Maximal expiratory flows generated by rapid chest compression following end-inspiratory occlusion or expiratory clamping in young children

Abstract

Partial forced expiratory flow-volume curves obtained by the rapid chest compression technique are being widely used to assess pulmonary function in infants and young children. The aim of this study is to assess whether in this age group flow limitation is achieved with the partial forced expiratory flow-volume curve with rapid chest compression. In eight infants and young children sedated with chloral hydrate, flow-volume curves were obtained by regular rapid chest compression technique, end-inspiratory airway occlusion prior to rapid chest compression, and expiratory clamping prior to rapid chest compression. In each technique, beginning with a cuff pressure of 20 cmH2O, the cuff pressure was increased by 10 cmH2O increments until the compression pressure reached 90 cmH2O. Maximal flow-volume curves were generated by each technique. End-inspiratory occlusion prior to rapid chest compression caused higher flows over the entire phase of expiration than the regular rapid chest compression. This increase could be observed over the entire phase of expiration. Forced expiratory flow at 50% and at 75% of vital capacity (V̇50 and V̇75) with regular rapid chest compression were 207±44 ml s-1 (mean±SD) and 138±59 ml·sec-1, respectively. When end-inspiratory occlusion preceded rapid chest compression, V̇50 and V̇75 increased to 283±114 and 206±61 ml·sec-1 respectively, with a mean increase in V̇50 of 34% and in V̇75 of 31%. When expiratory clamping preceded the compression, even higher expiratory flows resulted. V̇50 increased to 227±171 ml·sec-1 and V̇75 to 264±104 ml·sec-1 with a mean increase in V̇50 of 53% and in V̇75 of 55%, compared to regular rapid chest compression. Expiratory time corrected for expiratory volume shortened significantly from 12.8±7.4 mṡml-1 in regular rapid chest compression to 10.2±5.8 ms·ml-1 with end-inspiratory occlusion prior to rapid chest compression, and to 7.2±3.6 ms·ml-1 when expiratory clamping preceded rapid chest compression. This study suggests that the flow limitation is not always reached by the traditional rapid chest compression method.