Estimates of ventilation from measurements of rib cage and abdominal distances: a portable device

Abstract

To validate a new device designed to measure ventilation $\left( {\dot{V}_{\text{E}} } \right),$ tidal volume (V _T), inspiratory time (T _I), and expiratory time (T _E) during daily life activities. The anteroposterior displacement of the rib cage and abdomen and the axial displacements of the chest wall and the spine were measured using two pairs of magnetometers. $\dot{V}_{\text{E}}$ was estimated from these four signals, and was simultaneously measured using a spirometer. A total of 707, 732, and 1,138 breaths were analyzed in sitting, standing, and exercise conditions, respectively. We compared $\dot{V}_{\text{E}}$, V _T, T _I, and, T _E measured by magnetometers ($\dot{V}_{{{\text{E}}\;{\text{mag}}}}$, V _{T mag}, T _{I mag}, and T _{E mag}) with $\dot{V}_{\text{E}}$, V _T, T _I, and T _E measured by a spirometer ($\dot{V}_{{{\text{E}}\;{\text{spiro}}}}$, V _{T spiro}, T _{I spiro}, and T _{E spiro}, respectively). For pooled data $\dot{V}_{{{\text{E}}\;{\text{mag}}}}$, V _{T mag}, T _{I mag}, and T _{E mag} were significantly correlated (p < 0.001) with $\dot{V}_{{{\text{E}}\;{\text{spiro}}}}$, V _{T spiro}, T _{I spiro}, and T _{E spiro} in sitting and standing positions and during the walking exercise. The mean differences, between $\dot{V}_{{{\text{E}}\;{\text{mag}}}}$, and $\dot{V}_{{{\text{E}}\;{\text{spiro}}}}$ for the group, were 10.44, 10.74, and 12.06% in sitting, standing, and exercise conditions, respectively. These results demonstrate the capacity of this new device to measure $\dot{V}_{\text{E}}$ with reasonable accuracy in sitting, standing, and exercise conditions.