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Biomedical subjects

R R Martin

Publications and source records attributed to R R Martin.

262 records · Page 15Linked to original sources
PubMedDate not supplied

Bronchoconstriction due to isocapnic cold air inhalation minimally influences bronchial hyperresponsiveness to methacholine in asthmatic subjects.

The aim of this study was to investigate if bronchial hyperresponsiveness to methacholine could be influenced by a previous bronchoconstriction due to isocapnic inhalation of cold air. Twelve adult asthmatic subjects in a clinical steady state were seen on four different days in a randomized way according to three different sequences. After assessment of spirometry, bronchial responsiveness to inhaled methacholine was determined on each occasion by the provocative concentration causing a fall of 20% in FEV1 (PC20). On two occasions, the methacholine test was preceded by the inhalation of dry cold air which caused significant (greater than 20% change in FEV1) bronchoconstriction. The methacholine test was performed after functional recovery. There was a significant (t = 2.53; p less than 0.05) but minimal (mean changes of 0.65 single two-fold concentration difference) reduction in PC20 after cold air inhalation. It is concluded that cold air-induced bronchoconstriction causes significant but minimal changes in bronchial responsiveness to methacholine in asthmatic subjects.

Asthma↗
PubMedDate not supplied

Disturbances in pulmonary mechanics during serotonin perfusion.

The effect of i.v. perfused serotonin (75 microgram.kg-1.min-1) on bronchomotor tone was assessed in dogs by mechanical studies, with the result in an increase in total lung resistance. The increased residual volume (RV), closing capacity (CC) and slope of phase III (nitrogen single-breath washout) as well as the reduction of the helium response at low lung volumes suggest a peripheral action of the drug. Because of the large increase in total lung resistance and the decreased dead space (VD), bronchoconstriction of large airways must also be present. Vagal tone inhibition is incomplete whether by volume history or bilateral vagotomy and could be limited mainly to a segment which is situated between the equal pressure point and the most peripheral airways: maximal flows during partial expiratory flow-volume manoeuvres (PEFV) are lower than during maximal expiratory flow-volume manoeuvres (MEFV) and the volume of isoflow is higher in PEFV than in MEFV manoeuvers, suggesting that full inspiration reduces the bronchoconstriction induced by serotonin. On the other hand, the bilateral vagotomy did not reverse CC, RV, slope of phase III or VD back to control values. Isoproterenol i.v. injection improved all physiological measurements almost to the level of control values: beta-adrenergic stimulating drugs seem to inhibit completely serotonin induced bronchospasm, at all levels of the bronchial tree.

Airway Resistance↗
PubMedDate not supplied

Pulmonary function tests and airway responsiveness to methacholine in chronic bronchiectasis of the adult.

Fifty adults with chronic bronchiectasis (mean duration since diagnosis: 25 +/- 16.4 years), excluding those cases secondary to tuberculosis or hypogammaglobulinemia, were investigated by a questionnaire, a chest radiograph and lung function tests. Of these, 29 with an FEV1 greater than 1.5 1 underwent methacholine inhalation tests. Fourty-three subjects and three subjects respectively showed an obstructive or a mixed obstructive and restrictive defect, only four having normal lung function tests. Sixty-nine percent of subjects tested had a provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) less than 16 mg X ml-1. Subjects with daily sputum production had lower values of FEV1 and FEV1/forced vital capacity (FVC) compared to subjects with less than daily sputum. Subjects with clinical features of bronchial hyperexcitability had significantly lower baseline FEV1, vital capacity, and maximal mid-expiratory flow rate (FEF25-75). Subjects with lower PC20 values had significantly lower baseline FEV1, FEV1/FVC and FEF25-75. Finally, subjects with the greatest extent of radiological abnormalities had lower baseline FEV1, FEV1/FVC and diffusing capacity, and a higher residual volume. We conclude that chronic bronchiectasis is associated with significant changes in lung function tests and increased responsiveness to methacholine in the majority of affected individuals.

Adult↗
PubMedDate not supplied

Circadian variations of airway response to histamine in asthmatic subjects.

In 15 clinically stable asthmatic subjects, histamine inhalation challenges were carried out on six different days, at 8, 16 and 22 h, twice at each time. On each visit, baseline functional measurements including FEV1 and forced mid-expiratory flow rates (FEF25-75%) were followed by the assessment of the concentration of histamine causing a 20% fall in FEV1 (PC20). There was no significant difference in baseline lung function tests and PC20 for visits done either at the same or different times. The correlation coefficients of PC20 for the visits at 8, 16 and 22 h were 0.95, 0.88 and 0.78 respectively. The dispersion of results of PC20 was significantly (p less than 0.05) more pronounced at 22 h than at 8 h. The cosinor analysis which depicts biologic rhythms as sinusoidal curves [8] revealed that seven subjects had detectable diurnal rhythms with acrophases (time of least excitability) at 9.8, 10.0, 11.8, 15.3, 15.4, 22.2 and 23.1 h. In five and three of these seven subjects respectively, significant rhythms of FEV1 and FEF25-75% were also detected with similar acrophases.

Adult↗
PubMedDate not supplied

Regional hypoventilation and bronchoconstriction during pulmonary air embolism.

The hypothesis that experimental pulmonary air embolism would lead to bronchoconstriction in the upper lungs and a shift in ventilation toward the lower lung regions was tested in anaesthetized and paralyzed dogs. During constant rate air infusion (0.15 ml X kg-1 X min-1), regional distribution indices were obtained using radioactive xenon boli injected at the mouth at residual volume. The results show that there was a shift of inspired xenon toward the dependent lungs after 30 min of air infusion and that this shift was accompanied by a rise in pulmonary artery pressure, a slight decrease in vital capacity, a significant increase in closing volume and an increase in airway resistance. Inspiring 5% CO2 after the shift did not reverse the distribution of xenon boli. Intravenous injection of isoproterenol after the changes had occurred, on the other hand, invariably returned the distribution toward control values. These findings indicate that hypoventilation and bronchoconstriction occurred in the non-dependent lungs during pulmonary air embolism.

Airway Resistance↗