Objectives: Early detection of heart failure (HF) exacerbations has shown to reduce hospitalizations rate of HF patients (pts). However, currently used monitoring techniques are neither sensitive nor accurate enough. Exacerbation of HF is associated with pulmonary vein congestion, which affects lung compliance and respiratory work, even before the development of interstitial and alveolar edema. We propose a novel method for noninvasive monitoring of the respiratory dynamics that can quantify the severity of dyspnea.
Methods: Seven decompensated hospitalized patients (NYHA-3/4) were recruited (6 males).Their average age was 67years, the left ventricular ejection fraction was 24%. Three miniature motion sensors which measure the subsonic chest wall dynamics were attached to patient's thorax and epigastrium. The recorded signals were analyzed in time and frequency domain. We compared respiratory measurements with the clinical symptoms, from admission to discharge.
Results: Patients with decompensated HF showed an additional active phase during expiration, reflecting a larger respiratory effort to exhale air. The motions of the chest and abdomen were polyphasic and were associated with the appearance of significant additional work at frequencies higher than the breath frequency. The expiratory work and the increase in the breath rate yielded a decrease in the fraction of the quiescent (end expiratory) phase of the normal breath cycle. After several days of diuresis when heart failure was compensated, the pts showed a remarkable improvement in these novel indices, with a 30±16% reduction in the high frequency work and increase in the quiescent fraction by 50±25% (6 patients). The changes in the monitored indices correlated with the improvement in the symptoms.
Conclusions: Monitoring of the breath dynamic by miniature motion sensors may provide objective indices of dyspnea.
