American journal of respiratory and critical care medicine
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The purpose of this study was to determine whether diaphragmatic fatigue occurs after voluntary hyperpnea to task failure. Ten male subjects were asked to breathe at minute ventilation (V1) equal or slightly greater than 60% of their 12-s maximum voluntary ventilation (MVV) until task failure. Transdiaphragmatic pressure (Pdi) was measured during bilateral supramaximal stimulation of the phrenic nerves before and 10, 30, 60, and 120 min after hyperpnea. ⋯ The percentage fall in twitch Pdi after hyperpnea with the two techniques was not significantly correlated (r = 0.4). In conclusion, long-lasting contractile fatigue of the diaphragm reliably occurs after voluntary hyperpnea at levels sufficient to induce task failure. Cervical magnetic stimulation can detect diaphragmatic fatigue after a fatiguing task, but the results obtained with this technique may differ from those obtained with transcutaneous stimulation in individual subjects.
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Am. J. Respir. Crit. Care Med. · Jun 1996
Clinical TrialClarithromycin regimens for pulmonary Mycobacterium avium complex. The first 50 patients.
Intermediate results of the first 50 patients treated with clarithromycin (CLARI) regimens for Mycobacterium avium-intracellulare (MAI) lung disease were evaluated. Patients were HIV negative, and pretreatment isolates were susceptible to CLARI. Patients received CLARI 500 mg twice daily, ethambutol, rifampin (RMP), or rifabutin (RBT) and initial streptomycin, and they were treated until culture-negative 1 yr. ⋯ Of 23 patients who are alive and were culture-negative a mean of 12.0 mo while receiving therapy, all remain culture-negative without therapy a mean of 19.1 mo. Despite reduced CLARI serum levels in patients also receiving RMP, 10 of 13 patients (77%) receiving this regimen were successfully treated. Although not directly compared with previous regimens, the success of this regimen strongly suggests it is superior to previous non-CLARI-containing regimens.
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Am. J. Respir. Crit. Care Med. · Jun 1996
Comparative StudyInfluence of sleep onset on upper-airway muscle activity in apnea patients versus normal controls.
Current evidence suggests that patients with obstructive sleep apnea (OSA) may have augmented pharyngeal dilator muscle activity during wakefulness, to compensate for deficient anatomy. However, the isolated effect of sleep on the activity of these muscles (comparing OSA patients with controls) has not been studied. We therefore determined waking levels of genioglossus (GG) and tensor palatini (TP) muscle activity (% of maximum electromyographic [EMG] activity) in 10 OSA patients and eight controls, and then assessed the impact of the first two breaths of sleep (theta electroencephalographic [EEG] activity) following a period of stable wakefulness. ⋯ However, three OSA patients demonstrated small increments in GG EMG at sleep onset despite falling TP EMG and obstructive apnea or hypopnea. We conclude that sleep onset is associated with significantly larger decrements in TP muscle EMG activity in OSA patients than in controls, which may represent a loss of neuromuscular compensation that is present during wakefulness. However, our results for the GG muscle were more variable, and did not always support this hypothesis.