Anemia of Prematurity - Portal Neonatal

High-frequency ventilation:High-frequency ventilation (HFV) may improve blood gases because, in
addition to the gas transport by convection, other mechanisms of gas exchange may become active
at high frequencies (variable velocity profiles of gas during inspiration and exhalation, gas exchange
between parallel lung units, increased turbulence and diffusion). Extensive clinical use of the various
HFVs has occurred in newborns. High-frequency positive-pressure ventilators employ standard
ventilators modified with low-compliance tubing and connectors, thus an adequate tidal volume may
be delivered despite very short inspiratory time. High-frequency jet ventilation (HFJV) is characterized
by the delivery of gases from a high-pressure source through a small-bore injector cannula. The fast
gas flowing out of the cannula possibly produces areas of relative negative pressure that entrain
gases from their surroundings. High-frequency flow interruption (HFFI) also delivers small tidal
volumes by interrupting the flow of the pressure source, but in contrast to jet ventilation, HFFI does
not use an injector cannula. High-frequency oscillatory ventilation (HFOV) delivers very small volumes
(even smaller than dead space) at extremely high frequencies. Oscillatory ventilation is unique
because exhalation is generated actively, as opposed to other forms of HFV, in which exhalation is
passive. The largest randomized trial of HFV revealed that early use of HFOV did not improve
outcome. However, the trend is toward decreases in BPD, increases in severe intraventricular
hemorrhage and in periventricular leukomalacia, and small increases in air leaks with HFOV and/or
HFFI. However, if used properly, HFV is a safe alternative for infants for whom CMV fails.
Summary: Many advances in neonatal care have led to increased survival of smaller and critically ill
infants. CMV is being used on smaller and more ill infants for longer durations. Sound application of
the basic concepts of gas exchange, pulmonary mechanics, and control of breathing is necessary to
optimize mechanical ventilation. Employment of pathophysiology-based ventilatory strategies,
strategies to prevent lung injury, and alternative modes of ventilation should result in further
improvement in neonatal outcomes.
Table 1. CPAP or High Positive End-expiratory Pressure in Infants With RDS
Pros Cons
Increased alveolar volume and functional
residual capacity
Increased risk for air leaks
Alveolar recruitment Overdistention
Alveolar stability Carbon dioxide retention
Redistribution of lung water Cardiovascular impairment
Improved ventilation/perfusion matching Decreased compliance
May increase pulmonary vascular resistance
Table 2. High Rate, Low Tidal Volume (Low Peak Inspiratory Pressure)
Pros Cons
Decreased air leaks Gas trapping or inadvertent positive end-expiratory
pressure
Decreased volutrauma Generalized atelectasis
Decreased cardiovascular adverse effects Maldistribution of gas
Decreased risk of pulmonary edema Increased resistance