Inspiratory: expiratory ratio and pulmonary interstitial emphysema

Neuromuscular blockade and lung function during resuscitation of infants with congenital diaphragmatic hernia

BACKGROUND

There is no consensus or evidence as to whether a neuromuscular blocking agent should be used during the initial resuscitation of infants with congenital diaphragmatic hernia (CDH) in the labour ward.

OBJECTIVE

To determine if administration of a neuromuscular blocking agent affected the lung function of infants with CDH during their initial resuscitation in the labour ward.

METHODS

Fifteen infants with CDH were studied (median gestational age 38 weeks, range 34-41; birth weight 2,790 g, range 1,780-3,976). Six infants had undergone feto-endotracheal occlusion (FETO). Flow, airway pressure, tidal volume and dynamic lung compliance changes were recorded using a respiratory function monitor (NM3, Respironics). Twenty inflations immediately before, immediately after and 5 min after administration of a neuromuscular blocking agent (pancuronium bromide) were analysed.

RESULTS

The median dynamic lung compliance of the 15 infants was 0.22 ml/cm H2O/kg (range 0.1-0.4) before and 0.16 ml/cm H2O/kg (range 0.1-0.3) immediately after pancuronium bromide administration (p < 0.001) and remained at a similar low level 5 min after pancuronium bromide administration. The FETO compared to the non-FETO infants had a lower median dynamic compliance both before (p < 0.0001) and 5 min after pancuronium administration (p < 0.001) and required significantly longer durations of ventilation (p = 0.004), supplementary oxygen (p = 0.003) and hospitalisation (p = 0.007).

CONCLUSIONS

Infants with CDH, particularly those who have undergone FETO, have a low lung compliance at birth, and this is further reduced by administration of a neuromuscular blocking agent.

Failure of observation and impedance respirography to detect active expiration in ventilated preterm infants

Twenty preterm infants ventilated for the respiratory distress syndrome were studied on 44 occasions to identify the pattern of interaction between their spontaneous respiratory efforts and the ventilator, using three techniques: (1) an oesophageal balloon and pneumotachograph, (2) impedance respirography and (3) clinical scoring. The information was in agreement on 23 of the occasions. In 7 infants the balloon and pneumotachograph showed active expiration which was not detected by the other methods. Four of these infants sustained a pneumothorax, one after paralysis with pancuronium. This study shows that only a system incorporating an accurate assessment of the baby's own respiratory pattern is able to detect different patterns of interaction. Impedance respirography and clinical observation appear to be unsatisfactory in this context.