Eckmann D M, Gavriely N
Department of Anesthesia, Northwestern University Medical School, Evanston, Illinois, USA.
Crit Care Med. 1996 Mar;24(3):451-7. doi: 10.1097/00003246-199603000-00015.
To determine if high-frequency external chest wall vibration added to low flow intratracheal fresh gas insufflation alters the intra-airway CO2 distribution and the resistance to CO2 transport from the lungs.
Prospective study.
Experimental laboratory.
Six adult anesthesized and paralyzed mongrel dogs (mean weight 24.3+/- 4.4 kg).
Dogs were ventilated by three methods: a) intermittent positive pressure ventilation; b) intermittent positive pressure ventilation with tracheal insufflation of fresh gas (FIO2 of 0.4) flowing at 0.15 L/kg/min through a catheter positioned at the carina; and c) intermittent positive pressure ventilation with tracheal insufflation and with external high-frequency chest wall vibration of the dependent hemithorax.
We measured arterial blood gas values as an index of global gas exchange, and intrapulmonary airway CO2 concentrations as an index of local gas exchange. Intra-airway CO2 concentrations along the axis of the airways were measured via a sampling catheter. Airway axial concentration profiles were constructed and resistances to gas transport were calculated from the measured data. Vibration increased intraluminal CO2 concentrations from 1.1% to 2.5% mouthward of the insufflation catheter tip. Peak resistance to CO2 transport decreased by 65% during vibration relative to the insufflation-only value. Vibration displaced peak transport resistance from second- to fourth-generation airways.
Global gas exchange improves during ventilation by chest wall vibration with low flow insufflation. Local gas exchange in the central airways is also improved due to increased intraluminal mixing and CO2 elimination. This ventilation technique may confer therapeutic advantages over conventional mechanical ventilation in the treatment of ventilatory failure.
确定在低流量气管内新鲜气体吹入基础上增加高频胸壁振动是否会改变气道内二氧化碳分布以及肺内二氧化碳排出阻力。
前瞻性研究。
实验实验室。
6只成年麻醉且麻痹的杂种犬（平均体重24.3±4.4千克）。
犬采用三种通气方法：a）间歇正压通气；b）间歇正压通气并通过置于隆突处的导管以0.15升/千克/分钟的流速进行气管内新鲜气体吹入（吸入氧分数为0.4）；c）间歇正压通气、气管内新鲜气体吹入并对下垂侧半胸进行高频胸壁振动。
我们测量动脉血气值作为整体气体交换指标，测量肺内气道二氧化碳浓度作为局部气体交换指标。通过采样导管测量沿气道轴线的气道内二氧化碳浓度。构建气道轴向浓度分布图并根据测量数据计算气体排出阻力。振动使吹入导管尖端向口腔方向的管腔内二氧化碳浓度从1.1%增至2.5%。与仅进行吹入时相比，振动期间二氧化碳排出的峰值阻力降低了65%。振动使峰值排出阻力从第二代气道转移至第四代气道。
在低流量吹入基础上通过胸壁振动进行通气时，整体气体交换得到改善。由于管腔内混合增加及二氧化碳排出增加，中央气道的局部气体交换也得到改善。这种通气技术在治疗通气衰竭方面可能比传统机械通气具有治疗优势。
