Silke Wilitzki

Differential effects of immaturity and neonatal lung disease on the lung function of very low birth weight infants at 48–52 postconceptional weeks

The pathogenesis of chronic lung disease of prematurity involves maturational arrest and neonatal lung disease (NLD) followed by mechanical ventilation (MV). However, the effect of these factors on postnatal lung function is not well established. Therefore, the aim of this study was to examine the differential effects of immaturity and NLD requiring MV on lung function test (LFT) parameters within 4 months after discharge.

The lung clearance index in young infants: impact of tidal volume and dead space.

Lung clearance index (LCI), measured by multiple breath washout (MBW), is one of the most frequently used measures of ventilation inhomogeneity. This study was designed to investigate the effect of lung volumes on LCI in young infants. The dependence of LCI on dead space volume (VD), tidal volume (VT) and functional residual capacity (FRC) was investigated by mathematical modeling and by MBW measurements using sulfur hexafluoride (SF6) as a tracer gas. MBW was performed in 150 infants, of median postmenstrual age 46.7 weeks, followed up after neonatal intensive care. Wheezing was assessed in 90 of these infants by computerized respiratory sound analysis during quiet sleep. The strongest correlation was observed between LCI and the volume ratios VT/FRC (Spearman rank order correlation coefficient Rs = 0.688, p < 0.001), VD/VT (Rs = 0.733, p < 0.001) and VD/FRC (Rs = 0.854, p < 0.001). LCI calculated from VD, VT, and FRC was linearly related to measured LCI with a coefficient of determination of 75%. There were no significant differences between wheezers and non-wheezers in postmenstrual age and body weight, but FRC was significantly increased (p < 0.001) and median (interquartile range) LCI significantly decreased (5.83 (5.45-6.51) versus (6.54 (6.03-7.22), p < 0.001) in wheezing compared to non-wheezing infants. Model calculations also showed that LCI was significantly reduced in wheezing infants (5.09 (4.79-5.62) versus 5.43 (5.08-5.82), p < 0.018), indicating that the reduction can be explained by differences in the lung volumes, not by improved ventilation homogeneity. In conclusion, the strong dependence of LCI on lung volumes in young infants can lead to misinterpretations regarding the homogeneity of alveolar ventilation.

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

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.

Effect of intubation and mechanical ventilation on exhaled nitric oxide in preterm infants with and without bronchopulmonary dysplasia measured at a median postmenstrual age of 49 weeks

BackgroundExhaled nitric oxide (eNO) is a marker of established airway inflammation in adults and children, but conflicting results have been reported in preterm infants when postnatal eNO is measured during tidal breathing. This study investigated the extent to which intubation and mechanical ventilation (MV) affect eNO and NO production (V’NO) in preterm infants with and without bronchopulmonary dysplasia (BPD).Patients and methodsA total of 176 very low birth weight (VLBW) infants (birth weight <1500 g), including 74 (42%) with and 102 (58%) without BPD, were examined at a median postmenstrual age of 49 weeks. Of the 176 infants, 84 (48%) did not require MV, 47 (27%) required MV for <7 days and 45 (26%) required MV for ≥7 days. Exhaled NO and tidal breathing parameters were measured in sleeping infants during tidal breathing, respiratory mechanics were assessed by occlusion tests, and arterialized capillary blood gas was analyzed.ResultseNO was significantly correlated with tidal breathing parameters, while V’NO was correlated with growth parameters, including age and body length (p < 0.001 each). Infants who were intubated and received MV for <7 days had significantly lower eNO (p < 0.01) and V’NO (p < 0.01) than non-ventilated infants. In contrast, eNO and V’NO did not differ significantly in non-ventilated infants and those receiving MV for ≥7 days. Multivariate analysis showed that independent on the duration of MV eNO (p = 0.003) and V’NO (p = 0.018) were significantly increased in BPD infants comparable with the effects of intubation and MV on eNO (p = 0.002) and V’NO (p = 0.017).ConclusionsPreterm infants with BPD show only weak postnatal increases in eNO and V’NO, but these changes may be obscured by the distinct influences of breathing pattern and invasive respiratory support. This limits the diagnostic value of postnatal eNO measurements in the follow-up of BPD infants.

Reliability of Single-Use PEEP-Valves Attached to Self-Inflating Bags during Manual Ventilation of Neonates – An In Vitro Study

Introduction International resuscitation guidelines suggest to use positive end-expiratory pressure (PEEP) during manual ventilation of neonates. Aim of our study was to test the reliability of self-inflating bags (SIB) with single-use PEEP valves regarding PEEP delivery and the effect of different peak inflation pressures (PIP) and ventilation rates (VR) on the delivered PEEP. Methods Ten new single-use PEEP valves from 5 manufacturers were tested by ventilating an intubated 1kg neonatal manikin containing a lung model with a SIB that was actuated by an electromechanical plunger device. Standard settings: PIP 20cmH2O, VR 60/min, flow 8L/min. PEEP settings of 5 and 10cmH2O were studied. A second test was conducted with settings of PIP 40cmH2O and VR 40/min. The delivered PEEP was measured by a respiratory function monitor (CO2SMO+). Results Valves from one manufacturer delivered no relevant PEEP and were excluded. The remaining valves showed a continuous decay of the delivered pressure during expiration. The median (25th and 75th percentile) delivered PEEP with standard settings was 3.4(2.7–3.8)cmH2O when set to 5cmH2O and 6.1(4.9–7.1)cmH2O when set to 10cmH2O. Increasing the PIP from 20 to 40 cmH2O led to a median (25th and 75th percentile) decrease in PEEP to 2.3(1.8–2.7)cmH2O and 4.3(3.2–4.8)cmH2O; changing VR from 60 to 40/min led to a PEEP decrease to 2.8(2.1–3.3)cmH2O and 5.0(3.5–6.2)cmH2O for both PEEP settings. Conclusion Single-use PEEP valves do not reliably deliver the set PEEP. PIP and VR have an effect on the delivered PEEP. Operators should be aware of these limitations when manually ventilating neonates.

Early lung function testing in infants with aortic arch anomalies identifies patients at risk for airway obstruction.

Background Aortic arch anomalies (AAA) are rare cardio-vascular anomalies. Right-sided and double-sided aortic arch anomalies (RAAA, DAAA) are distinguished, both may cause airway obstructions. We studied the degree of airway obstruction in infants with AAA by neonatal lung function testing (LFT). Patients and Methods 17 patients (10 RAAA and 7 DAAA) with prenatal diagnosis of AAA were investigated. The median (range) post conception age at LFT was 40.3 (36.6–44.1) weeks, median body weight 3400 (2320–4665) g. Measurements included tidal breathing flow-volume loops (TBFVL), airway resistance (Raw) by bodyplethysmography and the maximal expiratory flow at functional residual capacity (V′maxFRC) by rapid thoracic-abdominal compression (RTC) technique. V′maxFRC was also expressed in Z-scores, based on published gender-, age and height-specific reference values. Results Abnormal lung function tests were seen in both RAAA and DAAA infants. Compared to RAAA infants, infants with DAAA had significantly more expiratory flow limitations in the TBFVL, (86% vs. 30%, p<0.05) and a significantly increased Raw (p = 0.015). Despite a significant correlation between Raw and the Z-score of V′maxFRC (r = 0.740, p<0.001), there were no statistically significant differences in V′maxFRC and its Z-scores between RAAA and DAAA infants. 4 (24%) infants (2 RAAA, 2 DAAA) were near or below the 10th percentile of V′maxFRC, indicating a high risk for airway obstruction. Conclusion Both, infants with RAAA and DAAA, are at risk for airway obstruction and early LFT helps to identify and to monitor these infants. This may support the decision for therapeutic interventions before clinical symptoms arise.

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.