Frans H. de Jongh

Changes in Lung Volume and Ventilation during Surfactant Treatment in Ventilated Preterm Infants

RATIONALE The immediate and regional effects of exogenous surfactant in open lung high-frequency oscillatory ventilated (HFOV) preterm infants are unknown. OBJECTIVES To assess regional changes in lung volume, mechanics, and ventilation during and after surfactant administration in HFOV preterm infants with respiratory distress syndrome (RDS). METHODS Using electrical impedance tomography, changes in lung volume were continuously recorded during a stepwise recruitment procedure before, during, and after surfactant administration in 15 preterm infants (gestational age: 28.3 wk; birth weight: 1,000 g). Deflation limbs of the pressure-impedance curve before and after surfactant were mapped and the effect of surfactant on oscillation volumes and ventilation was determined. Data were analyzed for the whole cross-section and the left, right, ventral, and dorsal lung regions. MEASUREMENTS AND MAIN RESULTS Surfactant increased lung volume by 61 ± 39% within a median time of 241 seconds. The ventral to dorsal ratio in lung volume changed significantly from 1.16 before to 0.81 after surfactant administration. The upper inflection point of the deflation limb after surfactant (10.4 ± 2.4 cm H(2)O) was significantly lower compared with before surfactant (16.4 ± 3.1 cm H(2)O). Surfactant increased maximal compliance of the respiratory system, and this effect was reached at lower airway pressures. Surfactant caused a transient decrease in oscillatory volume but did not alter its regional distribution. CONCLUSIONS Surfactant treatment in HFOV preterm infants with RDS causes a rapid increase and subsequent stabilization of lung volume, which is most prominent in dependent lung regions. It increased maximal compliance, but this effect is only reached at lower airway pressures.

Changes in Lung Volume and Ventilation during Lung Recruitment in High-Frequency Ventilated Preterm Infants with Respiratory Distress Syndrome

OBJECTIVES To assess global and regional changes in lung volume and ventilation during lung recruitment in preterm infants with respiratory distress syndrome. STUDY DESIGN Using electrical impedance tomography, changes in lung volume and ventilation were measured in 15 high-frequency oscillatory ventilated preterm infants during oxygenation-guided recruitment maneuvers. The inflation and deflation limbs were mapped, and the lower and upper inflection points were calculated using both oxygenation and impedance data. The impedance data were also used to determine recruitment-related changes in oscillation volume and distribution. RESULTS During inflation, lower and upper inflection points were identified in the majority of infants. The deflation limb showed clear lung hysteresis in all infants. The upper inflection point was significantly lower when comparing the pressure/oxygenation and pressure/impedance curves. Lung volume changes differed between the ventral and dorsal regions, but did not show a consistent pattern. Optimal recruitment increased the oscillation volume, but the distribution of ventilation was relatively homogeneous along the ventral-dorsal axis. CONCLUSIONS Lung hysteresis is present in preterm infants with respiratory distress syndrome. Regional differences in lung volume changes and ventilation during high-frequency oscillatory ventilation with lung recruitment are relatively modest and do not follow a gravity-dependent distribution.

Sleep Position Trainer versus Tennis Ball Technique in Positional Obstructive Sleep Apnea Syndrome

STUDY OBJECTIVE Positional therapy (PT) is an effective therapy in positional obstructive sleep apnea syndrome (POSAS) when used, but the compliance of PT is low. The objective of this study was to investigate whether a new kind of PT is effective and can improve compliance. METHODS 29 patients were treated with the Sleep Position Trainer (SPT), 26 patients with the Tennis Ball Technique (TBT). At baseline and 1 month polysomnography, Epworth Sleepiness Scale (ESS) and the Quebec Sleep Questionnaire (QSQ) were taken. Daily compliance was objectively measured in both groups. RESULTS Both therapies prevent supine sleep position to a median of 0% (min-max: SPT 0.0% to 67%, TBT 0.0% to 38.9%), resulting in a treatment success (AHI <5) in 68.0% of the SPT and 42.9% of the TBT patients. The ESS at baseline was <10 in both groups. Sleep quality parameters as wake after sleep onset (WASO; p = 0.001) and awakenings (p = 0.006) improved more in the SPT group. Total QSQ scores (0.4±0.2, p = 0.03) and the QSQ domains nocturnal symptoms (0.7±0.2, p = 0.01) and social interactions (0.8±0.3, p = 0.02) changed in favor of the SPT group. Effective compliance (≥4 h/night + ≥5 days/week) was 75.9% for the SPT and 42.3% for the TBT users (p = 0.01). CONCLUSION In mild POSAS with normal EES the new SPT device and the standard TBT are equally effective in reducing respiratory indices. However, compared to the TBT, sleep quality, quality of life, and compliance improved significantly more in the SPT group.

Monitoring pulmonary function during exercise in children with asthma

Objective Exercise-induced bronchoconstriction (EIB) is defined as acute, reversible bronchoconstriction induced by physical exercise. It is widely believed that EIB occurs after exercise. However, in children with asthma the time to maximal bronchoconstriction after exercise is short, suggesting that the onset of EIB in such children occurs during exercise. Aim In this study the authors investigate pulmonary function during exercise in cold air in children with asthma. Methods 33 Children with asthma with a mean age of 12.3 years and a clinical history of exercise induced symptoms, underwent a prolonged, submaximal, exercise test of 12 min duration at approximately 80% of the predicted maximum heart rate. Pulmonary function was measured before and each minute during exercise. If EIB occurred (fall in forced expiratory volume in 1 s >15% from baseline), exercise was terminated and salbutamol was administered. Results 19 Children showed EIB. In 12 of these children bronchoconstriction occurred during exercise (breakthrough EIB), while seven children showed bronchoconstriction immediately after exercise (non-breakthrough EIB). Breakthrough EIB occurred between 6 and 10 min of exercise (mean 7.75 min). Conclusion In the majority of children with EIB in this study (ie, 12 out of 19), bronchoconstriction started during, and not after, a submaximal exercise test.

ERS technical standard on bronchial challenge testing: General considerations and performance of methacholine challenge tests

This international task force report updates general considerations for bronchial challenge testing and the performance of the methacholine challenge test. There are notable changes from prior recommendations in order to accommodate newer delivery devices. Rather than basing the test result upon a methacholine concentration (provocative concentration (PC20) causing a 20% fall in forced expiratory volume in 1 s (FEV1)), the new recommendations base the result upon the delivered dose of methacholine causing a 20% fall in FEV1 (provocative dose (PD20)). This end-point allows comparable results from different devices or protocols, thus any suitable nebuliser or dosimeter may be used, so long as the delivery characteristics are known. Inhalation may be by tidal breathing using a breath-actuated or continuous nebuliser for 1 min (or more), or by a dosimeter with a suitable breath count. Tests requiring maximal inhalations to total lung capacity are not recommended because the bronchoprotective effect of a deep breath reduces the sensitivity of the test. The new ERS recommendation for methacholine challenge tests will be the provocative dose rather than concentration http://ow.ly/FBe5309yXn2

Association of the asthma control questionnaire with exercise-induced bronchoconstriction.

Introduction. Asthma is a common chronic disease in childhood which features bronchial hyperresponsiveness to exercise (EIB). In daily clinical practice, the report of EIB is used to assess the level of control of asthma. The asthma control questionnaire (ACQ) is a tool to evaluate the control of asthma in children. The aim of this study was to evaluate the relationship between the ACQ and EIB. Materials and methods. Two hundred children, aged 12.5 ± 2.5 years, with a pediatrician-diagnosed mild-to-moderate asthma filled out an ACQ and performed an exercise provocation test in cold air. EIB was defined as a fall in FEV1 of 15%. Results. Eighty six of the 200 children had a positive exercise challenge. There was no relationship between the categorical ACQ and the occurrence of EIB (p = .39). There was no difference in the occurrence of EIB between genders (p = .12). The positive predictive value of the ACQ for EIB was 51% and the negative predictive value for EIB was 59%. In comparison to the girls, the boys carried an odds ratio (OR) of 0.48 for having an indifferent control of asthma (p = .04; confidence interval (CI): 0.23–0.96), and an OR of 0.46 for having a not well-controlled asthma (p = .03; CI: 0.23–0.93). Conclusion. This study shows that the ACQ is not related to EIB in children with asthma. Remarkable is the percentage (41%) of children who, despite well-controlled asthma according to the ACQ, had EIB, which implies that their asthma is not well-controlled. Boys were more likely to report well-controlled asthma, although boys and girls were equally likely to have EIB.

Effect of an intranasal corticosteroid on exercise induced bronchoconstriction in asthmatic children

Allergic rhinitis and exercise induced bronchoconstriction (EIB) are common in asthmatic children. The aim of this study was to investigate whether treatment of allergic rhinitis with an intranasal corticosteroid protects against EIB in asthmatic children.

Effect of Minimally Invasive Surfactant Therapy on Lung Volume and Ventilation in Preterm Infants

OBJECTIVE To assess the changes in (regional) lung volume and gas exchange during minimally invasive surfactant therapy (MIST) in preterm infants with respiratory distress syndrome. STUDY DESIGN In this prospective observational study, infants requiring a fraction of inspired oxygen (FiO2) ≥ 0.30 during nasal continuous positive airway pressure of 6 cmH2O were eligible for MIST. Surfactant (160-240 mg/kg) was administered in supine position in 1-3 minutes via an umbilical catheter placed 2 cm below the vocal cords. Changes in end-expiratory lung volume (EELV), tidal volume, and its distribution were recorded continuously with electrical impedance tomography before and up to 60 minutes after MIST. Changes in transcutaneous oxygen saturation (SpO2) and partial carbon dioxide pressure, FiO2, respiratory rate, and minute ventilation were recorded. RESULTS A total of 16 preterm infants were included. One patient did not finish study protocol because of severe apnea 10 minutes after MIST. In the remaining infants (gestational age 29.8 ± 2.8 weeks, body weight 1545 ± 481 g) EELV showed a rapid and sustained increase, starting in the dependent lung regions, followed by the nondependent regions approximately 5 minutes later. Oxygenation, expressed as the SpO2/FiO2 ratio, increased from 233 (IQR 206-257) to 418 (IQR 356-446) after 60 minutes (P < .001). This change was significantly correlated with the change in EELV (ρ = 0.70, P < .01). Tidal volume and minute volume decreased significantly after MIST, but transcutaneous partial carbon dioxide pressure was comparable with pre-MIST values. Ventilation distribution remained unchanged. CONCLUSIONS MIST results in a rapid and homogeneous increase in EELV, which is associated with an improvement in oxygenation.

Changes in lung volume and ventilation following transition from invasive to noninvasive respiratory support and prone positioning in preterm infants

Background:To minimize secondary lung injury, ventilated preterm infants are extubated as soon as possible. To maximize extubation success, they are often placed in prone position. The effect of extubation and subsequent prone positioning on lung volumes is currently unknown.Methods:Changes in end-expiratory lung volume (ΔEELV), tidal volume (VT), and ventilation distribution were monitored during transition from endotracheal to nasal continuous positive airway pressure and following prone positioning using electrical impedance tomography. In addition, the continuous distending pressure (CDP) and oxygen need (FiO2) were recorded.Results:Twenty preterm infants (GA 28.7 ± 1.7 wk) were included. Following extubation, the CDP decreased from 7.9 ± 0.5 to 6.0 ± 0.2 cmH2O, while the FiO2 remained stable. Both ΔEELV and VT increased significantly (P < 0.05) after extubation, without changing ventilation distribution. Prone positioning resulted in a further increase in ΔEELV (P < 0.01) and a decrease in respiratory rate. VT remained stable but its distribution clearly shifted toward the ventral lung regions.Conclusion:Infants who are transitioned from invasive to noninvasive respiratory support are able to maintain their EELV and increase their VT. Prone positioning increases EELV and shifts tidal ventilation to the ventral lung regions. The latter suggests that infants should preferably be placed in prone position after extubation.

Diaphragmatic activity during weaning from respiratory support in preterm infants

Objective To determine if weaning from nasal continuous positive airway pressure (nCPAP) to lesser supportive low flow nasal cannula (LFNC) results in a change in electrical activity of the diaphragm in preterm infants. Design Prospective observational study. Setting Neonatal intensive care unit. Patients Stable preterm infants weaned from nCPAP to LFNC (1 L/min). Main outcome measures Change in diaphragmatic activity, expressed as amplitude, peak and tonic activity, measured by transcutaneous electromyography (dEMG) from 30 min before (baseline) until 180 min after weaning. Subgroup analysis was performed based on success or failure of the weaning attempt. Results Fifty-nine preterm infants (gestational age: 29.0±2.4 weeks, birth weight: 1210±443 g) accounting for 74 weaning attempts were included. A significant increase in dEMG amplitude (median, IQR: 21.3%, 3.6–41.4), peak (22.1%, 8.7–40.5) and tonic activity (14.3%, −1.9–38.1) was seen directly after weaning. This effect slowly decreased over time. Infants failing the weaning attempt tended to have a higher diaphragmatic activity than those successfully weaned. Conclusions Weaning from nCPAP to LFNC leads to an increase in diaphragmatic activity measured by dEMG and is most prominent in preterm infants failing the weaning attempt. dEMG monitoring might be a useful parameter to guide weaning from respiratory support in preterm infants.