Lung sounds in neonates with and without an added dead space

Computerized wheeze detection in young infants: comparison of signals from tracheal and chest wall sensors

Computerized wheeze detection is an established method for objective assessment of respiratory sounds. In infants, this method has been used to detect subclinical airway obstruction and to monitor treatment effects. The optimal location for the acoustic sensors, however, is unknown. The aim of this study was to evaluate the quality of respiratory sound recordings in young infants, and to determine whether the position of the sensor affected computerized wheeze detection. Respiratory sounds were recorded over the left lateral chest wall and the trachea in 112 sleeping infants (median postmenstrual age: 49 weeks) on 129 test occasions using an automatic wheeze detection device (PulmoTrack^®). Each recording lasted 10 min and the recordings were stored. A trained clinician retrospectively evaluated the recordings to determine sound quality and disturbances. The wheeze rates of all undisturbed tracheal and chest wall signals were compared using Bland-Altman plots. Comparison of wheeze rates measured over the trachea and the chest wall indicated strong correlation (r  ⩾  0.93, p  <  0.001), with a bias of 1% or less and limits of agreement of within 3% for the inspiratory wheeze rate and within 6% for the expiratory wheeze rate. However, sounds from the chest wall were more often affected by disturbances than sounds from the trachea (23% versus 6%, p  <  0.001). The study suggests that in young infants, a better quality of lung sound recordings can be obtained with the tracheal sensor.

Relationship between computerized wheeze detection and lung function parameters in young infants

OBJECTIVE

Computerized respiratory sound analysis (CORSA) has been validated in the assessment of wheeze in infants, but it is unknown whether automatically detected wheeze is associated with impaired lung function. This study investigated the relationship between wheeze detection and conventional lung function testing (LFT) parameters.

METHODS

CORSA was performed using the PulmoTrack® monitor in 110 infants, of median (interquartile range) postmenstrual age 50 (46-56) weeks and median body weight 4,810 (3,980-5,900) g, recovering from neonatal intensive care. In the same session, LFT was performed, including tidal breathing measurements, occlusion tests, body plethysmography, forced expiratory flow by rapid thoracoabdominal compression, sulfur hexafluoride (SF6 ) multiple breath washout (MBW), and capillary blood gas analysis. Infants were classified as wheezers or non-wheezers using predefined cut-off values for the duration of inspiratory and expiratory wheeze.

RESULTS

Wheezing was detected in 72 (65%) infants, with 43 (39%) having inspiratory and 53 (48%) having expiratory wheezing. Endotracheal mechanical ventilation in the neonatal period for > 24 hr was associated with inspiratory wheeze (P = 0.009). Airway resistance was increased in both inspiratory (P = 0.02) and expiratory (P = 0.004) wheezers and correlated with the duration of expiratory wheeze (r = 0.394, P < 0.001). Expiratory wheezers showed a significant increase in respiratory resistance (P = 0.001), time constant (0.012), and functional residual capacity using SF6 MBW (P = 0.019). There was no association between wheezing and forced expiratory flow or blood gases.

CONCLUSION

CORSA can help identify neonates and young infants with subclinical airway obstruction and may prove useful in the follow-up of high-risk infants.