Hedenstierna G, Tokics L, Lundquist H, Andersson T, Strandberg A, Brismar B
Department of Anesthesia, Huddinge University Hospital, Sweden.
Anesthesiology. 1994 Apr;80(4):751-60. doi: 10.1097/00000542-199404000-00006.
Atelectasis formation during anesthesia may be due to loss of respiratory muscle tone, in particular that of the diaphragm. This was tested by tensing the diaphragm by phrenic nerve stimulation (PNS) and observing the effect on atelectasis.
Twelve patients (mean age 48 yr) without preexisting lung disease were studied during halothane anesthesia. PNS was executed with an external electrode on the right side of the neck. Chest dimensions and area of atelectasis were studied by computed tomography of the chest.
Right-sided PNS against an occluded airway at functional residual capacity reduced the atelectatic area in the right lung from 5.1 to 3.8 cm2. The atelectasis was reduced to 1.1 cm2 after application of positive end-expiratory pressure (PEEP) of 10 cmH2O and large tidal volumes but increased to 2.5 cm2 within 1 min after discontinuation of PEEP. Commencement of PNS immediately after PEEP prevented the atelectasis from increasing, the mean area being 0.9 cm2. In seven patients, in whom the trachea was intubated with a double-lumen endobronchial catheter the atelectatic area was smaller during PNS with an open airway than during positive pressure inflation of the lung with the same volume as inspired during PNS (3.5 and 5.2 cm2, respectively.
The findings indicate that contracting the diaphragm in the anesthetized subject reduces the size of atelectasis.
麻醉期间肺不张的形成可能是由于呼吸肌张力丧失，尤其是膈肌张力丧失。通过膈神经刺激（PNS）使膈肌紧张并观察其对肺不张的影响来对此进行测试。
对12例无肺部基础疾病的患者（平均年龄48岁）在氟烷麻醉期间进行研究。通过颈部右侧的外部电极进行PNS。通过胸部计算机断层扫描研究胸部尺寸和肺不张面积。
在功能残气量时对闭塞气道进行右侧PNS可使右肺肺不张面积从5.1平方厘米减少至3.8平方厘米。施加10厘米水柱的呼气末正压（PEEP）和大潮气量后，肺不张面积减少至1.1平方厘米，但在停止PEEP后1分钟内增加至2.5平方厘米。在PEEP后立即开始PNS可防止肺不张增加，平均面积为0.9平方厘米。在7例使用双腔支气管内导管进行气管插管的患者中，气道开放时PNS期间的肺不张面积小于以与PNS期间吸气相同的容积对肺进行正压通气时的肺不张面积（分别为3.5平方厘米和5.2平方厘米）。
研究结果表明，使麻醉状态下的受试者的膈肌收缩可减小肺不张的大小。
