Clogging of Drainage Catheters: Quantitative and Longitudinal ...

Radiology
tive ID, respectively, during the 14-day
follow-up for each irrigation frequency.
Three to 14 days after catheter insertion,
the intracatheter pressure was significantly
lower in catheters with higher irrigation
frequencies than in those with
lower irrigation frequencies. Table 2 summarizes
the results of statistical analysis
of intracatheter pressure differences at
each irrigation frequency for each observation
during 14-day follow-up.
Microscopic examination of the catheters
after they were withdrawn showed
multifocal plugging of the side holes and
catheter lumen with white jellylike
pieces of tissue debris of various sizes and
frequencies. Results of histopathologic
examination revealed that this tissue debris
was inflammatory exudate that consisted
of lymphocytes, plasma cells, neutrophils,
and some eosinophils among a
background of delicate fibrillary collagenous
material. Results of scanning electron
microscopic examination revealed
that this tissue debris had irregular surfaces
(Fig 5), but the catheter surfaces
remained smooth in other areas without
debris.
Figure 2. Graphs show results of the in vitro experiment and theoretic curves. (a, b) Relationship
between ID of a catheter and intracatheter pressure (P). Colors of the plots and curves
indicate a specific preset infusion rate. In a, red 0.1 mL/sec, blue 1.0 mL/sec, orange 2.0
mL/sec, and black 3.0 mL/sec. In b, red 0.5 mL/sec, blue 1.5 mL/sec, and black 2.5
mL/sec. Data are plotted separately in a and b to avoid crowding. Plots indicate the pressures
measured in 48 combinations of catheter IDs and infusion rates. Solid curves were generated by
fitting Equation (4) derived from the data (plots), and the dotted curves represent the ideal curves
generated by the Poiseuille equation (Eq [2]). Note agreement between the data, fitting curves,
and ideal curves. A log 10 scale was used to plot P on the y axis.
DISCUSSION
In this study, we evaluated a method
with application of the Poiseuille law for
the quantitative and longitudinal assessment
of catheter clogging during percutaneous
drainage procedures. We verified
the validity of this method in two ways:
(a) by performing an in vitro experiment,
in which a series of catheters with different
IDs were used to simulate various degrees
of obstruction and (b) by observing
the results in an in vivo experiment, in
which the degree of clogging was graded
according to the irrigation frequency.
Furthermore, our results show that the
effective ID of a drainage catheter can be
estimated in vivo by means of the mathematically
based approach used in our
study.
To our knowledge, no method has
been reported for evaluating the effectiveness
of drainage procedures and the
catheters used in such procedures. Our
efforts to develop anticlogging drainage
catheters in recent years have demonstrated
to us that there is a need for an
objective method of quantifying catheter
clogging.
We previously determined the degree
of catheter clogging in animal models by
means of measurement of catheter
weight changes, microscopic morphologic
analysis of side holes and luminal
Figure 3. Graphs show intracatheter pressure changes in 12 rabbits during the 14-day follow-up.
Pressure was measured during the infusion of sterile saline at rates of (a) 0.1 and (b) 0.5 mL/sec.
The degree of catheter clogging was graded on the basis of the different frequencies of manual
irrigation: zero, Πone, two, and three times per day. Plots indicate means, and
error bars represent the standard errors of means. In b, pressures exceeding the measurable limit
(350 mm Hg) of the pressure-monitoring device were regarded as 350 mm Hg. Note that degrees
of catheter clogging were discriminated by means of the pressure measurement system illustrated
in Figure 1. A log 10 scale was used to plot pressure on the y axis.
surfaces, scanning electron microscopy,
or measurement of the infusion rate
through a catheter after it was withdrawn.
In our experience, morphologic
analysis is not an effective method because
it is labor intensive and tends to
836 Radiology June 2003 Lee et al