[The effects of a domestically made jet ventilator in dogs during interventional procedures by rigid bronchoscopy under general anesthesia].

OBJECTIVE

To observe the effects of a domestically made jet ventilator in dogs during interventional procedures by rigid bronchoscopy under general anesthesia.

METHODS

Ten healthy mongrel dogs were inserted with a rigid bronchoscope under general anesthesia, and the dogs underwent 3 different ventilation conditions randomly: spontaneous breathing alone (group A), and normal frequency jet ventilation with spontaneous breathing (group B), normal frequency jet ventilation without spontaneous breathing (group C). When the interventional procedure lasted 30 min, 60 min, 90 min, 120 min, blood gas analysis was performed. Arterial blood gas analysis under different driving pressures (0.20 mPa, 0.25 mPa, 0.30 mPa) was compared when dogs underwent normal frequency jet ventilation without spontaneous breathing. Oxygen concentrations at the proximal end and the distal end of the rigid bronchoscope were measured out-of-body, when high pressure oxygen (FiO(2) 100%) was used to drive the normal frequency jet ventilation.

RESULTS

After the operation, PaCO(2) increased all the groups. In group C, PaCO(2) increased and pH decreased remarkably as compared with group A and group B (P < 0.01). In group C, PaO(2) decreased after the operation: compared with group A and group B, the difference being significant (P < 0.05). The ventilation effects of the jet ventilator was closely related with its driving pressure, and higher driving pressure improved the dog's oxygenation and the discharge of carbon dioxide. Under high pressure oxygen (FiO(2) 100%), oxygen concentration in the distal end of the rigid bronchoscope was lower than 50% whether (the driving pressures and I:E) was adjusted or not (P > 0.05). The oxygen concentration at the distal end of the rigid bronchoscope was increased a little (but below 50%) when jet needle tip inserted superficially or deeply into the adapter, but the oxygen was lower than 40% at most situation when it was in the midrange (3 - 6 centimeters in the adapter).

CONCLUSIONS

This domestically made jet ventilator could not provide enough effective ventilation during interventional procedures with rigid bronchoscopy under general anesthesia because hypoxemia and hypercapnia occurred when the operation time was prolonged. The PaO(2) and PaCO(2) of the dogs were better when spontaneous breathing was maintained during the procedure. The ventilation effects of the jet ventilator was closely related with its driving pressure. The oxygen concentration at the distal end of the rigid bronchoscope was lower than 40% in most situation when it was in the midrange (3 - 6 centimeters in the adapter) under high pressure oxygen (FiO(2) 100%). There was no significant change in the oxygen concentration with adjustment of the driving pressure or the I:E ratio of the jet ventilator.