The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

Difference IN left and right lung Critical Opening pressures in post-operative taaa procedures

Raymond Wolff Jr. RRT, Brian Timon BS, RRT, Jennifer Ma BS, RRT, Ken Hargett RRT, The Methodist Hospital, Respiratory Care Services, Houston, TX.

The Thoracoabdominal Aortic Aneurysm (TAAA) Repair presents a unique population of patients. These patients have substantial acute unilateral lung injury as a result of the complete deflation and manipulation of the left lung during the TAAA repair surgery. Identifying appropriate PEEP for these patients is a difficult task. Current literature suggests inappropriate PEEP levels may contribute to lung injury and sheer stress may occur with the repeated opening and closing of the alveoli. It becomes a difficult task to protect one lung from hyperinflation and prevent the opposite lung from experiencing severe refractory atelectasis. Because of the techniques involved with a TAAA repair, there could be a dramatic difference in the critical opening pressures of the right and left lungs.

Data was collected by performing a slow flow inflection maneuver on 10 post-operative TAAA patients to find out the critical opening pressure of each lung. 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. The PEEP was set to zero and the FIO2 was set to 100% for two minutes prior to the maneuver. The tracheal and bronchial cuffs were inflated on the double-lumen endotracheal tube to isolate each lung. One lung was ventilated via self-inflating manual resuscitation bag while the opposite lung received the slow flow inflection maneuver. The Nellcor Puritan Bennett 840 Ventilator was used to perform the slow flow inflection maneuver using a strict protocol. Bedside staff was trained to identify the critical opening pressure on the pressure-volume loop produced by the maneuver.

A large variation was noted in the right and left lung measurements. The critical opening pressures from the right lung measured 4cmH2O to 10cmH2O with a mean of 6.04 cmH2O. The critical opening pressures from the left lung measured 5.5cmH2O to 18cmH2O with a mean of 11.6cmH2O. The difference in left to right lung critical opening pressures measured 1.6cmH2O to 14cmH2O with a mean of 5.46cmH2O.

Conclusions: Arbitrarily assigning a PEEP level to a TAAA repair patient potentially presents a problem of over-inflation of healthy lung units and failure to recruit atelectatic areas. With use of the slow flow inflection maneuver,we where able to identify a dramatic difference in left to right lung critical opening pressures. With these two pressures encompassing the potential for a large difference, there appears to be an added variable to the dilemma of identifying the optimal PEEP setting for the TAAA patient. Additional research is necessary to identify a possible key to the predicament of ventilating unilateral lung disease. Emphasis, likely will be placed on how to decrease the difference in critical opening pressure between the two lungs through targeted recruitment maneuvers of the manipulated lung, resulting in safer ventilation for the patient.

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