Pulmonary function impairment in patients with chronic heart failure: lower limit of normal versus conventional cutoff values

Objective: To determine the prevalence of pulmonary function abnormalities in patients with chronic heart failure (HF) according to recent American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines using the lower limit of normal (LLN) compared to conventional cutoff values.

Background: Recent ATS/ERS guidelines recommend the use of the LLN instead of the conventional cutoff values to define pulmonary function impairment to avoid misclassification of patients. However, studies addressing the prevalence of pulmonary function abnormalities according to both definitions in patients with chronic HF are lacking.

Methods: In this prospective cross-sectional study, 164 chronic HF outpatients (age 68 ± 10 years, 78% men, 88% New York Heart Association class I-II) with left ventricular ejection fraction < 40% underwent spirometry and measurement of diffusing capacity. Body plethysmography was performed in patients with abnormal spirometry results.

Results: Diffusion impairment and airway obstruction were found in 44-58% and 26-37% of the patients, respectively, depending on the definition used (LLN versus conventional cutoff values, p < 0.05). However, restriction was infrequent, irrespective of the definition used (7% versus 5%, respectively, p > 0.05). The LLN identified fewer patients with abnormal lung function, whereas the conventional cutoff values classified more patients with diffusion impairment, airway obstruction, or a mixed category. Twenty-seven percent of patients were misclassified by the conventional cutoff values.

Conclusion: Pulmonary function abnormalities, especially diffusion impairment and airway obstruction, were highly prevalent in patients with chronic HF. Conventional cutoff values classified more patients with diffusion impairment, airway obstruction, or a mixed category compared to the LLN.