Mechanical and morphometrical changes in progressive bilateral pneumothorax and pleural effusion in normal rats

Abstract

M Me ec ch ha an ni ic ca al l a an nd d m mo or rp ph ho om me et tr ri ic ca al l c ch ha an ng ge es s i in n p pr ro og gr re es ss si iv ve e b bi il la at te er ra al l p pn ne eu um mo ot th ho or ra ax x a an nd d p pl le eu ur ra al l e ef ff fu us si io on n i in n n no or rm ma al l r ra at ts s Respiratory system, lung, and chest wall resistances and elastances (static and dynamic) were determined in 14 animals. For this purpose, the end-inflation occlusion during constant inspiratory flow method was used. Chest wall configuration at both functional residual capacity (FRC) and end-inspiration tidal volume (i.e. FRC+(VT)) was also evaluated in: 1) 15 rats by measurements of lateral and anteroposterior diameters, and circumferences at the 3rd intercostal space and xiphoid levels; and 2) in 16 rats by measurements of thoracic cephalocaudal diameter. In addition, changes in functional residual capacity were measured.Both in pneumothorax and pleural effusion, resistances were not altered, but static and dynamic respiratory system and lung elastances increased progressively. Morphometric changes were similar at both functional residual capacity and endinspiration; however, whereas pleural effusion increased all diameters, pneumothorax did not modify lateral diameter. Functional residual capacity was decreased in both conditions.In conclusion, pneumothorax and pleural effusion induced similar mechanical changes, but thoracic configuration was differently affected, since lateral diameters were increased in pleural effusion only.

Respiratory mechanics and morphometric changes during pneumoperitoneum in normal rats

“…This apparent discrepancy could be explained by the different conformational changes of the chest wall between the two studies (see below). Interestingly, ∆P1,L and ∆P2,L did not change in other models of disease (pleural effusion, pneumothorax and intraperitoneal effusion) leading to a decrease in FRC [21,25], under experimen-tal conditions similar to the present one.…”

Pleural effusion in the mechanically ventilated patient

“…Lung recruitment maneuvers without subsequent positive end expiratory pressure (PEEP) application produced transient improvements in C L . Interestingly, respiratory system compliance mirrored C L response to pleural infusion and recruitment maneuvers -an observation also made in smaller animal models of PLEF [20].…”

“…If the chest wall is normal, the effects of PLEF drainage may be predicted by gas exchange and respiratory mechanics responses to a recruitment maneuver. Under these conditions respiratory system compliance largely reflects C L [19,20] and should help track lung volume response to recruitment maneuvers and drainage. If there is evidence of recruitment after a recruitment maneuver, PLEF drainage could help reduce the end-expiratory airway pressures needed to sustain it.…”

Efficacy of peritoneal oxygenation using a novel artificial oxygen carrier (TRM-645) in a rat respiratory insufficiency model

“…Right pneumothorax causes acute respiratory failure and is lethal. 18 The mechanism of cardiac arrest in this experiment is that hypoxemia due to pneumothorax causes respiratory arrest and subsequently causes respiratory acidosis. Extension of the time before the cardiac arrest by intraperitoneal injection of oxygenated oxygen carrier is thought to be caused by maintaining the oxygenation of blood, thus the duration of spontaneous respiration was prolonged.…”