Chest
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The importance of intrathoracic pressure in generating blood flow during cardiopulmonary resuscitation has recently been emphasized. The purpose of this study was to investigate the factors involved in generating intrathoracic pressure. Studies were performed in anesthetized paralyzed dogs with the circulation intact. ⋯ The combination of inflating the lung and compressing the chest produced the highest intrathoracic pressure (48 +/- 18 cm H2O; p less than 0.001). The pressure developed was highly variable and the distribution of pressures within the thorax was not uniform. As the intrathoracic pressure became large, a pressure gradient developed from thorax to abdomen, and the diaphragm everted; this pressure gradient could divert blood from the brain.
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A 31-year-old man had respiratory failure caused by bilateral vocal cord paralysis. He had had limited exercise tolerance since the age of five years, when he had had poliomyelitis. ⋯ Following relief of the upper airway obstruction by tracheostomy, the patient's tidal volume increased from 200 ml to 500 ml in two days, his carbon dioxide tension fell from 75 to 38 mm Hg, and his arterial bicarbonate level decreased from 39.8 to 25.6 mEq/L in five days. The patient is currently doing well with a permanent tracheostomy.
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Among the different etiologies of noncardiogenic acute pulmonary edema is found the administration or ingestion of various substances. We have studied two patients with ARDS secondary to the ingestion of toxic oil. ⋯ The two cases also showed a pulmonary compliance either normal or slightly diminished. With the aid of artificial ventilation, they evolved favorably, gaseous exchange and chest x-ray films returning to normal 16 and 22 days after admission.
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To establish guidelines for the interpretation of changes in arterial blood gas (ABG) values, we studied 29 clinically stable ICU patients for spontaneous variability in PaO2, PaCO2 and pH. ABGs were sampled six times over a 50-minute period, during which all patients received a fixed FIO2 of 0.5 via endotracheal tube and underwent no therapeutic interventions. Each sample was analyzed in duplicate with careful attention to method of collection and measurement. ⋯ Various clinical features were analyzed by multiple regression analysis for their relation to PaO2 variation. Only leukocyte count and mean arterial oxygen content were statistically significant associations (p less than 0.05), but together explained less than 35 percent of the variation observed. Because considerable spontaneous variation occurs, even in stable patients, clinicians should base therapeutic decisions on trends in PaO2 values rather than on isolated changes interpreted without appropriate clinical correlation.