The American review of respiratory disease
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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
Randomized Controlled Trial Comparative Study Clinical TrialUse and misuse of metered-dose inhalers by patients with chronic lung disease. A controlled, randomized trial of two instruction methods.
Metered-dose inhalers are often used incorrectly by patients with chronic airflow obstruction, and there is a lack of controlled studies designed to evaluate methods to teach the correct use of these devices. Therefore, we screened 100 consecutive stable outpatients for correct or incorrect inhaler use and then conducted a randomized trial of two methods to teach correct use. Patients were classified as correct or incorrect users with a modified metered-dose inhaler containing a thermistor that detected inspiration, inhaler activation, and the duration of breath-holding. ⋯ For all subjects, the proportion using correct technique declined over time, particularly for incorrect users. We also examined a series of patient characteristics, obtained by questionnaire and spirometry, to determine whether they could be used in the clinical setting to identify incorrect users. By discriminant analysis, a group of four variables predicted correct metered-dose inhaler use: bronchodilator responsiveness, a history of additional about proper technique, verbal knowledge of the correct inhaler maneuvers, and the patient's perception of whether it is important to use an inhaler.(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
Expiratory glottic widening in asthmatic subjects during exercise-induced bronchoconstriction.
Glottic caliber is modulated in a way that optimizes the airway resistance and the work of breathing. The midexpiratory glottic narrowing that normally occurs during tidal breathing is enhanced during histamine- or methacholine-induced airway narrowing. Exercise is associated with increased ventilatory demand and midexpiratory glottic widening in healthy subjects. ⋯ This midexpiratory glottic widening was also associated with increased tidal flow rates. We conclude that in marked contrast to airway obstruction induced by histamine or methacholine, exercise-induced asthma is associated with midexpiratory glottic widening, which occurs concomitantly with a decrease in lower airway caliber. We suggest that modulation of glottic aperture during acute asthma is heterogeneous and depends partly on the initiating stimulus.
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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.