American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Jun 1994
Comparative StudyEffects of inspired carbon dioxide on ventilation-perfusion matching in normoxia, hypoxia, and hyperoxia.
We studied the effect of low concentrations (2 to 4%) of inspired CO2 on gas exchange and ventilation-perfusion (VA/Q) relationships in healthy normocapnic anesthetized dogs during constant mechanical ventilation by the multiple inert gas elimination technique (MIGET). One group was studied at normal tidal volumes (12 to 14 ml/kg) and rates (13 to 15/min) in normoxia, and the other in mild hyperoxia (FIO2 = 0.50) and hypoxia (FIO2 = 0.15). In normoxic dogs there were progressive increases in arterial PO2 and reductions in the alveolar-to-arterial PO2 and arterial-to-mixed expired PCO2 differences in response to increases in FICO2. ⋯ In the second group, the effects of 3% inspired CO2 were of comparable magnitude in both mild hypoxia and hyperoxia. In this group (taking hyperoxic values as baseline), there were improved gas exchange and less VA/Q heterogeneity with inspired hypoxia, both with and without inspired CO2. In contrast to the effects of added inspired CO2, improved VA/Q matching with hypoxia was characterized by reductions in both log SDV and log SDQ.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Jun 1994
Effects of mechanical ventilation on diaphragmatic contractile properties in rats.
We measured in rats the effects of 48 h of mechanical ventilation on the weight, contractile properties, and enzymatic profile of the diaphragm, the soleus and the extensor digitorium longus (EDL) muscles. Eighteen animals were randomly divided into a mechanically ventilated (MV, n = 9) group or a control (C, n = 9) group. During the 48 h of mechanical ventilation, animals in the MV group were anesthetized with sodium thiopental and enterally fed with a gastric catheter. ⋯ The forces generated by the soleus and EDL were not significantly reduced in the MV group compared with those in the C group. Diaphragm, soleus, and EDL citrate synthase and lactate dehydrogenase activities were not significantly different in the two groups. We conclude that mechanical ventilation for 48 h in rats produces a selective force reduction in the diaphragm.
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Am. J. Respir. Crit. Care Med. · Jun 1994
Soluble TNF receptors (TNF-sR55 and TNF-sR75) in lung allograft recipients displaying cytomegalovirus pneumonitis.
Two distinct types of tumor necrosis factor receptors (TNF-R) have been identified (TNF-R55 and TNF-R75). Both TNF-R also exist in soluble forms (TNF-sR), resulting from the release of the extracellular domains (TNF-sR55 and TNF-sR75). TNF-sR may play an important role in vivo as they can bind to TNF alpha and prevent ligand binding to the cellular TNF-R, thus acting as naturally occurring inhibitors of TNF alpha. ⋯ Serum TNF alpha concentration was low in case of rejection or in control subjects (< 20 pg/ml). Conversely increased levels of TNF alpha were detected in the serum of six out of the 12 patients with CMV pneumonitis (p < 0.03 versus rejection and control subjects). Ganciclovir treatment of CMV pneumonitis led to a dramatic decrease of TNF alpha, TNF-sR55, and TNF-sR75 serum levels.(ABSTRACT TRUNCATED AT 250 WORDS)