American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Nov 1996
Mechanisms for diaphragmatic fatigue following high-intensity leg exercise.
Diaphragmatic fatigue can occur following high-intensity leg exercise to exhaustion. Exercise-induced diaphragmatic fatigue may be due to changes in the milieu to which the diaphragm is exposed (i.e., acidosis, etc.) and/or to increases in diaphragmatic activity during exercise. The purpose of this study was to determine whether changes in milieu are responsible for exercise-induced diaphragmatic fatigue. ⋯ In both groups, a significant lactic acidosis developed during exercise and the magnitude of this acidosis was similar for the two groups. The adductor pollicis muscle (a nonexercising muscle during cycle exercise) is exposed to the same milieu as the diaphragm. Because adductor pollicis twitch force was unchanged postexercise while twitch Pdi fell, changes in milieu cannot be solely responsible for exercise-induced diaphragmatic fatigue.
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Am. J. Respir. Crit. Care Med. · Nov 1996
Comparative StudyImproved arterial oxygenation after oleic acid lung injury in the pig using a computer-controlled mechanical ventilator.
We compared computer-controlled mechanical ventilation programmed for biologic variability of respiratory rate (RR) and tidal volume (VT) with conventional intermittent positive-pressure ventilation (IPPV) in an oleic acid (OA) lung injury model. Seventeen pigs were ventilated with an Ohio 7000 anesthesia ventilator. Minute ventilation (VE) was adjusted to maintain PaCO2 at 30 to 35 mm Hg at baseline and was not altered further. ⋯ By 180 min, respiratory system compliance (Crs) was significantly lower in the control group. The wet:dry lung weight ratios were greater in the control group. Thus, in a porcine model of OA lung injury, computer-controlled mechanical ventilation, which is programmed for biologic variability, resulted in improved blood oxygenation without increasing mean airway pressures when compared with conventional IPPV.
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Am. J. Respir. Crit. Care Med. · Nov 1996
Comparative StudyEfficacy of cardiopulmonary resuscitation using intratracheal insufflation.
The effects of constant-flow insufflation (CFI) of air in the trachea at the distal end of a modified endotracheal tube as the sole mode of ventilation during cardiopulmonary resuscitation (CPR) were studied in pigs. The ventilatory effect of CFI (15 +/- 2 L/min) generating a positive pressure of about 10 cm H2O with concomitant chest compression was studied first. In nine sedated, paralyzed animals disconnected from the ventilator, CFI alone did not significantly alter the decrease in PaO2 and the rise in PaCO2 observed during apnea. ⋯ Ventilatory parameters were identical in the two situations, whereas hemodynamic parameters were similar or better with CFI-CPR than with standard CPR. Significant differences were observed between standard CPR and CFI-CPR for systolic aortic pressure (72 +/- 22 versus 82 +/- 27 mm Hg, respectively; p < 0.02) and for systolic (322 +/- 216 versus 431 +/- 237 ml/s; p < 0.01) and mean (116 +/- 106 versus 143 +/- 108 ml/s; p < 0.01) common carotid blood flows. The ease of use of CFI together with its beneficial hemodynamic effects suggests that CFI deserves to be investigated further as a mode of ventilation during CPR.
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Am. J. Respir. Crit. Care Med. · Nov 1996
Rifampin preventive therapy for tuberculosis in Boston's homeless.
An epidemic of isoniazid (INH)- and streptomycin (SM)-resistant tuberculosis began among Boston's homeless population in 1984. Individuals with skin test conversions who agreed to preventive therapy received either INH, rifampin, or a combination of INH and rifampin. A total of 204 individuals with documented tuberculin skin test conversions who did not have active tuberculosis at the time of the clinical evaluation for their positive skin test were eligible for preventive therapy. ⋯ Patients in the rifampin group were significantly less likely to develop tuberculosis than patients in the no therapy group (p = 0.04; odds ratio [OR] = 0.00, 95% confidence interval [CI] = 0.00-0.91). Treatment with any rifampin-containing preventive therapy (rifampin or rifampin plus INH) was effective (p < 0.01 ) in preventing development of active disease. The three INH failures were with organisms that were resistant to INH.