Evaluation of nocturnal bronchoconstriction by all night tracheal sound monitoring

Lung sounds in bronchial asthma

Modern understanding of lung sounds started with a historical article by Forgacs. Since then, many studies have clarified the changes of lung sounds due to airway narrowing as well as the mechanism of genesis for these sounds. Studies using bronchoprovocation have shown that an increase of the frequency and/or intensity of lung sounds was a common finding of airway narrowing and correlated well with lung function. Bronchoprovocation studies have also disclosed that wheezing may not be as sensitive as changes in basic lung sounds in acute airway narrowing. A forced expiratory wheeze (FEW) may be an early sign of airway obstruction in patients with bronchial asthma. Studies of FEW showed that airway wall oscillation and vortex shedding in central airways are the most likely mechanisms of the generation of expiratory wheezes. Studies on the genesis of wheezes have disclosed that inspiratory and expiratory wheezes may have the same mechanism of generation as a flutter/flow limitation mechanism, either localized or generalized. In lung sound analysis, the narrower the airways are, the higher the frequency of breathing sounds is, and, if a patient has higher than normal breathing sounds, i.e., bronchial sounds, he or she may have airway narrowing or airway inflammation. It is sometimes difficult to detect subtle changes in lung sounds; therefore, we anticipate that automated analysis of lung sounds will be used to overcome these difficulties in the near future.

Children with nocturnal asthma wheeze intermittently during sleep

Nocturnal asthma indicates poor overall control of asthma and adversely affects the quality of life of the patient. The purpose of the present study was to compare the objective measurement of nocturnal wheeze with clinical state, recall of symptoms, and changes in lung function. Nine asthmatic children aged 9 to 16 years were followed with an asthma diary and diurnal measurement of peak flow for a week before the nocturnal study; all but two were apparently well controlled. Breath sounds were recorded and analyzed continuously overnight to quantify wheeze using a phonopneumography sensor attached over the trachea. The analytical system (PulmoTrack) utilized an algorithm to detect wheeze and reject interference. The wheeze rate (Tw/Ttot = duration of wheeze/duration of recording) was calculated minute by minute throughout the night. Recordings lasted over 8 hours and all but two children had wheeze lasting for a total time of between 11 and 87 minutes. The pattern of wheezing was very variable during sleep, with episodes of wheeze separated by periods of quiet breathing. There was no relationship between subjective perception of nocturnal asthma, forced expiratory volume in 1 s (FEV(1)) next morning, and the objective measurement of wheeze. Total overnight wheeze was significantly related to the total diary symptom score and to the (small) diurnal variability of peak expiratory flow (PEF). Four of the seven children with asthma who were apparently well controlled had considerable amounts of wheeze during the night that was episodic in nature and unrelated to conventional measures of lung function or nocturnal symptoms.

An unidentified monster in the bed--assessing nocturnal asthma in children

Nocturnal asthma (NA) is increasing in prevalence, affecting millions of people worldwide. In addition to being associated with increased mortality, NA is associated with a decreased quality of life. NA associated sleep disturbances and increased daytime sleepiness are especially important in children due to the accompanying behavioral and developmental difficulties. As diurnal spirometry is not a practical tool for the diagnosis and monitoring of NA, self or parental reports are used. Children underreport and underestimate their NA symptoms and parents are not fully aware of their child's NA indicators. In addition, there is the lack of physician familiarity regarding the assessment and treatment of NA. Therefore, NA is chronically underreported. The development of a non-invasive, objective, home-based diagnostic tool is crucial in diagnosing and monitoring children with NA. The presence of wheeze during sleep has been successfully employed as a tool to measure NA in children. This review discusses the increasing prevalence of NA, current diagnostic tools and the consequences of undiagnosed NA in children. In conclusion, this paper suggests that an automated wheeze detective device is an objective and practical tool to aid the diagnosis and monitoring of NA.

Spirometry and forced oscillometry assisted optimal frequency band determination for the computerized analysis of tracheal lung sounds in asthma

We analysed respiration sounds of individual asthmatic patients, in the scope of the development of a method for computerized recognition of the degree of airway obstruction. Respiration sounds were recorded during laboratory sessions of histamine-provoked airway obstruction. We applied an interpolation technique using supervised artificial neural networks to investigate the optimal frequency band required for studying tracheal asthmatic lung sounds. The optimal band was found to be 100-2300 Hz. The forced expiratory volume in 1 s (FEV1) and the respiratory resistance parameter Rrs(4) were used to describe the degree of airway obstruction that is associated with the lung sounds. By comparing the results obtained with the two parameters, we found that for parametrization of the associated degree of airway obstruction respiratory resistance measurements are preferable over forced expiratory volume measurements.

Nocturnal worsening of asthma and sleep-disordered breathing

Asthma has a tendency, to destabilize and get worse at night, probably due to a nocturnal increase in airiway inflammation and bronchial responsiveness. Nocturnal airway narrowing in asthma is often associated with sleep disorders, such as episodes of nocturnal and early morning awakening, difficulty in maintaining sleep, and day time sleepiness. On the other hand, an association has been documented between nocturnal sleep-disordered breathing and asthma. This review highlights the causes of nocturnal worsening of asthma and examines the evidence pointing toward a causal relationship between nocturnal asthma and sleep-disordered breathing.

Asthmatic airways obstruction assessment based on detailed analysis of respiratory sound spectra

This paper concerns the analysis of adventitious sounds produced by individual asthmatic patients, and relates the sounds to the degree of airways obstruction at the moment of sound recording. In this study, airways obstruction is represented by a parameter commonly used in clinical tests, the forced expiratory volume in one second. A nonrestrictive approach using spectral information in detail is followed, resulting in a fairly high resolution of respiration sounds with respect to airways obstruction. The beneficial effect of a power raising transformation is presented, together with an illumination of the background of this effect.

Characteristics and diagnostic significance of spontaneous wheezing in children with asthma: results of continuous in vivo sound recording

The characteristics and diagnostics of wheezing during induced airway obstruction are well documented. The present study addressed (a) the characteristics of spontaneous wheezing with respect to a possible distinction between wheezes during in vivo versus induced airway obstruction, and (b) the relationship between in vivo wheezing and fluctuations in peak expiratory flow (PEF). Tracheal sounds were continuously recorded from 50 children and adolescents with asthma and 10 without asthma in the home environment. Wheezes underwent a qualitative analysis, including their concomitant sound frequencies. Presence of wheezing was scored by two examiners independently and was related to PEF. Spontaneous wheeze varied from solitary rhonchi to prolonged rhythms of loud stridor, and resembled the "induced" wheezes recorded previously. Power spectra showed that the spectral contents (frequency distribution) were comparable, although the in vivo patterns were more prolonged in duration. The diagnostic sensitivity and specificity of wheezing for a reduction in PEF of >20% were 88% and 92%, respectively. It was concluded that in vivo wheeze resembled induced wheeze and was a diagnostically reliable symptom with respect to asthma exacerbations.

Detection of nocturnal wheezing in bronchial asthma using intermittent sleep tracheal sounds recording

Common clinical features of bronchial asthma include bronchoconstriction during the night, particularly while asleep. Although bronchoconstriction reduces the quality of life and can cause life-threatening events, a clinical technique for evaluating bronchoconstriction during sleep has not been widely applied. In this study, we measured nocturnal wheezing by intermittent sleep tracheal sounds recording (ISTSR) to detect bronchoconstriction during the hours of sleep. Using ISTSR, we studied the number and duration of nocturnal wheezing episodes in 27 adult patients with bronchial asthma. Nocturnal wheezing was detected in 36 of 39 recordings. Although the pattern of hourly nocturnal wheezing count (hourly NWC pattern) varied among subjects, there appeared to be a reproducible pattern within individuals. When wheezing alternated between long and short duration, bronchoconstriction tended to be more severe. The NWC in 1 h (NWC/H) was positively correlated with subjective symptoms and inversely correlated with the morning per cent peak expiratory flow. The hourly NWC was significantly greater at 05:00 than that at midnight. Intermittent sleep tracheal sounds recording has potential to be a non-invasive clinical tool for detecting nocturnal bronchoconstriction during hours of sleep in patients with asthma.