Pathophysiological and clinical relevance of simplified monitoring of nocturnal breathing disorders in heart failure patients

Abstract

Aims: Nocturnal breathing disorders in the form of periodic breathing (PB) are very common in heart failure (HF) patients. There is an increasing interest in simple and affordable tools to screen patients and monitor these disorders at home on a long-term basis. We aimed to assess the pathophysiological and clinical relevance of a simplified method for monitoring of PB suitable to be self-managed by the patient at home.

Methods and results: A night-time respiratory recording was performed in 397 optimally treated HF patients (age 60 +/- 11 years, NYHA class 2.4 +/- 0.6, left ventricular ejection fraction 29 +/- 7%) and the duration of PB (PB(Dur)) automatically computed. Patients were followed-up for 1 year and the prognostic value of PB(Dur) evaluated. In 45 patients, we assessed the association between PB(Dur) and severity of oxygen desaturations (number of desaturations >3%). Twenty six of the 397 patients died of cardiac causes. A PB(Dur) > or =2 h was significantly associated with an increased risk of cardiac death after adjustment for major clinical predictors [hazard ratio (95% CI): 3.5 (1.6-7.9), P = 0.002]. The correlation between PB(Dur) and severity of desaturations was 0.94 (P < 0.0001).

Conclusion: Relevant pathophysiological and clinical information can be obtained from simplified monitoring of breathing disorders managed by the patient. These results provide new perspectives in the investigation of the clinical impact of abnormal breathing in HF patients.

Figure 1

Representative example of respiratory signals recorded by the Embletta monitor during an episode of periodic breathing. From top to bottom: oronasal airflow, thorax and abdomen movements, O₂ saturation (SpO₂). The two lower signals, i.e. the sum of thoraco-abdominal movements and the continuous tidal volume signal, were obtained by dedicated software.

Figure 2

Representative example of the respiratory signal recorded by the Report-24 recorder during an episode of periodic breathing. The lower tracing shows the derived tidal volume signal.

Figure 3

Relationship between number of oxygen desaturations >3% and periodic breathing (PB) duration. Both measurements were derived from the Embletta recorder. Data are from a subgroup of 45 HF patients from one of the enrolling centres of the study.

Figure 4

(A) Relationship between the measurements of periodic breathing (PB) duration simultaneously obtained from Report-24 and Embletta recorders. (B) Relationship between number of oxygen desaturations >3% measured by the Embletta and duration of PB measured by the Report-24. Data are from a subgroup of 45 HF patients from one of the enrolling centres of the study.

Figure 5

Kaplan–Meier survival curves for patients stratified according to: (A) quartiles of periodic breathing (PB) duration; (B) PB duration ≥120 min vs. the rest of the sample. Suffix q1 denotes patients with a PB value between the minimum and the lower quartile, q2 those between the lower quartile and the median, q3 those between the median and the upper quartile, and q4 those between the upper quartile and the maximum. Data are from the cohort of 397 patients included in the prognostic study.