American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Aug 1994
ReviewReview and analysis of variation between spirometric values reported in 29 studies of healthy African adults.
Within- and between-population variation in spirometric measurements has been addressed in a systematic review of spirometric measurements from 29 studies published between 1965 and 1990 involving 9,690 men and 2,638 women of sub-Saharan African ancestry; FVC and FEV1 were age- and height-standardized at BTPS. Between- population differences were related to geographic region and sample source (workforce versus community). The effects of altitude, variation in sample mean height, and year of study publication were also significant variables in multivariate models explaining between-population differences. ⋯ A. (-35.3 ml/year), and positive trends (14.7 ml/year) in other regions. These differences in trend could not be explained. Population selection factors, altitude, date of study, and other biological sources of variation need to be taken into account in evaluating between- and within-population comparisons of spirometric measurements.
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Am. J. Respir. Crit. Care Med. · Aug 1994
Randomized Controlled Trial Clinical TrialEffects of sleep deprivation and sleep fragmentation on upper airway collapsibility in normal subjects.
Sleep deprivation can induce or worsen nocturnal respiratory disturbances. In patients with sleep apnea hypopnea, sleep abnormalities consist of repetitive episodes of arousals and awakenings that lead to sleep fragmentation. Because the propensity for upper airway collapse is increased in these patients, we wondered if sleep fragmentation could increase upper airway collapsibility and contribute to the pathogenesis of this disease. ⋯ Sleep-related breathing abnormalities were more frequent after sleep fragmentation than after sleep deprivation. Critical pressure was -17.1 +/- 6.8 cm H2O (mean +/- SEM) after sleep deprivation, and -12.3 +/- 6.3 cm H2O after sleep fragmentation (p < 0.05), corresponding to an earlier closing of the upper airway. We conclude that sleep fragmentation leads to a higher upper airway collapsibility than does sleep deprivation.
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Am. J. Respir. Crit. Care Med. · Aug 1994
Evaluation of definitions for adult respiratory distress syndrome.
We conducted a cohort study of 423 intensive care unit (ICU) admissions with a primary clinical diagnosis of acute respiratory failure, a PaO2/FIO2 on ICU admission of < 300 mm Hg, and an ICD-9 discharge diagnosis of adult respiratory distress syndrome (ARDS) (518.5 or 518.82) drawn from a nationally representative database of 17,440 ICU admissions to evaluate current and proposed revisions for definitions of ARDS. A variety of nonpulmonary physiologic risk factors, from shock to elevated serum bilirubin measurements, were significant (p < 0.01) for hospital mortality. Multivariable analysis using the admission APACHE III score, primary ICU admission diagnosis, and treatment location before ICU admission provided greater accuracy in prediction (ROC = 0.80) than the individual PaO2/FIO2 (ROC = 0.68). ⋯ We conclude that ARDS is a complex clinical entity with a variety of pulmonary and nonpulmonary risk factors for both its development and its prognosis. Current and proposed categorical definitions based on the severity of hypoxemia result in a wide distribution of individual patient risks. Use of these findings in the design and conduct of future clinical trials would improve the evaluation of new therapies.