mandatory ventilation and demonstrated a modest benefit
in pulmonary outcomes. Babies allocated to the HFOV
group were extubated at an earlier age (13 vs 21 d), and
there was a small but significant increase in survival with-
out supplemental oxygen at 36 weeks corrected age. The
United Kingdom trial, in which 3 different high-frequency
oscillation ventilators were used, showed no significant
differences in the incidence of BPD, death, or other com-
plications. It is important to recognize the substantial cen-
ter-to-center variability of experience with this ventilation
modality, which probably accounts for the differences in
reported outcomes.
51
Furthermore, the question of whether
high-frequency ventilation should be used as a primary
mode of ventilation or a rescue modality remains unre-
solved, mainly because of serious concerns regarding cen-
tral nervous system complications.
50
In recent years, permissive hypercapnia, a strategy in-
tended to minimize ventilator-induced lung injury, has
gained popularity. Briefly, in this approach, the patient’s
arterial carbon dioxide concentration is kept between 45
and 55 mm Hg. In animal models the use of permissive
hypercapnia was associated with less lung injury.
57
Fur-
thermore, clinical studies in adults with acute respiratory
distress syndrome have shown increased survival. Theo-
retically, the potential advantages from this approach in-
clude less volutrauma, fewer adverse effects from hypo-
capnia, and increased oxygen unloading. Whether this may
translate into a decrease in the incidence of BPD is un-
clear. Also, the potential disadvantages from sustained high
carbon dioxide levels in premature infants, including hy-
poxemia, cerebral vasodilation, increase in IVH, and ret-
inopathy of prematurity, cannot be ignored. Clearly, care-
ful evaluation of this approach is necessary. In a large,
multicenter, randomized, controlled trial, which included
220 patients with birthweights between 501 and 1,000 g,
permissive hypercapnia was not associated with a reduc-
tion of BPD. Interestingly, in the hypercapnia group there
was significantly less need for ventilatory support at 36
weeks corrected age (1% vs 16% in the control group),
whereas there were no differences in other morbidities.
Unfortunately, this study was terminated prematurely be-
cause of substantial complications (eg, spontaneous intes-
tinal perforation) arising from the concurrent use of ste-
roids.
58,59
All forms of mechanical ventilation of the immature
lung probably promote some degree of ventilator-induced
lung injury. Therefore, techniques that favor spontaneous
breathing with early lung recruitment may be required to
decrease BPD. Early lung recruitment is crucial and im-
perative to reduce the deleterious effect of atelectrauma
and should probably begin in the delivery room.
In recent years, there has been a renewed interest in
noninvasive modalities of respiratory support, specifically,
CPAP. The use of CPAP, originally introduced in the early
1970s by Gregory for the treatment of infants with RDS,
has steadily increased since the early 1990s and regained
an important place in the management of RDS. There are
clear benefits of CPAP over mechanical ventilation of the
immature lung. Animal studies with premature lambs
showed that CPAP decreases the influx of granulocytes
and the presence of hydrogen peroxide formation (a marker
of white cell activation) in alveolar lavage cells, compared
to mechanically ventilated animals.
60
In a randomized, con-
trolled trial by the National Institute of Child Health and
Human Development Neonatal Research Network, the use
of surfactant and early extubation to CPAP in babies be-
tween 1,250 and 2,000 g showed a decreased need for and
duration of mechanical ventilation.
61
Unfortunately, the
trial was halted early because of lack of enrollment. A
similar multicenter, randomized trial by Verder et al showed
similar results.
62
None of these studies showed a reduction
in oxygen dependence at 28 days or 36 weeks corrected
gestational age. From current available evidence, one could
conclude that nasal CPAP after surfactant replacement is a
reasonable alternative treatment for premature infants with
RDS; however, the effect on the incidence of BPD is less
clear. Whether the addition of synchronized intermittent
mandatory ventilation to nasal CPAP will reduce the need
for reintubation in some of the smaller patients, who fre-
quently develop apnea, is not clear.
63
Increasing gesta-
tional age and prophylactic surfactant are important vari-
ables associated with a higher success rate.
The development of new ventilatory modalities may be
required to decrease ventilator-induced lung injury and to
maximize the beneficial effects of surfactant therapy. The
challenge to improve long-term pulmonary outcomes in
the high-risk population has not yet been met.
Nitric Oxide for Premature Babies with Respiratory
Distress Syndrome
Several randomized, controlled trials performed during
the last decade provide solid scientific evidence about
safety, patient selection criteria, dosage, and short-term
and long-term outcomes associated with inhaled nitric ox-
ide in term and near-term babies.
64,65
Therefore, in 1999
inhaled nitric oxide received United States Food and Drug
Administration approval and is now widely used for the
treatment of infants with hypoxic respiratory failure, pri-
marily persistent pulmonary hypertension of the newborn.
Some preterm infants with severe RDS, who develop per-
sistent hypoxemia due to pulmonary vasoconstriction, could
potentially benefit from this therapy. Several small trials
have now evaluated acute responses to inhaled nitric oxide
in preterm infants and demonstrated significant improve-
ment in oxygenation, but no differences in mortality.
66 – 68
However, little is known about the potential adverse ef-
fects of inhaled nitric oxide in this population of patients,
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