Clinical implications of Hoover's sign in chronic obstructive pulmonary disease

Abstract

Background: The objective of the study was to evaluate whether Hoover's sign—the paradoxical inspiratory movement of the lateral rib margin—may have clinical implications in patients with COPD. Methods: The study included two groups of male patients with stable COPD—30 with and 30 without Hoover's sign—who were matched for age and smoking habits. Spirometric values were assessed for both groups. Degree of dyspnea, measured for normal activities with the Medical Research Council (MRC) scale and for climbing two flights of stairs with the Borg scale, and utilization of health resources, including hospitalization, were compared. Results: Patients with Hoover's sign had a higher degree of dyspnea [MRC 2.2 (S.D.: 1.2) and 1.0 (0.8), p<0.0001; Borg 5.6 (2.4) and 3.1 (2.3), p=0.0001] and a higher number of hospitalizations [0.87 (1.0) and 0.27 (0.5), p=0.005] and emergency visits [2.5 (2.3) and 0.9 (2.3), p=0.01] than patient's without it. FEV₁ significantly correlated with dyspnea scales only in patients with Hoover's sign (MRC r=0.48; Borg r=0.49; p<0.05). Conclusions: Our study shows that Hoover's sign in COPD identifies a group of patients with a higher level of dyspnea and a higher use of health care resources, regardless of the degree of functional impairment. Consequently, establishing the presence of Hoover's sign would appear to be valuable in treating patients with COPD.

Introduction

The measure of forced expiratory volume in one second (FEV₁) is recommended to assess and monitor patients with chronic obstructive pulmonary disease (COPD) [1]. It has been clearly established that a low FEV₁ is associated with a greatly increased mortality from chronic lung disease [2] as well as from a wide range of diseases [3]. However, the severity of COPD that is established by FEV₁ only partly explains the health-related quality of life in these patients [4]. In fact, in COPD patients, the degree of airflow obstruction is a poor predictor of dyspnea [5], [6], exercise tolerance [7], [8], and utilization of health resources including hospitalization [9], [10], [11]. There is accumulating evidence that inspiratory muscle function plays an important role in these aspects [12], [13]. Hyperinflated lungs flatten the curvature of the diaphragm and enlarge the rib cage. The altered configuration of the chest wall cavity places the respiratory muscles, including the diaphragm, at a mechanical disadvantage and impairs their force-generating capacity [14], [15]. However, the function of the diaphragm during breathing is not routinely assessed in COPD.

It is known that paradoxical inspiratory in-drawing of the lateral rib margin (Hoover's sign) can be observed in a significant number of patients with COPD [16], [17], [18]. This abnormal movement of the chest wall has been attributed to direct traction by the flattened diaphragm on the lateral rib margins [16], [19]. Although its presence has been reported in as many as 77% of patients with airflow obstruction [19], this sign is frequently forgotten. We hypothesized that Hoover's sign could reflect disadvantaged inspiratory muscle activity and, consequently, that its presence may have implications for exercise tolerance or for utilization of health resources. In order to ascertain these possibilities, we conducted a clinical study comparing two matched groups of patients with stable COPD, half of whom had Hoover's sign and half of whom did not.