Purpose: In chronic obstructive pulmonary disease (COPD) some patients develop paradoxical inspiratory rib motion, which is termed Hoover's sign. Our objective was to determine whether Hoover's sign is associated with a difference in the maximal expiratory pressure (MEP), the maximal inspiratory pressure (MIP), the MEP/MIP ratio, and other features on pulmonary function tests (PFTs).
Methods: This observational prospective single-center cohort study enrolled patients with an established diagnosis of COPD with Global initiative for chronic Obstructive Lung Disease (GOLD) stage 3 (severe) and 4 (very severe) based on PFTs. Respiratory pressure measurements were also collected. Patients were examined for the presence or absence of Hoover's sign on physical examination by 2 internal medicine resident physicians trained in examining for Hoover's sign by a pulmonologist.
Results: A total of 71 patients were examined for the presence of Hoover's sign. Hoover's sign was present in 49.3% of patients. Observer agreement (k statistic) was 0.8 for Hoover's sign. Median MEP/MIP was significantly greater in patients with Hoover's sign than those without Hoover's sign (1.88 versus 1.16, p<0.001). Patients with Hoover's sign also had a significantly lower MIP (39.0 versus 58.0, p<0.001) and higher residual volume (RV) to total lung capacity (TLC) ratio indicating a higher degree of air trapping (65 versus 59.5, p<0.014).
Conclusion: The presence of Hoover's sign in patients with COPD is associated with a higher MEP/MIP ratio. This suggests respiratory pressure measurements can predict diaphragm dysfunction in patients with GOLD stage 3 and 4 COPD. Patients with Hoover's sign were also found to have a lower MIP and more air trapping.
Keywords: Hoover’s sign; chronic obstructive pulmonary disease; diaphragm dysfunction; maximal expiratory pressure to maximal inspiratory.
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