Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria, Australia.
Menzies Institute for Medical Research, College of Health and Medicine, University of Tasmania, Hobart, Tasmania, Australia.
J Appl Physiol (1985). 2023 Oct 1;135(4):747-752. doi: 10.1152/japplphysiol.00693.2022. Epub 2023 Aug 17.
How the heterogeneous distribution of lung volumes changes in response to different mechanical ventilation (MV) strategies is unclear. Using our well-developed four-dimensional computed tomography (4DCT) high-resolution imaging technique, we aimed to assess the effect of different MV strategies on the distribution and heterogeneity of regional lung volumes. Healthy adult female BALB/c mice received either 2 h of "injurious" MV [ = 6, mechanical ventilation at high PIP with zero PEEP (HPZP)] with a peak inspiratory pressure (PIP) of 20 cmHO and zero positive end-expiratory pressure (PEEP), or 2 h of "protective" MV [ = 8, mechanical ventilation at low PIP with PEEP (LPP)] with PIP = 12 cmHO and PEEP = 2 cmHO. 4DCT images were obtained at baseline (0 h) and after 2 h of MV. Tidal volume (Vt) and end-expiratory lung volume (EEV) were measured throughout the whole lung on a voxel-by-voxel basis. Heterogeneity of ventilation was determined by the coefficient of variation (COV) of Vt and EEV. Our data showed that MV had minimal impact on global Vt but decreased EEV in the HPZP group ( < 0.05). Both ventilation modes decreased the COV of Vt (39.4% for HPZP and 9.7% for LPP) but increased the COV in EEV (36.4% for HPZP and 29.2% for LPP). This was consistent with the redistribution index, which was significantly higher in the HVZP group than in the LPP group ( < 0.001). We concluded that regional assessment of the change in EEV showed different patterns in progression between LPP and HPZP strategies. Both ventilation strategies decreased heterogeneity in Vt after 2 h of MV but increased heterogeneity in EEV. Further work is required to determine the link between these effects and ventilator-induced lung injury. Tidal volume heterogeneity decreases over time in response to mechanical ventilation, in contrast to end-expiratory volume heterogeneity which increases.
不同机械通气（MV）策略对肺容积异质性分布的影响尚不清楚。本研究使用我们成熟的四维 CT（4DCT）高分辨率成像技术，旨在评估不同 MV 策略对区域性肺容积分布和异质性的影响。健康成年雌性 BALB/c 小鼠接受 2 小时“损伤性”MV[=6，高峰压机械通气伴零呼气末正压（PEEP）（HPZP）]，吸气峰压（PIP）为 20 cmH2O，零 PEEP；或 2 小时“保护性”MV[=8，低 PIP 机械通气伴 PEEP（LPP）]，PIP=12 cmH2O，PEEP=2 cmH2O。在 MV 前（0 小时）和 2 小时后进行 4DCT 成像。在体素基础上测量全肺潮气量（Vt）和呼气末肺容积（EEV）。通过 Vt 和 EEV 的变异系数（COV）来确定通气的异质性。研究数据显示，MV 对整体 Vt 的影响最小，但 HPZP 组的 EEV 降低（<0.05）。两种通气模式均降低了 Vt 的 COV（HPZP 为 39.4%，LPP 为 9.7%），但增加了 EEV 的 COV（HPZP 为 36.4%，LPP 为 29.2%）。这与重新分布指数一致，HPZP 组明显高于 LPP 组（<0.001）。研究结果表明，EEV 区域评估显示 LPP 和 HPZP 策略之间的进展模式不同。两种通气策略在 2 小时 MV 后均降低了 Vt 的异质性，但增加了 EEV 的异质性。需要进一步研究这些影响与呼吸机相关性肺损伤之间的关系。与 EEV 异质性增加相反，潮气量异质性随时间推移而降低。
