Authors - N

Newell, J.C.; Edic, P.M.; Ren, X.D.; Larsonwiseman, J.L.;
        Danyleiko, M.D.
Title   Assessment of acute pulmonary edema in dogs by electrical
        impedance imaging
Journal IEEE Transactions on Biomedical Engineering
        43
        2
        FEB
Year    1996
Page    133-138
Address JC Newell
        Rensselaer Polytech Inst
        Dept Biomed Engn
        Troy, NY 12180 USA
Serial# 0018-9294
Abs.    Acute pulmonary edema was assessed quantitatively in 12
        experiments on six anesthetized dogs. Thirty-two copper
        foil electrodes were placed around each animal's thorax at
        the level of the third intercostal space. A real-time
        electrical impedance tomograph was used to form images of
        the electrical admittivity of the thorax in and near the
        plane of these electrodes, The lungs were identified by
        studying the change in admittivity associated with
        inspiration. Mean admittivity in these lung regions was
        assessed at 40-min intervals for the next 36 hours. In six
        control experiments, each having a duration of 200 min, the
        initial admittivity of the lung regions was 102 +/- 16(SD)
        mS/m, Lung admittivity usually increased during the first
        80 min, and then remained within 2 mS/m of its value at 80
        min for the remaining 120 min. In six experiments with
        pulmonary edema, an initial period of change followed by
        stability was observed, When stability had been attained,
        0.07 ml/kg of oleic acid was injected slowly into a central
        venous site, Five animals received oleic acid, the sixth
        received a sham injection of saline, In the five receiving
        oleic acid, lung admittivity rose steadily for the
        remainder of the experiment. The increase in lung
        admittivity in these five animals was between 4 and 16
        mS/m. In the sham injected experiment, the lung admittivity
        changed by 1 mS/m, We conclude that impedance imaging can
        provide semiquantitative assessment of the development of
        acute pulmonary edema.
 
Nierman, D.M.; Eisen, D.I.; Fein, E.D.; Hannon, E.;
        Mechanick, J.I.; Benjamin, E.
Title   Transthoracic bioimpedance can measure extravascular lung
        water in acute lung injury
Journal Journal of Surgical Research
        65
        2
        OCT
Year    1996
Page    101-108
Address DM Nierman
        Mt Sinai Med Ctr
        Dept Med
        New York, NY 10029 USA
Serial# 0022-4804
Keys    ELECTRICAL IMPEDANCE; RESUSCITATION; ENDOTOXEMIA; LACTATE;
        VOLUME; GUIDE
Abs.    We used a porcine endotoxemic model of acute lung injury to
        compare extravascular lung water (EVLW) measured by right
        transthoracic bioimpedance to postmortem gravimetric EVLW
        measurements. Adult pigs were randomized into control (N =
        5) or endotoxin groups [150 mu g/kg Escherichia coli
        lipopolysaccharide B for 1 hr followed by 3 hr of
        resuscitation for a thermodilution cardiac output less than
        90% of baseline using either isotonic saline (N = 5) or
        isooncotic albumin (N = 5)]. Right lung resistance was
        measured using a novel electrode array and a highly
        sensitive analyzer and was used to calculate right lung
        resistivity. At the end of the experiment, animals in the
        endotoxin-albumin group had higher gravimetric EVLWs than
        those in the endotoxin-saline or control groups (P < 0.05).
        Right lung resistivity corrected for body weight
        significantly correlated with gravimetric EVLW (r(2) = 0.49;
        SEE = 0.96; P = 0.0038). Using multiple regression analysis,
        a predictive equation for EVLW based on right lung
        resistivity, body weight, and mean pulmonary artery
        pressure was generated (r(2) = 0.81; SEE = 0.60; P <
        0.0001). These results demonstrate that right lung
        resistivity measurements can provide a noninvasive estimate
        of EVLW. In addition, crystalloid may be preferable to
        colloid for fluid resuscitation in noncardiogenic pulmonary
        edema. (C) 1996 Academic Press, Inc.

Noordegraaf-A-V; Van-Der-Meer-B-J-M; De-Vries-J-P-P-M; De-Vries-P-
M-J-M
Determination of the relation between alteration of total body
water and thoracic fluid content during ultrafiltration by
bioelectrical impedance analysis.
Nephrology Dialysis Transplantation 10(3): 382-385
1995
English
Total body impedance (TBI) is used to monitor alterations in total
body water (TBW), e.g. during haemodialysis. However, 80% of the
TBI signal is due to the resistance in extremities. Therefore TBI
measurements give little information about alterations in thoracic
fluid content (TF). Measuring both total body impedance and
thoracic impedance (THI) can be a useful method to monitor TBW and
TF changes during haemodialysis. In this study TBI and THI
measurements were performed during 30 dialysis sessions and also
in one group of 24 control subjects with normal tissue hydration.
During haemodialysis TBI and THI significantly increased,
demonstrating a decrease of TBW and TF. The ratio THI/TBI did not
differ significantly during haemodialysis, indicating a similar
effect of ultrafiltration on TBW and TF. The finding that TF
decreased during haemodialysis was rather surprising, whereas
pulmonary oedema is not an evident clinical problem in patients on
maintenance haemodialysis treatment. THI measurements after
dialysis proved to be significantly higher in comparison to the
control subjects. This finding supports the hypothesis that the
decrease in TF during dialysis is partly due to the sudden
ultrafiltration-induced hypovolaemia leading to a fall in thoracic
blood volume.

Nopp, P.; Zhao, T.X.; Brown, B.H.; Wang, W.
Title   Cardiac-related changes in lung resistivity as a function of
        frequency and location obtained from EITS images
Journal Physiological Measurement
        17
         Suppl. 4A
        NOV
Year    1996
Page    A213-A225
Address P Nopp
        Royal Hallamshire Hosp
        Dept Med Phys
        Glossop Rd
        Sheffield S10 2JF
        S Yorkshire, England
Serial# 0967-3334
Keys    IMPEDANCE CARDIOGRAPHY; MODEL
Abs.    ECG-gated electrical impedance tomographic spectroscopy
        (EITS) measurements of the lungs were taken on seven normal
        subjects in the frequency range 9.6 kHz to 614.4 kHz. The
        results show that in late systole the resistivity rho'
        relative to the R-wave (i.e. rho' = I at the R-wave)
        decreases consistently within the lung. In addition there
        arises an increase in rho' in early systole towards the
        periphery of the lung. Frequency behaviour of rho' changes
        with location. At all times after the R-wave, in the centre
        of the lung rho' is higher at higher frequency f whereas in
        the periphery it is lower at higher f. The principal
        decrease in rho' can be explained by increasing pulmonary
        blood volume due to cardiac contraction. The early systolic
        increase is presumably due to venous return to the left
        atrium locally leading blood output from the right
        ventricle which is delayed by the windkessel effect. Based
        on a model taking extracapillary and capillary blood volume
        increase into account, the change in frequency behaviour of
        rho' is explained by regional variations in extracapillary
        blood vessel size determining the relative contributions of
        extracapillary blood volume change and capillary blood
        volume change to rho' at a certain frequency.

Author   - Nyren M
Author   - Ollmar S
Author   - Nicander I
Author   - Emtestam L
Title    - An electrical impedance technique for assessment of
           wheals.
         - English
         - Article
         - Nyren M, Huddinge Univ Hosp, Dept Dermatol, S 14186
           Huddinge, SWEDEN
         - In previous studies of the electrical impedance of the
           skin, we introduced a set of physical indices which could
           be used to distinguish between the cutaneous effects
           produced by different irritants and allergic contact
           reactions. In this study, wheals were induced in 10
           allergic patients by performing prick tests on the forearm
           with the relevant allergen and histamine, respectively.
           Normal skin was used for control. The wheals were
           evaluated by visual scoring, laser Doppler, and electrical
           impedance. As expected, there was a close agreement
           between the visual and laser Doppler readings. Compared to
           the controls, there were significant changes in the
           electrical impedance of the wheals, especially in the
           index related to the phase angle. The changes in the
           indices were found to follow a particular pattern, which
           diverged from those obtained in contact skin reactions of
           both allergic and irritant type. Our results indicate
           that, by the application of the impedance technique, it
           will be possible to characterize objectively and quantify
           the wheal reaction. The results also suggest that
           cutaneous reactions of completely different causes, such
           as allergic skin reactions of the late and immediate type,
           and irritant contact reactions, may be distinguished on
           the basis of their effects on the electrical impedance of
           the skin.
Journal  - Allergy 1996 DEC;51(12):923-926