Chest
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Sixty-one consecutive medical intensive care unit patients who were intubated for more than three days were prospectively studied for complications. Patients who were reintubated had a higher incidence of all complications (chi square = 5.4; p less than .025), as did those with prolonged intubation (chi square = 16.1; p less than .005). Neither route nor urgency had an adverse clinical effect. In contrast there was a 13 percent incidence of acute tracheolaryngeal complications, but no association was found with reintubation, route, urgency, or total duration of endotracheal intubation.
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In the past year we have seen three cases of life-threatening toxic pneumonitis caused by exposure to mixtures of household ammonia and bleach. This particular mixture forms intermediary chloramine compounds that cause toxic pneumonitis. Each patient had a prolonged hospitalization and was left with symptomatic residual roentgenographic changes. Exposure to mixtures of household ammonia and bleach may be a frequent cause of acute pneumonitis that is not well recognized.
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The work of chest inflation, WI, is a primary determinant of the need for ventilatory support and an integrative index of elastic and resistive impedance. Although the mechanical work performed by a ventilator in moving gas into the passive chest (WI = integral of PV dt) can be determined by measuring the area enclosed by a display of airway pressure (P) against delivered volume (V), the instrumentation required is not routinely available at the bedside. Under conditions of constant flow, however, inspiratory time represents an analog of delivered volume, and airway pressure can be recorded easily by equipment normally employed to monitor pulmonary vascular pressures. ⋯ PV and PT estimates agreed closely; across the four setting combinations tested, the difference between PV and PT estimates averaged 2.4 +/- 5.6 percent (means +/- SD, r = 0.99). Furthermore, the reproducible geometric configuration of the curves generated allowed accurate estimation of WI from routine beside observations of tidal volume and peak dynamic and static inflation pressures, without the need for specialized equipment or area measurement. Such simplified estimates could serve in clinical practice to gauge the ventilatory workload and to monitor changes in respiratory impedance.
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Comparative Study
Conservation of oxygen supply using a reservoir nasal cannula in hypoxemic patients at rest and during exercise.
A reservoir nasal cannula which stores oxygen during exhalation and delivers it as a bolus during inhalation has been reported to conserve oxygen delivery in patients with chronic obstructive pulmonary disease (COPD) at rest. We compared the effects upon arterial oxygen saturation (SaO2) of the reservoir cannula and a standard nasal cannula in hypoxemic obstructed and restricted patients at rest and during exercise. The SaO2 was monitored by ear oximeter. ⋯ The SaO2 during exercise with the reservoir cannula was comparable to that with the standard cannula at approximately half of the oxygen flow rate. The ratio of the oxygen flow rate of the standard to the reservoir cannula to produce 90 percent saturation was estimated and found to be 2.5 +/- 0.8 (mean +/- SD) for patients at rest and 2.9 +/- 1.8 during exercise. We conclude that in hypoxemic patients at rest and during exercise, the reservoir cannula uses less than half the oxygen of a standard cannula to produce similar improvement in SaO2 and thus has advantages of a reduced cost of ambulatory therapy with low-flow oxygen and a longer time permitted away from a stationary source of oxygen.