In this study, we examined how the height of the pillow on which a person's head rests affects the respiratory function. We measured tidal volume (TV), vital capacity(VC), expiratory reserve volume (ERV), forced expiratory volume in the first second (FEV_<1.0>), percentage of forced expiratory volume in the first second (FEV_<1.0>%), obstructive index (OI), and angle of the cervical region under the conditions of various pillow heights (3cm, 7cm, 11cm), pillow materials (urethane, buckwheat chaff feather), and postures (sitting position, supine position). The high pillow decreased VC, ERV and FEV_<l.0>, while increased OI. The subjects complained of a choking sensation in each of the experiments. The angle of the cervical region increased in direct proportion to the height of pillow and a choking sensation.
