Pathophysiology of respiratory distress syndrome

Respiratory distress syndrome (RDS) is a major cause of neonatal mortality and morbidity, especially in preterm infants. Its aetiology includes developmental immaturity of the lungs, particularly of the surfactant synthesizing system. Surfactant is produced, stored and recycled by type II pneumocytes and is detectable from about 24 weeks’ gestation. It is a mixture of phospholipids, neutral lipids and proteins and is spread as a film over the alveolar surface to lower surface tension and to prevent alveolar collapse. The resulting clinical correlates of RDS can be predicted from the immature lung structure and atelectasis which occur due to surfactant deficiency. Various clinical factors are known to dysregulate surfactant production and function, leading to the development of RDS. Apart from preventing the incidence of prematurity, antenatal steroids and prophylactic surfactant are of proven benefit in reducing the incidence of RDS

Electromagnetic inductance plethysmography to measure tidal breathing in preterm and term infants

Tidal breathing measurements which provide a non-invasive measure of lung function in preterm and term infants are particularly useful to guide respiratory support. We used a new technique of electromagnetic inductance plethysmography (EIP) to measure tidal breathing in infants between 32 and 42 weeks postconceptional age (PCA). Tidal breathing was measured in 49 healthy spontaneously breathing infants between 32 and 42 weeks PCA. The weight-corrected tidal volume (V(T) ) and minute volume (MV) decreased with advancing PCA (V(T) 6.5 ± 1.5 ml/kg and MV 0.44 ± 0.04 L/kg/min at 32-33 weeks, respectively; 6.3 ± 0.9 ml/kg and 0.38 ± 0.02 L/kg/min at 34-36 weeks; and 5.1 ± 1.1 ml/kg and 0.28 ± 0.02 L/kg/min at term, V(T) P < 0.001 and MV P < 0.01 for 32-33 weeks PCA vs. term; V(T) P = 0.016 and MV P = 0.015 for 34-36 weeks PCA vs. term). Respiratory frequency and the phase angle decreased significantly with advancing PCA but the flow parameter t(PTEF) /t(E) did not change significantly. Using a new technique to measure tidal breathing parameters in newborn infants, our data confirms its usability in clinical practice and establishes normative data which can guide future respiratory management of newborn infants. Pediatr Pulmonol. © 2012 Wiley Periodicals, Inc

Tidal breathing in preterm infants receiving and weaning from continuous positive airway pressure

Objective: To compare tidal breathing on different continuous positive airway pressure (CPAP) devices and pressures and to serially measure tidal breathing during weaning off CPAP using electromagnetic inductive plethysmography. Study design: Using electromagnetic inductive plethysmography, tidal breathing was measured in 29 preterm infants receiving CPAP, gestational age 28 ± 2 weeks. Variable-flow nasal CPAP (nCPAP), bubble CPAP (bCPAP) at pressures of 5, 7, and 9 cmH2O, nasal bi-level positive airway pressure (nBiPAP) system at pressures of 5, 7/5, and 9/5 cmH2O, and unsupported breathing were studied. Twenty-one infants had weekly tidal breathing measurements on and off nCPAP. Results: Minute volume (MV/kg) was similar between all devices (0.30-0.33 L/kg/min). On bCPAP, weight corrected tidal volume (VT/kg) was the least, changing little with increasing pressures. On nCPAP and nBiPAP, VT/kg increased with increasing pressure and the respiratory rate (fR) decreased. The delivered pressure varied slightly from the set pressure being most dissimilar on nBiPAP and similar on bCPAP. Compared with unsupported breathing, all devices decreased VT/kg, MV/kg, and phase angle, but did not alter fR. Serial tidal breathing measurements showed decreasing difference for VT/kg over time on and off nCPAP. Conclusions: At different pressure settings, on all CPAP devices the measured MV/kg was similar either through increasing VT/kg and decreasing fR (nCPAP and nBiPAP) or maintaining both (bCPAP). Serial tidal breathing measurements may aid weaning from CPAP

Estimation of tidal ventilation in preterm and term newborn infants using electromagnetic inductance plethysmography

Tidal volume (VT) measurements in newborn infants remain largely a research tool. Tidal ventilation and breathing pattern were measured using a new device, FloRight, which uses electromagnetic inductive plethysmography, and compared simultaneously with pneumotachography in 43 infants either receiving no respiratory support or continuous positive airway pressure (CPAP). Twenty-three infants were receiving CPAP (gestational age 28 ± 2 weeks, mean ± SD) and 20 were breathing spontaneously (gestational age 34 ± 4 weeks). The two methods were in reasonable agreement, with VT (r2 = 0.69) ranging from 5 to 23 ml (4–11 ml kg−1) with a mean difference of 0.4 ml and limit of agreement of −4.7 to + 5.5 ml. For respiratory rate, minute ventilation, peak flow and breathing pattern indices, the mean difference between the two methods ranged between 0.7% and 5.8%. The facemask increased the respiratory rate (P < 0.001) in both groups with the change in VT being more pronounced in the infants receiving no respiratory support. Thus, FloRight provides an easy to use technique to measure term and preterm infants in the clinical environment without altering the infant's breathing pattern

Cardiovascular function in children who had chronic lung disease of prematurity

Objectives: Although increased pulmonary arterial pressure is common in infancy in preterm infants who develop chronic lung disease of prematurity (CLD), it is unknown if the increase persists into childhood. We, therefore, assessed if 8–12-year-old children with documented CLD in infancy had evidence of right ventricular dysfunction or pulmonary arterial hypertension at rest or in response to acute hypoxia when compared to preterm and term-born controls. Methods: We studied 90 children: 60 born at ≤32 weeks of gestation (28 with CLD and 32 preterm controls), and 30 term-born controls. All had echocardiography including myocardial velocity imaging, at rest and while breathing 15% oxygen and 12% oxygen for 20 min each. Results: Baseline oxygen saturation, heart rate, blood pressure and echocardiographic markers of left and right ventricular function were similar in all three groups. While breathing 12% oxygen, the oxygen saturation decreased to 81.9% in the CLD group compared to 85.1% (p<0.05) and 84.7% (p<0.01) in the preterm and term controls, respectively. In response to hypoxia, all three groups showed increases in velocity of tricuspid regurgitation, end-diastolic velocity of pulmonary regurgitation, and right ventricular relaxation time; and decreases in pulmonary arterial acceleration time and the ratio of right ventricular acceleration time to ejection time. However, there were no differences between groups. Conclusions: Childhood survivors of CLD have comparable left and right ventricular function at 8–12 years of age to preterm and term-born children, and no evidence of increased pulmonary arterial pressure even after hypoxic exposure

Which clinical features distinguish inflicted from non-inflicted brain injury? A systematic review

Aim: A systematic review of the scientific literature to define clinical indicators distinguishing inflicted (iBI) from non-inflicted brain injury (niBI). Methods: An all language literature search of 20 electronic databases, websites, references and bibliographies from 1970–2008 was carried out. Relevant studies were independently reviewed by two trained reviewers, with a third review where required. Inclusion criteria included primary comparative studies of iBI and niBI in children aged <18 years, with high surety of diagnosis describing key clinical features. Multilevel logistic regression analysis was conducted, determining the positive predictive value (PPV) and odds ratios (OR) with p values for retinal haemorrhage, rib/long bone/skull fractures, apnoea, seizures and bruising to head/neck. Results: 8151 studies were identified, 320 were reviewed and 14 included, representing 1655 children, 779 with iBI. Gender was not a discriminatory feature. In a child with intracranial injury, apnoea (PPV 93%, OR 17.06, p<0.001) and retinal haemorrhage (PPV 71%, OR 3.504, p = 0.03) were the features most predictive of iBI. Rib fractures (PPV 73%, OR 3.03, p = 0.13) had a similar PPV to retinal haemorrhages, but there were less data for analysis. Seizures and long bone fractures were not discriminatory, and skull fracture and head/neck bruising were more associated with niBI, although not significantly so. Conclusions: This systematic review shows that apnoea and retinal haemorrhage have a high odds ratio for association with iBI. This review identifies key features that should be recorded in the assessment of children where iBI is suspected and may help clinicians to define the likelihood of iBI