Lung compartmentalization of inflammatory cells in sepsis

Lung injury commonly occurs in the setting of systemic inflammatory response syndrome occurring during bacterial sepsis. There has been little work quantifying different leukocytes within the different compartments of the lung and their association with overt lung injury in sepsis. We examined the pathogenesis of lung injury after cecal ligation and puncture (CLP), a clinically relevant model of sepsis. To assess the sequestration and migration of leukocytes, leukocyte differentials were obtained for the lung vascular compartment and the bronchoalveolar airspace. At 24 h post CLP, there were signs of edema in the lung, while at 48 h after CLP, there were clear indications of alveolar wall thickening with increased cellularity and diffuse alveolar hemorrhage. The number of lymphocytes in the pulmonary vascular compartment dropped by 50% and doubled in the (bronchoalveolar lavage) BAL, 24 h after CLP compared to sham controls suggesting that there was transendothelial migration of lymphocytes. At 48 h after CLP, lymphocyte numbers in the vasculature was similar to controls but BAL lymphocyte numbers were still raised. The number of pulmonary intravascular neutrophils were similar to controls at 24 h post CLP but were greatly elevated 48 h after CLP. The increase in neutrophils was partly due to a substantial increase in the percentage of immature band cells, indicating recruitment of neutrophils from the bone marrow. There were very few neutrophils in the BAL of sham controls and CLP rats. Perfusate monocyte/macrophages were significantly increased 48 h after CLP and a similar increase in macrophages was observed in the BAL. These results strongly suggest a role for lymphocytes and macrophages in the development of overt lung injury as the migration of these cells corresponds to that of the appearance of lung injury 48 h after CLP. Importantly our data also demonstrates the compartmentalization and migration of different inflammatory cell-types during the development of sepsis.

Time-dependent cardiovascular and inflammatory changes in acute endotoxemia

The pathophysiology of experimental acute endotoxemia is a complex process involving both cardiovascular dysfunction and an inflammatory response. We have examined the correlation in hemodynamic changes and the pulmonary inflammatory response after lipopolysaccharide (LPS) administration with respect to time. Importantly, we have measured the lung and plasma levels of nitric oxide (NO) over time, as well as rapid generation of lung superoxide after LPS administration. In anesthetized rats given a bolus injection of LPS (10 mg/kg intravenously, from Salmonella enteritidis), mean arterial blood pressure dropped by 63-70% within 15 min, and cardiac output fell by 57-63% within 20 min compared with saline controls. Mean arterial blood pressure recovered slightly but was still 51, 30, and 25% less than that of saline controls 45, 105, and 165 min after LPS administration, respectively. Cardiac output remained depressed throughout the experimental period and was 35% lower than in saline controls 165 min after LPS treatment. There was a small increase in plasma nitrite/nitrate as an index of plasma NO production after 45 min and a 10-fold increase 165 min after LPS addition compared with controls, strongly suggesting that NO mediates the hypotension that occurs 165 min after LPS administration. Lung NO production increased twofold 105 min after LPS administration and remained higher than in saline controls. Histological sections showed that there was fluid accumulation and alveolar collapse in the lung 45 min after LPS, whereas after 165 min, there was extensive tissue damage and increased leukocyte accumulation compared with controls. These results suggest that there was no correlation between early (1 h) tissue damage and NO production. We found an increase in lung superoxide generation 15 min after injection of LPS that coincided with the alterations in cardiovascular function. These results suggest that early lung tissue damage and/or hemodynamic changes may be due to superoxide generation from the lung.

Metabolic responses of women to exercise attributable to long term use of a manual wheelchair

The purpose of this study was to determine the effects of long term use of a manual wheelchair by wheelchair-confined women (means = 14.6 years) on physiological responses to wheelchair ergometry. Six experimental subjects were compared to six able bodied women during maximal exercise as well as submaximal wheelchair ergometry at 50 and 80% of peak VO2. The wheelchair dependent women achieved higher power outputs, greater efficiency at the higher submaximal workload, less metabolic acidosis during submaximal exercise as well as less ventilatory stress. There was no significant difference in peak VO2 between the two groups of women. Because these were not athletically trained women, it was concluded that the long term use of a manual wheelchair leads to physiological adaptations favourable to the daily requirements of wheelchair locomotion.