The American review of respiratory disease
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Am. Rev. Respir. Dis. · Aug 1993
Bicarbonate does not increase left ventricular contractility during L-lactic acidemia in pigs.
Lactic acidosis decreases left ventricular contractility, but whether bicarbonate increases left ventricular contractility during lactic acidosis in vivo is controversial. Therefore, we measured hemodynamics and left ventricular mechanics before and after bicarbonate administration during L-lactic acid infusion in 15 anesthetized pigs. The pigs were beta-blocked and atrially paced to minimize indirect effects of acidosis on contractility. ⋯ These effects were not significantly different from the effects of saline. Bicarbonate did not significantly increase Emax (4.2 +/- 0.8 to 4.9 +/- 0.8 mm Hg/ml) and was indistinguishable from saline (5.0 +/- 0.7 to 5.2 +/- 0.7 mm Hg/ml). We conclude that bicarbonate infusion does not directly increase left ventricular contractility during lactic acidemia in pigs within this pH range.
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Am. Rev. Respir. Dis. · Aug 1993
Effects of periodic obstructive apneas on venous return in closed-chest dogs.
With sleep apnea syndrome, mean cardiac output (CO) may fall. This implies a fall in venous return (VR) that is equal to the product of the pressure gradient for VR (GVR)--mean circulatory pressure (MCP)--right ventricular end-diastolic pressure and the conductance for VR (Gv). During airway obstruction there could also be shifts of blood volume between central and peripheral circulatory compartments. ⋯ With RA apneas, GVR and MCP increased by 55% (p < 0.05) and Gv decreased by 63% (p < 0.05). On O2, there were no changes in GVR or Gv, and changes in CO were predictable from the baseline VR curve. With O2 there was an increase in central blood volume by 21.0% (p < 0.01) during the apneic phase.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Aug 1993
Use of capnography for assessment of the adequacy of alveolar ventilation during weaning from mechanical ventilation.
A prospective study was conducted to determine the reliability of noninvasive end-tidal CO2 (PETCO2) monitoring as a reflection of arterial CO2 tension (PaCO2) during weaning from mechanical ventilation (MV). Simultaneous PaCO2 and PETCO2 determinations were compared during MV and again during a spontaneous breathing trial just before returning the patient to MV. Three groups of patients recovering from acute respiratory failure were evaluated. ⋯ However, PETCO2 is less sensitive to changes in PaCO2 for patients with parenchymal lung disease, particularly patients with emphysema. Interpretation of capnographic data requires a full understanding of its limitations. An approach to capnographic monitoring during weaning is discussed.
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Am. Rev. Respir. Dis. · Aug 1993
Gastric and pharyngeal flora in nosocomial pneumonia acquired during mechanical ventilation.
We studied the interrelations between gastric, pharyngeal, proximal, and distal airway bacterial flora in ventilator-associated pneumonia (VAP) on 36 patients with nosocomial pneumonia acquired during mechanical ventilation (MV) and 27 mechanically ventilated control subjects without pulmonary infection. Gastric, pharyngeal, and endotracheal (EA) sampling for quantitative cultures were performed upon all patients, as well as fiberoptic bronchoscopy with protected specimen brush (PSB) sampling. Mean bacterial and fungi colony counts were significantly increased in pharyngeal, EA, and PSB samples in patients with VAP compared with control subjects. ⋯ In summary, the present study shows that the coincidence between microorganisms isolated in PSB cultures and those from gastric and oropharynx increase in MV patients with pneumonia, indicating that both reservoirs play a key role in the pathogenesis of pneumonia. Conceivably, preventing both gastric and pharyngeal colonization may reduce the incidence of ventilator-associated pneumonia. From all the noninvasive samples studied only endotracheal aspirate cultures were useful for inferring the etiology of some VAP pneumonias.
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Am. Rev. Respir. Dis. · Aug 1993
Comparative StudyResponse time and reliability of three neonatal patient-triggered ventilators.
We studied the response time (RT) and reliability of three neonatal patient-triggered ventilator (PTV) systems: the Draeger Babylog 8000, the Bear Cub enhancement module (CEM), and the Infrasonics Star Sync. In 10 adult rabbits, airway flow and pressure recordings showed the RT of the Star Sync to be shorter than that of the Bear CEM (53 +/- 13 versus 65 +/- 15 ms, p < 0.05), and both were shorter than that of the Babylog (95 +/- 24 ms, p < 0.01) by ANOVA. The RT of the Bear CEM and the Babylog increased significantly at decreased trigger sensitivity settings. ⋯ The Star Sync and Bear CEM triggered successfully on A/C (100%) and had low rates of asynchrony on SIMV (1 to 3%). The Babylog had a lower success rate on A/C (70 +/- 12%) and a higher rate of asynchrony on SIMV (29 +/- 30%) than the other two ventilators; p < 0.01. The lower reliability of the Babylog was due to its variable refractory period (0.2 to 0.5 s, to equal the set Ti).(ABSTRACT TRUNCATED AT 250 WORDS)