Silva M F, Zin W A, Saldiva P H
Laboratório de Poluição Atmosférica Experimental, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
Am J Respir Crit Care Med. 1998 Oct;158(4):1230-4. doi: 10.1164/ajrccm.158.4.9710067.
The aim of this study is to evaluate histoarchitecture of airspaces at different positive transpulmonary pressures, both during inflation and deflation of excised normal and paraquat-damaged rat lungs. Freshly excised lungs were placed in a plethysmograph connected to a graded pipette. Immediately after the achievement of the desired pressure level (5, 15, 25 cm H2O during inflation, and 15 and 5 cm H2O during deflation), the tracheal cannula was occluded and lungs were quick-frozen by immersion in liquid nitrogen, and fixed using Carnoy's solution. Sections representing the central and peripheral areas of the lungs were sampled and processed for paraffin embedding and stained with hematoxylin-eosin. By means of stereological techniques, surface-to-volume ratio (S/V) and the fraction of large-volume gas-exchanging airspaces (LVGEAS) were determined. We observed in paraquat-treated animals evidence of alveolar instability close to the resting volume. Structural unevenness was minimized by massive recruitment followed by alveolar pressurization. In conclusion, this work demonstrates that morphological evidence of uneven distribution of inspired air may be partially reversed by applying larger alveolar pressures. These larger pressures applied at the end-expiration in vivo (positive end-expiratory pressure, PEEP) can minimize the distortion of lung microarchitecture during ventilation.
本研究的目的是评估在不同的正跨肺压下，正常大鼠和百草枯损伤大鼠离体肺在充气和放气过程中肺腔的组织架构。将新鲜离体肺置于连接有分级移液管的体积描记器中。在达到所需压力水平后（充气时为5、15、25 cm H₂O，放气时为15和5 cm H₂O），立即阻塞气管插管，将肺浸入液氮中快速冷冻，并用卡诺伊氏液固定。对代表肺中央和周边区域的切片进行取样，进行石蜡包埋，并用苏木精-伊红染色。通过体视学技术，测定表面与体积比（S/V）和大容积气体交换肺腔（LVGEAS）的比例。我们在百草枯处理的动物中观察到，在接近静息容积时存在肺泡不稳定的证据。通过大量肺复张继而肺泡加压，结构不均匀性降至最低。总之，这项工作表明，通过施加更大的肺泡压力，吸入气体分布不均的形态学证据可能会部分得到改善。在体内呼气末施加这些更大的压力（呼气末正压，PEEP）可以使通气过程中肺微结构的扭曲最小化。
