ABSTRACT
BACKGROUND: Pulmonary gas exchange under jet ventilation is usually controlled by pulse-oxymetry and blood gas analysis. Capnometry is not common in clinical use. Rigid bronchoscopes with pressure measurements are not known. Our aim was the development of a rigid bronchoscope with a built-in tube for the online measurement of airway pressure and gas composition. METHODS: We measured the distribution of inspiratory pressure under jet ventilation over the length inside a 8 x 400 mm rigid bronchoscope in a lung model and in patients. A measuring tube was constructed for obtaining representative values of airway pressure and capnometry. Using a prototype of a new rigid bronchoscope with the built-in measuring tube (R. Wolf Company, Knittlingen, Germany) inspiratory pressure and expiratory CO2 were measured during interventional bronchoscopy. The measuring tube was connected to the pressure control port of the jet ventilator. We applied jet ventilation with frequencies of 10 to 12 pulses per minute. RESULTS: The inspiratory pressure reaches after 10 cm distally the instrumental port a significant constant plateau. Via the built-in measuring tube representative measurement of pressure and gas can be made there. The correlation between arterial CO2 (paCO2) and expiratory CO2 (petCO2) was excellent (r = 0.96). To maintain normocapnia in 25 patients undergoing interventional bronchoscopy, the jet pressure had to be adjusted to values between 0.5 and 3.5 bar (median 2.5 bar). The responding inspiratory pressure varied from 3 to 25 mbar (median 15 mbar). A flexible bronchoscope in the working channel raises the airway pressure from 18 to 23 mbar. The automatic interruption of the jet-pulses by connecting the measuring tube to the pressure control port of the ventilator in order to prevent a barotrauma was found feasible. CONCLUSIONS: Simultaneous online control of airway pressure and gas is possible with the new rigid bronchoscope. Pressure depending jet ventilators can be controlled via the measuring tube to minimise the risk of barotrauma.
