Temporary limited peak pressure increase following endotracheal suctioning in ventilated patients.

Mechanical ventilation is one of the mainstays of paediatric intensive care.
Part of routine care for ventilated patients is frequent endotracheal (ET)
suctioning in order to remove bronchial secretions. This procedure may lead to
a significant, but usually transient, loss of lung volume and a concomitant
decrease in oxygenation. Literature data suggest the beneficial effect of
temporarily increasing airway pressures to reopen collapsed lung regions.
The optimal method for this rerectuitment of lung volume has not yet been
established however. Titration of pressures based on the quasi static pressure
volume curve of the respiratory system has been suggested, but this method is
labour intensive, lacks regional information and has no real scientific
foundation (5). Other studies suggest the use of high inspiratory and
expiratory pressures during a brief period. These manoeuvres may have
significant unwanted circulatory effects .
In our clinical practice, we use manoeuvres aimed at recruiting lung volume, in
order to ventilate the respiratory in its most compliant situation, but given
the unwanted side effects of application of high airway pressures, we try to
avoid the procedure when possible. For this reason, we do not routinely apply
high pressure recruitment procedures following ET suctioning, but temporarily
increase peak airway pressures with 2 cm H2O, based on the knowledge that
recruitment is not only pressure, but also time dependent; lower pressures for
a longer period of time might be effective as pressure pulses in recruiting
lung volume. This practice however lacks scientific foundation. We therefore
designed this study, in order to assess the safety and efficacy of temporary
limited peak pressure increase following ET suctioning in ventilated paediatric
patients.

the aim of the study is to assess whether short lived limited increases in
airway pressure are sufficient to combat ET suction induced hypoxemia

Suction procedure: ET suctioning will be performed with 2 hour intervals, as is
routine in our department. When needed, based on clinical evaluation, time
between may be reduced. The catheter will be inserted to the tip of te ET tube.
Suction will be applied at a pressure of -100 mmHg (13.3 kPa) for 6 seconds
while simultaneously withdrawing the catheter. Ventilator setting changes will
be according to protocol. Saline will not be installed during ET suctioning.
During measurements, patients will not be handled, and ventilator settings will
only be changed as dictated by this protocol. During the suction protocol,
patients will be ventilated in a pressure controlled mode, according to
randomisation peak pressure above PEEP will be maintained at baseline level or
will be increased by 2 cm H2O for 10 minutes following initiation of ET
suctioning.
Changes in lung volume will be estimated from 30 sec. before (baseline) ET
suctioning until 600 sec following ET suctioning using continuous respiratory
inductive plethysmography (11). Recordings will be devided in four phases:
baseline (pre suction), suction (from the onset of application of negative
pressure), immediate post suction (first 60 seconds following withdrawal of the
catheter) and late post suction (a period until 10 minutes following withdrawal
of the suction catheter). At the end of each phase, chages in end expiratory
lung volume will be determined and expressed relative to the value at baseline.
Pulseoxymetry values will be noted and written down at baseline (prior to the
introduction of the suction catheter), at the end of each period as described
above, additionally time between initiation of ET suctioning (phase 2) and
restoration of saturation at its baseline will be recorded.

intervention: 10 minutes increase of inspiratory pressure,
control: unchanged ventilator settings.

none expected