PEDIATRICIAN Spring 2003 - AAP-CA

Twenty-Five Years of Home Mechanical
Ventilation in Children:
The Program at Childrens Hospital Los Angeles
Manisha Witmans, M.D., Sheila S. Kun, R.N., M.S., and Thomas G. Keens, M.D.
Braun introduced the idea of mechanical
ventilation in 1889 and by the
mid 1940s hospitals were able to
care for adults with respiratory failure with
large ventilators called “iron lungs.” The technology
has continued to evolve from a large,
intrusive hospital based system to a lighter,
portable system that allows families to care for
medically complicated patients at home.
Home mechanical ventilation has
changed tremendously in the last 25 years.
The home mechanical ventilation program at
Childrens Hospital Los Angeles (CHLA) is
an example of what is achievable in children
with chronic respiratory failure who require
mechanical ventilation. Since the inception
of the home ventilator program in 1977, the
CHLA program has grown to include over 375
children who are followed for home mechanical
ventilation. The program children requiring
assisted mechanical ventilation have ventilatory
muscle weakness (45%), chronic lung disease
(hypoplastic lungs and chest wall defects)
(26%) and central hypoventilation syndromes
(29%). The CHLA program is unique in that
there is a large number of small infants with
chronic lung disease.
The need for mechanical ventilation
is likely when there is either an increase in
respiratory load or deficiency in the ventilatory
muscle power or central drive, such that
adequate oxygenation and ventilation cannot
be achieved without assistance. Chronic ventilatory
failure is defined as a medical condition
from which an infant or a child, who is
otherwise medically stable, requires mechanical
ventilation and cannot be weaned from
ventilation, despite repeated attempts. Unlike
adults, infants and children are more prone
to respiratory failure because of decreased
ventilatory muscle strength, diaphragm muscle
fatiguability, and smaller airways prone to atelectasis
and obstruction, and proportionately
increased respiratory loads. Thus, infants and
children require different ventilatory strategies
compared to adults.
The philosophy of home ventilation is
quite different from the intensive care perspective
because the goal is to provide chronic,
not acute, support of ventilation. The ventilator
is adjusted to completely meet the child’s
age-appropriate physiological ventilatory
requirements rather than just providing support
to minimize work of breathing. Using the
ventilatory parameters from the intensive care
setting often underestimates ventilatory needs
for home, as children are more likely to be
active at home. This approach allows the child
to expend energy for activities of daily living,
rather than ventilation alone. The strategy
for chronic ventilation is also different from
intensive care units. Smaller, uncuffed tracheostomy
tubes are better alternatives because
they prevent tracheomalacia, iatrogenic tracheal
trauma and allow room for ventilation to
bypass the tracheostomy in the event of tube
obstruction. In addition, they allow children to
speak, as many children on home mechanical
ventilation are able to attend school and other
social events where speaking is necessary.
Ideally, the ventilator parameters are adjusted
to meet the patients’ needs instead of making
the patient adapt to the ventilators mechanical
capabilities.
A variety of modes of ventilation and
types of ventilators are available in the United
States. The choice of ventilator is dependent on
the underlying medical condition and the individual
patient needs. The modes of ventilation
include: non-invasive positive pressure ventilation
with bi-level positive airway pressure,
positive pressure ventilation with a tracheostomy,
negative pressure ventilation and diaphragmatic
pacing. The most common mode of
ventilation is via a tracheostomy and a portable
home ventilator. Compared to older ventilators,
the advantages of the newer ventilators
include: continuous flow, ventilatory strategies
that provide pressure support and/or positive
end-expiratory pressure and have a lightweight
internal battery. Ventilator malfunction is also
surprisingly uncommon. The newer ventilators
are able to provide ventilation for children with
more severe lung disease at home, which has
resulted in improved survival quality of life.
A popular method of providing assisted
ventilation non-invasively is bi-level positive
airway pressure (B-PAP). The interface
consists of a nasal or facemask that delivers
compressed air to splint the airway open
and provide positive inspiratory pressure.
Currently, over 100 children on B-PAP are
followed at CHLA. Children with congenital
hypoventilation, ventilatory muscle weakness
and certain types of chronic lung disease can
be ventilated with B-PAP, especially if the
ventilatory requirements are sleep related. This
type of ventilation does not require a tracheostomy,
has minimal side effects (nasal irritation,
skin breakdown, intolerance of the mask) and
is well tolerated in children.
Children that need mechanical ventilation
have some special requirements related
to ongoing care and follow-up. During acute
illnesses, these children have to be monitored
closely as they may not show signs of respiratory
distress as noticeably as other children.
They may need increased bronchodilator
treatments, more airway clearance treatments,
diuretics, and/or chest physiotherapy. They
often need increased ventilatory support during
respiratory tract infections and hospitalizations.
Two relatively easy monitoring methods
are: pulse oximetry and end tidal Pco 2
monitoring
to ensure adequate oxygenation and
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CALIFORNIA PEDIATRICIAN — SPRING 2003/ 21