1. Lung injury can be initiated at birth with the
delivery room resuscitation. Adequate tidal
volume must be achieved gradually and
adjusted with each subsequent breath to
achieve adequate, but not excessive, tidal
volume delivery. Time constants vary greatly
within the lung because some alveoli are
collapsed, and some are inflated
2. Pulmonary volutrauma — Volutrauma is
essentially damage to the lung caused by
overdistention by a mechanical ventilator set
for an excessively high tidal volume; resulting
in a syndrome similar to adult respiratory
distress syndrome.[1] Volutrauma is separate
from Pulmonary barotrauma because the
mechanism of injury is excessive volume
(volutrauma), instead of pressure
(barotrauma).
3.
4.
5.
6. AVOIDANCE OF VENTILATOR-INDUCED LUNG
INJURY
The pressure volume curve of the lung has both
upper and lower inflection points. The lower inflection
point is the pressure at which lung volume begins to
decline sharply with falling airway pressure. This represents
the pressure below which atelectasis rapidly
accumulates during deflation. The upper inflection point
is the pressure at which lung volume ceases to increase
sharply with rising airway pressure. This represents
the pressure at which the lung begins to stiffen and
over distend during inflation.
Lung injury might be avoided by ventilating the
lung at a PEEP above the lower inflection point, to prevent
opening and closure of alveoli, while restricting
tidal volume so that end-inspiratory pressure does not
exceed the upper inflection point.
7. Excessive pressure or volume may lead to high
stretch injury when already open alveoli are
overdistended. Sufficient alveoli must be
recruited to establish the optimal functional
residual capacity. This establishes an inflation
history of the lung that tends to resist alveolar
collapse at the end of expiration, provided that
adequate mean airway pressure is provided
throughout the ventilatory cycle. The best
volume of inflation is achieved at the lowest
pressure cost.
8. Maintaining alveolar recruitment with the use
of exogenous surfactant and positive end-
expiratory pressure avoids alveolar collapse
and injury with succeeding distending breaths.
Although there have been significant advances
in neonatal respiratory care, further
improvement in outcomes may be expected by
successfully avoiding ventilator-induced lung
injury.
9. as a treatment of infants, children, and adults
with acute respiratory failure. In HFOV, high mean
airway pressure is maintained by rapid flow of gas across
an outlet valve. The air column is oscillated 5 to 15
times per second, generating tidal volumes smaller than
the patient’s dead space. This oscillation facilitates movement
of CO2 from the patient to the respiratory circuit
of the oscillator, from which it is removed by the brisk
flow of gas toward the outlet valve. This technique
provides excellent lung expansion. Its high mean airway
pressure minimizes the opening and closure of
alveoli. The small oscillations in alveolar pressure avoid
peak pressures above the upper inflection point, as well
as expiratory pressures below the lower inflection point.
HFOV has been shown to reduce direct oxidative injury
to the lung in a surfactant washout model of respiratory
distress[11].
10. Inhaled nitric oxide Nitric Oxide (NO) is a gaseous
pulmonary vasodilator that may be delivered by
inhalation. By that route, it dilates distal vessels of
alveoli, if and only if they are ventilated. This facilitates
matching of ventilation to perfusion in the lung. It has
been argued that inhaled NO may reduce the airway
pressure needed to ventilate the lung and adequately
oxygenate the patient. Documentation that NO improves
outcome in patients with respiratory failure is lacking,
though it is of clear benefit in the treatment of
pulmonary
hypertension[12].
11. Extracorporeal membrane oxygenation Extracorporeal
membrane oxygenation (ECMO) is partial
cardiopulmonary bypass. It entails removal of venous
blood from the right atrium and re-infusion of oxygenated
blood into a vein, the right atrium or the aorta.
ECMO is not, of itself, therapeutic. It does, however,
clearly reduce the need for injurious ventilatory
strategies. The goal of mechanical ventilation during
ECMO can focus on maintaining the lung in an open
position. Like HFOV, ECMO eliminates the need to
apply airway pressures beyond the upper and lower inflection
points. ECMO has been shown to improve
outcome in the neonate with persistent pulmonary hypertension
of the newborn, presumably by reducing the
tendency to injure the lung in the course of supporting
the patient’s gas exchange[13].
Liquid ventilation Partial liquid
12. Liquid ventilation Partial liquid ventilation (PLV)
and total or tidal liquid ventilation (TLV) are experimental
techniques in which the lungs are filled to some volume
with a perfluorochemical liquid having high solubilities
for oxygen and carbon dioxide and low surfacetension. The lungs are then
ventilated with gas
(PLV)[14] or oxygenated perfluorocarbon (TLV)[15].
These techniques take advantage of the low surface
tension of the perfluorocarbon to reduce the airway
pressures required to ventilate the surfactant deficient
lung. They maintain alveolar expansion in expiration by
maintaining an alveolar volume of perfluorocarbon. They
further take advantage of anti-inflammatory properties
of the perfluorocarbon to reduce lung inflammation[16]
and oxidative injury[17,18]. Other means of delivering
perfluorochemicals, such as nebulization and vaporization,
have also been used to apply the beneficial properties
of these liquids to the lungs. Though laboratory
studies demonstrate lung protection by PLV, neither
technique has