Respiratory Mechanics and Fluid Dynamics After Lung Resection Surgery
Section snippets
Prologue: active and passive drainage of the pleural cavity
Postoperative thoracic surgery poses the problem of draining the pleural cavity after closure of the thorax. Two phases in the draining process can be identified. Immediately after closure of the chest, there is a need to drain air to allow lung expansion and volume oscillation during the breathing cycle. Gas drainage ought to be performed by having the tip of the chest tube where the gas bubble is going to collect during the suction process, namely in the less dependent portion of the chest
Mechanics
Thoracic surgery that requires resection of a portion of lung or of a whole lung profoundly alters the mechanical and fluid dynamic setting of the lung-chest wall coupling, as well as the water balance in the pleural space and in the remaining lung. The most frequent postoperative complications are of a respiratory nature, and their incidence increases the more the preoperative respiratory condition seems compromised.3 There is an obvious need to identify risk factors concerning mainly the
Lung Fluid Balance and Tissue Mechanics in Physiologic Conditions
The pressure existing in the interstitial space of the lung is subatmospheric,15 about −10 cm H2O, reflecting, as much as for the pleural space, a strong draining lymphatic action, in the face of a low permeability of the capillary endothelium providing fluid filtration (Fig. 7). A subatmospheric interstitial pressure keeps the endothelium well glued to the epithelium, and in this way the volume of the extravascular water is kept at a minimum so that the overall thickness of the air-blood
The Postoperative Residual Pleural Space
As described in the analysis of Fig. 5, complete gas removal is a major cause of lung over distension that in turn leads to the 3 main postoperative respiratory complications: air leak, hydrothorax, and lung edema. To avoid over distension, a gas bubble has to remain in the chest in the immediate postoperative period after placing a suction tube. Gas is slowly reabsorbed (∼1%/d) from the chest; washing the cavity with oxygen would speed up the reabsorption process. Within the gas bubble,
Suggestions: how to improve pre- to early postoperative evaluation
Because surgeons are attaining considerable technical refinement,42 there is an obvious need to also refine the identification of risk factors for respiratory distress to reduce morbidity and mortality. The postoperative period seems to be the most critical period, when cofactors of respiratory morbidity may be present.
To prevent over distension, knowledge of the elastic properties of the lung would be useful. To follow the time evolution of the lung fluid balance, 2 methods can be suggested.
Respiratory Mechanics
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In emphysema, lobectomy and pneumonectomy result in over distension of the remaining lung, thus implying a greater risk of air leak.
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In fibrosis, pleural pressures become remarkably subatmospheric implying a greater risk for persistence of the gas bubble (potentially misinterpreted as air leak) and formation of hydrothorax.
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Respiratory work increases after lobectomy and pneumonectomy, because lung compliance decreases in inverse proportion to the volume resected.
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The increase in respiratory work
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2022, Journal of the Mechanical Behavior of Biomedical MaterialsExternal Suction and Fluid Output in Chest Drains After Lobectomy: A Randomized Clinical Trial
2018, Annals of Thoracic SurgeryCitation Excerpt :The surgical approach (VATS versus thoracotomy) was also a notable predictor of fluid production, which was higher after thoracotomy, and, although it is purely speculative, this may be due to more extensive tissue damage during thoracotomy. Our results therefore confirm the assumption that both the level of suction and the extent of the surgical insult per se can influence fluid production [4, 5]. The Polish study included patients who underwent lung resection for both benign and malignant disease, which we believe is a limitation because mediastinal lymph node dissection is only performed in malignant disease, which will likely increase fluid output in the postoperative period.
Management of Chest Drains After Thoracic Resections
2017, Thoracic Surgery ClinicsCitation Excerpt :The pleural space is a perfect biological system capable of accomplishing at least 2 fundamental functions: (1) to maintain the lung perfectly expanded in the chest, and (2) to preserve a perfect sliding between visceral and parietal pleura, with a very low coefficient of friction. Pleural fluid is kept in a subatmospheric range, which results by balancing its filtration and drainage.1 From an anatomic point of view, the pleural space is delimited by the visceral pleura, which wraps the entire lung and the fissures, and the parietal one, which covers the rib cage along with the diaphragmatic surface.
Studies reported in this review have been sponsored by funding from Italian Ministry of University, University Milano-Bicocca, ASI (Agenzia Spaziale Italiana).