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PubMed1995

Volume detection threshold: quantitative comparison of computed radiography and screen-film radiography in detection of pneumothoraces in an animal model that simulates the neonate.

PURPOSE: To quantitatively compare computed radiography (CR) and screen-film radiography (SFR) in the detection of pneumothorax in an animal model that simulates the neonate. MATERIALS AND METHODS: Three rabbits underwent placement of 5-F catheters in the right pleural space. Eight CR and eight SFR images were obtained. Volume-controlled pneumothorax was induced by incrementally injecting 4 cm3 of air (24 cm3 total) and four CR and four SFR images were obtained after each injection. Four radiologists blindly viewed the images twice (eight readings per image, 1,600 total observations). A dichotomous yes-no score for the presence of pneumothorax was used to calculate the volume detection threshold (VDT), defined as the air volume at which 50% of the pneumothoraces can be detected. The authors plotted the likelihood of a pneumothorax against the air volume by using the confidence indicator. RESULTS: Intraobserver VDT values for CR and SFR were not significantly different. CONCLUSION: CR is as accurate as SFR in the detection of pneumothorax in this quantitative animal model.

Animals↗
PubMed1980

Elevations in plasma ADH levels during PEEP ventilation in the dog: mechanisms involved.

In an attempt to define more precisely the various mechanisms involved in antidiuretic hormone (ADH) release during positive end-expiratory pressure ventilation (PEEP), experiments were performed on seven groups of dogs. PEEP-10 and PEEP-15 cmH2O caused significant elevations of plasma ADH from basal values of 24.9 +/- 5.2 pg/ml (mean +/- SE) to 64.6 +/- 14.2 and 106.0 +/- 20.6, respectively (P < 0.02, P < 0.005). The ADH levels returned to basal values after cessation of PEEP. This rise in ADH levels was prevented by an infusion of dextran prior to PEEP. The fall in blood pressure and cardiac output that occurred during PEEP was also prevented by the dextran infusion. Changes in ADH levels were unrelated to lung volume, left transmural pressure, and serum osmolality. Bilateral vagotomy and carotid sinus denervation was followed by an attenuated rise in ADH levels in terms of the percent rise above base line, but it did not significantly alter the absolute rise in ADH during PEEP. ADH levels were, however, reduced significantly by decreasing intracranial pressure by the removal of cerebrospinal fluid during PEEP. Propranolol administration prior to PEEP completely blocked plasma renin activity. Although the peak ADH levels were unaffected by propranolol, the rise was delayed. The results obtained indicate that a number of physiological factors may affect plasma ADH levels during PEEP. These include the carotid body and aortic arch baroreceptors as wells as sensors of intracranial pressure.

Animals↗
PubMed1982

Action of costal and crural parts of the diaphragm on the rib cage in dog.

We studied the action of the costal and crural (vertebral) parts of the diaphragm on the lower rib cage in normal supine dogs. The two parts of the diaphragm were separately stimulated by electrodes directly implanted in the muscle or via the different phrenic nerve roots in the neck. The results of the experiments indicate the following. 1) The costal and crural parts of the diaphragm have a different segmental innervation and a different mechanical action on the rib cage. 2) The costal diaphragm expands the lower rib cage when it contracts. This rib-cage expansion is due mostly to the fulcrum of the abdominal contents and partly to the rise in abdominal pressure that takes place during diaphragmatic contraction. The pericardial attachments play no role in this action of the diaphragm. 3) The action of the crural diaphragm on the lower rib cage depends only on the balance between the inspiratory force exerted by the rise in abdominal pressure and the expiratory force exerted by the fall in pleural pressure. In the intact animal at functional residual capacity, these two opposite effects cancel each other. 4) The inflationary action of both parts on the rib cage decreases progressively as lung volume increases. The findings also suggest that the rise in abdominal pressure which occurs when the diaphragm contracts expands the lower rib cage by acting through the area of apposition of the diaphragm to the rib cage. These findings also strengthen the idea that the diaphragm actually consists of two muscles.

Abdomen↗
PubMed1984

How alterations in pleural pressure influence esophageal pressure.

Although esophageal pressures have been substituted for direct pleural pressure measurement in humans, we have investigated the validity of this approach under circumstances when left and right pleural pressures are not equal. Esophageal and bilateral pleural pressures in awake sheep were compared by using matched balloon catheters in close proximity. In standing sheep, both end-expiratory pressures and inspiratory pressure swings were similar in all three catheter systems. However, when pleural pressures were made unequal, as during lateral recumbency or unilateral pneumothorax, the esophageal pressure reflected predominantly the right pleural pressure. These results suggest that esophageal pressures are useful estimates of pleural pressure under normal conditions when pleural pressures are equal bilaterally. However, the usefulness of esophageal pressures is limited in the presence of unilateral pneumothorax or other conditions where left and right pleural pressures are unequal. In the lateral decubitus position, positive end-expiratory pleural pressures were consistently observed. This was believed to be due to a combination of contraction of expiratory muscles, rapid respiratory rate resulting in insufficient expiratory time to reach an equilibrium pressure, and increased airways resistance resulting from compression of the dependent lung by the abdominal viscera. A single study in a paralyzed ventilated sheep showed less positive expiratory pressures, which were further reduced to zero or less when the respiratory rate was slowed to 10 breaths/min.

Abdominal Muscles↗
PubMed2002

DNA sequences of the immunoglobulin heavy chain variable region gene in pyothorax-associated lymphoma.

B cell lymphoma develops in the pleural cavity of patients affected by long-standing pyothorax resulting from lung tuberculosis, thus termed pyothorax-associated lymphoma (PAL). PAL usually shows a diffuse large cell morphology, and constantly contains Epstein-Barr virus (EBV) genome. To investigate whether PAL cells proliferate in response to specific antigenic stimuli and its stage in B cell differentiation, immunoglobulin heavy chain gene in 7 cases and 2 cell lines from PAL, all confirmed by histological studies to be EBV-positive diffuse large B cell lymphoma, were examined by using polymerase chain reaction (PCR) method. Clonal rearrangement of the gene was detected in 4 cases of PAL tissues and one cell line. As for the usage of the V region gene (V(H)), the V(H)3 family gene was used in 3 of these 5 cases with different homologous germlines, suggesting that the origin of PAL cells from a repertoire of B lymphocytes responsive to specific antigenic epitope was unlikely. Compared to the homologous germline, the mutation frequency of PAL was 9% on average. Only one case might have more replacement mutations in the complementarity-determining regions than expected by chance, thus antigen-selected maturation might not take place in PAL. Intraclonal sequence heterogeneity in the V(H) gene was found in another case. From these findings, it is concluded that PAL is composed of B lymphocytes at the differentiation stage of the postgerminal center. Antigen-selected maturation might not take place in PAL, which is distinct from the majority of B cell lymphomas.

Aged↗
PubMed2004

Circulatory and respiratory complications of carbon dioxide insufflation.

BACKGROUND: Although providing excellent outcome results, laparoscopy also induces particular pathophysiological changes in response to pneumoperitoneum. Knowledge of the pathophysiology of a CO(2) pneumoperitoneum can help minimize complications while profiting from the benefits of laparoscopic surgery without concerns about its safety. METHODS: A review of articles on the pathophysiological changes and complications of carbon dioxide pneumoperitoneum as well as prevention and treatment of these complications was performed using the Medline database. RESULTS: The main pathophysiological changes during CO(2) pneumoperitoneum refer to the cardiovascular system and are mainly correlated with the amount of intra-abdominal pressure in combination with the patient's position on the operating table. These changes are well tolerated even in older and more debilitated patients, and except for a slight increase in the incidence of cardiac arrhythmias, no other significant cardiovascular complications occur. Although there are important pulmonary pathophysiological changes, hypercarbia, hypoxemia and barotraumas, they would develop rarely since effective ventilation monitoring and techniques are applied. The alteration in splanchnic perfusion is proportional with the increase in intra-abdominal pressure and duration of pneumoperitoneum. CONCLUSION: A moderate-to-low intra-abdominal pressure (<12 mm Hg) can help limit the extent of the pathophysiological changes since consecutive organ dysfunctions are minimal, transient and do not influence the outcome.

Animals↗