不同体位对全麻病人双肺或单肺通气时呼吸力学的影响

Effects of different positions of the patients mechanically ventilated under general anesthesia on respiratory mechanics during one or both lung ventilation before thoracotomy

目的观察全麻病人双肺或单肺通气时不同体位对呼吸力学的影响。方法择期胸科手术病人12例,ASA Ⅰ或Ⅱ级,年龄33-63岁,体重62-85 kg。全麻诱导后插入左双腔支气管导管, 行间歇正压通气,潮气量8-10 ml／kg,呼吸频率12次/min,吸呼比1:1．5。摆放平卧位、左侧卧位、右侧卧位,每个体位分别行双肺通气、左肺通气、右肺通气。经气道旁路监测气道峰压(Peak)、气道阻力 (Raw)、胸肺顺应性(CT)和呼气末二氧化碳分压(PETCO2),每次通气10 min后采集数据。结果双肺通气时,与平卧位比较,左、右侧卧位的Peak升高,CT降低;单肺通气时,与平卧位及下侧肺比较,上侧肺的Peak升高,CT、PETCO2降低;右肺通气时,与平卧位比较,右侧卧位的CT升高;双肺通气和左肺通气时,与平卧位比较,左侧卧位的Raw升高(P<0．01)。结论全麻机械通气下开胸前体位对呼吸力学影响较大,双肺通气时体位由平卧位变为侧卧位时CT降低,气道压力增加;单肺通气侧卧位时, 上侧CT降低,气道压力增加。

Objective To investigate the effects of different positions of the patients mechanically ventilated under general anesthesia on respiratory mechanics during one or both lung ventilation before thoracotomy. Methods Twelve ASA Ⅰ or Ⅱ patients of both sexes （8 males, 4 females） aged 33-63 years weighing 62-85 kg scheduled for general thoracic surgery were studied. The preoperative lung function of the patients was normal. The patients were premedicated with intramuscular pethidine, promethazine and atropine. Anesthesia was induced with fentanyl, droperidol, midazolam, propofol and vecuronium. Left-sided double-lumen tube was inserted and correct placement was confirmed using a fiberoptic bronchoscope inserted through the bronchial lumen. Anesthesia was maintained with propofol and vecuronium infusion. The magnitude of neuro-muscular blockade was monitored by stimulation of radial nerve with TOF pulses. T4/T1 was maintained at 0 during study. The patients were placed in supine, left and right lateral position. In each position both lungs, left and right lung were ventilated for 10 rain respectively. The non-ventilated bronchial lumen was open to the air during one-lung ventilation. The ventilatory parameters were kept unchanged during the study （ VT = 8-10 ml·kg^-1, RR = 12 bpm, I ： E = 1 ： 2）. Pressure-volume loop （ P-V loop）, peak airway pressure （Ppeak）, airway resistance （Raw）, total compliance （CT） （lung and thorax） and PETCO2 were measured and recorded at the end of each 10 rain ventilation using S/5 monitor （Datex-Ohmeda Finland）.Results During both lung ventilation Ppeak was significantly increased and CT was significantly decreased in left and right lateral position as compared with supine position （ P 〈0.01）. In supine position during one lung ventilation, either left or right, Ppeak and Raw were significantly increased and CT was significantly decreased as compared with the both lung ventilation. During right lung ventilation there was no significant difference in Ppeak and Raw but CT was significantly increased when the patients were turned from supine position to right lateral position （right lung down） （P 〈 0.01）. During left lung ventilation there was no significant change in Ppeak and CT but Raw was significantly increased when the patients were turned from supine position to left lateral position （left lung down） （P 〈 0.01 ） . Conclusion There is significant increase in Ppeak and decrease in CT from supine to the lateral position during both lung ventilation. During one lung ventilation when the patient is turned from supine to the lateral position with the lower lung being ventilated there is no significant change in Ppeak but Raw （left lateral） or CT （right lateral） is increased significantly but the increase is moderate.