Department of Pulmonary Research, Regions Hospital, 640 Jackson Street, St Paul MN 55101, USA.
Respir Care. 2010 Nov;55(11):1464-8.
The measurement of functional residual capacity (FRC) in ventilated patients could help track the extent of acute lung disease, monitor recruitment of unstable lung units, or guide the use of PEEP. Quantitative analysis of computed tomography (CT) images of the lungs is currently the accepted standard for FRC measurement (FRC-CT), but is impractical for routine use. Gas dilution and gas tracer technologies, while attractive for research applications, require specialized equipment and skills missing from the clinical setting. We simultaneously evaluated FRC-CT and FRC determined by a ventilator-incorporated wash-in/wash-out (FRC-WI/WO) method in an animal model of unilateral pleural effusion that varied the fluid volume instilled and the applied PEEP.
A swine model (n = 6) of unilateral pleural effusion was created by injecting boluses of radio-opaque fluid (iopromide) (13 mL/kg and then 26 mL/kg) into the right thoracic cavity. FRC-CT and FRC-WI/WO were simultaneously obtained, at 2 PEEP levels, at baseline and at both pleural-effusion volumes.
A correlation coefficient (r²) of 0.89 between FRC-CT and FRC-WI/WO revealed concordance between the techniques, with directional agreement and acceptable bias and precision under all tested conditions.
We found excellent concordance between FRC-WI/WO and FRC-CT in an animal model of unilateral pleural effusion that stressed the capability of this technology. The technical advantage of the wash-in/wash-out technique is its incorporation into ventilator operation without requiring adjustments to ventilation.
在通气患者中测量功能残气量（FRC）有助于跟踪急性肺疾病的程度，监测不稳定肺单位的募集情况，或指导使用 PEEP。肺部计算机断层扫描（CT）图像的定量分析是目前 FRC 测量的公认标准（FRC-CT），但不适合常规使用。气体稀释和气体示踪技术虽然适用于研究应用，但需要临床环境中缺少的专业设备和技能。我们同时评估了单侧胸腔积液动物模型中 FRC-CT 和呼吸机结合的灌洗/冲洗（FRC-WI/WO）方法测定的 FRC，该模型改变了注入的液体量和应用的 PEEP。
通过向右侧胸腔注入放射性不透射线的液体（碘普罗胺）（13 mL/kg，然后 26 mL/kg）创建单侧胸腔积液的猪模型（n = 6）。在 2 个 PEEP 水平下，在基线和两种胸腔积液量下同时获得 FRC-CT 和 FRC-WI/WO。
FRC-CT 和 FRC-WI/WO 的相关系数（r²）为 0.89，表明两种技术之间存在一致性，在所有测试条件下均具有方向性一致性和可接受的偏差和精度。
我们在单侧胸腔积液的动物模型中发现 FRC-WI/WO 和 FRC-CT 之间具有极好的一致性，该技术具有良好的应用潜力。灌洗/冲洗技术的技术优势在于它可以整合到呼吸机操作中，而无需对通气进行调整。
