Critical care medicine
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Critical care medicine · May 1984
Conjunctival and transcutaneous oxygen monitoring during cardiac arrest and cardiopulmonary resuscitation.
To define the utility of transcutaneous and conjunctival oxygen sensors in the emergency setting, we measured serial conjunctival (PcjO2) and transcutaneous (PtcO2) oxygen tensions during CPR in 11 patients. There was no significant correlation between PaO2 and PtcO2 or PcjO2. ⋯ PcjO2 responded to changes in physiologic state more rapidly than did PtcO2, with a reaction time of approximately 60 sec. Conjunctival and transcutaneous oxygen sensors provided continuous information on the effectiveness of CPR in terms of peripheral perfusion and tissue oxygenation, and were a valuable adjunct in monitoring the clinical condition of these critically ill patients.
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Critical care medicine · May 1984
Functional residual capacity and lung mechanics at different levels of mechanical ventilation.
We assessed the effects of rapid ventilatory rates (60 to 120 breath/min) and high mechanical ventilation pressures (30/5 to 40/10 cm H2O) on lung mechanics and intravascular pressures in 9 paralyzed, sedated rabbits ventilated with a time-cycled, pressure-limited flow generator (Baby bird). Measurements of tidal volume, ventilator line pressure, tracheal pressure, functional residual capacity (FRC), and arterial and venous blood pressures showed that: 68% of the peak pressure developed by the ventilator was transmitted to the trachea at 60 breath/min, 74% at 120 breath/min, and 87% when ventilation pressures were increased to 40/10 cm H2O; when the ventilatory rate and the PEEP were increased, the end-expiratory pressure in the trachea became progressively greater than that indicated on the ventilator pressure gauge; FRC increased when the PEEP and mean tracheal pressure increased; tidal volume and dynamic compliance decreased and minute ventilation increased as ventilatory rate increased; compliance decreased whenever FRC increased, and increased whenever FRC decreased; and there was little effect on mean central venous or arterial pressure. ⋯ In normal animals, this may interfere with gas exchange and pulmonary blood flow. In abnormal lungs, the gas trapping may increase FRC and improve gas exchange within the lung.