VENTILATION WITH RIGID BRONCHOSCOPES - EVALUATION OF RESISTANCE BY PRESSURE-DROP BY A PROPOSED INTERNATIONAL STANDARD

The ISO 8600-2-1 draft standard concerns measuring methods for ventila tion properties in rigid bronchoscopes. Two lung models were designed in accordance with this draft, one for conventional ventilation, and t he other for jet-ventilation (venturi ventilation). Lung model I: An a ir supply was connected to a 4 liter container. The test object (bronc hoscope),vas exposed to air flowing out of the container through the b ronchoscope, and the pressure in the container was recorded. The flow velocities were 20-60 l.min(-1). Lung model II: A pressure gauge was c onnected to a 2 liter container. The test object was introduced into t he container through an gastight opening. A pressure gas injector was connected to either the instrument port or the ventilation port of the bronchoscope. The injected pressures were 100-500 kPa. Results: Study I, The pressure drop increased exponentially with increasing air flow . It also increased rapidly with decreasing diameter of the bronchosco pe. Study II. The pressure in small bronchoscopes increased very fast with increasing injection pressure. Dangerous pressures (above 50 cmH( 2)O) were reached already at 2 kg.cm(-2) with the smallest bronchoscop es. We suggest that the results should be given as ''pressure drop'' a nd not as ''resitance''