High-frequency nasal ventilation for 21 d maintains gas exchange with lower respiratory pressures and promotes alveolarization in preterm lambs

Abstract

BackgroundShort-term high-frequency nasal ventilation (HFNV) of preterm neonates provides acceptable gas exchange compared to endotracheal intubation and intermittent mandatory ventilation (IMV). Whether long-term HFNV will provide acceptable gas exchange is unknown. We hypothesized that HFNV for up to 21d would lead to acceptable gas exchange at lower inspired oxygen (O2) levels and airway pressures compared to intubation and IMV.MethodsPreterm lambs were exposed to antenatal steroids, and treated with perinatal surfactant and postnatal caffeine. Lambs were intubated and resuscitated by IMV. At ~3h of age, half of the lambs were switched to non-invasive HFNV. Support was for 3d or 21d. By design, PaO2 and PaCO2 were not different between groups.ResultsAt 3d (n=5) and 21d (n=4) of HFNV, fractional inspired O2 (FiO2), peak inspiratory pressure, mean airway, intra-tracheal, and positive end-expiratory pressures, oxygenation index, and Alveolar-arterial gradient were significantly lower than matched periods of intubation and IMV. PaO2/FiO2 ratio was significantly higher at 3d and 21d of HFNV compared to matched intubation and IMV. HFNV led to better alveolarization at 3d and 21d.ConclusionLong-term HFNV provides acceptable gas exchange at lower inspired O2 levels and respiratory pressures compared to intubation and IMV.

Utility of large-animal models of BPD: chronically ventilated preterm lambs

“…Another physiological result in our most recent report is that intratracheal pressure is very low during less invasive HFNV (135). We measured intratracheal pressure in situ while the preterm lambs breathed spontaneously.…”

“…Another difference, at least during the initial years using the preterm lamb model, is that the ductus arteriosus was surgically ligated within a few days of preterm birth (6,20,139). The protocol was subsequently changed to let the ductus close spontaneously (5,135,150). Rationale for eliminating ductal ligation was to minimize surgical trauma to the lung and postoperative edema, inflammation, infection, and atelectasis.…”

“…This deficiency of capillary vascular surface area is compounded by fewer pre-and postcapillary arterioles and venules (6,20). The breadth of diminished growth of pulmonary capillaries and microvessels contributes to the respiratory failure that necessitates continued invasive mechanical ventilation with oxygen-rich gas (6,135).…”

“…Adapted and modified from Ref. 135. of ventilation lead to less inflammation (91), more production of surfactant (131), and better alveolarization and capillary growth compared with invasive mechanical ventilation (91,135,150,182).…”

“…Two recent physiological reports by our group shows that less invasive high-frequency nasal ventilation (HFNV) in spontaneously breathing preterm lambs is associated with appropriate respiratory gas exchange for 3 days or 21 days (135,150). We use a high-frequency, flow-interruption ventilator that also provides background conventional breaths (model VDR4, Percussionaire, Sand Point, ID).…”