HIGH-FREQUENCY JET VENTILATION VS CONTINUOUS POSITIVE AIRWAY PRESSUREFOR DIFFERENTIAL LUNG VENTILATION IN PATIENTS UNDERGOING RESECTION OFTHORACOABDOMINAL AORTIC-ANEURYSM

Twenty patients, scheduled for surgical resection of thoracoabdominal aortic aneurysm were divided into two groups according to the type of differential lung ventilation used during graft replacement of the des cending thoracic aorta. In the high-frequency jet ventilation (HFJV) g roup of ten patients, HFJV was applied to the left lung once collapsed and retracted by the surgeon, the patient lying in the right lateral decubitus and being intubated by a Carlens' tube. In the continuous po sitive airway pressure (CPAP) group of ten patients, CPAP was applied to the left lung at the same mean airway pressure as HFJV (1 kPa). Bef ore anaesthetic induction, an arterial and a Swan-Ganz catheter were i nserted for cardiovascular monitoring. The same anaesthetic technique using Fentanyl 6 mu g.kg(-1), flunitrazepam 0.02 mg.kg(-1) and pancuro nium 0.1 mg.kg(-1) was used for each patient. Haemodynamic and respira tory measurements were made: 15 min after positioning the patients in the light lateral decubitus using two-lung ventilation; 15 min after c ollapse and retraction of the left lung using one-lung ventilation and 15 min after using differential lung ventilation with CPAP or HFJV. L eft lung collapse with conventional one-lung ventilation induced a dra matic decrease in arterial oxygenation: Pao(2)/Fio(2) ratio decreased from 43 +/- 6 kPa to 20 +/- 8 kPa, alveolo-arterial oxygen difference increased from 24 +/- 7 kPa to 72 +/- 11 kPa and pulmonary shunt incre ased from 17 +/- 2% to 37 +/- 3%. Whereas differential lung ventilatio n with CPAP did not improve any of the respiratory parameters measured , differential lung ventilation with HFJV, significantly increased Pao (2)/Fio(2) ratio to 41 +/- 14 kPa. Therefore, since HFJV improves gas exchange without altering the conditions of surgical comfort, differen t lung ventilation with HFJV appears to be superior to differential lu ng ventilation with CPAP.