Estimating pulmonary congestion in elderly patients using bio-impedance technique: Correlation with clinical examination and X-ray results
Introduction
Congestive heart failure is caused by various cardiac diseases, but may also be caused, or precipitated, by other pathologies such as pneumonia, sepsis, viral infection, acute mountain sickness, over hydration, and anaphylaxis. In congestive heart failure (CHF) patients, an inadequacy of the heart to maintain blood circulation in accordance with the tissue's metabolic needs, results in congestion and edema of the lungs, as well as in other body tissues [1].
Current pulmonary congestion monitoring methods have limited applicability. The thermal dye double-indicator dilution is an invasive technique for monitoring lung fluids with an accuracy of ∼20%, which is difficult to employ as a standard monitoring routine since it incorporates the insertion of two catheters. Moreover, it underestimates congestion level in patients with intravascular pulmonary shunts, and may be inappropriate in some cases such as asymmetrical lung fluid content (unilateral pulmonary congestion) or poorly perfused lung regions [2], [3]. Non-invasive techniques include mainly imaging modalities such as X-ray chest radiography. Although widely practiced, the clinical diagnostic value of X-ray chest radiographs has been found to be inconsistent [4], [5], [6], [7], and the technique suffers from limitations due to interpretation difficulties caused by coexisting lung diseases [8]. Other imaging modalities, e.g. CT, NMR or MRI, demonstrate high accuracy of as much as ∼3%, however involve large expenses that preclude them from frequent utilization [9], [10].
In the present study, we have estimated pulmonary congestion in elderly patients using a novel bio-impedance system (CardioInspect, Israel). The system consists of an eight-electrode belt, and uses multiple current injection combinations and voltage measurements for reconstruction. Unlike tomographic bio-impedance modalities (e.g. electrical impedance tomography, EIT), which are sensitive to electrical and geometrical noise, the system utilizes a parametric inverse problem algorithm, to reconstruct only two parameters—the specific left and the right lung resistivity values. This results in a robust, stable reconstruction, and noise sensitivity is much reduced. In previous publications, we have demonstrated the system's reproducibility and capability to discriminate between healthy and congested patients [11], [12]. We have also shown that the system follows lung resistivity changes during administration of diuretics [13]. In this study we further validate the applicability of the system in diagnosing pulmonary congestion by correlating its measurements to clinical examinations and X-ray chest radiographs.
Section snippets
Study group
The study comprised of 14 patients (mean age 79 ± 10 years, n = 9 females/5 males) with clinical signs of pulmonary congestion of varying degrees, that were hospitalized in the departments of internal or geriatric medicine in Sheba Medical Center. The study was approved by a local ethics committee. Patients’ condition was diagnosed by medical history, physical findings, chest radiography, electrocardiogram and echocardiography. None of the patients had history or clinical signs of chronic pulmonary
Results
The mean lung bio-impedance measurements at the reference and post-treatment phases are summarized in Table 2. Significant differences in the mean left and right lung resistivity values (a total of 28 measurements, two per patient, that include pre- and post-treatment values), were found between patients who were clinically diagnosed by the physician as suffering from high level pulmonary congestion and those diagnosed with a low level: 838 ± 133 Ω cm (n = 10 measurements) vs. 1002 ± 164 Ω cm (n = 18
Discussion
Pulmonary congestion in congestive heart failure arises from the accumulation of excessive amount of fluids, transferred from the pulmonary capillaries to the pulmonary interstitium, or into the alveoli, due to the increased hydrostatic pressure in the capillaries. As a consequence, the lungs become less compliant, a condition that results in dyspnea, hypoxemia and tachypnea. The lack of appropriate treatment of this condition, usually by diuretic agents, will cause deterioration and severe
Conflict of interest
None.
References (26)
- et al.
Electrical impedance tomography in the assessment of extravascular lung water in noncardiogenic acute respiratory failure
Chest
(1999) Clinical use of lung water measurements. Report of a workshop
Chest
(1986)- et al.
Clinical, radiographic, and hemodynamic correlations in chronic congestive heart failure: conflicting results may lead to inappropriate care
Am J Med
(1991) - et al.
Diagnostic value of the portable chest X-ray technic in pulmonary edema
Am J Surg
(1978) - et al.
The pulmonary manifestations of left heart failure
Chest
(2004) - et al.
A portable bio-impedance system for monitoring lung resistivity
Med Eng Phys
(2007) The use of transthoracic electrical bioimpedance in assessing thoracic fluid status in emergency department patients
Am J Emerg Med
(1988)- et al.
Bioimpedance: a novel method for the determination of extravascular lung water
J Surg Res
(1990) Textbook of medical physiology
(2007)- et al.
EITS changes following oleic acid induced lung water
Physiol Meas
(1996)