Yan S, Sliwinski P, Macklem P T
Montreal Chest Institute Research Centre, McGill University, Montreal, Quebec, Canada.
J Appl Physiol (1985). 1996 Oct;81(4):1528-34. doi: 10.1152/jappl.1996.81.4.1528.
The purpose of this study is to investigate the effect of chest wall configuration at end expiration on tidal volume (VT) response during CO2 rebreathing. In a group of 11 healthy male subjects, the changes in end-expiratory and end-inspiratory volume of the rib cage (delta Vrc,E and delta Vrc,I, respectively) and abdomen (delta Vab,E and delta Vab,I, respectively) measured by linearized magnetometers were expressed as a function of end-tidal PCO2 (PETCO2. The changes in end-expiratory and end-inspiratory volumes of the chest wall (delta Vcw,E and delta Vcw,I, respectively) were calculated as the sum of the respective rib cage and abdominal volumes. The magnetometer coils were placed at the level of the nipples and 1-2 cm above the umbilicus and calibrated during quiet breathing against the VT measured from a pneumotachograph. The delta Vrc,E/delta PETCO2 slope was quite variable among subjects. It was significantly positive (P < 0.05) in five subjects, significantly negative in four subjects (P < 0.05), and not different from zero in the remaining two subjects. The delta Vab,E/delta PETCO2 slope was significantly negative in all subjects (P < 0.05) with a much smaller intersubject variation, probably suggesting a relatively more uniform recruitment of abdominal expiratory muscles and a variable recruitment of rib cage muscles during CO2 rebreathing in different subjects. As a group, the mean delta Vrc,E/delta PETCO2, delta Vab,E/delta PETCO2, and delta Vcw,E/delta PETCO2, slopes were 0.010 +/- 0.034, -0.030 +/- 0.007, and -0.020 +/- 0.032 1/Torr, respectively; only the delta Vab,E/delta PETCO2, slope was significantly different from zero. More interestingly, the individual delta VT/delta PETCO2 slope was negatively associated with the delta Vcr,E/delta PETCO2 (r = 0.68, P = 0.021) and delta Vcw,E/delta PETCO2 slopes (r = 0.63, P = 0.037) but was not associated with the delta Vab,E/delta PETCO2 slope (r = 0.40, P = 0.223). There was no correlation of the delta Vrc,E/delta PETCO2 and delta Vcw,E/delta PETCO2 slopes with age, body size, forced expiratory volume in 1 s, or expiratory time. The group delta Vab,I/delta PETCO2 slope (0.004 +/- 0.014 1/Torr) was not significantly different from zero despite the VT nearly being tripled at the end of CO2 rebreathing. In conclusion, the individual VT response to CO2, although independent of delta Vab,E, is a function of delta Vrc,E to the extent that as the delta Vrc,E/delta PETCO2 slope increases (more positive) among subjects, the VT response to CO2 decreases. These results may be explained on the basis of the respiratory muscle actions and interactions on the rib cage.
本研究的目的是调查呼气末胸壁形态对二氧化碳重吸入期间潮气量（VT）反应的影响。在一组11名健康男性受试者中，通过线性化磁力计测量的胸廓（分别为ΔVrc,E和ΔVrc,I）和腹部（分别为ΔVab,E和ΔVab,I）呼气末和吸气末容积的变化表示为呼气末二氧化碳分压（PETCO2）的函数。胸壁呼气末和吸气末容积的变化（分别为ΔVcw,E和ΔVcw,I）计算为相应胸廓和腹部容积之和。磁力计线圈放置在乳头水平和脐上1 - 2 cm处，并在安静呼吸期间根据呼吸流速仪测量的VT进行校准。受试者之间的ΔVrc,E/ΔPETCO2斜率变化很大。5名受试者中该斜率显著为正（P < 0.05），4名受试者中显著为负（P < 0.05），其余2名受试者中与零无差异。所有受试者的ΔVab,E/ΔPETCO2斜率均显著为负（P < 0.05），受试者间差异小得多，这可能表明在不同受试者的二氧化碳重吸入过程中，腹部呼气肌的募集相对更均匀，而胸廓肌肉的募集存在差异。作为一个整体，平均ΔVrc,E/ΔPETCO2、ΔVab,E/ΔPETCO2和ΔVcw,E/ΔPETCO2斜率分别为0.010±0.034、-0.030±0.007和-0.020±0.032 1/Torr；只有ΔVab,E/ΔPETCO2斜率显著不同于零。更有趣的是，个体ΔVT/ΔPETCO2斜率与ΔVcr,E/ΔPETCO2（r = 0.68，P = 0.021）和ΔVcw,E/ΔPETCO2斜率（r = 0.63，P = 0.037）呈负相关，但与ΔVab,E/ΔPETCO2斜率无关（r = 0.40，P = 0.223）。ΔVrc,E/ΔPETCO2和ΔVcw,E/ΔPETCO2斜率与年龄、体型、1秒用力呼气量或呼气时间均无相关性。尽管在二氧化碳重吸入结束时VT几乎增加了两倍，但该组的ΔVab,I/ΔPETCO2斜率（0.004±0.014 1/Torr）与零无显著差异。总之，个体对二氧化碳的VT反应虽然独立于ΔVab,E，但在一定程度上是ΔVrc,E的函数，即随着受试者中ΔVrc,E/ΔPETCO2斜率增加（更正向），对二氧化碳的VT反应降低。这些结果可以根据胸廓上呼吸肌的作用和相互作用来解释。
