Multicenter, prospective study on respiratory stability during recovery from deterioration of chronic heart failure

Background: The respiratory instability frequently observed in advanced heart failure (HF) is likely to mirror the clinical status of worsening HF. The present multicenter study was conducted to examine whether the noble respiratory stability index (RSI), a quantitative measure of respiratory instability, reflects the recovery process from HF decompensation. Methods and Results: Thirty-six of 44 patients hospitalized for worsening HF completed all-night measurements of RSI both at deterioration and recovery phases. Based on the signs, symptoms, and laboratory data during hospitalization, the Central Adjudication Committee identified 22 convalescent patients and 14 patients with less extent of recovery in a blinded manner without any information on RSI or other respiratory variables. The all-night RSI in the convalescent patients was increased from 27.8±18.4 to 34.6±15.8 (P<0.05). There was no significant improvement of RSI, however, in the remaining patients with little clinical improvement. Of the clinical and laboratory variables, on stepwise linear regression modeling, body weight, peripheral edema, and lung congestion were closely related to the RSI of recovered patients and accounted for 56% of the changes in RSI (coefficient of determination, R²=0.56). Conclusions: All-night RSI, a quantitative measure of respiratory instability, could faithfully reflect congestive signs and clinical status of HF during the recovery process from acute decompensation.