Evaluation of Pulmonary Edema: Stereological versus Gravimetrical Analysis

Abstract

Assessment of lung edema by gravimetrical analysis is a standard method to evaluate the severity of experimentally induced ischemia/reperfusion (IR) injury. The aim of this study was to compare gravimetrical assessment of pulmonary edema with a stereological approach which allows for qualitative and quantitative distinction between intravascular and edematous fluids by light microscopy. Eight experimental groups which differed in mode of preservation, ischemic storage and pharmacological treatments were studied in an extracorporeal rat lung model. Analysis of the pooled data showed that the wet/dry ratio values mainly reflected the amount of intra-alveolar edema (r_s = 0.442; p = 0.0057) but only stereological assessment of edema formation revealed differences depending on the treatment used. Only stereological data correlated significantly with oxygen tension measured at the end of reperfusion (r_s = –0.530; p = 0.0009). We conclude that gravimetry is of minor functional importance compared to assessment by stereological methods which prove to be a reliable and efficient tool for the evaluation of IR injury in the different experimental settings.

Pre-ischaemic exogenous surfactant reduces pulmonary injury in rat ischaemia/reperfusion

“…This high sensitivity is important since, in the present study, the amount of intra-alveolar oedema is rather low. A previous direct structural-functional correlation study demonstrated that with a volume fraction of .3%, intra-alveolar oedema formation becomes functionally relevant [46]. In the present study, only the two reperfused groups that did not receive surfactant had an intra-alveolar oedema volume fraction .3% of the parenchymal volume: group 4 (3.6%) and group 5 (7.9%; table 1).…”

“…The current authors used design-based stereological methods in order to quantify the degree of oedema formation in its preserved micro-organisation and localisation within the organ. These parameters are more sensitive indicators for impaired lung function and better correlate with the respiratory capacities of the organ than the wet-to-dry ratio [5,9,46]. This high sensitivity is important since, in the present study, the amount of intra-alveolar oedema is rather low.…”

Stereological analysis of acute lung injury

“…In contrast, a stereological approach allows for quantitative lung oedema analysis in its preserved microorganisation and location within the organ, as well as for the dissection of the particular contributions of peribronchovascular, septal and intra-alveolar oedema. This approach has been used successfully in various animal models of I/R injury, where it has been demonstrated that intra-alveolar oedema is the functionally most significant [42,[55][56][57]. These studies have also shown that oedema assessment by stereology better reflects the functional status of the lung than does wet/dry ratio analysis.…”

Impact of preservation solution on the extent of blood‐air barrier damage and edema formation in experimental lung transplantation

“…Most of the surface appeared swollen. lar edema (Fehrenbach et al, , 2001Ochs et al, 2000). At the level of alveoli, the fine structural details of the blood-air barrier can only be resolved by transmission electron microscopy.…”

“…Moreover, edema fluid is not homogeneously distributed in the lung. We have shown previously that pulmonary edema, which is commonly assessed globally by the lung wet/dry ratio, can be quantitated and differentiated into intra-alveolar, septal, and peribronchovascular edema by using a stereological approach after lung fixation by vascular perfusion (Fehrenbach et al, , 2001Ochs et al, 2000).…”