To the Editor:—
"Delivery Pressure at the Catheter Tip in Selective Angiography" by Lim and Cadwallader (199:11, 1967) presents interesting quantitative observations on an in vitro model. In that those conclusions carry strong implications, the following comments are presented.
The frequency response of the pressure transducer was not given. This prevents a complete appraisal of the delivery pressure curve, specifically the oscillations in the early portion of the curves. The time scale in these curves is missing.
The outflow orifice size and relative geometric configuration are not explicitly shown; both will be intimately related to the transient response of the delivery pressure. As an example, were the outflow orifice 3 cm in diameter, one would not expect as sharp a peak nor as constant a plateau during injection. Also, the transient response will be very closely related to the pliability of the enclosure's walls. One would not