Bégin P, Peslin R, Hannhart B, Gallina C
J Appl Physiol (1985). 1985 Feb;58(2):346-51. doi: 10.1152/jappl.1985.58.2.346.
We investigated two methods of decreasing the error on plethysmographic determinations of thoracic gas volume (TGV) related to cheeks movements during panting maneuvers: lowering gas density in the airways with an 80% He-20% O2 mixture and computing TGV from the in-phase component of the plethysmographic signal (TGVr). The methods were tested by measuring how TGV estimates varied when panting frequency was raised from 0.8 to 2.5 Hz during the same occlusion. The measurements were performed in 6 normal subjects and 12 patients with chronic bronchitis with and without cheeks support and when the airway was connected to an external device simulating an increased cheeks compliance. A small negative frequency dependence of TGV (delta TGV/delta f = -1.2 +/- 0.8%/Hz with cheeks support), most probably unrelated to upper airway walls, was found in normal subjects. Delta TGV/delta f was positive and algebraically larger in patients than in normals, reaching 2.2 +/- 3.4%/Hz without cheeks support and 11.8 +/- 8.0%/Hz with the additional cheeks. The latter value was only 20% smaller when computed on the basis of TGVr, demonstrating the limited usefulness of the phase-based correction. In contrast, breathing He-O2 decreased delta TGV/delta f to approximately 50% of its air value (P less than 0.01) and appears as an effective way to diminish the error in obstructive patients.
我们研究了两种方法，以减少在呼吸动作期间与脸颊运动相关的胸廓气体容积（TGV）体积描记法测定中的误差：用80%氦-20%氧气混合气体降低气道中的气体密度，以及根据体积描记信号的同相分量（TGVr）计算TGV。通过测量在相同阻塞期间呼吸频率从0.8 Hz提高到2.5 Hz时TGV估计值的变化来测试这些方法。在6名正常受试者和12名慢性支气管炎患者中进行了测量，测量时有无脸颊支撑，以及气道连接到模拟脸颊顺应性增加的外部装置时的情况。在正常受试者中发现TGV存在轻微的负频率依赖性（有脸颊支撑时，δTGV/δf = -1.2±0.8%/Hz），这很可能与上气道壁无关。患者的δTGV/δf为正值，且代数上大于正常受试者，在无脸颊支撑时达到2.2±3.4%/Hz，有额外脸颊支撑时达到11.8±8.0%/Hz。基于TGVr计算时，后一个值仅小20%，这表明基于相位的校正作用有限。相比之下，呼吸氦氧混合气可使δTGV/δf降至其空气值的约50%（P<0.01），这似乎是减少阻塞性患者误差的有效方法。
