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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↗
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↗
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↗
PubMed1976

Evaluation of lung function indices for bronchodilator trials. Results of a cross-over study of fenoterol.

In 10 patients with airway obstruction, spirographic indices and maximal expiratory flow rates were measured before inhalation of fenoterol and at different time intervals, for 5 h, following the inhalation of 200 mug of this substance. 10 min after inhalation of fenoterol, there was a statistically significant increase in all lung function indices. A further increase was observed later. 3 h after inhalation of fenoterol, all indices were still significantly higher than control values. No side effects were observed. At all time intervals, the increase of the forced expiratory volume in 1 sec (FEV1.0), peak expiratory flow rate (PEFR) and maximal expiratory flow rate at 50 and 75% of the vital capacity reached a similar level of statistical significance. It is concluded that for the trial of the bronchodilator drugs, any of these indices may be used, and for practical purposes FEV1.0 and PEFR are best suited.

Adult↗
PubMed1975

Functional abnormalities in young asymptomatic smokers with special reference to flow volume curves breathing various gases.

Functional abnormalities have been described in healthy, asymptomatic young smokers. Fifteen subjects between 22 and 30 years of age, who smoked but were completely asymptomatic, were compared with 10 nonsmokers of the same age group using lung volumes, maximal expiratory flow rates, closing volumes, and maximal expiratory flow volume curves breathing air and a helium-oxygen mixture. Lower maximal mid-expiratory flow rates, higher closing volumes, and significant differences in flow volume curves with the helium-oxygen mixture were found in smokers. Special attention was given to the volume expressed as percentage of vital capacity at which the flows with air and the helium-oxygen mixture were equal for each subject ("equal-flow volume"). This volume was found to be significantly higher for smokers than nonsmokers. The authors offer explanations for these differences and suggest that smoking may alter compliance, as reflected by abnormal closing volumes, and resistance of the small airways as determined by differing responses in flow rates after helium-oxygen breathing at low volumes.

Adult↗
PubMed1976

Effect of wool dust on respiratory function.

A group of 252 workers (176 women and 76 men) employed in two wool mills was studied. The mean age of 36 years; mean exposure, 11 years. All women were nonsmokers, and 47 per cent of the men were regular smokers. Ventilatory function was measured by recording maximal expiratory flow-volume curves and forced expiratory volume in 1 sec on the first working day of the week (Monday) before and after the work shift. On maximal expiratory flow-volume curves the flow rates at 50 per cent of the control vital capacity were read. Workers exposed to wool dust for more than 10 years had a higher prevalence of chronic respiratory symptoms than did those with less than 10 years' exposure, but the difference was not significant. Significant reductions during the work shift were found in maximal expiratory flow rates at 50 per cent of the control vital capapity and 1-sec forced expiratory volume, the first test being considerably more sensitive. Workers exposed to wool dust for more than 10 years had signficantly lower than predicted pre-shift values for maximal expiratory flow rates at 50 per cent of the control vital capapcity. Inhalation of wool dust extract caused a significant decrease of maximal expiratory flow rates at 40 per cent of the control vital capacity on partial expiratory flow-volume curves during the 100 min after exposure. Comparison with the same concentration of cotton dust extract revealed a similar effect during the first 40 min after exposure but a significantly larger effect of the cotton dust extract after 40 min. The data suggest that preventive measures, especially medical supervision, are necessary in wool-processing mills to protect workers sensitive to dust.

Adult↗
PubMed1977

Assessment of therapy of upper airway obstruction.

Five patients with fixed upper airway obstruction were evaluated with maximum expiratory and inspiratory flow-volume curves before and after surgical repair of the obstruction. Flow-volume curves improved notably in two patients, improved moderately in two, and deteriorated in one. Symptoms and direct visualization of the obstruction before and after surgery correlated well with the changes seen in the flow-volume curves. None of the peak expiratory flow rates returned to predicted values after surgery, indicating at least some residual obstruction in all patients. It is concluded that flow-volume curves are an accurate, noninvasive technique for the diagnosis and subsequent assessment of therapy in patients with fixed upper airway obstruction.

Adult↗
PubMed1977

The compliance curve for the flow limiting segments of the airway. II. Experiments with human subjects.

Maximum effort flow-static recoil curves were obtained in 5 healthy subjects breathing air, He/O2, and SF6/O2 mixtures. In 4 of them maximum effort flows corresponded to really maximal flows and their curves were transformed into compliance curves for the flow limiting segments of the airway and analyzed from the point of view of a previously presented lung model (Pedersen and Nielsen 1976). The results showed, that viscosity dependent pressure losses from the alveoli to the flow limiting segments were minimal for air and SF6/O2, but not for He/O2. When viscosity dependent pressure lossess could be negleted, then expiration of gases of different densities gave almost identical compliance curves for the flow limiting segments. This supported the applicability of the model. The calculated compliance curves for the flow limiting segments were compared with data from the literature, and the findings indicated that flow limitation during expirations with just maximal flows throughout began in the extrapulmonary airways and moved upstream during the expiration.

Adolescent↗
PubMed1975

Respiratory function during prostaglandin-induced labor.

In a group of patients receiving intraamniotic injection of prostaglandin F2alpha or intramuscular injection of a methyl analogue of prostaglandin E2 for the termination of pregnancy, significant ariway constriction was demonstrated. The greatest responses were seen in 2 patients who had personal or family histories of asthma. If such patients receive prostaglandins, they should be carefully monitored to detect clinically important airway obstruction.

Amnion↗
PubMed1976

The influence of clinical factors on site of airway obstruction in asthma.

The effect of breathing a gas mixture less dense than room air (80% helium, 20% 02) on the maximal expiratory flow-volume curve was used to determine the influence of clinical factors on the site and nature of the airway obstruction in asthmatics. If an asthmatic did not smoke or have chronic bronchitis or recurrent respiratory infections, the site of obstruction was in more central airways than it was in the presence of these factors, when the main site was more likely to be in more peripheral airways. Both the peripheral and the central airway obstruction were at least in part due to bronchoconstriction and could be reversed with bronchodilators. Comparison of maximal expiratory flow-volume curves when the subject was breathing air and when he or she was breathing a less dense gas mixture may indicate change in the mechanical properties of the lung after the use of bronchodilators that are not apparent breathing air alone. In some instances, bronchodilators produced no change in the maximal expiratory flow-volume curve when the subject was breathing air, but there were substantial changes when he or she was breathing a mixture of helium and O2.

Adolescent↗
PubMed1978

Responses to isoproterenol in a general population sample.

The response of forced expiratory flow to inhalation of isoproterenol was evaluated in a general population sample of 1,063 subjects. Percentage changes in the forced expiratory volume in 1 sec and in the maximal flow measured at 50 percent of the initial expired forced vital capacity appeared to be the best indicators of responsiveness to bronchodilator. Subjects with a history of asthma more often showed responsiveness than did the remainder of the population, even when their initial function was within normal limits. Over-all, a high proportion of subjects with abnormalities in baseline forced expiratory volume in 1 sec or maximal flow after exhalation of 50 per cent of the forced vital capacity showed sufficient improvement after bronchodilator to cause their values after isoproterenol to fall within the normal range. The data suggest that responsiveness to bronchodilator aerosol may be a useful guide to the presence of bronchial reactivity in epidemiologic studies of obstructive airway diseases.

Adult↗
PubMed1979

Pulmonary function in identical twins: comparison of nonsmokers and smokers.

Forty-five apparently normal pairs of identical twins were given pulmonary function tests to determine the role of genetics in bronchial susceptibility to cigarette smoke. Maximal expiratory flow at 60 per cent of total lung capacity (Vmax60) was the best discriminator of smokers from nonsmokers among pairs in which one member smoked and the other did not. The intrapair difference of Vmax60 values in pairs in which both members smoked was the same as in pairs in which both members did not smoke. These data support the view that genetic factors are important in determining the vulnerability of the airways to cigarette smoke.

Adult↗
PubMed1976

The effect of CO2 on peripheral airways.

In each of ten healthy young subjects breathing different concentrations of CO2 in O2, four alveolar CO2-tension levels were obtained, ranging from about 20 mmHg when hyperventilating in O2 to 50 mmHg. Maximum expiratory flows at 60% total lung capacity were measured at each level and corrected for the influence of the expired gas on the flow. The corrected maximum flow decreased significantly when the alveolar CO2 tension was below 30-35 mmHg, while there was only slight or no influence of CO2 on the maximal flow when the tension was above 35 mmHg. The decrease is taken as evidence of a constrictor effect on peripheral bronchi of hypocapnia.

Adult↗
PubMed1975

Comparison of the cardiopulmonary effects of subcutaneously administered epinephrine and terbutaline in patients with reversible airway obstruction.

The cardiopulmonary effects of epinephrine and terbutaline were compared in a doubleblind crossover study in 23 subjects with chronic obstructive airway disease. On each of three days each subject received a single subcutaneous dose of saline, 0.25 mg of epinephrine or 0.5 mg of terbutaline. Treatment with epinephrine produced significant increases in forced vital capacity (FVC), forced expiratory volume in one second (FEV-1), maximal expiratory flow rate (MEFR) and maximal mid-expiratory flow (MMEF). Terbutaline caused even more pronounced increases in all four parameters and exhibited a longer duration of action. Neither drug altered arterial pH, arterial oxygen pressure (PaO-2), or arterial carbon dioxide pressure (PaCO-2). With regard to cardiovascular effects, no alterations in either systolic or diastolic pressure were observed. Administration of epinephrine and terbutaline caused statistically significant increases in heart rate. The effect of terbutaline was more pronounced that that of epinephrine. In addition, terbutaline caused a heart rate-related depression of the T-wave of the lead 2 ECG. Neither drug altered any of the hematologic, hemochemical or urinary parameters monitored before and after treatment. Side effects were seen in eight subjects after administration of saline solution, in 13 subjects after epinephrine and in 19 subjects after terbutaline. None of these side effects was considered clinically serious and none required treatment. It is concluded from this study that subcutaneously administered terbutaline is a more effective bronchodilator than epinephrine.

Adult↗