Association of Hoover's Sign with Maximal Expiratory-to-Inspiratory Pressure Ratio in Patients with COPD

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).

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.

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).

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.