound in the English language. It is recognized by health professionals as well as by lay people, although often with a different meaning. Wheezing is an indicator of airway obstruction and therefore of interest particularly for the assessment of young children and in other situations where objective documentation of lung function is not generally available. This review summarizes our current understanding of mechanisms producing wheeze, its subjective perception and description, its objective measurement, and visualization, and its relevance in clinical practice.

Methacholine challenge test by wheezing and oxygen saturation in preschool children with asthma

Methacholine challenge test (MCT) performed with spirometry is a commonly used test to evaluate bronchial hyperreactivity (BHR) in children. However, preschoolers do not usually collaborate.

OBJECTIVES

To assess the usefulness of MCT through clinical evaluation (wheezing auscultation and decreased pulse arterial oxygen saturation [SpO2]) in recurrent wheezing preschoolers with asthma, in comparison to healthy controls.

METHODS

We performed the MCT (modified Cockroft method) on healthy and on asthmatic preschoolers. The end point was determined by the presence of wheezing in the chest and/or tracheal auscultation (PCw) and/or a decrease in SpO2 of ≥5 from the baseline value (PCSpO2). Maximal methacholine concentration was 8 mg/ml.

RESULTS

The study population comprised 65 children: 32 healthy and 33 asthmatic children. There were no differences in demographic characteristics between the groups. The median methacholine doses for PCw and for PCSpO2 were significantly lower among asthmatic than healthy children: 0.5 mg/ml (0.25-0.5 mg/ml) vs. 2 mg/ml (1-4 mg/ml), respectively, p<0.001; and 0.25 mg/ml (0.25-0.5 mg/ml) and 2 mg/ml (0.5-4 mg/ml), respectively, p<0.001. The best cut-off point of PCw was observed at a methacholine concentration of 0.5 mg/ml (AUC=0.72 [95% CI=0.66-0.77]), its sensitivity was 91%, specificity 43%, PPV 16% and NPV 98%. For PCSpO2 the best cut-off point was a methacholine concentration of 1 mg/ml (AUC=0.85 [95% CI 0.81-0.89]), with sensitivity of 80%, specificity 74%, PPV 49%, and NPV 92%. There were no adverse reactions.

CONCLUSION

MCT using clinical parameters such as wheezing auscultation and SpO2 measurement could be a useful and safe test to confirm BHR among preschoolers.