2004 OPEN FORUM Abstracts
APRV USING THE BIVENT MODE ON THE SERVO i VENTILATOR
Paul Luehrs RRT, Kara McKilvain
RRT, Zach Frazier RRT CoxHealth Respiratory Care Springfield,
MO.
INTRODUCTION: Airway Pressure
Release Ventilation (APRV, Drager) has gained in popularity over the
past several years as a mode of mechanical ventilation. APRV, a style
of inverse-ratio ventilation, is most commonly used to support
hypoxemic respiratory failure patients. The majority of published
information regarding APRV references the Drager Evita and the
Puritan Bennett 840 (BiLevel) ventilators. The MAQUET (formerly
SIEMENS) Servo i has the capabilities of performing APRV using
BiVent mode. We compared our use of APRV in the BiVent mode to the
Evita published information.
METHODS: The Servo i
BiVent mode allows the practitioner to set independent
inspiratory (P High) and expiratory (PEEP) pressure settings. Time
spent in each phase is controlled by adjusting inspiratory (T High)
and expiratory (T PEEP) time. These set times determine the I:E ratio
and the frequency of pressure releases. In the severely hypoxemic
patient, the T High and T PEEP are adjusted to produce an inverse
ratio that results in a higher mean airway pressure (MAP). The goal
of the inverse ratio is to inflate the lungs to a set peak pressure
(P High) and periodically release the pressure to a set PEEP, for a
short time (T Peep), in order to allow for exhalation of CO2 while
trapping air and preventing alveolar derecruitment. A randomly
selected group of intubated, acutely hypoxemic respiratory failure
patients (n=11) were placed on the Servo i in the Bivent mode
with a mean P High of 26 cmH2O (24-28), set PEEP 0, mean T High of
4.5 s (3.0-5.5), mean T PEEP of 0.4 s (0.2-0.7). The percent of peak
expiratory flow (%PEF) where T High began was monitored and recorded
every two hours. Manipulations in T PEEP were made in order to
maintain a %PEF between 25% and 75% in an attempt to keep the
PaO2/FiO2 >300.
RESULTS: The mean P High of
27 and mean T PEEP of 0.35 s resulted in a mean %PEF of 51. These
settings resulted in an average MAP of 25 cmH2O. We applied an
average PS above P High of 3 cmH2O to achieve an average total
respiratory rate of 22 breaths/min.
DISCUSSION: Upon initiating
the BiVent mode on the Servo i, we found differences between
the reported APRV settings on a Drager Evita ventilator and the
needed BiVent settings on the Servo i. We analyzed a random
group of patients on the Maquet Servo i BiVent mode in the
various intensive care units. The demographic data between the two
groups comparing age, gender, patients with acute lung injury or
acute respiratory distress syndrome, and the number of extrapulmonary
organ systems in failure, were all found to be similar. In order to
maintain adequate oxygenation, the Servo i requires a shorter
T PEEP (0.4 s), compared to 0.7 s on the Drager. We maintained a set
Peep of 0. We used a low level of PS (3 cmH2O) above P High, and a
moderate T High (4.5 s) to encourage spontaneous breathing. With all
patients, we adjusted the P High to maintain adequate oxygenation and
ventilation.
CONCLUSIONS: APRV using the
Servo i BiVent mode required shorter T PEEP. BiVent allows
settings to be monitored and adjusted to achieve adequate P/F ratios
and successfully meet ventilation requirements for hypoxic
respiratory failure patients.