Variability in pulmonary diffusing capacity in heart failure.

Area of Science:

• Pulmonary Medicine
• Cardiology
• Respiratory Physiology

Background:

• Pulmonary diffusing capacity is a critical indicator of mortality risk and prognosis in heart failure (HF) patients.
• Frequent measurement of pulmonary diffusing capacity necessitates understanding its week-to-week variability for accurate clinical interpretation.
• Assessing the reproducibility of diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO) is essential for managing HF patients.

Purpose of the Study:

• To determine the week-to-week reproducibility of DLCO and DLNO in patients with heart failure.
• To establish clinically meaningful change thresholds for DLCO and DLNO based on their variability.
• To compare the reproducibility of DLNO and DLCO in heart failure patients.

Main Methods:

• Forty heart failure patients completed DLCO and DLNO testing on three separate occasions over ten weeks.
• DLCO was measured using 4-second and 10-second breath-hold maneuvers.
• DLNO was measured using a 4-second breath-hold maneuver.

Main Results:

• Reproducibility was 18.9 mL/min/mmHg⁻¹ for DLNO (4s), 8.2 mL/min/mmHg⁻¹ for DLCO (4s), and 5.9 mL/min/mmHg⁻¹ for DLCO (10s).
• A significant proportion of HF patients (50% for DLCO, 78% for DLNO) presented below the lower limit of normal.
• All patients below the lower limit of normal for DLCO were also below it for DLNO.

Conclusions:

• Week-to-week fluctuation in DLNO (4s) is less pronounced than in DLCO (4s) in heart failure patients.
• The reproducibility of DLNO in heart failure patients is comparable to that observed in healthy individuals.
• These findings aid clinicians in interpreting changes in DLCO and DLNO in heart failure management.