2006 OPEN FORUM Abstracts
SYNCHRONIZING PHIGH AND PLOW DURING AIRWAY PRESSURE RELEASE VENTILATION IN A PEDIATRIC PATIENT
Keith R. Hirst RRT, Peter Betit RRT-NPS, David Heitz RRT-NPS, David A. Turner
MD.
Children's Hospital Boston and
Introduction:
Airway pressure release ventilation (APRV) is a ventilator mode aimed at
recruiting and maintaining lung volume, while preserving spontaneous
ventilation1. In our center, APRV is applied with the AveaT
ventilator (Viasys Healthcare,
Background: The patient was a child
with Bardet Biedl Syndrome admitted for suspected aspiration during induction
for an endoscopy. The patient subsequently developed ARDS, and required
high-frequency oscillatory ventilation (HFOV) and muscle relaxation due to
worsening lung compliance and gas exchange. Over the 7 day HFOV course, gas
exchange improved and the patient was transitioned to APRV in order to promote
spontaneous ventilation. Initial APRV settings were; FIO2
0.6, PHIGH /PLOW of 25/0 cmH2O, and THIGH
/TLOW 6.0/0.8 seconds, Paw 22 cmH2O. At hour 36 of APRV the patient developed a
pneumothorax, received a chest tube, and transitioned to PSV/PEEP of 10/8 cmH2O
in order to minimize further barotrauma. Over the next 48 hours, the patient's
gas exchange worsened and work of breathing increased. The mode was changed to
SIMV-PCV + PSV with no improvement. In an attempt to avoid HFOV and the need
for paralysis, a second trial of APRV was employed with the settings; FIO2
0.7, PHIGH/PLOW of 23/0 cmH2O, and THIGH
/TLOW of 5.5/0.3 sec, Paw 22 cmH2O. During the transition
to APRV, the patient became tachypneic, tachycardic, hypertensive, diaphoretic,
and accessory muscle use was noted. The increase in work of breathing was
presumed to be from under-recruited lungs and increases in PHIGH
were attempted and were unsuccessful. The APRV synchronization features were
added; 20% TLOW Synch
for PLOW to PHIGH transition, and 5% THIGH Synch for PHIGH to PLOW
transition. After these changes were made, work of breathing and RR
subsequently decreased, and the patient appeared more comfortable. Blood
pressure and heart rate returned to clinically acceptable levels, and there was
no recurrence of air leak. Gas exchange improved over the next 9 days and the
patient was transitioned from APRV settings of FIO2 0.45 PHIGH/PLOW
16/0 cm H2O THIGH/TLOW 10/0.7 sec, to PSV/PEEP
of
12/8 cmH2O. The
patient was successfully extubated 2 days later.
Discussion: The addition of TLOW
Synch and THIGH Synch
in this case improved the patient / ventilator interaction during APRV. The
APRV advanced settings of TLOW
Synch and THIGH Synch
are adjusted as a percentage of TLOW
and THIGH and are unique to the AveaT. It is possible that the lack of improvement
and the development of a pnuemothorax may have been avoided if the
synchronization features were used in the initial APRV attempt. Prior to this patient, we had not used this
feature as part of our APRV settings. This
case has assisted us with further developing our APRV protocol, and we now
routinely synchronize to improve patient/ventilator interactions. Clinical trials are warranted to validate the
benefits of synchronization during APRV.
1. Habashi N, Andrew P
(2004). Ventilator strategies for posttraumatic acute respiratory distress
syndrome: airway pressure release ventilation and the role of spontaneous
breathing in critically ill patients. Curr
Opin Crit Care 10(6):549.