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

The analysis of lung sounds in infants and children with a history of wheezing/asthma using an automatic procedure

BACKGROUND

Lung sound analysis parameters have been reported to be useful biomarkers for evaluating airway condition. We developed an automatic lung sound analysis software program for infants and children based on lung sound spectral curves of frequency and power by leveraging machine learning (ML) technology.

METHODS

To put this software program into clinical practice, in Study 1, the reliability and reproducibility of the software program using data from younger children were examined. In Study 2, the relationship between lung sound parameters and respiratory flow (L/s) was evaluated using data from older children. In Study 3, we conducted a survey using the ATS-DLD questionnaire to evaluate the clinical usefulness. The survey focused on the history of wheezing and allergies, among healthy 3-year-old infants, and then measured lung sounds. The clinical usefulness was evaluated by comparing the questionnaire results with the results of the new lung sound parameters.

RESULTS

In Studies 1 and 2, the parameters of the new software program demonstrated excellent reproducibility and reliability, and were not affected by airflow (L/s). In Study 3, infants with a history of wheezing showed lower FAP0 and RPF75p (p < 0.001 and p = 0.025, respectively) and higher PAP0 (p = 0.001) than healthy infants. Furthermore, infants with asthma/asthma-like bronchitis showed lower FAP0 (p = 0.002) and higher PAP0 (p = 0.001) than healthy infants.

CONCLUSIONS

Lung sound parameters obtained using the ML algorithm were able to accurately assess the respiratory condition of infants. These parameters are useful for the early detection and intervention of childhood asthma.

The Usefulness of Continuous Respiratory Sound Monitoring for the Detection of Pulmonary Atelectasis in a Ventilated Extremely Low Birth Weight Infant

The assessment of auscultation using a stethoscope is unsuitable for continuous monitoring. Therefore, we developed a novel acoustic monitoring system that continuously, objectively, and visually evaluates respiratory sounds. In this report, we assess the usefulness of our revised system in a ventilated extremely low birth weight infant (ELBWI) for the diagnosis of pulmonary atelectasis and evaluation of treatment by lung lavage. A female infant was born at 24 weeks of age with a birth weight of 636 g after emergency cesarean section. The patient received invasive mechanical ventilation immediately after birth in our neonatal (NICU). After obtaining informed consent, we monitored her respiratory status using the respiratory-sound monitoring system by attaching a sound collection sensor to the right anterior chest wall. On day 26, lung-sound spectrograms showed that the breath sounds were attenuated simultaneously as hypoxemia progressed. Finally, chest radiography confirmed the diagnosis as pulmonary atelectasis. To relieve atelectasis, surfactant lavage was performed, after which the lung-sound spectrograms returned to normal. Hypoxemia and chest radiographic findings improved significantly. On day 138, the patient was discharged from the NICU without complications. The continuous respiratory-sound monitoring system enabled the visual, quantitative, and noninvasive detection of acute regional lung abnormalities at the bedside. We, therefore, believe that this system can resolve several problems associated with neonatal respiratory management and save lives.

Lung sound analysis for predicting recurrent wheezing in preschool children

Background

In young healthy children, assessing airflow limitation may be difficult because of narrowing of the airways, which is a pathology of asthma, and responsiveness to bronchodilators.

Objective

We investigated whether lung sound analysis could predict the development of recurrent wheezing (RW), which is one of the signs of asthma.

Methods

In healthy children aged 3 to 24 months, we recorded and analyzed lung sounds before and after inhalation of bronchodilators and conducted a questionnaire survey. The children were followed up and assessed for the development of RW at age 3 years.

Results

Of the 62 patients analyzed, 19 (30.6%) developed RW. The parameters ratio of power and frequency at 50% of the highest frequency of the dB power spectrum (RPF50) and ratio of power and frequency at 75% of the highest frequency of the dB power spectrum (RPF75), calculated by lung sound analysis, were lower in the RW group, with odds ratios of 0.77 (95% CI = 0.61-0.98) and 0.81 (95% CI = 0.66-0.99), respectively. The rate of change of lung sound analysis parameters after bronchodilator inhalation did not differ among the participants as a group; however, in the subgroup of children with a history of atopic dermatitis, the fourth area under the curve (B4) divided by the total area under the curve of 100 Hz to the highest frequency of the dB power spectrum (AT) and difference between the values of the ratio of power and frequency at 50% of the highest frequency of the dB power spectrum (ΔRPF50) were elevated in the RW group (P = .015 and P = .041, respectively). In the subgroup of children with total a IgE level greater than 20 kUA/L, the sensitivities and specificities for predicting the development of RW were 85.7% (95% CI = 48.7-99.3) and 68.8% (95% CI = 44.4-85.8), respectively, when the cutoff value of ΔRPF50 was set at 10.5%.

Conclusion

The method of lung sound analysis allows noninvasive assessment of the airway, including airway hypersensitivity, in young children and may predict the risk of development of RW.

Effect of wheeze and lung function on lung sound parameters in children with asthma

BACKGROUND

In children with asthma, there are many cases in which wheeze is confirmed by auscultation with a normal lung function, or in which the lung function is decreased without wheeze. Using an objective lung sound analysis, we examined the effect of wheeze and the lung function on lung sound parameters in children with asthma.

METHODS

A total of 114 children with asthma (males to females = 80: 34, median age 10 years old) were analyzed for their lung sound parameters using conventional methods, and wheeze and the lung function were checked. The effects of wheeze and the lung function on lung sound parameters were examined.

RESULTS

The patients with wheeze or decreased forced expiratory flow and volume in 1 s (FEV1) (% pred) showed a significantly higher sound power of respiration and expiration-to-inspiration sound power ratio (E/I) than those without wheeze and a normal FEV1 (% pred). There was no marked difference in the sound power of respiration or E/I between the patients without wheeze and a decreased FEV1 (% pred) and the patients with wheeze and a normal FEV1 (% pred).

CONCLUSIONS

Our data suggest that bronchial constriction in the asthmatic children with wheeze similarly exists in the asthmatic children with a decreased lung function. A lung sound analysis is likely to enable an accurate understanding of airway conditions.

Clinical application of a lung sound analysis in infants with respiratory syncytial virus acute bronchiolitis

BACKGROUND

Objective investigation of the characteristics of acute bronchiolitis in infants is important for its diagnosis and treatment.

METHODS

Lung sound data of 50 patients diagnosed with respiratory syncytial virus (RSV) acute bronchiolitis (m:f = 29:21, median of age 7 months), 20 patients with RSV acute respiratory tract infections without acute bronchiolitis (m:f = 10:10, 5 months) and 38 age-matched control infants (m:f = 23:15, 8 months) were analyzed using a conventional method and compared. Furthermore, the relationships between lung sound parameters and clinical symptoms (clinical score, length of hospital stay and SpO2 level) in the bronchiolitis and the non-bronchiolitis patients were examined.

RESULTS

Results of lung sound analysis showed that the inspiratory sound power of patients with RSV respiratory tract infections was low and the expiratory sound power was high compared with those of the controls. When the patients with RSV respiratory tract infections were divided into the bronchiolitis and non-bronchiolitis groups, the expiratory/inspiratory ratio of the bronchiolitis patients was greater than that of the non-bronchiolitis patients. There was no difference in the clinical symptoms, clinical score and length of hospital stay between the bronchiolitis and non-bronchiolitis patients, except for the SpO2 level on admission.

CONCLUSION

Lung sound analysis confirmed that patients with RSV acute bronchiolitis present with marked airway narrowing. Considering these results as a characteristic of acute bronchiolitis, it would be meaningful to reflect it in the improvement of diagnosis, treatment and subsequent management.

Breath sound analyses of infants with respiratory syncytial virus acute bronchiolitis

INTRODUCTION

The reliability of a breath sound analysis using an objective method in infants has been reported.

OBJECTIVE

Breath sounds of infants with respiratory syncytial virus (RSV) acute bronchiolitis were analyzed via a breath sound spectrogram to evaluate their characteristics and examine their relationship with the severity.

SUBJECTS AND METHODS

We evaluated the inspiratory and expiratory breath sound parameters of 33 infants diagnosed with RSV acute bronchiolitis. The sound powers of inspiration and expiration were evaluated at the acute phase and recovery phase of infection. Furthermore, the relationship between the breath sound parameters and the clinical severity of acute bronchiolitis was examined.

RESULTS

Analyses of the breath sound spectrogram showed that the power of expiration as well as the expiration-to-inspiration sound ratio in the mid-frequency (E/I MF) was increased in the acute phase and decreased during the recovery phase. The E/I MF was inversely correlated with the SpO₂ and positively correlated with the severity score.

CONCLUSION

In infants with RSV acute bronchiolitis, the sound power of respiration was large at the acute phase, significantly decreasing in the recovery phase. In 61% of participants, nonuniform, granular bands were shown in the low-pitched region of the expiratory spectrogram.

Lung sound analysis in infants with risk factors for asthma development

BACKGROUND AND OBJECTIVES

Using a lung sound analysis, the prognosis of asthma was investigated in infants with risk factors for asthma development by a long-term observation.

METHODS

A total of 268 infants were included (median age: 8 months old). The lung sound parameters (the ratio of the third and fourth area to the 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 [RPF50 and RPF75]) were evaluated at the first visit. At 3 years old, using a questionnaire, we examined the relationship between the lung sound parameters and risk factors of asthma development.

RESULTS

Among the 268 infants, 175 infants were in good health and 93 had a history of acute respiratory infection (ARI) within 7 days at the first visit. Among the 3- to 12-month-old infants with an ARI, the A3/AT, B4/AT values in those with a history of asthma/asthmatic bronchitis, atopic dermatitis, and atopy were smaller than in the infants without such histories. Among the 13- to 24-month-old infants with an ARI, the A3/AT and B4/AT values in those with a wheezing history were larger than in the infants without such a history.

CONCLUSIONS

The characteristics of the lung sounds in infants with risk factors for asthma development were demonstrated over long-term follow-up. Lung sound analyses may be useful for assessing the airway condition of infants.

Real-World Verification of Artificial Intelligence Algorithm-Assisted Auscultation of Breath Sounds in Children

Objective: Lung auscultation plays an important role in the diagnosis of pulmonary diseases in children. The objective of this study was to evaluate the use of an artificial intelligence (AI) algorithm for the detection of breath sounds in a real clinical environment among children with pulmonary diseases. Method: The auscultations of breath sounds were collected in the respiratory department of Shanghai Children's Medical Center (SCMC) by using an electronic stethoscope. The discrimination results for all chest locations with respect to a gold standard (GS) established by 2 experienced pediatric pulmonologists from SCMC and 6 general pediatricians were recorded. The accuracy, sensitivity, specificity, precision, and F1-score of the AI algorithm and general pediatricians with respect to the GS were evaluated. Meanwhile, the performance of the AI algorithm for different patient ages and recording locations was evaluated. Result: A total of 112 hospitalized children with pulmonary diseases were recruited for the study from May to December 2019. A total of 672 breath sounds were collected, and 627 (93.3%) breath sounds, including 159 crackles (23.1%), 264 wheeze (38.4%), and 264 normal breath sounds (38.4%), were fully analyzed by the AI algorithm. The accuracy of the detection of adventitious breath sounds by the AI algorithm and general pediatricians with respect to the GS were 77.7% and 59.9% (p < 0.001), respectively. The sensitivity, specificity, and F1-score in the detection of crackles and wheeze from the AI algorithm were higher than those from the general pediatricians (crackles 81.1 vs. 47.8%, 94.1 vs. 77.1%, and 80.9 vs. 42.74%, respectively; wheeze 86.4 vs. 82.2%, 83.0 vs. 72.1%, and 80.9 vs. 72.5%, respectively; p < 0.001). Performance varied according to the age of the patient, with patients younger than 12 months yielding the highest accuracy (81.3%, p < 0.001) among the age groups. Conclusion: In a real clinical environment, children's breath sounds were collected and transmitted remotely by an electronic stethoscope; these breath sounds could be recognized by both pediatricians and an AI algorithm. The ability of the AI algorithm to analyze adventitious breath sounds was better than that of the general pediatricians.

A Lung Sound Analysis in Infants with Risk Factors for Asthma During Acute Respiratory Infection

Background: The parameters of lung sounds have been suggested as biomarkers of airway changes. Using a commercially available lung sound analyzer, we investigated the characteristics of the lung sounds in infants with acute respiratory infection (ARI). Methods: Infants with ARI who were 6 to 18 months of age were included in this study. The lung sound parameters, the ratio of the third area and fourth areas to the total area under the curve of the sound spectrum (A₃/A_T and B₄/A_T), and the ratio of power and frequency at 75% and 50% of the highest frequency of the power spectrum (RPF₇₅ and RPF₅₀) were evaluated. With an original Japanese questionnaire based on American Thoracic Society-Division of Lung Disease, the risk factors of asthma development in infants were examined. Results: One hundred ten infants with ARI and 248 infants in good health for comparison were included. All infants were completely analyzed, and then divided into 2 age groups for a stratification analysis (6-12 and 13-18 months). In the overall analysis, among infants with a history of wheezing, recurrent wheezing, allergy, and atopic dermatitis, the values of RPF₅₀ of infants with ARI were significantly lower compared with those without ARI. In the 6- to 12-month-old group, the RPF₅₀ values of atopy-positive infants with ARI were lower compared with those without ARI (P = 0.003). Conclusions: The lung sounds of the infants with asthma-developing risk factors were more affected by ARI than those of infants without risk factors. Analyzing the changes in the lung sounds induced by ARI may be useful for evaluating the characteristics of the airways in infants.

Objective evaluation of wheezing in normal infants

BACKGROUND

To evaluate the frequency of wheezing in infants, the presence of wheezing was examined in normal infants using a breath sound analyzer, METHODS: A total of 443 infants (age range, 3-24 months) were included in the present study. The existence of audible wheezing and faint wheezing/inaudible wheezing-like noises (FW) was confirmed on chest auscultation and a sound spectrogram. The breath sound parameters of the sound spectrum, frequency limiting 99% of power spectrum (F₉₉ ), roll-off from 600 to 1,200 Hz (slope) and spectrum curve indices, total area under the curve of dB data (A₃ /A_T and B₄ /A_T ), and ratio of power and frequency at 50% and 75% of the highest frequency of the power spectrum (RPF₅₀ and RPF₇₅ ) were calculated. Using an original Japanese questionnaire, we examined the characteristics of the airway condition of all infants.

RESULTS

Finally, a total of 398 infants were analyzed in the present study, and 283 were in good health while 115 had acute respiratory infection (ARI) in the last 7 days. No infants had audible wheezing on auscultation. Three infants without ARI (1.1%) and 10 infants with ARI (8.7%) had FW. In the evaluation of breath sound parameters, there were no marked differences between the infants with and without FW.

CONCLUSIONS

Using a breath sound analyzer, wheezing and FW were recognized in only a few infants in good health. Infants recognized to have audible wheezing in daily practice may be at risk of developing recurrent wheezing/asthma.

The acoustic characteristics of fine crackles predict honeycombing on high-resolution computed tomography

Background

Honeycombing on high-resolution computed tomography (HRCT) is a distinguishing feature of usual interstitial pneumonia and predictive of poor outcome in interstitial lung diseases (ILDs). Although fine crackles are common in ILD patients, the relationship between their acoustic features and honeycombing on HRCT has not been well characterized.

Methods

Lung sounds were digitally recorded from 71 patients with fine crackles and ILD findings on chest HRCT. Lung sounds were analyzed by fast Fourier analysis using a sound spectrometer (Easy-LSA; Fukuoka, Japan). The relationships between the acoustic features of fine crackles in inspiration phases (onset timing, number, frequency parameters, and time-expanded waveform parameters) and honeycombing in HRCT were investigated using multivariate logistic regression analysis.

Results

On analysis, the presence of honeycombing on HRCT was independently associated with onset timing (early vs. not early period; odds ratios [OR] 10.407, 95% confidence interval [95% CI] 1.366–79.298, P = 0.024), F99 value (the percentile frequency below which 99% of the total signal power is accumulated) (unit Hz = 100; OR 5.953, 95% CI 1.221–28.317, P = 0.029), and number of fine crackles in the inspiratory phase (unit number = 5; OR 4.256, 95% CI 1.098–16.507, P = 0.036). In the receiver-operating characteristic curves for number of crackles and F99 value, the cutoff levels for predicting the presence of honeycombing on HRCT were calculated as 13.2 (area under the curve [AUC], 0.913; sensitivity, 95.8%; specificity, 75.6%) and 752 Hz (AUC, 0.911; sensitivity, 91.7%; specificity, 85.2%), respectively. The multivariate logistic regression analysis additionally using these cutoff values revealed an independent association of number of fine crackles in the inspiratory phase, F99 value, and onset timing with the presence of honeycombing (OR 33.907, 95% CI 2.576–446.337, P = 0.007; OR 19.397, 95% CI 2.311–162.813, P = 0.006; and OR 12.383, 95% CI 1.443–106.293, P = 0.022; respectively).

Conclusions

The acoustic properties of fine crackles distinguish the honeycombing from the non-honeycombing group. Furthermore, onset timing, number of crackles in the inspiratory phase, and F99 value of fine crackles were independently associated with the presence of honeycombing on HRCT. Thus, auscultation routinely performed in clinical settings combined with a respiratory sound analysis may be predictive of the presence of honeycombing on HRCT.

Detection of intratracheal accumulation of thick secretions by using continuous monitoring of respiratory acoustic spectrum: a preliminary analysis

The accumulation of tracheobronchial secretions may contribute to a deterioration in pulmonary function and its early detection is important. In this study, we analyzed the respiratory sound spectrum in patients with intratracheal secretion, and compared acoustic characteristics before and after therapeutic endotracheal suctioning. After review of anesthetic records of liver transplant recipients, we included recipients with identified intratracheal secretion during surgery. Intraoperative breath sounds recorded through esophageal stethoscope were sampled in 20 s-period before and after suctioning of secretion and analyzed using fast Fourier transform. We also analyzed normal breath sounds from recipients without any respiratory problem as control group. The maximal power (dBm_Max), total power from whole frequency range of 80-500 Hz (P_t), total power of each frequency range (80-200 Hz, P_80-200; 200-300 Hz, P_200-300; 300-400 Hz, P_300-400; 400-500 Hz, P_400-500), and their ratio (P_80-200/P_t, P_200-300/P_t, P_300-400/P_t, P_400-500/P_t) were compared. Breath sounds were obtained from 20 recipients; 9 pairs of breath sound before and after suctioning of secretion and 11 normal breath sounds. Patients with intratracheal secretion showed significantly higher P_80-200, P_200-300, P_300-400, P_400-500 when compared to the those of normal control patients (P = 0.003, P = 0.002, and P = 0.009, respectively), while dBm_Max did not differ. Elimination of secretions attenuated P_80-200, P_200-300, P_300-400, and P_400-500 by 22.4%, 25.7%, 48.5%, and 15.3%, respectively (P = 0.002, 0.024, 0.009, and 0.016, respectively). Identifying the presence of intratracheal secretions with power ratio at 80-200 Hz and 300-400 Hz showed the highest area under the curve of 0.955 in receiver operating characteristic curve analysis. We suggest that spectral analysis of breath sounds obtained from the esophageal stethoscope might be a useful non-invasive respiratory monitor for accumulation of intratracheal secretion. Further prospective studies to evaluate the utility of acoustic analysis in surgical patients are warranted.

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.

Characteristics of breath sound in infants with risk factors for asthma development

BACKGROUND

Breath sound parameters have been suggested as biomarkers of the airway narrowing in children. Using a commercially available breath sound analyzer, the characteristics of the airway condition were investigated in infants with the risk factors for asthma development.

METHODS

A total of 443 infants (mean age, 9.9 months; range, 3-24 months) were included in the present study. The breath sound parameters of the frequency limiting 99% of the power spectrum (F₉₉), the roll-off from 600 to 1200 Hz (Slope) and spectrum curve indices, the total area under the curve of the dBm data (A₃/A_T) and the ratio of power and frequency at 50% and 75% of the highest frequency of the power spectrum (RPF₇₅ and RPF₅₀), were evaluated. Using an ATS-DLD based original Japanese questionnaire, we examined the characteristics of airway condition of infants.

RESULTS

Finally, 283 infants in good health were included in the present study. The RPF₇₅, RPF₅₀, Slope and F₉₉ in infants with positive results of allergy and atopic dermatitis were significantly increased more than those in the infants with negative result.

CONCLUSIONS

Our data highlight the characteristics of breath sounds in infants with risk factors for asthma. The breath sound analysis may be useful for assessing the airways of infants for asthma development.

Color spectrographic respiratory monitoring from the external ear canal

The need for simple and reliable means of respiratory monitoring has existed since the beginnings of medicine. In the present study, we describe the use of color spectrographic analysis of breathing sounds recorded from the external ear canal as a candidate technology to meet this need. A miniature electret microphone was modified with the addition of an adapter to allow it to be placed comfortably in the external ear canal. The amplified signal was then connected to a real-time color spectrogram program running on a laptop personal computer utilizing the Windows operating system. Based on the results obtained, we hypothesize that the real-time display of color spectrogram breathing patterns locally or at a central monitoring station may turn out to be a useful means of respiratory monitoring in patients at increased risk of respiratory depression or other respiratory problems. Finally, we conducted a statistical analysis that suggests that significant spectrogram differences may exist among some groups investigated in the study.

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

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/P_T and P₄/P_T), total area under the curve (A₃/A_T and B₄/A_T), 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/A_T, B₄/A_T, 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/A_T and B₄/A_T 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.

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

BACKGROUND AND OBJECTIVE

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.

METHODS

The study population included 49 children with atopic asthma (male = 33; mean age: 10.2 years). We evaluated breath sound parameters of the highest frequency of the power spectrum (HFp), frequency limiting 50% and 99% of the power spectrum (F₅₀ and F₉₉ ) and roll-off from 600 Hz to the HFp (Slope). We also assessed new parameters obtained using the ratios of sound spectrum parameters (spectrum curve indices), such as the ratio of the third and fourth power area to the total power area (P₃ /P_T and P₄ /P_T ), the ratio of the third and fourth areas to the total area under the curve (A₃ /A_T and B₄ /A_T ) and the ratio of power and frequency at 75% of HFp and 50% of HFp (RPF₇₅ and RPF₅₀ ). This was measured before and after methacholine inhalation challenge and after β₂ agonist inhalation.

RESULTS

The parameters, F₅₀ and F₉₉ , showed no changes after methacholine inhalation. Conversely, the A₃ /A_T (12.5-10.0%, P < 0.001), B₄ /A_T (7.6-5.5%, P < 0.001), RPF₇₅ (6.7-4.0 dBm/Hz, P < 0.001) and RPF₅₀ (5.8-4.3 dBm/Hz, P < 0.001) were significantly decreased. These values returned to the original level after β₂ agonist inhalation.

CONCLUSION

Spectrum curve indices indicate bronchoconstriction and bronchodilation. These parameters may play a role in the assessment of airway narrowing in asthmatic children.

Advances in Audio-Based Systems to Monitor Patient Adherence and Inhaler Drug Delivery

Hundreds of millions of people worldwide have asthma and COPD. Current medications to control these chronic respiratory diseases can be administered using inhaler devices, such as the pressurized metered dose inhaler and the dry powder inhaler. Provided that they are used as prescribed, inhalers can improve patient clinical outcomes and quality of life. Poor patient inhaler adherence (both time of use and user technique) is, however, a major clinical concern and is associated with poor disease control, increased hospital admissions, and increased mortality rates, particularly in low- and middle-income countries. There are currently limited methods available to health-care professionals to objectively and remotely monitor patient inhaler adherence. This review describes recent sensor-based technologies that use audio-based approaches that show promising opportunities for monitoring inhaler adherence in clinical practice. This review discusses how one form of sensor-based technology, audio-based monitoring systems, can provide clinically pertinent information regarding patient inhaler use over the course of treatment. Audio-based monitoring can provide health-care professionals with quantitative measurements of the drug delivery of inhalers, signifying a clear clinical advantage over other methods of assessment. Furthermore, objective audio-based adherence measures can improve the predictability of patient outcomes to treatment compared with current standard methods of adherence assessment used in clinical practice. Objective feedback on patient inhaler adherence can be used to personalize treatment to the patient, which may enhance precision medicine in the treatment of chronic respiratory diseases.

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/A_T and B₄/A_T, 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/A_T (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/A_T 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.