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Biomedical subjects

S D Anderson

Publications and source records attributed to S D Anderson.

At least 109 records · Page 6Linked to original sources
PubMed1985

Increased responsiveness to methacholine and histamine after challenge with ultrasonically nebulised water in asthmatic subjects.

Responsiveness to inhaled methacholine was compared before and 40-60 minutes after a challenge with ultrasonically nebulised water (UNH2O) in 16 asthmatic patients. The sensitivity to methacholine increased after UNH2O challenge (p less than 0.001). The mean dose of methacholine producing a 20% fall in forced expiratory volume in one second was 0.4 (95% confidence limits 0.2, 0.8) mumol, compared with 0.9 (95% confidence limits 0.5, 1.6) mumol in the first methacholine challenge. When the study was repeated in six asthmatic patients with histamine substituted for methacholine, five of the patients were significantly more sensitive to histamine after UNH2O challenge. It is concluded that challenge with UNH2O produces an increase in airway responsiveness.

Adult↗
PubMed1985

Beta-adrenoceptor blockade with propranolol and bronchial responsiveness to a number of bronchial provocation tests in non-asthmatic subjects.

The role of beta-adrenoceptors in the mechanisms of bronchial hyperresponsiveness was studied in 20 normal subjects. Propranolol 120 mg b.d. or placebo was taken for one week. Four bronchial provocation tests: exercise, inhalation of nebulised water, histamine, and methacholine, were carried out before and during the last 2 days of the treatments. FEV1 and flow rate at 50% of vital capacity (V50) were measured. Cardio-vascular beta-blockade with propranolol, measured by reduction in exercise heart rate, was shown in 17 subjects. Propranolol enhanced bronchial responsiveness to some tests in some subjects, but there was no consistent pattern. For the group, the only significant increases in response were 1) the maximum fall in V50 on methacholine challenge (P less than 0.05, paired t-test, n = 17), 2) the dose of methacholine giving a 10% fall (PD10 value) in FEV1 (p less than 0.05 n = 11). These results do not support the concept of decreased beta-adrenoceptor responsiveness as a single lesion leading to abnormal bronchial reactivity.

Adolescent↗
PubMed1985

Airway cooling as the stimulus to exercise-induced asthma--a re-evaluation.

Exercise-induced asthma (EIA) was recorded in 20 of 22 asthmatic children who cycled for 8 min while inspiring hot (32-40 degrees C) dry (3-10 mg H2O L-1) air. The mean +/- 1SD reduction in forced expiratory volume in one second was 39.8% +/- 22.3 of the pre-exercise value. To determine the relationship between respiratory heat loss (RHL) and retrotracheal temperature (RTT) under these inspired air conditions we studied 11 non-asthmatic adults who performed steady-state and incremental bicycle exercise. Exercise tests were also carried out while inspiring cold dry air. At the equivalent RHL, RTT was reduced by only 0.1 +/- 0.35 degrees C breathing hot air compared with 1.0 +/- 0.81 degrees C when cold air was inhaled. These data suggest that abnormal cooling of the airways is not occurring during the inhalation of hot dry air. Thus an additional stimulus to airway cooling must have been acting to induce asthma in the children. We propose that water loss and not heat loss is the stimulus to EIA under these inspired air conditions.

Adolescent↗
PubMed1984

Is there a unifying hypothesis for exercise-induced asthma?

We believe that it is the loss of water per se and not heat loss that is the most important stimulus to exercise-induced asthma (EIA). The evidence to support this concept comes from a number of observations. First, EIA may occur when expired air temperature during exercise is close to body temperature and higher than that normally observed at rest. This suggests that EIA is not always associated with cooling of the airways. Second, there is evidence to show that the temperature of the inspired air is less critical than was previously thought. Providing that the water loss is the same, the airway response is reproducible even though the heat loss may vary because of differences in the temperature of the inspired air. Because expired water concentration is relatively constant, the airway response relates well to the water concentration of the inspired air. We believe that evaporative water loss from the airway mucosa induces a transient change in osmolarity in the epithelial fluid and that this change is a more potent stimulus to bronchoconstriction than is airway cooling. We believe this hypothesis accounts for many known facts about EIA and should merit further investigation by which it may be proved or disproved.

Aerosols↗
PubMed1984

A reinterpretation of the effect of temperature and water content of the inspired air in exercise-induced asthma.

To compare the importance of water loss with heat loss in the mechanism of exercise-induced asthma (EIA), we conditioned the air inspired during exercise to the same water content (Wi) while changing its temperature (Ti), and vice versa. We calculated separately the amount of heat and water required to bring the inspired air to alveolar conditions. Ten asthmatics ran for 8 min on 4 occasions in an environmental chamber. The air was conditioned to a Ti of 9 to 10 degrees C or 35 degrees C, with a Wi of 9 to 10 mg H2OL-1. The airway response to exercise was not significantly different when Ti varied by 25 degrees C, but the amount of water required to saturate the inspired air remained the same. However, the amount of heat required was significantly greater with cooler air (p less than 0.005). We conclude that it is the osmotic and not the cooling effects induced by the vaporization of water that is the more important factor determining EIA.

Adolescent↗
PubMed1984

Exercise testing in the evaluation of diffuse interstitial lung disease.

The cardio-pulmonary response to incremental and steady-state bicycle exercise was measured in a group of 22 patients with diffuse interstitial lung disease (DILD). In most patients the lung volumes were less than 80% of their predicted normal value. In 19 patients the uptake of carbon monoxide was less than 60% of the value predicted for the observed lung volume. Maximum working capacity (Wmax) was reduced in 20 patients. Eight patients stopped exercising before they achieved their predicted maximum heart rate. In all patients ventilation (VE) was increased in relation to oxygen consumption. The increase in VE resulted from an increased frequency of breathing. Exercise induced a decrease in arterial oxygen tension in 11 patients. When 60% oxygen was inspired during exercise the endurance time at 80% Wmax increased from 8.0 +/- 5.5 to 13.9 +/- 8.7 min. The increase in endurance time related to the extent of desaturation during exercise with air breathing. Oxygen breathing did not improve Wmax. We conclude that exercise testing in patients with DILD is useful for determining the severity of disease and provides additional information in relation to gas exchange.

Adult↗
PubMed1983

Sodium cromoglycate as a pressurised aerosol (vicrom) in exercise-induced asthma.

We investigated the effect of sodium cromoglycate (SCG), delivered as a pressurised aerosol, in a dose of 2 or 4 mg in 15 patients known to have exercise-induced asthma (EIA). All patients had a fall in peak expiratory flow rate (PEFR) greater than 20% of the pre-exercise level following placebo (Range 21.1 to 74.7%). When an identical exercise test was performed after 2 mg of SCG aerosol, nine of the 15 patients had falls in PEFR less than 50% of the value observed on placebo. Of the remaining six patients, four had greater than 50% protection afforded by 4 mg of SCG. Of the 15 patients, 12 had falls in PEFR less than 11% after either 2 or 4 mg of SCG aerosol. The dose of aerosol SCG required to inhibit EIA is only 10 to 20% of that delivered by conventional spinhaler. The apparent superiority of the pressurised aerosol may be due to its site of deposition in the airways.

Adolescent↗
PubMed1983

Evaluation of ultrasonically nebulised solutions for provocation testing in patients with asthma.

The airway response to the inhalation of ultrasonically nebulised distilled water was determined in 55 asthmatic patients and 16 normal subjects. We calculated the dose of water required to induce a 20% reduction (PD20) in forced expiratory volume in one second (FEV1) by measuring the output of the nebuliser and the volume ventilated by each subject. Forty-eight of the asthmatic patients had a PD20 of 9 ml or less but three patients required as much as 24 ml. A PD20 was not recorded in the normal subjects and the challenge was stopped after 33 ml. In 12 patients the challenge was repeated within six months and the airway response was shown to be reproducible at equivalent doses of water. In a separate group of 11 patients there was, however, a highly significant reduction in the percentage fall in FEV1 when equivalent doses of water were given on two occasions 40 minutes apart. When the temperature of the inhaled water was increased from 22 degrees C to 36 degrees C eight of 10 patients had a similar change in FEV1 with equivalent doses of water. The airways obstruction induced by the inhalation of water was readily reversed with salbutamol administered by aerosol. In some patients a challenge with water or 3.6% saline was repeated after pretreatment with sodium cromoglycate, atropine methonitrate, and verapamil hydrochloride, all given as aerosols. The airway response to the equivalent dose of water or saline was significantly reduced after treatment with sodium cromoglycate but not atropine or verapamil.

Adolescent↗
PubMed1983

Recent advances in the understanding of exercise-induced asthma.

Most asthmatic patients have less exercise-induced asthma (EIA) after a second challenge. However, the degree to which a patient becomes refractory is variable. The mechanism of refractoriness is unknown. Heat loss from the airways, the initiating stimulus in EIA, remains unchanged on repeated challenge. It is unlikely that bronchial smooth muscle becomes refractory, or that residual catecholamines induce protection since histamine sensitivity remains relatively unchanged during a refractory period. Histamine release has been measured in some patients during EIA, but further studies are needed to elucidate the role of histamine in EIA and the refractory period. In patients who do not become refractory, EIA may be induced by stimuli independent of mediator release and perhaps vagal in origin. In some patients EIA may be blocked by small doses of anticholinergic agents while, in others, these drugs have no effect. Similar observations have been made with sodium cromoglycate. The superiority of aerosols in preventing EIA suggests that exercise induces changes in the airways mucosa. The loss of water during exercise may change the osmotic environment of irritant receptors or mast cells triggering bronchoconstriction.

Asthma↗
PubMed1982

Bicycle endurance performance of patients with interstitial lung disease breathing air and oxygen.

The effect of supplemental oxygen breathing on bicycle exercise performance was studied in 16 patients in the assessment of their extent of impairment with interstitial lung disease (ILD). The mean maximal working capacity (W-Max) +/- 1 SD with incremental exercise breathing air was 107 +/- 43 W (60% predicted). There was no significant increase in W-Max with oxygen breathing (p less than 0.10, n = 12). On a separate day each patient performed 2 endurance studies at a constant submaximal work load (80% W-Max) inspiring air and 60% oxygen. The mean fall in arterial oxyhemoglobin saturation (SaO2%) during exercise in air was 8% (range, 1 to 23%). There was a significant improvement in exercise time (p less than 0.001) when patients exercised with oxygen. This increase in endurance was significantly correlated with the fall in SaO2% during the air study. The improvement in exercise time with oxygen was greatest in those with the most marked lung restriction. Blood lactic acid was reduced with oxygen breathing.

Air↗
PubMed1982

Sensitivity to heat and water loss at rest and during exercise in asthmatic patients.

We investigated the respiratory heat and water loss in 24 asthmatic patients who performed bicycle exercise while inspiring air conditioned to varying temperatures and water contents. Measurements of peak expiratory flow and forced expiratory volume in 1 s were made at rest, during and after exercise to determine changes in airways resistance. Respiratory heat and water loss were measured using rapid thermistors and a mass spectrometer to measure inspired and expired temperature and water vapour pressure. Exercise-induced asthma (EIA) was enhanced as the inspired water content of the air was reduced. However, there was a wide variation in sensitivity to the loss of heat and water between individual patients. This variability could not be accounted for by differences in body size. When patients inspired air conditioned to body temperature and fully saturated with water vapour, EIA was significantly reduced; however, half the patients still had an attack of asthma following exercise which had induced no significant loss of heat or water. It is suggested that the bronchoconstriction induced by water loss from the airways during exercise may be due to a change in osmolarity in the respiratory tract fluid.

Adolescent↗
PubMed1982

Respiratory heat and water loss during exercise in patients with asthma. Effect of repeated exercise challenge.

A study was performed to investigate the loss of heat and water from the airways during repeated exercise challenge. Twenty-six asthmatic patients performed 6-8 min exercise on a bicycle ergometer at a workload equivalent to 57-85% of their predicted maximum working capacity. Sixteen patients performed two exercise tests separated by 40-52 min. Exercise-induced asthma (EIA) occurred in all patients after initial challenge but eight had significant protection from EIA following a second challenge. This protection was not associated with a reduction in heat and water loss from the airways during exercise. A further 10 patients performed two exercise tests 2-3 h apart. The second test was preceded by the administration of 200 microgram salbutamol aerosol. There was no significant difference between the two tests in loss of heat and water from the airways during exercise. Exercise-induced asthma occurred in all patients after the initial challenge but was inhibited by the salbutamol after the second challenge. Thus the reduction in EIA as a result of a refractory period or in response to aerosol salbutamol is not due to changes in heat and water loss from the airways during exercise.

Adolescent↗
PubMed1981

Bronchial hyperreactivity in response to inhalation of ultrasonically nebulised solutions of distilled water and saline.

To assess non-specific bronchial reactivity the effect of inhaling ultrasonically nebulised solutions of distilled water and hypotonic (0.3%), isotonic (0.9%), and hypertonic (2.7%, 3.6%) saline was investigated in 10 asthmatic patients and nine normal subjects. Expired ventilation and the maximum percentage fall in forced expiratory volume in one second (FEV1) were recorded. The sensitivity to the inhaled solutions was determined by measuring the ventilation required to induce a fall in FEV1 of 20% from the prechallenge value. Hypotonic and hypertonic but not isotonic solutions caused a significant fall in FEV1 in the asthmatic subjects. Normal subjects showed no response to either distilled water or 3.6% saline, the only solutions with which they were challenged. The method used for this challenge is rapid, simple, and inexpensive and provides a new means of diagnosing non-immunologically mediated bronchial hyperreactivity.

Adolescent↗
PubMed1981

Evaluation of exercise training in patients with chronic airway obstruction.

The efficacy of an exercise training program should be evaluated by adequate assessment of the patient's physical work capacity before and after training. In this study the effect of a 12-week bicycle training program on the exercise tolerance of 10 patients with chronic airway obstruction was assessed. There was a statistically significant improvement in maximum working capacity and in the distance walked in 12 minutes following training (p less than .02 and p less than .001, respectively). The improvement in work performance was not accompanied by any significant change in forced expiratory volume in one second. At equivalent workloads the ventilation and frequency of breathing were lower following training (p less than .02 and p less than .05, respectively).

Aged↗