American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Apr 1995
Randomized Controlled Trial Clinical TrialCO2 rebreathing during BiPAP ventilatory assistance.
BiPAP ventilatory assistance can increase minute ventilation and reduce respiratory effort, but does not always reduce PaCO2. We studied the effects of BiPAP ventilatory assistance on PaCO2 and examined specific mechanisms whereby BiPAP ventilatory assistance may not lower PaCO2. BiPAP ventilatory assistance using a non-rebreather valve and volume cycled ventilation at similar settings produced significantly lower PaCO2 than BiPAP ventilatory assistance using a standard exhalation device. ⋯ Changing exhalation devices had no significant effect on BiPAP pressure generation or sensing capabilities. Our results indicate that the use of a standard exhalation device during BiPAP ventilatory assistance causes CO2 rebreathing, which can blunt any effect of BiPAP on PaCO2. Use of an appropriate alternative exhalation device can eliminate this problem.
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Am. J. Respir. Crit. Care Med. · Apr 1995
Inspiratory muscle weakness in chronic heart failure: role of nutrition and electrolyte status and systemic myopathy.
Inspiratory muscle weakness has been demonstrated in ambulatory, stable chronic heart failure (CHF) and may contribute to dyspnea during daily living. However, the mechanisms underlying this weakness are unknown. Malnutrition and electrolyte depletion are recognized complications of CHF that may impair skeletal muscle function, and limb muscle weakness and myopathic changes have also been demonstrated in CHF. ⋯ As compared with the matched controls, the CHF patients had reduced inspiratory muscle strength (p < 0.0025), but their expiratory and limb muscle strength were not significantly reduced. CHF patients were not malnourished; they were heavier than matched controls because of increased body fat (p < 0.05). Serum sodium was significantly lower in the CHF patients than in the controls (p < 0.01), but was within the normal range in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Apr 1995
Interfacing between spontaneous breathing and mechanical ventilation affects ventilation-perfusion distributions in experimental bronchoconstriction.
The effect of interfacing between spontaneous and mechanical ventilation on ventilation-perfusion (VA/Q) distributions was determined during pressure-support ventilation (PSV) and in the presence and absence of spontaneous breathing during biphasic positive airway pressure (BIPAP) in 10 pigs with methacholine-induced bronchoconstriction. Whereas BIPAP without spontaneous breathing provides full and PSV breath-to-breath synchronized ventilatory support, BIPAP allows unrestricted spontaneous breathing throughout the mechanical cycle. Compared with BIPAP with and without spontaneous breathing, PSV effected an increase in ventilatory rate (p < 0.05) and a higher minute ventilation (VE) (p < 0.05). ⋯ Dead space ventilation decreased with spontaneous breathing during BIPAP by 12% compared with PSV (p < 0.05). Dispersion of ventilation distribution was lowest during BIPAP. Uncoupling of spontaneous and mechanical ventilation during BIPAP improved gas exchange by allowing better VA/Q matching during experimental bronchoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)