Duranti R, Misuri G, Gorini M, Goti P, Gigliotti F, Scano G
Istituto di Clinica Medica III, Università di Firenze, Italy.
Thorax. 1995 Feb;50(2):127-33. doi: 10.1136/thx.50.2.127.
High neural drive to the respiratory muscles and rapid and shallow breathing are frequently observed in patients with chronic obstructive pulmonary disease (COPD), and both mechanical and chemical factors are thought to play a part. However, the interrelation between these factors and the modifications in the control of breathing are not clearly defined. The effects of an acute decrease in mechanical load by the administration of a high dose of a beta 2 agonist were studied.
Nine spontaneously breathing patients with severe COPD took part in the study. Criteria for entry were FEV1 of < 40% of predicted and an improvement in FEV1 of < 200 ml after inhalation of 400 micrograms fenoterol. The following parameters were measured: lung volumes, tidal volume (VT), respiratory frequency (Rf), maximal pleural pressure during a sniff manoeuvre (PPLmax), pleural pressure swings (PPLsw), lung resistance (RL), RL/PPLmax ratio, and surface electromyographic activity (EMG) of diaphragm (EDI) and parasternal (EPS) muscles. Arterial oxygen saturation (SaO2), end tidal carbon dioxide pressure (PETCO2), and the electrocardiogram were also monitored. Each variable was measured under control conditions and 20 and 40 minutes after the inhalation of 800 micrograms fenoterol. In five patients the effects of placebo were also studied.
Fenoterol resulted in an increase in FEV1 and decrease in FRC. SaO2 did not change, while PETCO2 fell and heart rate increased. The VT increased, and Rf decreased, PPLsw fell and PPLmax increased, thus the PPLsw/PPLmax ratio fell. Both RL and RL/PPLmax also fell, and a substantial decrease in EDI and EPS was observed. Changes in PPLsw were related to changes in FEV1 and RL. Changes in VT and Rf, and EDI/TI and EPS/TI were also related to changes in PPLsw and RL/PPLmax ratio, but not to changes in FEV1. No variation was observed with placebo.
In patients with severe COPD a decrease in inspiratory muscle loading relative to the maximal available strength, as expressed by the RL/PPLmax and PPLsw/PPLmax ratios, appears to be the major determinant of changes in breathing pattern and inspiratory muscle activity (decrease in EMG).
慢性阻塞性肺疾病（COPD）患者常出现呼吸肌的高神经驱动以及快速浅呼吸，机械因素和化学因素都被认为起了一定作用。然而，这些因素之间的相互关系以及呼吸控制的改变尚未明确界定。本研究探讨了高剂量β2激动剂给药导致机械负荷急性降低的影响。
9例重度COPD自主呼吸患者参与研究。入选标准为FEV1<预测值的40%，吸入400微克非诺特罗后FEV1改善<200毫升。测量以下参数：肺容积、潮气量（VT）、呼吸频率（Rf）、吸气动作时的最大胸膜压力（PPLmax）、胸膜压力波动（PPLsw）、肺阻力（RL）、RL/PPLmax比值以及膈肌（EDI）和胸骨旁肌（EPS）的表面肌电图活动（EMG）。还监测动脉血氧饱和度（SaO2）、呼气末二氧化碳分压（PETCO2）和心电图。每个变量在对照条件下以及吸入800微克非诺特罗后20分钟和40分钟时测量。在5例患者中还研究了安慰剂的作用。
非诺特罗使FEV1增加，FRC降低。SaO2未改变，而PETCO2下降，心率增加。VT增加，Rf降低，PPLsw下降，PPLmax增加，因此PPLsw/PPLmax比值下降。RL和RL/PPLmax也下降，并且观察到EDI和EPS显著降低。PPLsw的变化与FEV1和RL的变化相关。VT和Rf以及EDI/TI和EPS/TI的变化也与PPLsw和RL/PPLmax比值的变化相关，但与FEV1的变化无关。安慰剂组未观察到变化。
在重度COPD患者中，相对于最大可用力量而言吸气肌负荷的降低，如通过RL/PPLmax和PPLsw/PPLmax比值所表示的，似乎是呼吸模式和吸气肌活动变化（EMG降低）的主要决定因素。
