Introduction
Respiratory distress syndrome (RDS) is the most common cause of neonatal
morbidity and mortality in preterm infants 1. The
incidence of RDS is inversely proportional to gestational age, occurring
in > 90% in preterm infants born < 28 weeks2. These infants are rescued with surfactant
administration via an endotracheal tube and supported with nasal
continuous positive airway pressure after a brief period of mechanical
ventilation. The European guidelines for management of RDS in preterm
infants reserve the use of mechanical ventilation to rescue babies who
are not responding to positive pressure ventilation via face mask nasal
prongs. Tracheal extubation is expected to ensue shortly after
surfactant administration and stabilization of oxygenation3. However, due to certain limitations, this practice
has not been fully adopted outside the Western world, thereby allowing
mechanical ventilation for several days.
Both mechanical ventilation and tracheal intubation are independently
associated with intraventricular hemorrhage in premature infants4. The exposure of infants to multiple intubations is
not a safe practice. Studies demonstrated significant hemodynamic
derangements that occur during intubation of premature infants5. Consequently, intubation has been associated with
increased risk for intraventricular hemorrhage in premature infants4. Since there is no clear criteria to guide
clinicians when to extubate, infants may not necessarily succeed the
extubation attempt and are subsequently re-intubated. Therefore, there
is an unmet need to device an indicator for readiness to extubate in
order to avoid the risks associated with re-intubation.
Lung ultrasound can recognize a normal aerated lung in contrast to
interstitial or alveolar patterns. In the last decade, lung ultrasounds
have been increasingly used in critically ill patients, and evidence
based international guidelines are published for the use of lung
ultrasounds in adult critical care 6. It is simple and
raises no threat of radiation. Evidence-based guidelines for lung
ultrasound utilization in neonates have been recently published7.
Echocardiography is considered the gold standard tool to detect
anatomical cardiovascular defects, assess cardiac function, evaluate
abnormal pulmonary circulation and estimate the response to therapeutic
interventions. However, it requires specific skills and detailed
training for a caregiver to perform neonatal echocardiography8. Focused heart ultrasound is a simplified protocol
of bedside ultrasound screening of pulmonary hypertension by measuring
left ventricular eccentricity index (LVEI). LVEI is a quantifiable
measure of the amount of distortion of ventricular septal geometry that
is related to increased right ventricular systolic or diastolic
pressures and volumes. LVEI has been associated with pulmonary
hypertension in children and adults but has not been validated in
premature infants 9.
This prospective study was conducted on premature infants supported with
mechanical ventilation for several days. Infants had point of care lung
ultrasound and LVEI measurements. The aim of this study was to test the
hypothesis that a LUS combined with LVEI would predict success of
extubation in mechanically ventilated preterm infants. In addition,
correlations of LVEI with pulmonary artery pressures and patent ductus
arteriosus were made.