Bronchial responsiveness to histamine: relationship to diurnal variation of peak flow rate, improvement after bronchodilator, and airway calibre.

Features of asthma include increases in both bronchial responsiveness and variability of airflow rates. We examined the relationship between bronchial responsiveness to histamine and the variation of peak expiratory flow rate (PFR) during the day and in response to salbutamol (200 μg), and the initial FEV at the time of the histamine test and FEV response to salbutamol. Bronchial responsiveness to histamine was expressed as the provocation concentration causing a fall in FEV of 20% (PC).

Long-term stability of bronchial responsiveness to histamine.

Bronchial responsiveness to histamine was measured in 35 adult asthmatics whose symptoms were controlled on a minimum of medication. The tests were carried out on two occasions separated by 10-30 months. On each occasion the subjects had no symptoms of respiratory infection and no exposure to relevant allergens for at least six weeks.

Control of asthma.

Developments of the past decade have greatly improved the likelihood that patients can control their asthma. Inhaled medications are basic to a regimen that may include bronchodilators only, or bronchodilators along with cromoglycate and steroid to the extent required to achieve and maintain control. The regimen is modified for the individual and designed to control symptoms while avoiding an overdose of any one agent and overuse of inhaled bronchodilators (a sign of their lessening effectiveness).

Asthma induced by cold air and its relation to nonspecific bronchial responsiveness to methacholine.

We compared bronchial responsiveness to isocapnic hyperventilation of cold dry air at -18 degrees C and 0% humidity with bronchial responsiveness to inhaled methacholine in 24 subjects with current or previous asthma and 2 nonasthmatics. Two inhalation tests with each agent were carried out in random order on 4 consecutive days. The response to cold air was expressed as the respiratory heat exchange required to reduce the FEV1 by 10% (PD10 RHE) and the response to methacholine as the provocation concentration required to reduce the FEV1 by 20% (PC20 methacholine).

Bronchial responsiveness to histamine or methacholine in asthma: measurement and clinical significance.

Quantitative measurement of nonspecific bronchial responsiveness can be simply and reproducibly made by inhalation tests with histamine or methacholine. Responsiveness to histamine correlates closely with responsiveness to methacholine. The degree of responsiveness relates closely with the presence and severity of asthma.

Comparison of bronchial responses to prostaglandin F2 alpha and methacholine.

We examined bronchial responsiveness to prostaglandin (PG) F2 alpha to determine its applicability in clinical practice and to compare it with bronchial responsiveness to the pharmacologically dissimilar agent, methacholine. Inhalation tests with two fold increasing concentrations of the two agents were carried out in 19 asthmatic and four normal subjects. The results were expressed as the provocation concentration causing a 20% fall in forced expiratory volume in 1 sec (PC20).

Airway responsiveness to histamine and methacholine: relationship to minimum treatment to control symptoms of asthma.

We have prospectively examined in 51 patients the relationship between the level of airway responsiveness to histamine and methacholine and the minimum medications required to control asthma. First we determined the least medication that was required to control symptoms so that they did not disturb sleep, were not present on waking, and did not require use of inhaled salbutamol (200 microgram) more than four times daily. When baseline FEV1 was greater than 70% of predicted and when there had been no respiratory infection or allergen exposure for six weeks, histamine and methacholine inhalation tests were carried out on separate days to determine the provocation concentration causing a fall in FEV1 of 20% (PC20).

Standardization of inhalation provocation tests: influence of nebulizer output, particle size, and method of inhalation.

Standardization of inhalation tests requires a knowledge of factors that will affect the response. We measured the output and particle size of six types of nebulizers used for inhalation tests. Output varied considerably between nebulizers of different types (0.

Standardization of inhalation provocation tests: two techniques of aerosol generation and inhalation compared.

Comparison of methods of aerosol generation and inhalation is required to improve standardization of inhalation provocation tests. We compared two widely used methods in 10 asthmatics, by measuring the dose and distribution of radiolabeled aerosol deposited in the throat and lung, and the provocation concentration of inhaled histamine required to reduce the FEV1 by 20% (PC20). In one method, aerosol was generated by a DeVilbiss 646 nebulizer attached to a dosimeter, and was inhaled by 5 inspiratory capacity breaths.

Effects of oxatomide compared with chlorpheniramine in allergic rhinoconjunctivitis.

Oxatomide is an H1 receptor antagonist, which also inhibits antigen-induced mediator release from sensitized mast cells and basophils. The effects of ingested oxatomide (30 mg/capsule) were compared with those of chlorpheniramine (5 mg/capsule) in a double-blind non-crossover study in two groups of twenty-five subjects with ragweed pollen-induced hay fever during the pollen season. Oxatomide or chlorpheniramine was started when symptoms became troublesome and was used in a dose of two to four capsules daily according to severity.

Inhibition of allergen-induced asthma by three forms of sodium cromoglycate.

The effect of three forms of sodium cromoglycate (SCG), 20 mg, on allergen-induced early asthmatic responses was examined in ten stable asthmatics. Dose response allergen inhalation tests were performed on five occasions at intervals of from 1 to 2 weeks to determine the provocation concentration producing a 20% reduction (PC20 allergen) in FEV1. Placebo was given before the first and the last tests to determine the reproducibility of responses to allergen over the study period; reduced responsiveness was observed in eight of the ten subjects.

Asthma caused by occupational exposure to a furan-based binder system.

A 50-yr-old mold maker developed severe asthma a few weeks after commencing work with a furan binder. Asthma recurred within hours of subsequent exposure and was confirmed by measurements every 2 hr of peak flow rate. The molds were prepared by mixing sand with a resin (containing furfuryl alcohol, paraformaldehyde, and xylene) and a catalyst (containing sulfuric acid, phosphoric acid, and butyl alcohol).

The use of radioactive isotopes for analysis of cutaneous allergic responses.

Local exudation at the sites of allergic and histamine-induced cutaneous reactions, was measured with an in vivo double-labelling procedure, based upon local serial simultaneous measurements of indium-113 m (113mIn) labelled transferrin and technitium-99m labeled red blood cells (99mTc RBC). Analyses depended upon the reaction index i.e.

Investigation and management of rhinitis.

The family physician is ideally situated to deal with most chronic-recurrent nasal problems. The physician is alerted to the real problem by the recognition that terms such as 'sinus' and 'colds' often camouflage the problem of chronic rhinitis and chronic nasal obstruction. Avoidance of offending substances, the use of medications, the occasional judicious use of allergen injection treatment and sometimes surgical intervention for nasal polyps provide different modalities of treatment which can have a major beneficial effect upon symptoms.

Assessment and treatment of asthma.

The objectives of treating asthma are to control symptoms by a minimum of medication, and to prevent severe attacks in the future. However, before these can be achieved the presence of asthma must be recognized, its severity determined, and the individual triggering factors identified. Full assessment is simple and practical: it involves history, measurement of airflow rates and allergy skin tests.

The effect of helium on nasal resistance and nasal flows.

Nasal inspiratory resistance and maximal inspiratory nasal flow were measured in 10 normal subjects while they breathed air and while they breathed a mixture of 80% helium and 20% O2. After the less dense helium-O2 mixture, there was a nonsignificant increase in K1 (15 +/- 93%), a 56 +/- 20% decrease in K2 (P less than 0.001), and a 48 +/- 20% increase in maximal inspiratory nasal flow (P less than 0.

Human sensitization to Ganoderma antigen.

Continuous air sampling with a Hirst volumetric spore trap over 3 yr has identified basidiospores of Ganoderma applanatum, a bracket fungus, as the most numerous fungal spores in two southern Ontario locations. The particle size is small and the calculated total spore mass approximates that of the spores of Cladosporium and Alternaria. Extracts of Ganoderma applanatum bracket fungus and spores in w/v, 1:10 concentration were prepared after collection of samples of the fungus from local woods.

Nasal airway inspiratory resistance.

The relationship between transnasal pressure and nasal flow is markedly curvilinear during tidal breathing in man, and there is poor agreement among the results of various methods used to define this characteristic with a single number. We used Rohrer's equation (P = K1 V + K2 V2), where P = pressure and V = flow, and calculated values for K1 and K2 from 474 nasal inspiratory pressure/flow curves obtained from 34 human subjects by a standard method of posterior rhinometry. Nasal airway inspiratory resistance at an air flow of 0.

Bronchial responsiveness to inhaled histamine and exercise.

Bronchial responsiveness to inhaled histamine and exercise was measured in 19 asthmatics. Histamine aerosol was inhaled to determine the provocative concentration producing a 20% fall in forced expired volume in one second (FEV1) (PC20). Exercise was performed on a treadmill and a cycle ergometer; following each procedure the percent fall in the FEV1 (delta FEV1) and the exercise lability (percent rise in FEV1 plus percent fall in FEV1) were calculated.