Hammer J, Newth C J
Division of Pediatric Critical Care, Children's Hospital of Los Angeles, University of Southern California 90027, USA.
J Appl Physiol (1985). 1995 May;78(5):1993-7. doi: 10.1152/jappl.1995.78.5.1993.
The rapid thoracoabdominal compression (RTC) technique is commonly used in pulmonary function laboratories to assess flow-volume relationships in infants unable to produce a voluntary forced expiration maneuver. This technique produces forced expiratory flows over only a small lung volume segment (i.e., tidal volume). It has been argued that the RTC technique should be modified to measure flow-volume relationships over a larger portion of the vital capacity range to imitate the voluntary maximal forced expiratory maneuver obtained in older children and adults. We examined the effect of volume history on forced expiratory flows by generating forced expiratory flow-volume curves by RTC from well-defined inspiratory volumes delineated by inspiratory pressures of 10, 20, 30, and 40 cmH2O down to residual volume (i.e., the reference volume) in seven intubated and anesthetized infants with normal lungs [age 8.0 +/- 2.0 (SE) mo, weight 6.7 +/- 0.6 kg]. We compared maximal expiratory flows at isovolume points (25 and 10% of forced vital capacity) and found no significant differences in maximal isovolume flow rates measured from the different lung volumes. We conclude that there is no obvious need to initiate RTC from higher lung volumes if the technique is used for flow comparisons. However, compared with measurements of maximal flows at functional residual capacity by RTC from end-tidal inspiration, the initiation of RTC from a defined and reproducible inspiratory level appears to decrease the intrasubject variability of the maximal expiratory flows at low lung volumes.
快速胸腹按压（RTC）技术常用于肺功能实验室，以评估无法进行自主用力呼气动作的婴儿的流量-容积关系。该技术仅在小肺容积段（即潮气量）产生用力呼气流量。有人认为，RTC技术应进行改进，以测量更大肺活量范围内的流量-容积关系，以模拟大龄儿童和成人的自主最大用力呼气动作。我们通过RTC从由10、20、30和40 cmH₂O吸气压力界定的明确吸气容积降至残气量（即参考容积），在7名肺功能正常的插管麻醉婴儿[年龄8.0±2.0（标准误）个月，体重6.7±0.6 kg]中生成用力呼气流量-容积曲线，研究容积历史对用力呼气流量的影响。我们比较了等容积点（用力肺活量的25%和10%）的最大呼气流量，发现从不同肺容积测量的最大等容积流速没有显著差异。我们得出结论，如果该技术用于流量比较，没有明显必要从更高的肺容积开始进行RTC。然而，与从潮气末吸气通过RTC测量功能残气量时的最大流量相比，从定义明确且可重复的吸气水平开始进行RTC似乎可降低低肺容积时最大呼气流量的受试者内变异性。
