Chest
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to characterize gas exchange and cardiopulmonary performance during maximal progressive arm crank exercise. ⋯ Maximal arm crank exercise represents a submaximal cardiopulmonary stress compared to maximal leg exercise. The differences in gas exchange observed at peak exercise between arm crank and leg exercise for the most part reflect the lower VO2 achieved. However, the persistence of these gas exchange differences even at a comparable level of VO2 suggests that factors other than VO2 may be operative. These factors may include differences in alveolar ventilation, CO2 production, ventilation-perfusion inequality, diffusion, and control of breathing.
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Diaphragmatic muscle performance during acute ventilatory failure due to Guillain-Barré syndrome and myasthenia gravis was assessed to evaluate (1) diaphragmatic function during weaning from ventilatory support and (2) diaphragmatic tension-time integral (TTdi) during ventilatory failure. We used a multilumen nasogastric tube and a pneumotachograph to measure transdiaphragmatic pressure per breath (Pdi), maximum transdiaphragmatic pressure (Pdimax), tidal volume (VT), and inspiratory time fraction during 74 spontaneous breathing trials in nine patients. Diaphragmatic performance was poor in all patients. ⋯ Maximal inspiratory force correlated with Pdimax (r = 0.48; p less than 0.005), but FVC did not. The TTdi rarely exceeded the expected fatigue threshold of 0.15 in spite of the patient's inability to sustain ventilation. Although our patients demonstrated diaphragmatic weakness, TTdi did not demonstrate diaphragmatic fatigue.
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Intermittent positive pressure ventilation reduces inspiratory muscle electromyographic activity among patients with restrictive ventilatory failure. It has therefore been suggested that the reduction of energy expenditure at night could result in improved inspiratory muscle function during the day. Reported successes with nocturnal ventilation have not included measurements of inspiratory muscle endurance. ⋯ Inspiratory muscle endurance measured using a pressure threshold load (mean mouth pressure = 45 percent MIPRV) improved from 7.1 +/- 3.4 minutes at baseline to 14.8 +/- 7.6 minutes at 3 months, an improvement sustained at 14 months. There was no change in measured lung volumes or respiratory muscle strength. We conclude that the improvement in nocturnal gas exchange, daytime functioning, and arterial blood gases resulting from nocturnal positive pressure ventilation is associated with an increase in inspiratory muscle endurance sustained at 14 months.
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We used a pain questionnaire to evaluate the prevalence and functional significance of long-term postthoracotomy pain. Data on 56 patients who were at least 2 months postsurgery were analyzed. Thirty patients (54 percent) with a median follow-up of 19.5 months had persistent pain; 26 others were pain free at a median of 30.5 months postthoracotomy. ⋯ Five of 56 patients had sufficiently severe chronic pain to require either daily analgesic use, nerve blocks, relaxation therapy, acupuncture, or referral to a pain clinic. We conclude that long-term chest wall pain is common postthoracotomy. It is generally not severe, but a small proportion of patients may experience persistent, moderately disabling pain.