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Biomedical subjects

L J Brooks

Publications and source records attributed to L J Brooks.

11 recordsLinked to original sources
PubMed1992

Size and mechanical properties of the pharynx in healthy men and women.

Obstructive sleep apnea (OSA) has a marked male predominance. To determine whether there are differences in the mechanical properties of the pharynx of men and women that may contribute to the gender difference in disease incidence, we measured pharyngeal cross-sectional area during quiet breathing in 77 normal men and 98 normal women using the acoustic pulse technique. Standard pulmonary function tests were also performed. Pharyngeal mechanics were studied in 23 men and 34 women by measuring the change in pharyngeal area during a slow vital capacity maneuver. Gender was found to be the most important independent factor contributing to pharyngeal size. The men had a significantly larger pharynx than the women (3.63 +/- 0.10 versus 3.20 +/- 0.09 cm2, mean +/- SEM; p < 0.01). Pharyngeal mechanics were also different between men and women. The men had a larger change in pharyngeal area with changing lung volume than the women (0.60 +/- 0.14 versus 0.12 +/- 0.12 cm2, mean +/- SEM; p < 0.02). This difference persisted even after normalizing the data for pharyngeal size. We found that there are gender-related differences in the size and mechanical properties of the pharynx and speculate that the larger pharynx of men may be more than offset by greater changes in pharyngeal size with changing lung volume, contributing to the greater incidence of OSA in men.

Acoustics↗
PubMed1991

Behavioral assessment and management of food refusal in children with cystic fibrosis.

Four children with cystic fibrosis, ranging in age from 10 to 40 months, were admitted to a specialized pediatric unit for evaluation and treatment of malnutrition. All were below the fifth percentile for weight despite appropriate pancreatic enzyme replacement and outpatient nutritional counseling. Dietary evaluation revealed oral intake of 48% to 62% of that required for growth. Standardized nursing and psychological assessments of feeding behaviors during meals indicated a low acceptance rate of foods and a high rate of maladaptive feeding behaviors. Treatment consisted of behavioral management using positive reinforcement of food acceptance, extinction of negative behaviors, and parent training. Mean percentage of caloric intake increased from 54% to 92% for the four patients. At long-term follow-up, the patients who continued the program demonstrated substantial and persistent catch-up growth. Behavioral feeding disorders may contribute to failure to thrive in patients with cystic fibrosis and must be considered when growth failure occurs despite correct medical management and apparently mild pulmonary and gastrointestinal involvement.

Behavior Therapy↗
PubMed1990

Tracheal size and distensibility in patients with cystic fibrosis.

Retrospective studies have reported that tracheal enlargement is common in patients with cystic fibrosis (CF). To determine whether significant tracheal enlargement occurs in these patients, we used the acoustic reflection technique to prospectively measure the tracheal cross-sectional area near functional residual capacity (FRC) in 39 stable outpatients with CF and 39 age- and sex-matched normal control subjects. The patients with CF had a mean age of 19.0 yr with a mean percent predicted FEV1 of 69%. The mean +/- SEM tracheal area of the patients with CF was 1.99 +/- 0.13 cm2, compared with a mean tracheal area of 1.87 +/- 0.10 cm2 in the control subjects (t = 0.79, NS). CF tracheal area was not a function of age nor of disease severity, as assessed by percent predicted FEV1. To determine whether tracheomegaly might occur only in older patients, we examined the six patients with CF who were 28 yr of age or older. Mean tracheal area for these older patients with CF was 2.46 +/- 0.26 cm2, compared with 2.27 +/- 0.10 cm2 for the control subjects (t = 0.70, NS). Eleven patients with CF also had their tracheal area measured near TLC. At this high lung volume, the tracheal area of the patients with CF was 2.62 +/- 0.23 cm2, significantly larger than the 1.91 +/- 0.13 cm2 in 11 control subjects (t = 2.68, p less than 0.02). The increase in tracheal area per change in lung volume was also significantly greater in the patients with CF than in the control subjects (t = 3.33, p less than 0.01). We conclude that near FRC the tracheal size of patients with CF is not different from that of age- and sex-matched control subjects. The tracheas of patients with CF expand more than do the tracheas of control subjects when higher lung volumes are attained, suggesting increased airway distensibility.

Adolescent↗
PubMed1989

A prospective randomized double-blind study to evaluate the effect of dexamethasone in acute laryngotracheitis.

To determine whether a single dose of dexamethasone (0.6 mg/kg) is useful in the treatment of acute laryngotracheitis (croup), 29 hospitalized patients with acute laryngotracheitis were randomly assigned in a double-blind fashion to receive either parenterally administered dexamethasone (n = 16) or a saline placebo (n = 13). Severity of the illness was assessed by a clinical croup score based on retractions, stridor, air entry, cyanosis, and level of consciousness. Twelve hours from the time of injection, the patients receiving the dexamethasone had a statistically significant decline in median croup score from 4.5 to 1.0 (p less than 0.001), whereas the patients receiving the placebo did not. By 24 hours, a decline of two or more points in the total croup score was noted in 85% of the patients in the dexamethasone group compared with 33% of the patients in the placebo group (p = 0.027). During this same period, only 19% of patients receiving dexamethasone required two or more racemic epinephrine treatments in comparison with 62% of patients who received the placebo (p less than 0.05). There was no statistical difference between the two groups in improvement in oxygen saturation, respiratory rates, or duration of hospitalization. We conclude that dexamethasone is beneficial in reducing the overall severity of moderate to severe acute laryngotracheitis during the first 24 hours after injection.

Acute Disease↗
PubMed1989

Reproducibility of measurements of upper airway area by acoustic reflection.

To evaluate the extent and nature of the variability of measurements of upper airway area by acoustic reflection (AAAR), we made repeated measures of pharyngeal AAAR in 10 normal adult volunteers. We selected mean pharyngeal area as a better index of upper airway size than peak pharyngeal area or pharyngeal volume. Within-run variability of this measure was 8 +/- 4% (SD) (coeff of variation). This variability could not be explained by changes in lung volume or differences in phase of respiration. Five subjects had tracheal and pharyngeal area measured by using both the custom-made wax mouthpiece (W) and a commercial rubber pulmonary function mouthpiece (R). Reproducibility of pharyngeal AAAR was within 10% (coeff of variation) using R, but measurements of pharyngeal AAAR varied with the different types of mouthpiece, as W/R ranged from 0.72 to 1.70. In contrast, measurements of midtracheal area were similar for both mouthpiece types [mean W/R = 0.97 +/- 14 (SD)]. The acoustic reflection technique yields a reproducible index of pharyngeal size that does not vary with phase of respiration or modest changes in lung volume. Either W or R may be used to make clinical measurements, but the type of mouthpiece should be consistent and specified.

Acoustics↗
PubMed1988

Relationship between lung volume and tracheal area as assessed by acoustic reflection.

To determine whether airway size correlates with measures of lung or body size, we used the acoustic reflection technique to calculate tracheal cross-sectional area in 103 healthy young adults. Men have significantly larger tracheas than women [2.48 +/- 0.08 vs. 1.91 +/- 0.05 (SE) cm2, P less than 0.001]. Within each sex, there is no correlation between tracheal size and body size or maximal expiratory flows. There is a significant positive correlation between tracheal area and vital capacity in males only (r = 0.36, P less than 0.01). These results support the concept of dysanapsis, relatively independent growth of the airways and lung parenchyma, as well as sex-related differences in airway size and growth. Inherent airway size may be a factor in the development and/or progression of lung disease.

Acoustic Impedance Tests↗