Early detection of heart failure (HF) exacerbations has shown to reduce hospitalizations rate of HF patients. However, currently used monitoring techniques are not sensitive and accurate enough.
Hypothesis: Changes in the respiratory effort during cardiac decompensation are reflected in chest wall dynamics. Monitoring the chest wall dynamics can provide precise and objective measures for the degree of cardiac decompensation.
Methods: Twelve decompensated (NYHA 3-4) male patients that were electively hospitalized with moderate dyspnea were recruited. The average Age was 69±9 years. The ejection fraction was 28.2±8.4%. BNP level at admission was 1356 ±1071. Three miniature motion sensors which measure the subsonic chest dynamics were attached to patient`s thorax and epigastrium to record the respiratory dynamics. The respiratory effort was quantified by calculating the energy of the signals during inspiration and expiration. We compared the respiratory effort with the clinical symptoms, at admission and discharge, and evaluated their effect on the time to readmission.
Results: Patients with decompensated HF showed restless breath with mild increase in breath rate and a prominent active expiration. The active expiration yielded expiratory polyphasic motion. A novel parameter, Expiratory-Effort Index (EEI), was defined as the ratio of expiratory to inspiratory effort. The effect of treatment was assessed by monitoring the decrease in EEI between admission and discharge (∆EEI). The decrease in body weight and breath rate poorly predicted the outcomes. However, patients who were not readmitted with cardiac decompensation during the first month post hospital discharge had significant (p<0.01) reduction in ∆EEI (-35±18%) while patients who were re-hospitalized within 30 days presented no change or even an increase in ∆EEI.
Conclusions: Quantification of the respiratory effort provides objective indices for monitoring decompensated HF patients. A novel expiratory effort index was established and it may be used for better decision making before discharging patients from the hospital.
