Transthoracic monitoring of the impedance of the right lung in patients with cardiogenic pulmonary edema.
OBJECTIVE
To evaluate the suitability of the new electrical impedance monitor RS-205 for monitoring of cardiogenic pulmonary edema (CPE).


METHODS
Prospective, controlled study.


METHODS
A department of internal medicine in a 1,200-bed university-affiliated, teaching hospital.


METHODS
Sixty patients, aged 52-80 yrs, 30 without CPE (controls) and 30 with or at high risk for CPE.


METHODS
Internal thoracic impedance (ITI) was monitored by the RS-205. 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 impedance. This is achieved by eliminating skin electrode impedance by a special algorithm, thus allowing measurement of ITI rather than total transthoracic impedance. Measuring ITI, the main component of which is lung impedance, is a noninvasive and safe method. CPE was diagnosed in accordance with well-accepted clinical and roentgenological criteria.


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 controls (22.25 +/- 9.82%, p <.001). In patients at the peak of pulmonary edema, 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 patients at all stages of CPE.
Charach
G
G
Department of Internal Medicine "C," Tel Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Rabinovich
P
P
Grosskopf
I
I
Weintraub
M
M
D000368:Aged; D000369:Aged, 80 and over; D002307:Cardiography, Impedance / Q000295:instrumentation*; D016022:Case-Control Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011654:Pulmonary Edema / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric