G. Charach et al., Transthoracic monitoring of the impedance of the right lung in patients with cardiogenic pulmonary edema, CRIT CARE M, 29(6), 2001, pp. 1137-1144
Objective: To evaluate the suitability of the new electrical impedance moni
tor RS-205 for monitoring of cardiogenic pulmonary edema (CPE).
Design: Prospective, controlled study.
Setting: A department of internal medicine in a 1,200-bed university-affili
ated, teaching hospital.
Patients: Sixty patients, aged 52-80 yrs, 30 without CPE (controls) and 30
with or at high risk for CPE.
Interventions: Internal thoracic impedance (ITI) was monitored by the RS-20
5. The RS-205 is approximately three times more sensitive than the Kubicek
monitor, and it eliminates the effect of the drift of skin-to-electrode imp
edance. This is achieved by eliminating skin electrode impedance by a speci
al algorithm, thus allowing measurement of ITI rather than total transthora
cic impedance. Measuring ITI, the main component of which is lung impedance
, is a noninvasive and safe method. CPE was diagnosed in accordance with we
ll-accepted clinical and roentgenological criteria.
Measurements and Main Results: The controls' initial ITI was 68.3 +/- 12.38
ohms. During 6 hrs of monitoring, the ITI attained a minimum average value
of -1.3 +/- 2.08% and a maximum average value of 4.6 +/- 3.56% relative to
baseline. In all patients entering CPE, ITI decreased by 14.4 +/- 5.42% on
the average (p < .001) 1 hr before the appearance of clinical symptoms. In
patients with evolving CPE, ITI decreased significantly compared with cont
rols (22.25 +/- 9.82%, p < .001). In patients at the peak of pulmonary edem
a, ITI was 2.1 times lower than in the control group (33.1 +/- 10.90 ohms,
p < .001). In the last hour before the resolution of CPE, ITI increased in
all patients by 17.7 +/- 19.74% compared with the peak of disease (p < .05)
. After the resolution of pulmonary edema, ITI increased in all patients by
44.14 +/- 26.90% compared with the peak of disease (p < .001). Importantly
, the trend in ITI in all patients changed in accordance with the dynamics
of CPE. A mixed general linear model shows that ITI values correlated well
with the degree of crepitation, a direct characteristics of CPE.
Conclusions: The RS-205 is suitable for monitoring patients at high risk of
CPE development. It enables detection of CPE and the monitoring of patient
s at all stages of CPE.