Respiration; international review of thoracic diseases
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Piston driven volume-cycled home ventilators increase work of breathing in the synchronized intermittent mandatory ventilation mode. A 2-year-old trisomy 21 patient with chronic lung disease due to recurrent aspiration pneumonia required a ventilator rate of 6-8 breaths per minute awake and 15 asleep, with peak pressure of 32 cm H2O and positive end-expiratory pressure (PEEP) of 10 cm H2O. Two circuits were designed to facilitate breathing and respiratory mechanics of his spontaneous breaths on both were compared. ⋯ The continuous positive airway pressure (CPAP) system provided continuous flow with a CPAP device set to deliver a pressure 2 cmH2O higher than the PEEP valve. On the CPAP system, compared to the reservoir system, dynamic compliance was greater [1.52 (0.14 SD) ml/cm H2O/kg vs. 0.39 (0.02), p < 0.001] and resistance less [8.15 (1.26) cm H2O/l/s vs. 45.86 (0.87), p < 0.001] as measured with a PeDS machine. This is an innovative use of a CPAP device.
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Remarkable augmentation of breathing discomfort has been noted when ventilation is constrained to the steady state level during progressive hypercapnia. However, the effect of willful enhancement of ventilation on breathing discomfort remains to be evaluated. The present study examined the effects of moderate willful increases or decreases in ventilation during progressive hypercapnia on breathing discomfort in 12 subjects. ⋯ However, the sensational response did not change (6.3 +/- 0.8 vs. 5.8 +/- 0.7 mm/Torr). These rebreathing studies indicate that willful control of respiration decreases respiratory sensation even at comparable levels of ventilation. In particular, moderate willful increases in ventilation produce an ameliorating effect on the sensation of breathing discomfort.
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We investigated the influence of low oxygen ventilation, air-bubble infusion into the pulmonary artery and their synergistic effect on pulmonary hemodynamics and microvascular permeability in isolated perfused rat lungs. Pulmonary arterial pressure was significantly increased by 70 min of ventilation with 3% O2 (hypoxia, group H); by 0.2-ml air-bubble infusion (pulmonary air embolism, group AE), and by 0.2-ml air-bubble infusion and 70 min of 3% O2 ventilation (hypoxia and pulmonary air embolism, group H & AE) compared with that of a control group (0.2 ml saline infusion, group C). Neither total (TPR) nor arterial (Ra) pulmonary vascular resistance in group H showed any difference compared to control values. ⋯ The pulmonary capillary fluid filtration coefficient, dry lung to wet lung weight ratio and white blood cell count in the perfusate of group H were not changed, while those of the groups AE and H & AE were significantly increased compared to those of controls. However, there was no significant difference in these values between groups AE and H & AE. Since hypoxia did not damage isolated perfused rat lungs, as determined by hemodynamics and permeability, nor enhance lung injury caused by air embolism, it was suggested that air embolism contributed more to high-altitude lung injury than low oxygen.
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A 49-year-old woman was admitted to the hospital for hypercapnia. Pulmonary function testing showed small lung volumes without parenchymal lung disease. ⋯ Finally, muscle biopsy revealed abundant nemaline bodies characteristic of nemaline myopathy. Nasal intermittent pressure ventilation was started with a preset pressure ventilator during sleeping hours with a good response.
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Review
Physical and functional properties of airway secretions in cystic fibrosis--therapeutic approaches.
The airway secretions which line the respiratory tract form a biphasic layer composed of an aqueous 'sol' layer and a more superficial 'gel' layer. In the sol layer, also described as the 'periciliary' layer or 'airway surface fluid', the cilia beat and relax. The lubricant sol layer enables the gel mucus present at the tips of the cilia to be transported by the ciliary beating of the ciliated cells. ⋯ In view of these alterations in the physical and functional properties of CF airway secretions, pharmacologic approaches should aim to rehydrate the mucus and to restore normal mucociliary or cough transport by stimulating chloride ion secretion (i.e. using UTP or ATP associated with amiloride in order to block sodium ion and water reabsorption). During acute episodes of infection, recombinant human DNase (rhDNase) may rapidly prevent mucus stasis by improving its rheologic properties. Lubrication of the mucus at the sol phase interface by 'surfactant' therapy may also represent a very promising therapeutic perspective to reduce the hyperviscosity and hyperadhesivity of airway secretions.