Variability in pulmonary diffusing capacity in heart failure

As pulmonary diffusing capacity is related to mortality risk and prognosis in patients with heart failure (HF), it is measured frequently. As such, it would be essential to know the week-to-week variability (reproducibility) of pulmonary diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO). This variability would let clinicians understand what a clinically measurable change in DLCO and DLNO would be in these patients.

On three different days spanning over ten weeks, 40 H F patients underwent testing for DLCO and DLNO. DLCO was determined after a 4 s and 10 s breath-hold maneuver, while DLNO was determined after a 4 s breath-hold maneuver.

Forty heart failure patients (66 ± 10 years; BMI = 28.4 ± 4.6 kg∙m^-2; 28 males), that were referred to our clinic were able to complete the protocol. DLCO (4 s breath-hold) and DLNO (4 s breath-hold) were 79 ± 19 % and 59 ± 14 % predicted, respectively. Fifty percent of patients (n = 20) were below the lower limit of normal (LLN, below the 5th percentile) for predicted DLCO (4 s), while 78 % of patients (n = 31) were below the LLN for predicted DLNO. All 16 patients that were below the LLN for DLCO were also below the LLN for DLNO. Over a ten week period, the reproducibility of DLNO (4 s) DLCO (4 s) and DLCO (10 s) was 18.9, 8.2, and 5.9 mL min mmHg^-1, respectively.

The week-to-week fluctuation in DLNO (4 s), as a percentage, is less than DLCO (4 s) in patients with HF. The reproducibility of DLNO in patients with HF is like that of healthy subjects.