Effect of different ventilatory strategies on local and systemic cytokine production in intact swine lungs in vivo.

The purpose of the study was to investigate the effect of different ventilatory strategies on local and systemic cytokine production in swine with intact lungs in vivo after 4 h of mechanical ventilation. Twenty-five swine were anesthetized and then randomized into five groups (n = 5): (1) low tidal volume zero PEEP (LVZP); (2) medium tidal volume zero PEEP (MVZP); (3) high tidal volume zero PEEP (HVZP); (4) low tidal volume PEEP (LVP); (4) high tidal volume PEEP (HVP). Respiratory rate was adjusted to maintain normocapnia and fraction of inspired oxygen (FiO2) was 1.0. TNF-alpha and IL-10 were measured in BALF and serum at baseline, 2 h, and 4 h of MV. One animal in LVZP (2 h) and two in HVP (3 h) group died before the end of the experiment. TNF-alpha level in BALF was significantly higher in LVZP and LVP at 4 h compared to baseline and the other groups. IL-10 level in BALF was significantly higher in LVP at 4h compared to baseline and the other groups. There was a statistically significant increase in serum TNF-alpha levels at 4 h in LVP group compared to baseline and the other groups at 4 h. There was statistically significant increase in serum IL-10 levels in HVZP and LVP groups at 2 and 4 h which was significantly higher compared to the other groups at 4 h. Our results show that a) low volume MV may induce local and systemic pro- and anti-inflammatory cytokine increase b) in the presence of pro-inflammatory cytokine response there is also an anti-inflammatory response in the same compartment (lungs, circulation). c) There maybe loss of alveolar-to-systemic cytokine compartmentalization.

Venous pressure measurements in the superior and inferior vena cava: the influence of intra-abdominal pressure.

BACKGROUND/AIMS: To investigate the relationship of pressure in the inferior vena cava (Pivc) with a) pressure in the superior vena cava (Psvc), b) intra-abdominal pressure as measured in the urinary bladder (Pcyst). METHODOLOGY: A prospective study of 38 mechanically ventilated patients. Simultaneous measurements of Psvc, Pivc and Pcyst (151 sets of measurements) were performed. Measurements were divided in: Group A (Pcyst < 10 mmHg), group B (10 mmHg < or = Pcyst < 15 mmHg), group C (Pcyst > or = 15 mmHg). Statistical analysis was performed with paired t-test, Pearson correlation. Results are expressed in mean +/- SEM. RESULTS: In Groups A and B, Psvc and Pivc were not significantly different and they were highly correlated (10.8+/-0.5 mmHg vs. 10.9+/-0.5 mmHg, r=0.93 for Group A and 14.4+/-0.7 mmHg vs. 14.7+/-0.6 mmHg, r=0.87 for Group B). Pcyst was significantly lower than Pivc in both groups. In Group C, Pivc was significantly higher than Psvc (18.9+/-0.7 mmHg vs. 16.4+/-0.7 mmHg). There was no significant difference between Pivc and Pcyst (19.2+/-0.6 mmHg). Pivc significantly correlated with Pcyst (r=0.78) and Psvc (r=0.7). A. When Pcyst > Psvc, Pivc was higher than Psvc (p<0.01). With Pcyst < 15 mmHg, no significant difference was found between Pcyst and Pivc and they were correlated (r=0.766, p<0.05). Pressures in the superior and inferior vena cava were also correlated (r=0.764, p<0.05). With Pcyst > or = 15 mmHg, Pivc was lower than Pcyst (p<0.01). It correlated highly with Pcyst (r=0.85, p<0.01) and less strongly with Psvc (r=0.701, p<0.01). B. When Pcyst < or = Psvc, no difference between Pivc and Psvc was observed. With Pcyst < 15 mmHg, Pivc was higher than Pcyst (p<0.01) and highly correlated with Psvc (r=0.932, p<0.01). Pivc also correlated with Pcyst (r=0.69, p<0.01). With Pcyst > or = 15 mmHg, Pivc was higher than Pcyst (p<0.01) and correlated with Psvc (r=0.74, p<0.01) and Pcyst (r=0.789, p<0.01). CONCLUSIONS: Although Psvc and Pivc are interchangeable in the absence of an increased Pcyst, when Pcyst is high, measurements of Pivc are misleading. A Pcyst > Psvc results in a "waterfall" effect, and Pivc does not accurately reflect Psvc any more.