Loyd J E, Nolop K B, Parker R E, Roselli R J, Brigham K L
J Appl Physiol (1985). 1986 Jan;60(1):198-203. doi: 10.1152/jappl.1986.60.1.198.
Because pulmonary edema has been associated clinically with airway obstruction, we sought to determine whether decreased intrathoracic pressure, created by selective inspiratory obstruction, would affect lung fluid balance. We reasoned that if decreased intrathoracic pressure caused an increase in the transvascular hydrostatic pressure gradient, then lung lymph flow would increase and the lymph-to-plasma protein concentration ratio (L/P) would decrease. We performed experiments in six awake sheep with chronic lung lymph cannulas. After a base-line period, we added an inspiratory load (20 cmH2O) and allowed normal expiration at atmospheric pressure. Inspiratory loading was associated with a 12-cmH2O decrease in mean central airway pressure. Mean left atrial pressure fell 11 cmH2O, and mean pulmonary arterial pressure was unchanged; calculated microvascular pressure decreased 8 cmH2O. The changes that occurred in lung lymph were characteristic of those seen after other causes of increased transvascular hydrostatic gradient, such as increased intravascular pressure. Lung lymph flow increased twice base line, and L/P decreased. We conclude that inspiratory loading is associated with an increase in the pulmonary transvascular hydrostatic gradient, possibly by causing a greater fall in interstitial perimicrovascular pressure than in microvascular pressure.
由于临床上肺水肿与气道阻塞有关，我们试图确定选择性吸气阻塞所产生的胸腔内压力降低是否会影响肺液平衡。我们推断，如果胸腔内压力降低导致跨血管流体静压梯度增加，那么肺淋巴流量将会增加，而淋巴与血浆蛋白浓度比（L/P）将会降低。我们对六只带有慢性肺淋巴插管的清醒绵羊进行了实验。在基线期之后，我们增加了吸气负荷（20 cmH₂O），并让其在大气压下正常呼气。吸气负荷与平均中心气道压力降低12 cmH₂O有关。平均左心房压力下降11 cmH₂O，平均肺动脉压力未变；计算得出的微血管压力降低8 cmH₂O。肺淋巴发生的变化是其他导致跨血管流体静压梯度增加的原因（如血管内压力增加）后所出现变化的特征。肺淋巴流量增加至基线的两倍，L/P降低。我们得出结论，吸气负荷与肺跨血管流体静压梯度增加有关，可能是因为与微血管压力相比，间质微血管周围压力下降幅度更大。
