Michael Prendergast

Work of Breathing and Different Levels of Volume-Targeted Ventilation

OBJECTIVES. The objectives of this study were to determine the impact of different volume-targeted levels on the work of breathing and to investigate whether a level that reduced the work of breathing below that experienced during ventilatory support without volume targeting could be determined. METHODS. The transdiaphragmatic pressure-time product, as an estimate of the work of breathing, was measured for 20 infants (median gestational age: 28 weeks) who were being weaned from respiratory support by using patient-triggered ventilation (either assist-control ventilation or synchronous intermittent mandatory ventilation). The transdiaphragmatic pressure-time product was measured first without volume targeting (baseline) and then at volume-targeted levels of 4, 5, and 6 mL/kg, delivered in random order. After each volume-targeted level, the infants were returned to baseline. Each step was maintained for 20 minutes. RESULTS. The mean transdiaphragmatic pressure-time product was higher with volume targeting at 4 mL/kg in comparison with baseline, regardless of the patient-triggered mode. The transdiaphragmatic pressure-time product was higher at a volume-targeted level of 4 mL/kg in comparison with 5 mL/kg and at 5 mL/kg in comparison with 6 mL/kg. The mean work of breathing was below that at baseline only at a volume-targeted level of 6 mL/kg. CONCLUSIONS. Low volume-targeted levels increase the work of breathing during volume-targeted ventilation. Our results suggest that, during weaning, a volume-targeted level of 6 mL/kg, rather than a lower level, could be used to avoid an increase in the work of breathing.

Chorioamnionitis, lung function and bronchopulmonary dysplasia in prematurely born infants

Objective To determine whether prematurely born infants exposed to chorioamnionitis compared to those not exposed have poorer lung function and are more likely to develop severe bronchopulmonary dysplasia (BPD). Design Results were analysed from consecutive infants born at <33 weeks gestation with placental histology results and lung function measurement results on days 2 and/or 7 after birth and/or at 36 weeks postmenstrual age (PMA). Setting Tertiary neonatal intensive care unit. Patients 120 infants with a median gestational age of 29 (range 23–32) weeks were studied, 76 (63%) developed BPD and 41 (34%) had been exposed to chorioamnionitis and/or funisitis. Interventions Chorioamnionitis was diagnosed histologically. Main outcome measures Lung function was assessed by measurement of lung volume and compliance and resistance of the respiratory system. If the infants remained oxygen dependent beyond 28 days, they were diagnosed at 36 weeks PMA to have mild BPD (no longer oxygen dependent), moderate BPD (required less than 30% oxygen) or severe BPD (required more than 30% oxygen and/or positive pressure support). Results No significant differences were found in the lung function results between the chorioamnionitis and non-chorioamnionitis groups at any postnatal age. There was no significant relationship between chorioamnionitis and the occurrence or severity of BPD. Regression analysis demonstrated BPD was significantly related only to birth weight, gestational age and use of surfactant. Conclusion In prematurely born infants, routinely exposed to antenatal steroids and postnatal surfactant, chorioamnionitis was not associated with worse lung function or more severe BPD.

Difficult extubation in low birthweight infants

Randomised trials have demonstrated that ventilation techniques which support every spontaneous breath are the most efficacious weaning modes. Nasal continuous positive airway pressure after extubation reduces the likelihood of incidents leading to the need for reintubation in very low birthweight infants; further work is needed to determine if there are advantages of particular delivery techniques. Both methylxanthines and dexamethasone facilitate weaning and extubation; the efficacy of low-dose dexamethasone merits further investigation. Assessments of the efficacy of respiratory efforts and hence the balance of respiratory drive, muscle performance and respiratory load appear to best predict weaning and extubation success. Essential to the success of weaning and extubation are dedicated staff, whether this will be assisted by computerised decision-making tools requires testing. The above approaches are not mutually exclusive and those indicated by this review as appropriately evidence based should be considered by practitioners for current use to reduce difficult/unsuccessful extubation.

Three‐dimensional ultrasound fetal lung volumes and infant respiratory outcome: a prospective observational study

Please cite this paper as: Prendergast M, Rafferty G, Davenport M, Persico N, Jani J, Nicolaides K, Greenough A. Three‐dimensional ultrasound fetal lung volumes and infant respiratory outcome: a prospective observational study. BJOG 2011;118:608–614.

Chest radiograph thoracic areas and lung volumes in infants developing bronchopulmonary dysplasia.

To determine whether chest radiograph (CXR) thoracic areas and lung volumes differed between infants who did and did not develop BPD and according to the severity of BPD developed.

Lung function at follow-up of infants with surgically correctable anomalies

Infants with congenital diaphragmatic hernia (CDH) or anterior wall defects (AWD) can suffer abnormal antenatal lung growth, the risk, however, may be greater for CDH infants. The objectives of this study were to test the hypothesis that following surgical correction, CDH infants would have worse lung function at follow‐up than AWD infants and to determine whether fetal lung volume (FLV) results correlated with the lung function results at follow‐up.

Risk factors for the development of bronchopulmonary dysplasia: the role of antenatal infection and inflammation

Bronchopulmonary dysplasia, chronic oxygen dependency, is a common adverse outcome of very premature birth. It has important implications for health resource utilization, since affected children require frequent readmissions to hospital in the first 2 years after birth and, even as adolescents, have lung function abnormalities and troublesome respiratory symptoms. The current population of very prematurely born infants may develop chronic oxygen dependency in the absence of severe, acute respiratory distress, so-called ‘new’ bronchopulmonary dysplasia. This appears to be the result of impaired antenatal lung growth; antenatal infection and inflammation make the premature infant’s lungs more vulnerable to injury.

Three-dimensional ultrasound fetal lung volumes and infant respiratory outcome

Please cite this paper as: Prendergast M, Rafferty G, Davenport M, Persico N, Jani J, Nicolaides K, Greenough A. Three‐dimensional ultrasound fetal lung volumes and infant respiratory outcome: a prospective observational study. BJOG 2011;118:608–614.

Three-dimensional ultrasound fetal lung volumes and infant respiratory outcome: a prospective observational study: Fetal lung volumes

Please cite this paper as: Prendergast M, Rafferty G, Davenport M, Persico N, Jani J, Nicolaides K, Greenough A. Three‐dimensional ultrasound fetal lung volumes and infant respiratory outcome: a prospective observational study. BJOG 2011;118:608–614.