Robatto F M, Simard S, Orana H, Macklem P T, Ludwig M S
Meakins-Christie Laboratories, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
J Appl Physiol (1985). 1992 Nov;73(5):1908-13. doi: 10.1152/jappl.1992.73.5.1908.
We have recently shown in dogs that much of the increase in lung resistance (RL) after induced constriction can be attributed to increases in tissue resistance, the pressure drop in phase with flow across the lung tissues (Rti). Rti is dependent on lung volume (VL) even after induced constriction. As maximal responses in RL to constrictor agonists can also be affected by changes in VL, we questioned whether changes in the plateau response with VL could be attributed in part to changes in the resistive properties of lung tissues. We studied the effect of changes in VL on RL, Rti, airway resistance (Raw), and lung elastance (EL) during maximal methacholine (MCh)-induced constriction in 8 anesthetized, paralyzed, open-chest mongrel dogs. We measured tracheal flow and pressure (Ptr) and alveolar pressure (PA), the latter using alveolar capsules, during tidal ventilation [positive end-expiratory pressure (PEEP) = 5.0 cmH2O, tidal volume = 15 ml/kg, frequency = 0.3 Hz]. Measurements were recorded at baseline and after the aerosolization of increasing concentrations of MCh until a clear plateau response had been achieved. VL was then altered by changing PEEP to 2.5, 7.5, and 10 cmH2O. RL changed only when PEEP was altered from 5 to 10 cmH2O (P < 0.01). EL changed when PEEP was changed from 5 to 7.5 and 5 to 10 cmH2O (P < 0.05). Rti and Raw varied significantly with all three maneuvers (P < 0.05). Our data demonstrate that the effects of VL on the plateau response reflect a complex combination of changes in tissue resistance, airway caliber, and lung recoil.
我们最近在犬类实验中发现，诱导性收缩后肺阻力（RL）的增加，很大程度上可归因于组织阻力的增加，即与流经肺组织的气流同步的压力降（Rti）。即使在诱导性收缩后，Rti仍依赖于肺容积（VL）。由于RL对收缩剂激动剂的最大反应也会受到VL变化的影响，我们不禁要问，VL变化导致的平台反应变化，是否部分归因于肺组织阻力特性的改变。我们研究了在8只麻醉、麻痹、开胸的杂种犬中，最大剂量乙酰甲胆碱（MCh）诱导收缩期间，VL变化对RL、Rti、气道阻力（Raw）和肺弹性（EL）的影响。在潮气量通气时[呼气末正压（PEEP）= 5.0 cmH₂O，潮气量 = 15 ml/kg，频率 = 0.3 Hz]，我们测量了气管流量与压力（Ptr）以及肺泡压力（PA，使用肺泡囊测量）。在基线以及雾化递增浓度的MCh直至达到明显的平台反应后进行测量。然后通过将PEEP分别改为2.5、7.5和10 cmH₂O来改变VL。仅当PEEP从5改为10 cmH₂O时，RL才发生变化（P < 0.01）。当PEEP从5改为7.5以及从5改为10 cmH₂O时，EL发生变化（P < 0.05）。Rti和Raw在所有三种操作下均有显著变化（P < 0.05）。我们的数据表明，VL对平台反应的影响反映了组织阻力、气道口径和肺回缩变化的复杂组合。
