Chen Han, Zhou Jing, Lin Yi-Qin, Zhou Jian-Xin, Yu Rong-Guo
Surgical Intensive Care Unit, Fujian Provincial Clinical College, Fujian Medical University, No 134, Dongjie Street, Gulou District, Fuzhou, 350001, Fujian, China.
Department of Critical Care Medicine, Beijing Tiantan Hospital, Capital Medical University, Beijing, China.
BMC Neurol. 2018 Nov 5;18(1):183. doi: 10.1186/s12883-018-1191-4.
Respiratory mechanics affects the effect of positive end-expiratory pressure (PEEP) on intracranial pressure (ICP). Respiratory mechanics of the lung and the chest wall was not differentiated in previous studies. In the present study, we investigated the influence of the following possible determinants of ICP responsiveness to PEEP: chest wall elastance (E), lung elastance (E), and baseline ICP.
Eight healthy Bama miniature pigs were studied. The increase of E was induced by instillation of hydrochloride, and the increase of E was induced by strapping the animals' chest wall and abdomen. A balloon-tipped catheter was placed intracranially for inducing intracranial hypertension. Six experimental conditions were investigated in sequence: 1) Normal; 2) Stiff Chest Wall; 3) Lung Injury; 4) Lung Injury + Stiff Chest Wall; 5) Lung Injury + Stiff Chest Wall + Intracranial Hypertension and 6) Lung Injury + Intracranial Hypertension. PEEP was gradually increased in a 5 cm HO interval from 5 to 25 cm HO in each condition. Blood pressure, central venous pressure, ICP, airway pressure and esophageal pressure were measured.
Hydrochloride instillation significantly increased E in conditions with lung injury. E significantly increased in the conditions with chest wall and abdomen strapping (all p < 0.05). ICP significantly increased with increments of PEEP in all non-intracranial hypertension conditions (p < 0.001). The greatest cumulative increase in ICP was observed in the Stiff Chest Wall condition (6 [5.3, 6.8] mm Hg), while the lowest cumulative increase in ICP was observed in the Lung Injury condition (2 [1.3, 3.8] mm Hg). ICP significantly decreased when PEEP was increased in the intracranial hypertension conditions (p < 0.001). There was no significant difference in cumulative ICP change between the two intracranial hypertension conditions (p = 0.924).
Different respiratory mechanics models can be established via hydrochloride induced lung injury and chest wall and abdominal strapping. The effect of PEEP on ICP is determined by respiratory mechanics in pigs with normal ICP. However, the responsiveness of ICP to PEEP is independent of respiratory mechanics when there is intracranial hypertension.
呼吸力学影响呼气末正压（PEEP）对颅内压（ICP）的作用。以往研究未区分肺和胸壁的呼吸力学。在本研究中，我们调查了以下可能决定ICP对PEEP反应性的因素：胸壁弹性（E）、肺弹性（E）和基线ICP。
对8只健康的巴马小型猪进行研究。通过滴注盐酸诱导E增加，通过捆绑动物胸壁和腹部诱导E增加。将带球囊导管置于颅内以诱导颅内高压。依次研究6种实验条件：1）正常；2）胸壁僵硬；3）肺损伤；4）肺损伤+胸壁僵硬；5）肺损伤+胸壁僵硬+颅内高压；6）肺损伤+颅内高压。在每种条件下，PEEP以5 cmH₂O的间隔从5 cmH₂O逐渐增加至25 cmH₂O。测量血压、中心静脉压、ICP、气道压力和食管压力。
在肺损伤条件下，滴注盐酸显著增加E。在胸壁和腹部捆绑条件下，E显著增加（均p<0.05）。在所有非颅内高压条件下，ICP随PEEP增加而显著增加（p<0.001）。在胸壁僵硬条件下观察到ICP的最大累积增加（6[5.3,6.8]mmHg），而在肺损伤条件下观察到ICP的最低累积增加（2[1.3,3.8]mmHg）。在颅内高压条件下，当PEEP增加时，ICP显著降低（p<0.001）。两种颅内高压条件下的累积ICP变化无显著差异（p=0.924）。
通过盐酸诱导的肺损伤以及胸壁和腹部捆绑可建立不同的呼吸力学模型。在ICP正常的猪中，PEEP对ICP的作用由呼吸力学决定。然而，当存在颅内高压时，ICP对PEEP的反应性与呼吸力学无关。
