Flow-synchronized Nasal IMV in Preterm Infants

The use of non-invasive methods of respiratory support to reduce complications of prolonged invasive mechanical ventilation in preterm infants has increased. The most common mode is nasal intermittent mandatory ventilation (NIMV). In NIMV, the interval between mechanical breaths is fixed and is determined by the frequency dialed by the clinician. Asynchrony between the infant's spontaneous breathing may exist since mechanical breaths delivered at fixed intervals can occur at different times over the inspiratory or expiratory phases of the infant's spontaneous breathing. Synchronized-NIMV is a mode similar to NIMV where the ventilator cycle is delivered in synchrony with the infant's spontaneous inspiration. This has been achieved by using techniques to detect the infant's spontaneous inspiration. The advantages or disadvantages of synchronized compared to non-synchronized NIMV remain to be determined. This study seeks to evaluate the effect of synchronized NIMV versus non-synchronized NIMV on ventilation and gas exchange in premature infants who require supplemental oxygen. The hypothesis is that the use of flow synchronized nasal intermittent mandatory ventilation (S-NIMV) in comparison to non-synchronized NIMV will improve ventilation and gas exchange and reduce breathing effort. The objective of the study is to compare the effect of flow synchronized-NIMV to non-synchronized-NIMV on tidal volume (VT), minute ventilation (VE), gas exchange, breathing effort, apnea and chest wall distortion in preterm neonates with lung disease.

During the study infants assigned to this arm will undergo a 2-hour period of non-synchronized NIMV followed by a 2-hour period of Synchronized-NIMV.

During the study infants assigned to this arm will undergo a 2-hour period of synchronized NIMV followed by a 2-hour period of non-synchronized NIMV.

During the study each infant will undergo a 2-hour period of NIMV at a frequency of 30 cycles per minute. NIMV will be provided by a time cycled, pressure limited neonatal ventilator (Puritan Bennett 840, Covidien, Boulder, CO).

During the study each infant will undergo a 2-hour period of S-NIMV at a frequency of 30 cycles per minute. S-NIMV will be provided by a time cycled, pressure limited neonatal ventilator, with leak compensation capacity and nasal flow triggered ventilation (Puritan Bennett 840, Covidien, Boulder, CO). Synchronization will be achieved by the leak compensation software and the internal sensor of the ventilator.

Measurements of minute ventilation (VE in ml-units/min/Kg) by respiratory inductance plethysmography during flow synchronized-NIMV will be compared to measurements during non-synchronized-NIMV

Measurements of tidal volume (VT in ml-units/Kg) by respiratory inductance plethysmography during flow synchronized-NIMV will be compared to measurements during non-synchronized-NIMV

Measurements of arterial oxygen saturation (%) by pulse oximetry obtained during flow synchronized-NIMV will be compared to measurements obtained during non-synchronized-NIMV

Required fraction of inspired oxygen during flow synchronized-NIMV will be compared to measurements obtained during non-synchronized-NIMV

Measurements of transcutaneous carbon dioxide tension (mmHg) obtained during flow synchronized-NIMV will be compared to measurements obtained during non-synchronized-NIMV

Measurements of inspiratory breathing effort obtained by esophageal manometry (cmH2O) during flow synchronized-NIMV will be compared to measurements obtained during non-synchronized-NIMV

Measurements of inspiratory chest wall distortion (Tcd/Vt ratio) obtained during flow synchronized-NIMV will be compared to measurements obtained during non-synchronized-NIMV

Measurements of inspiratory chest wall distortion (phase lag in degrees) obtained during flow synchronized-NIMV will be compared to measurements obtained during non-synchronized-NIMV

Measurements of apneic respiratory pauses (#/hour) obtained during flow synchronized-NIMV will be compared to measurements obtained during non-synchronized-NIMV

Inclusion Criteria: Preterm infants of 30 or less weeks of gestational age Receiving NIMV Requiring Fi02 > 0.21 to keep Sp02 > 90% Parental written informed consent Exclusion Criteria: Major congenital anomalies Proven sepsis within 72 hours of the study Hypotension requiring pressors within 72 hours of the study Pneumothorax or pneumomediastinum within 72 hours of the study Current suspected necrotizing enterocolitis, spontaneous perforation or severe abdominal distention