Assessment of Thoracic Blood Volume by Computerized Tomography in Patients With Heart Failure and Periodic Breathing

Background: Periodic breathing (PB) is often observed in patients with HF at rest, with sleep and during exercise. However, mechanisms underlying abnormal ventilatory control are not entirely established. Methods: Eleven subjects with HF (10 males, age = 69 ± 12 y) and 12 age-matched control subjects (8 males, age = 65 ± 9 y) participated in the study. PB was defined as a peak in the 0.003–0.04 Hz frequency range of the flow signal during 6 minutes of awake resting breathing. Thoracic blood volumes (V _t , thorax; V _h , heart; V _p , pulmonary), mean transit times (MTTs), and extravascular lung water (EVLW) were quantified using computerized tomography. Results: PB was observed in 7 subjects with HF and was associated with worse functional status. The HF PB-present group had thoracic blood volumes nearly double those of control and HF PB-absent subjects (volumes reported as mL/m ² body surface area, P values vs control: control = 813 ± 246, HF PB-absent = 822 ± 161 P =.981, HF PB-present = 1579 ± 548 P =.002). PB was associated with longer pulmonary MTT (control = 6.7 ± 1.2 s, HF PB-absent = 6.0 ± 0.8 s, HF PB-present = 8.4 ± 1.6 s; P =.033, HF PB-present vs HF PB-absent). EVLW was not elevated in the PB group. Conclusions: Subjects with HF and PB at rest have greater centralization of blood volume.