Critical care medicine
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Critical care medicine · Jun 1997
Variation of inhaled nitric oxide concentration with the use of a continuous flow ventilator.
To investigate the homogeneity of nitric oxide concentrations at different ventilator settings in a delivery system using a continuous flow ventilator. ⋯ Mixing a nitrogen/nitric oxide gas mixture 20 cm before the Y-connector results in an increase of the mean nitric oxide concentration with increasing ventilator rates. This phenomenon does not occur with the nitrogen/nitric oxide gas mixture mixed at the inlet of the humidifier, using a ventilator with a throughout constant flow at the inspiratory outlet of the ventilator. The fluctuations of the main ventilator circuit flow result in changing ratios of nitrogen/nitric oxide gas mixture and the ventilator gas flow. We speculate this changing flow ratio produces the increase in mean nitric oxide concentration within the ventilatory circuit. To ensure a constant concentration of nitric oxide by blending a nitrogen/nitric oxide gas mixture in the ventilator circuit of a continuous flow ventilator, the site of injection of the nitrogen/nitric oxide gas mixture should be at the point where ventilator circuit flow fluctuations are minimal.
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Critical care medicine · Jun 1997
Randomized Controlled Trial Clinical TrialEffects of varying levels of positive end-expiratory pressure on intracranial pressure and cerebral perfusion pressure.
To determine the influence of positive end-expiratory pressure (PEEP) on intracranial pressure and cerebral perfusion pressure. ⋯ In patients with normal intracranial pressure, PEEP at 5 cm H2O did not significantly alter intracranial pressure. The clinical relevance of the intracranial pressure increase at PEEP levels of 10 and 15 cm H2O is questionable because cerebral perfusion pressure did not change and remained > 60 mm Hg. In patients with increased intracranial pressure, higher levels of PEEP did not significantly change intracranial pressure or cerebral perfusion pressure.
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Critical care medicine · Jun 1997
Clinical TrialHigh-frequency oscillatory ventilation for adult respiratory distress syndrome--a pilot study.
To evaluate the safety and effectiveness of high-frequency oscillatory ventilation using a protocol designed to recruit and maintain optimal lung volume in patients with severe adult respiratory distress syndrome (ARDS). ⋯ High-frequency oscillatory ventilation is both safe and effective in adult patients with severe ARDS failing conventional ventilation. A lung volume recruitment strategy during high-frequency oscillatory ventilation produced improved gas exchange without a compromise in DO2. These results are encouraging and support the need for a prospective, randomized trial of algorithm-controlled conventional ventilation vs. high-frequency oscillatory ventilation for adults with severe ARDS.