PT - JOURNAL ARTICLE AU - Masahiko Izumizaki AU - Fujiyasu Kakizaki AU - Kazumasa Tanaka AU - Ikuo Homma TI - Immediate Effects of Thixotropy Conditioning of Inspiratory Muscles on Chest-Wall Volume in Chronic Obstructive Pulmonary Disease DP - 2006 Jul 01 TA - Respiratory Care PG - 750--757 VI - 51 IP - 7 4099 - http://rc.rcjournal.com/content/51/7/750.short 4100 - http://rc.rcjournal.com/content/51/7/750.full AB - INTRODUCTION: Thixotropy is a passive property of the skeletal muscle that depends on the muscle's immediate history of contraction and length change. Inspiratory-muscle thixotropy affects the end-expiratory position of the rib cage in normal subjects. OBJECTIVE: To determine whether a reduction in end-expiratory chest-wall volume occurs after thixotropy conditioning of inspiratory muscles in patients with chronic obstructive pulmonary disease. METHODS: Ten male subjects with chronic obstructive pulmonary disease (mean ± SD forced expiratory volume in the first second 70 ± 20% of predicted) showed an increased ratio of residual volume to total lung capacity (49 ± 4.7%). The subjects conducted inspiratory muscle thixotropy conditioning maneuvers at 3 different chest-wall volumes (end-expiratory volume of baseline breathing, residual volume plus 40% of expiratory reserve volume, and residual volume) and with 3 levels of inspiratory effort (0%, 30%, and 100% of maximal inspiratory mouth pressure at each volume), with airway-closure, in the sitting position. Using respiratory induction plethysmography, we measured the effect of effortintensity and volume at the time of the conditioning maneuver on the end-expiratory chest-wall volume of the 5 respiratory cycles immediately following the conditioning maneuver. RESULTS: There was a reduction in end-expiratory chest-wall volume after the conditioning maneuver, except when conditioning was performed at end-expiratory baseline with 0% effort. The reduction increased as effort intensity increased (p = 0.011) and as volume decreased (p < 0.001), and the reduction was attained by rib-cage movement rather than abdominal movement. CONCLUSIONS: Thixotropy conditioning of inspiratory muscles, at a reduced chest-wall volume, decreased end-expiratory chest-wall volume in the 5 subsequent breaths in patients with chronic obstructive pulmonary disease.