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At least 19 recordsLinked to original sources
PubMed1976

A method to correct for the influence of gas density on maximal expiratory flow rate.

Maximal expiratory flow rate (Vmax) was measured at 20, 35, 50, 65, and 80% vital capacity in 4 young healthy subjects breathing air, SF6/O2, and He/O2 mixtures. The flows of SF6/O2 and He/O2 were corrected to normal alveolar gasflow by means of only the density of the gases. The values for normal alveolar gasflow and corrected SF6/O2 flow were identical at 35% VC and larger volumes while the values for normal alveolar gasflow and corrected He/O2 flow were not. The results indicate that in young healthy subjects it is possible to correct Vmax at lung volumes above 35% VC for the changes induced by an increase in density of the gas breathed, provided viscosity is not much changed. Without correction, Vmax after O2-breathing will be underestimated by about 6%, compared with Vmax for normal alveolar gas, whereas a change in alveolar CO2 concentrations between 3 and 9% only causes a 1% decrease of Vmax.

Adolescent↗
PubMed1985

Bronchial hyperreactivity to leucotriene D4 and histamine in exogenous asthma.

Reactivity of the small and large airways to inhaled leucotriene D4, one of the leucotrienes that constitute slow reacting substance of anaphylaxis, was studied in eight patients with exogenous asthma and nine healthy subjects with no history of atopy. Non-cumulative dose response relations were constructed for leucotriene D4 in a randomised, double blind set up. Reactivity to the leucotriene was compared with reactivity to histamine in the two groups. Both groups reacted to leucotriene D4 with significant airway obstruction evident in forced expiratory volume in one second (FEV1), peak expiratory flow rate, maximal expiratory flow rate at 30% of forced vital capacity estimated from a partial flow volume curve initiated at 50% of vital capacity (V30), and an increase in volume of trapped gas. The airways of the patients were significantly (p less than 0.01) more reactive to leucotriene D4 than those of the controls. The differences were in order of magnitude, 10(2)-10(3) for FEV1 but only about 15 for V30 (p less than 0.05). The hyperreactivity of the airways of the asthmatic subjects to leucotriene D4 was comparable to that to histamine. Inhalation of leucotriene D4 caused pronounced dyspnoea only among the patients. The findings suggest a role for leucotriene D4 in human bronchial asthma.

Adolescent↗
PubMed1989

Occupational lung function impairment in never-smoking Danish welders.

In order to study the effect of welding fumes on lung function, 74 high-exposed welders and 31 age-matched electricians were examined in 1982. None had ever smoked tobacco or been exposed to known or potentially noxious agents to the lungs. A significant difference was found between the welders and the control group in vital capacity, total lung capacity, forced expiratory volume in one second, peak expiratory flow rate, maximal expiratory flow rate at 75% of vital capacity, diffusion capacity and slope of the alveolar plateau. The lungs of the welders were physiologically 10-15 years older than those of the control group. Thirty percent of the welders had a well defined respiratory disease. Their lung function impairment was predominantly obstructive (16 persons), but restrictive patterns were also seen (6 persons).

Adult↗
PubMed1979

Constancy of effort and variability of maximal expiratory flow rates.

In 14 normal subjects and in 13 patients with obstructive pulmonary diseases, we studied the variability within an individual of values for the maximal expiratory flow rate (Vmax) recorded simultaneously vs expired pulmonary volume (at the mouth) and vs thoracic volume (measured with a body plethysmograph). We found that the variance of Vmax within an individual at 25, 50, and 75 percent of the expired vital capacity did not differ statistically whether pulmonary volume was the expired or the thoracic gas volume. In ten healthy subjects on two occasions (at an interval of 12 days, on the average), we measured the peak expiratory flow rate and Vmax at different levels of inflation, with respect to either expired or thoracic volume. There was no statistical differences in Vmax between the first and the last day. A larger variability of Vmax measured vs expired volume implies a change in the expiratory effort from one forced expiration to another and a different degree of compression of intrathoracic air. Since this was not the case, we conclude that muscular effort during repeated forced expirations is similar. The good reproducibility of effort explains in great measure the good reproducibility of Vmax.

Adult↗
PubMed1986

In vivo human tracheal pressure-area curves using computerized tomographic scans. Correlation with maximal expiratory flow rates.

In order to develop a simple technique to measure in vivo pressure-area (P-A) curves of the extrathoracic trachea in humans, we studied 14 normal male subjects. Valsalva and Mueller maneuvers were performed at FRC, and tracheal cross-sectional area (TXSA) was measured using computed tomography. Extrathoracic tracheal transmural pressure (TMP) was obtained as airway opening minus atmospheric pressure (Pat). Tracheal "compliance" (TC) was measured on the "inflation" limb of the P-A curve. Tracheal compliance was not a significant predictor of maximal expiratory flow rates, and TXSA at zero TMP was a significant predictor of peak expiratory flow rate but not of FEV1 or Vmax50. P-A curves showed an unexpected configuration characterized by a plateau or an increase in TXSA with TMP lower than -15 cm H2O. P-A curves obtained in 5 subjects using extrathoracic esophageal pressure as tracheal external pressure instead of atmospheric pressure did not show a plateau or an increase in TXSA with Mueller maneuvers. In these 5 subjects, TC using esophageal pressure rather than Pat did not aid in the prediction of flow. We conclude that extrathoracic tracheal external pressure is not Pat because this pressure is probably affected by transmission of pleural pressure to the cervical interstitial tissue as well as by the contraction of cervical accessory inspiratory muscles. Therefore, true tracheal compliance cannot be simply measured since it requires placement of an esophageal balloon.

Adult↗
PubMed1976

Density-dependence of maximal expiratory flow rates before and after bronchodilators in patients with obstructive airways disease.

1.Gas-density-dependence of maximal expiratory flow rats (V max), defined as the ratio of V max. while breathing helium/oxygen (80:20) to V max. while breathing air at the same lung volume, was examined in relation to other measurements of airways obstruction in patients with obstructive airways disease before and after administration of bronchodilators. 2. Seventeen patients showed a 45% or greater increase in specific conductance (sG aw) after bronchodilator therapy (group A) and thirteen patients demonstrated a lesser response (group B). 3. Before the administration of bronchodilators, the degree of obstruction in two groups was not different as measured by lung volumes, sG aw, forced expiratory volume in 1 s, and flow rates high in the vital capacity; yet the maximal mid-expiratory flow rate and the degree of density-dependence were significantly lower in group B. 4. After bronchodilators, both groups of patients showed significant improvements in sG aw, flow rates and lung volumes. However, group A patients showed a signifcant increase in density-dependence whereas group B patients did not. 5. Increased density-dependence after bronchodilators in the group A patients was associated with an increase in the computed resistance of the upstream segment with air and a decrease in resistance with helium/oxygen. These changes could be explained by a more mouthward of equal pressure points, and therefore a further increase in the relative contribution of the larger density-dependent airways to limitation of flow. 6. The fact that density-dependence was not altered after bronchodilators in the group B patients suggests that the site of limitation of flow did not change appreciably. The shift in the pressure-flow curve for the upstream airways was such that the computed resistance of these airways fell. Thus it appears that the airways comprising the upstream segment were dilated.

Airway Obstruction↗