The American review of respiratory disease
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Sleep loss is common in patients with respiratory disorders. To determine whether sleep loss affects respiratory muscle function, we compared respiratory muscle and pulmonary functions after normal sleep with those measured after a 30-h sleepless period in 30 normal male subjects. The respiratory muscle strength was estimated by the maximal static inspiratory and expiratory pressures. ⋯ Twelve-second maximal voluntary ventilation was also significantly reduced after sleep loss. Nevertheless, the respiratory muscle strength, FEV1, and FVC were unaltered. We therefore conclude that inspiratory muscle endurance may deteriorate after a 30-h sleep loss.
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Am. Rev. Respir. Dis. · Oct 1989
Airway insufflation: physiologic effects on acute and chronic gas exchange in humans.
Reduction in dead space through conventional tracheostomy has been used to treat patients with chronic CO2 retention. The insufflation of air directly into the trachea by transtracheal catheter (airway insufflation, AI) provides reductions in dead space as great or greater than those of tracheostomy. The physiologic effects of AI on gas exchange have not been adequately studied because instillation of gases into the trachea contaminates minute ventilation (VL), dead space volume (VD), tidal volume (VT), and other indices of gas exchange, as measured by usual technics. ⋯ We studied 5 patients with chronic CO2 retention from either COPD, scoliosis, or muscular dystrophy (annual average PaCO2 = 45 to 75 mm Hg) during 75 min of AI with serial gas exchange and arterial blood gas measurements. AI at about 5 L/min of room air through the trachea in 5 patients reduced VL by 18% (from 7.91 to 6.48 L/min), VT by 25% (from 450 to 338 ml), and VD by 37% (from 223 to 141 ml), while not affecting PaCO2 (from 51.8 to 48.2 mm Hg) or PaO2 (from 65.1 to 63.4 mm Hg). In 2 patients, AI administered continuously for 4 to 12 months (as 30 to 50% O2) maintained PaCO2 as well as or better than breathing enriched O2 from a tracheal collar via an open tracheostomy.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Oct 1989
Effect of opposite changes in cardiac output and arterial PO2 on the relationship between mixed venous PO2 and oxygen transport.
We examined the relationship between changes in systemic oxygen transport (SO2T) and mixed venous PO2 (PvO2) in nine critically ill patients with acute respiratory failure and analyzed the effect of like and opposite changes in cardiac output (CO) and arterial PO2 (PaO2) on this relationship. Paired measurements of oxygen consumption (VO2), SO2T, and PvO2 were obtained before and after changes in the level of positive end-expiratory pressure (PEEP) equal to or more than 5 cm H2O. VO2 was measured with a rebreathing circuit adapted to a volume ventilator, and SO2T was calculated from thermodilution CO, PaO2, SaO2, and hemoglobin. ⋯ When PaO2 and CO changed in the same direction, PvO2 increased on the higher level of SO2T (average difference 3.0 +/- 3.7 mm Hg, p less than 0.05) and there was a strong positive correlation between the difference in SO2T on lower and higher levels of PEEP and the difference in PvO2 (r = 0.83). When PaO2 and CO changed in opposite directions, PvO2 was unchanged on the higher level of SO2T, and there was no correlation between the difference in SO2T on lower and higher levels of PEEP and the difference in PvO2 (r = -0.45). VO2 was not different at the lower and higher levels of SO2T in both groups, indicating that VO2 was not transport-limited in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Sep 1989
ReviewChronic obstructive pulmonary disease: a definition and implications of structural determinants of airflow obstruction for epidemiology.
Chronic obstructive pulmonary disease (COPD) may be defined as a process characterized by the presence of chronic bronchitis or emphysema that may lead to the development of airways obstruction; airways obstruction need not be present at all stage of the process and may be partially reversible. The pathologic changes in the lungs due to smoking affect three regions: the bronchi, bronchioles, and parenchyma. The bronchi show enlargement of the submucosal glands with dilation of their ducts; infiltration with neutrophils and lymphocytes is present but not prominent. ⋯ The compliance of the lungs of smokers is decreased even when a emphysema and airflow limitation are mild. Standard epidemiologic tools do not differentiate emphysema from other causes of airflow obstruction. Most persons dying of COPD will have severe emphysema.
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Although adult respiratory distress syndrome (ARDS) has been a recognized entity for over 20 years, estimates of its incidence have been very controversial. The most quoted figure is from a 1972 National Heart and Lung Institute Task Force, which estimated 150,000 cases/year in the United States, an incidence of about 75 cases/100,000 population. No experimental study, however, has adequately addressed this issue. ⋯ An average of ten patients per year, representing an incidence of 1.5 cases/100,000 population, were diagnosed as having ARDS and the mortality rate was 70%. Using a more liberal clinical criterion of PaO2 less than or equal to 75 mm Hg with FIO2 greater than or equal to 0.5, 44 more patients with ARDS, representing a total incidence of 3.5 cases/100,000 population, were identified. In conclusion, the overall incidence of ARDS was 1.5 to 3.5 cases/100,000 population, an incidence that is much lower than most previously published estimates.