Kota Hirai

Forced Oscillation Technique and Childhood Asthma

Most infants and preschool children are not able to voluntarily perform the physiological maneuvers required to complete the pulmonary function tests that are used in adults and older children. Recently, commercial devices using forced oscillation technique (FOT) suitable for young children have become available. In devices with FOT, an oscillation pressure wave is generated by a loud speaker, is applied to the respiratory system, usually at the mouth, and the resulting pressure-flow relationship is analyzed in terms of impedance (Zrs). Zrs encompasses both resistance (Rrs) and reactance (Xrs). Rrs is calculated from pressure and flow signals, and is a measure of central and peripheral airway caliber. Xrs is derived from the pressure in the phase with volume and is related to compliance (Crs) and inertance (Irs). These parameters individually indicate the condition of the small and large airways in each patient and indirectly suggest the presence of airway inflammation. It is agreed that the clinical diagnostic capacity of FOT is comparable to that of spirometry. One of the advantages of FOT is that minimal cooperation of the patient is needed and no respiratory maneuvers are required. The use of FOT should be considered in patients in whom spirometry or other pulmonary function tests cannot be performed or in cases where the results of other tests appear to be unreliable. In addition, this approach is effective in assessing bronchial hyperresponsiveness. Considering these qualities, FOT is a useful method to study pulmonary function in preschool children with asthma.

A novel method for detecting airway narrowing using breath sound spectrum analysis in children

BACKGROUND Using a breath sound analyzer, we investigated new clinical parameters that are rarely affected by airflow in young children. METHODS A total of 65 children with asthma participated in this study (mean age 9.6 years). In Study 1, the intra- and inter-observer variability was measured. Common breath sound parameters, frequency at 99%, 75%, and 50% of the maximum frequency (F99, F75, and F50) and the highest frequency of inspiratory breath sounds were calculated. In addition, new parameters obtained using the ratio of sound spectra parameters, i.e., the spectrum curve indexes including the ratio of the third and fourth area to the total area and the ratio of power and frequency at F75 and F50, were calculated. In Study 2, 51 children underwent breath sound analyses. In Study 3, breath sounds were studied before and after methacholine inhalation. RESULTS In Study 1, the data showed good inter- and intra-observer reliability. In Study 2, there were significant relationships between the airflow rate, age, height, and spirometric and common breath sound parameters. However, there were no significant relationships between the airflow rate and the spectrum curve indexes. Moreover, the spectrum curve indexes showed no relationships with age, height, or spirometric parameters. In Study 3, all parameters significantly changed after methacholine inhalation. CONCLUSIONS Some spectrum curve indexes are not significantly affected by the airflow rate at the mouth, although they successfully indicate airway narrowing. These parameters may play a role in the assessment of bronchoconstriction in children.

A clinical method for detecting bronchial reversibility using a breath sound spectrum analysis in infants

BACKGROUND Using a breath sound analyzer, we investigated clinical parameters for detecting bronchial reversibility in infants. METHODS A total of 59 infants (4-39 months, mean age 7.8 months) were included. In Study 1, the intra- and inter-observer variability was measured in 23 of 59 infants. Breath sound parameters, the frequency at 99% of the maximum frequency (F99), frequency at 25%, 50%, and 75% of the power spectrum (Q25, Q50, and Q75), and highest frequency of inspiratory breath sounds (HFI), and parameters obtained using the ratio of parameters, i.e. spectrum curve indices, the ratio of the third and fourth area to total area (A3/AT and B4/AT, respectively) and ratio of power and frequency at F75 and F50 (RPF75 and RPF50), were calculated. In Study 2, the relationship between parameters of breath sounds and age and stature were studied. In Study 3, breath sounds were studied before and after β2 agonist inhalation. RESULTS In Study 1, the data showed statistical intra- and inter-observer reliability in A3/AT (p=0.042 and 0.034, respectively) and RPF50 (p=0.001 and 0.001, respectively). In Study 2, there were no significant relationships between age, height, weight, and BMI. In Study 3, A3/AT and RPF50 significantly changed after β2 agonist inhalation (p=0.001 and p<0.001, respectively). CONCLUSIONS Breath sound analysis can be performed in infants, as in older children, and the spectrum curve indices are not significantly affected by age-related factors. These sound parameters may play a role in the assessment of bronchial reversibility in infants.

A lung sound analysis in a child thought to have cough variant asthma: A case report

Cough variant asthma (CVA) is an asthma phenotype and a common cause of chronic cough.1 Clinically, CVA is diagnosed by a prolonged cough without wheezing, bronchial hyperresponsiveness and effectiveness of b2 agonist inhalation.2 Recently, the utility of lung sound analyses for assessing airway constriction has been studied.3,4 In this report, we describe a child diagnosed with CVA who underwent a lung sound analysis from the first visit to the day after developing asthma. A 5-year-old boy attended our hospital for an investigation of prolonged dry coughing in February, 2013. He had been healthy all his life, with no history of wheezing. His total serum IgE was 24 IU/ml, and no specific IgEs tomain allergens were detected (positivity to Japanese cedar pollen developed at 7 year of age). A chest X-ray examination showed no abnormalities. Other diseases, such as asthma, post nasal drip syndromes and prolonged cough with respiratory infections, were ruled out. Although we were unable to perform spirometry due to the patients refusal, bronchial reversibility wasmeasured by a forced oscillation technique. The total respiratory resistance (R5) was decreased by 2.8 cmH2O/L/sec ( 20.4%) after b2 agonist inhalation.5 An analysis of the lung sounds was carried out using an exclusive pulmonary sound analysis device (LSA-2000, Kenz Medico, Saitama, Japan).4 The sound spectrogram (Fig. 1a) was used to confirm the existence of wheezing. In addition, the inspiratory lung sounds were analyzed by a fast Fourier analysis and displayed as a spectrogram (Fig. 1b). The parameters of the sound spectrum were determined for a single segment, which had the maximum power and the highest frequency range (Fig. 1c). The data were automatically calculated by an original personal computer software program.4 Common parameters, namely the frequency limiting 99% of the power spectrum (F99) and the parameters obtained using the ratio of parameters, the ratio of the third and fourth area to total area under the curve (A3/AT and B4/AT [dBm

A new method for objectively evaluating childhood nocturnal cough

Hz]) and the ratio of power and frequency at F75 and F50 (RPF75 and RPF50 [dBm/Hz]), were calculated.6 It has been reported that bronchodilatation with b2 agonist inhalation increases A3/AT, B4/AT, RPF50 and RPF75 values.6 At the first visit, no wheezes were detected. We noted no marked changes in the sound spectrogram (Fig. 2a, b), and the main lung sound parameters before and after b2 agonist inhalation (A3/AT; 12.4e9.7, B4/AT; 6.4e6.3, RPF75; 4.7e3.1, RPF50; 4.5e4.7). Two-week treatment of inhaled b2 agonist was clearly effective

Consistently high levels of exhaled nitric oxide in children with asthma

Cough is so common that the best method for evaluating nocturnal cough in children is required.

Changes in the breath sound spectrum during methacholine inhalation in children with asthma

Background:  Exhaled nitric oxide (eNO) levels in children are unstable because they are regulated by many potent factors. The purpose of the current study was to evaluate the reliability of eNO levels between a long interval and other lung functions in normal and asthmatic children.

Objective measurement of frequency and pattern of nocturnal cough in children with asthma exacerbation

An effort‐independent breath sound analysis is expected to be a safe and simple method for clinical assessment of changes in airway function. The effects of bronchoconstriction and bronchodilation on novel breath sound parameters in asthmatic children were investigated.

Changes in the breath sound spectrum with bronchodilation in children with asthma

BACKGROUND Although a number of patients with asthma report experiencing persistent cough during sleep, it has not yet been objectively investigated. OBJECTIVE To classify cough severity and evaluate a characteristic pattern of cough frequency in children with asthma using an objective cough monitoring system. METHODS An objective cough monitoring system that specialized in children was used to measure cough frequency and nocturnal cough patterns. Coughs were recorded with microphone and accelerometer and analyzed using a customized software program. The number of nocturnal coughs and the pattern of cough frequency in 30-minute intervals were measured along with the severity of each asthma exacerbation, and the results were compared with children without asthma. RESULTS The total overnight cough count of 34 children with asthma was higher than that of 15 children without asthma (P < .001). The total overnight cough count in children with severe asthma exacerbation was higher than that in children with moderate asthma exacerbation (P < .05). The cough counts were significantly increased at the time of falling asleep and waking. This pattern was not observed in children without asthma. The total cough counts and cough patterns in children with asthma were not affected by sex, age, cause of asthma exacerbation, or therapy. CONCLUSION Our data indicate huge cough counts and characteristic nocturnal cough patterns in children with asthma. Objective and precise cough monitoring is useful for the management of childhood asthma.

An objective evaluation of nocturnal cough count and cough pattern in children with psychogenic cough

BACKGROUND Breath sound parameters have been suggested to be new biomarkers of airway function in patients with asthma. METHODS We investigated the effect of bronchodilation on breath sound parameters in sixty-four children (mean age, 8.9 years; range, 6-16 years) using a breath sound analyzer. The breath sound parameters included frequency limiting 50% and 99% of the power spectrum (F50 and F99), roll-off from 600-1200 Hz (slope), and spectrum curve indices such as the ratios of the third and fourth power area to the total area of the power spectrum (P3/PT and P4/PT), total area under the curve (A3/AT and B4/AT), and the ratio of power and frequency at 50% and 75% of the highest frequency of the power spectrum (RPF75 and RPF50). Lung function was assessed using spirometry and the forced oscillation technique (FOT). All variables were assessed before and after inhalation of a β2-agonist. RESULTS The spectrum curve indices, A3/AT, B4/AT, RPF75, and RPF50, showed statistically significant increase following β2-agonist inhalation. The increase in RPF50 was correlated with the decrease in the difference between resistance at 5 Hz and 20 Hz, R5-R20, measured by FOT. In the multiple regression analysis adjusted for the effect of ΔRPF75, the changes in A3/AT and B4/AT were positively correlated with that in the forced expiratory volume in one second. CONCLUSIONS The spectrum curve indices indicated bronchodilation, and may be useful for the assessment of bronchial reversibility in children with asthma.