2004 OPEN FORUM Abstracts
The use of a slow flow inflation manuever to reduce differences in left and right lung critical opening pressures in post-operative TAAA patients
Raymond
Wolff Jr. RRT, Brian Timon BS, RRT, Ken Hargett BS RRT The
Methodist Hospital, Respiratory Care Department, Houston, TX.
Background:
The Thoracotomy Abdominal Aortic Aneurysm (TAAA) Repair presents
a unique population of patients. Post operative respiratory
complications are reported as high as 35%. These patients have
substantial acute unilateral lung injury as a result of the extreme
manipulation to the left lung during the TAAA repair surgery.
Previous data collected at our institution revealed a large variation
in the right and left lung critical opening pressure. This results in
the complicated task of protecting one lung from hyperinflation and
preventing the opposite lung from experiencing severe refractory
atelectasis during post-op mechanical ventilation. Critical opening
pressure is used at our institution to set PEEP and differences
between lungs makes selecting the correct PEEP difficult. Minimizing
the difference in left and right lung critical opening pressures has
become a goal in this patient population. We investigated a process
of implementing a series of recruitment maneuvers immediately post-op
to improve the left lung compliance.
Method: Data was
collected by performing slow flow inflection maneuvers on 10
post-operative TAAA patients to separately determine the critical
opening pressure of each lung. The Nellcor Puritan Bennett 840
Ventilator was used to perform the inflection maneuver using a strict
protocol and therapists were trained to identify the critical opening
pressure on the pressure-volume curve produced by the maneuver. All
patients had a double-lumen endotracheal tube inserted
pre-operatively which allowed for isolation of left and right lungs.
The maneuvers were done on heavily sedated patients in the absence of
spontaneous breathing. After identifying the critical opening
pressure of the left lung, a recruitment maneuver series was
performed to only the left lung. On the final maneuver of the series
a critical opening pressure was recorded for the left lung.
Results:
The mean results of pre and post recruitment maneuver critical
opening pressure from the 10 patients are listed in the table below.
| Both | Pre Right | Pre Left | Pre Diff | Post Right | Post Left | Post Diff | |
| Average | 6.15 | 6.10 | 11.75 | 5.65 | 5.10 | 7.95 | 2.85 |
There
was initially a significant difference between right and left lung
critical opening pressure and when both lungs were measured together
the critical opening pressure reflected the right lung only. After
performing one recruitment maneuver series the left lung, critical
opening pressure average decreased to 7.9 cmH2O. The left
and right lung critical opening pressure difference was reduced to an
average of 2.8 cmH20.
Conclusions: Using the
inflection maneuver allows you to identify the potentially dramatic
difference in the right to left lung critical opening pressure within
the TAAA population. Our data indicates that differences in critical
opening pressure can be reduced through selective slow flow
recruitment maneuvers immediately post-op in this patient population.
Additional trials are necessary to determine if these maneuvers
reduce post-op respiratory complications.