Syringe and catheter apparatus

To inflate the balloon element on the distal end of a pulmonary artery catheter an improved gas syringe is provided which is both volume and pressure-limited so that the syringe is capable of discharging into the catheter no more than the maximum design gas inlet volume thereof while at the same reducing the maximum attainable pressure within the catheter to a predeterminable level substantially below that reached when a conventional volume-limited syringe of the same gas discharge capacity is used. The syringe volume delivery limitation is achieved by forming rearwardly disposed plunger stop members, or a suitable vent opening, in a sidewall portion of the syringe body. The pressure limitation is obtained by forming a pressure absorption zone which defines a substantially inextensible enlargement of the gas-receiving interior of the catheter. In an alternate embodiment of the syringe, an orifice plate having a small orifice opening therein is secured across the syringe outlet to limit the balloon inflation rate during an initial portion of the operation of the syringe.