Bronchoscopy with normoventilation. Automatic ventilation with Sanders technique. A clinical investigation

Forty six patients, who had to be subjected to diagnostic bronchoscopy under general anaesthesia (thiopental, pethidine, O2-N2O, suxamethonium) were ventilated using Wolf's injectomat (automated Sanders principle) in an attempt to find a setting for the apparatus that would provide normoventilation of the patient, independently of the diagnostic procedure. The first 24 patients were ventilated with the apparatus having a fixed setting: the latter being presumed to provide normo- or hyperventilation. This was confirmed and a steady state of PaCO2 was reached after ventilation for 10 min. This PaCO2 was well correlated with the vital capacity of the patients expressed factorially, in relation to the expected normal value. The investigation renders probable the observation that patients with a greatly reduced vital capacity (less than 50% of the normal value) can rarely be ventilated with the apparatus. On the other hand, a reduced FEV1 has little influence on the efficiency of the apparatus. The apparatus was adjusted in agreement with the above mentioned relation to vital capacity for the following 21 patients, in as much as the change in ventilation was carried out by a change in frequency, while the driving pressure of the apparatus and the inspiration time were maintained unchanged. Normoventilation was obtained in these patients independently of the fact that the bronchoscope was constantly open for the insertion of instruments.