Validity of peak expiratory flow measurement in assessing reversibility of airflow obstruction

BACKGROUND

Assessing the reversibility of airflow obstruction by peak expiratory (PEF) measurements would be practicable in general practice, but its usefulness has not been investigated.

METHODS

PEF measurements were performed (miniWright peak flow meter) in 73 general practice patients (aged 40 to 84) with a history of asthma or chronic obstructive lung disease before and after 400 micrograms inhaled sulbutamol. The change in PEF was compared with the change in forced expiratory volume in one second (FEV1). Reversible airflow obstruction was analysed in two ways according to previous criteria. When defined as a 9% or greater increase in FEV1 expressed as a percentage of predicted values reversibility was observed in 42% of patients. Relative operating characteristic analysis showed that an absolute improvement in PEF of 60 l/min or more gave optimal discrimination between patients with reversible and irreversible airflow obstruction (the sensitivity and specificity of an increase of 60 l/min in detecting a 9% or more increase in FEV1 as a percentage of predicted values were 68% and 93% respectively, with a positive predictive value of 87%). When defined as an increase of 190 ml or more in FEV1, reversible airflow obstruction was observed in 53% of patients. Again an absolute improvement in PEF of 60 l/min or more gave optimal discrimination between patients with reversible and irreversible airflow obstruction (sensitivity 56%, specificity 94%, and positive predictive value 92%).

CONCLUSION

Absolute changes in PEF can be used as a simple technique to diagnose reversible airflow obstruction in patients from general practice.

Long-term multicentre trial in chronic nonspecific lung disease: methodology and baseline assessment in adult patients. Dutch CNSLD Study Group

Airways obstruction and airways hyperresponsiveness are two dominant features in patients with chronic nonspecific lung disease (asthma and chronic obstructive pulmonary disease (COPD)). We set up a study to determine whether long-term (3 yrs) therapeutic intervention directed at airways obstruction and hyperresponsiveness is superior to one directed at airways obstruction alone. Patients were selected on functional criteria (age, baseline forced expiratory volume in one second (FEV1), and airways hyperresponsiveness) and, furthermore, extensively characterized by history, smoking habits, allergy, reversibility of airways obstruction and quality of life. The methodology and practical problems of setting up this large multicentre study are outlined, together with an analysis of baseline data. Standardization of methods and techniques and recruitment of patients required much effort, recruitment taking about twice as long as expected. A 3 month feasibility study allowed us to eliminate minor problems in the protocol. Over a 16 month period, 274 adult patients (18-60 yrs) from the out-patient clinics of six university centres entered the study; 99 met the diagnostic criteria for asthma, 51 for COPD, 88 for asthmatic bronchitis, and 36 could not be classified. Their mean (SD) FEV1% pred was 65.1 (15.2)%. Their geometric mean provoking concentration of histamine producing a 20% fall in FEV1 (PC20 histamine) was 0.28 mg.ml-1. In a multiple regression analysis, more severe airways hyperresponsiveness was associated with lower prechallenge FEV1% pred (p less than 0.0001), higher pack-years of smoking (p = 0.0099), blood eosinophil count (p = 0.0004), skin test reactivity (p = 0.0047) and with female sex (p = 0.0302). We conclude that setting up long-term multicentre trials in chronic nonspecific lung disease (CNSLD) is feasible and that these may offer valuable information on treatment and outcome of the disease.

Long-term multicentre trial in chronic nonspecific lung disease: methodology and baseline assessment in adult patients. Dutch CNSLD Study Group

Airways obstruction and airways hyperresponsiveness are two dominant features in patients with chronic nonspecific lung disease (asthma and chronic obstructive pulmonary disease (COPD)). We set up a study to determine whether long-term (3 yrs) therapeutic intervention directed at airways obstruction and hyperresponsiveness is superior to one directed at airways obstruction alone. Patients were selected on functional criteria (age, baseline forced expiratory volume in one second (FEV1), and airways hyperresponsiveness) and, furthermore, extensively characterized by history, smoking habits, allergy, reversibility of airways obstruction and quality of life. The methodology and practical problems of setting up this large multicentre study are outlined, together with an analysis of baseline data. Standardization of methods and techniques and recruitment of patients required much effort, recruitment taking about twice as long as expected. A 3 month feasibility study allowed us to eliminate minor problems in the protocol. Over a 16 month period, 274 adult patients (18-60 yrs) from the out-patient clinics of six university centres entered the study; 99 met the diagnostic criteria for asthma, 51 for COPD, 88 for asthmatic bronchitis, and 36 could not be classified. Their mean (SD) FEV1% pred was 65.1 (15.2)%. Their geometric mean provoking concentration of histamine producing a 20% fall in FEV1 (PC20 histamine) was 0.28 mg.ml-1. In a multiple regression analysis, more severe airways hyperresponsiveness was associated with lower prechallenge FEV1% pred (p less than 0.0001), higher pack-years of smoking (p = 0.0099), blood eosinophil count (p = 0.0004), skin test reactivity (p = 0.0047) and with female sex (p = 0.0302). We conclude that setting up long-term multicentre trials in chronic nonspecific lung disease (CNSLD) is feasible and that these may offer valuable information on treatment and outcome of the disease.

Oxygen-assisted exercise training in adult cystic fibrosis patients with pulmonary limitation to exercise

Exercise training has been considered suitable only in cystic fibrosis (CF) patients with mild to moderate pulmonary dysfunction without progressive hypoxaemia during exercise. We trained 16 CF patients, all with advanced lung disease (mean standardized forced expiratory volume in 1 s (FEV1), 30% pred.), with a ventilatory limitation to exercise and a progressive hypoxaemia and hypercapnia at low maximal exercise capacity, Wmax (mean Wmax, 50% pred). Exercise training was performed on a cycle ergometer twice a day for 20 min at approximately 75% of the maximal predicted heart rate for at least 3 weeks. Supplemental oxygen was administered to reach a haemoglobin oxygen saturation of 90% during training. Patients considered malnourished because of a Quetelet Index of less than 20 kg m-2 received hyperalimentation orally or by duodenal tube (total 3500-4000 kcal day-1). Evaluation directly after the training period showed a statistically significant improvement in Wmax, maximal oxygen consumption, maximal minute ventilation, pulse, PaCO2 at rest, FEV1 and body weight. None of the pretraining variables was able to predict the outcome of the training programme in the individual patient. We detected no adverse effects of the programme. This study shows that oxygen-assisted exercise training in combination with correction of the nutritional status is safe and beneficial in CF patients with severe lung disease.

Comparison of maximal airway narrowing to methacholine between children and adults

Bronchial hyperresponsiveness in adults is characterized by an increased sensitivity as well as an elevated maximal response to inhaled bronchoconstrictors. In children, however, it is unknown whether the maximal response increases with increasing sensitivity. We investigated the maximal degree of airway narrowing to methacholine in nonasthmatic and asthmatic children (7-12 yrs), and compared it to that in adults. Nineteen children (9 normals, 10 asthmatics) and 19 adults (8 normals, 11 asthmatics) were selected in order to cover a wide distribution of bronchial responsiveness. All subjects underwent 2 methacholine challenge tests on separate days, by inhaling doubling doses using a standardized dosimeter technique (up to a noncumulative dose of 59 mumol). The response was measured by forced expiratory volume in one second (FEV1) and expressed as a percentage fall from baseline value. The complete dose-response curves were characterized by their position (PD20, the provocative dose causing a 20% fall in FEV1) and maximal response (MFEV1, the mean response on the plateau, defined as greater than or equal to 2 points within a 5% response range). Plateaus were observed in 13 children and 9 adults, the coefficient of repeatability of MFEV1 being 10.8 and 10.4% fall, respectively. There was an inverse relationship between log PD20 and MFEV1, which did not differ between children and adults (p greater than 0.15). In most of the asthmatic children and adults the plateau could not be measured (exceeding 50% fall in FEV1) if PD20 was less than 1 mumol. We conclude that, for a given bronchial sensitivity, the maximal response to inhaled methacholine is similar between children and adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of maximal airway narrowing to methacholine between children and adults

Bronchial hyperresponsiveness in adults is characterized by an increased sensitivity as well as an elevated maximal response to inhaled bronchoconstrictors. In children, however, it is unknown whether the maximal response increases with increasing sensitivity. We investigated the maximal degree of airway narrowing to methacholine in nonasthmatic and asthmatic children (7-12 yrs), and compared it to that in adults. Nineteen children (9 normals, 10 asthmatics) and 19 adults (8 normals, 11 asthmatics) were selected in order to cover a wide distribution of bronchial responsiveness. All subjects underwent 2 methacholine challenge tests on separate days, by inhaling doubling doses using a standardized dosimeter technique (up to a noncumulative dose of 59 mumol). The response was measured by forced expiratory volume in one second (FEV1) and expressed as a percentage fall from baseline value. The complete dose-response curves were characterized by their position (PD20, the provocative dose causing a 20% fall in FEV1) and maximal response (MFEV1, the mean response on the plateau, defined as greater than or equal to 2 points within a 5% response range). Plateaus were observed in 13 children and 9 adults, the coefficient of repeatability of MFEV1 being 10.8 and 10.4% fall, respectively. There was an inverse relationship between log PD20 and MFEV1, which did not differ between children and adults (p greater than 0.15). In most of the asthmatic children and adults the plateau could not be measured (exceeding 50% fall in FEV1) if PD20 was less than 1 mumol. We conclude that, for a given bronchial sensitivity, the maximal response to inhaled methacholine is similar between children and adults.(ABSTRACT TRUNCATED AT 250 WORDS)

The protective effect of a beta 2 agonist against excessive airway narrowing in response to bronchoconstrictor stimuli in asthma and chronic obstructive lung disease

Beta 2 agonists reduce airway hypersensitivity to bronchoconstrictor stimuli acutely in patients with asthma and chronic obstructive lung disease. To determine whether these drugs also protect against excessive airway narrowing, the effect of inhaled salbutamol on the position and shape of the dose-response curves for histamine or methacholine was investigated in 12 patients with asthma and 11 with chronic obstructive lung disease. After pretreatment with salbutamol (200 or 400 micrograms) or placebo in a double blind manner dose-response curves for inhaled histamine and methacholine were obtained by a standard method on six days in random order. Airway sensitivity was defined as the concentration of histamine or methacholine causing a 20% fall in FEV1 (PC20). A maximal response plateau on the log dose-response curve was considered to be present if two or more data points for FEV1 fell within a 5% response range. In the absence of a plateau, the test was continued until a predetermined level of severe bronchoconstriction was reached. Salbutamol caused an acute increase in FEV1 (mean increase 11.5% predicted in asthma, 7.2% in chronic obstructive lung disease), and increase in PC20 (mean 15 fold in asthma, fivefold in chronic obstructive lung disease), and an increase in the slope of the dose-response curves in both groups. In subjects in whom a plateau of FEV1 response could be measured salbutamol did not change the level of the plateau. In subjects without a plateau salbutamol did not lead to the development of a plateau, despite achieving a median FEV1 of 44% predicted in asthma and 39% in chronic obstructive lung disease. These results show that, although beta 2 agonists acutely reduce the airway response to a given strength of bronchoconstrictor stimulus, they do not protect against excessive airflow obstruction if there is exposure to relatively strong stimuli. This, together with the steepening of the dose-response curve, could be a disadvantage of beta 2 agonists in the treatment of moderate and severe asthma or chronic obstructive lung disease.

The effect of inhaled corticosteroids on the maximal degree of airway narrowing to methacholine in asthmatic subjects

Airway hyperresponsiveness in asthma is characterized by an increase in sensitivity and in maximal response to airway-narrowing stimuli. Long-term therapy with inhaled corticosteroids is known to reduce airway hypersensitivity in asthmatic patients. To investigate whether these drugs also reduce the maximal degree of airway narrowing we studied the effects of inhaled budesonide on the maximal response plateau of the dose-response curve to inhaled methacholine in mildly asthmatic patients in whom a raised plateau could be measured. Sixteen atopic patients with mild asthma were placed randomly into two parallel treatment groups to receive double-blindly either budesonide (400 micrograms twice daily) or placebo, inhaled via a Turbuhaler, for 4 wk. Before treatment, after 2 and 4 wk of treatment, and after 2 and 4 wk of wash-out, complete dose-response curves to methacholine were obtained using a standardized 2-min tidal breathing method. The response was measured by FEV1, expressed in % fall from baseline. A plateau on the log dose-response curve was considered if three or more data points fell within a 5% response range. The maximal response was obtained by averaging the values on the plateau (MFEV1), and the sensitivity was calculated from the provocative concentration of methacholine, causing a 20% fall in FEV1 (PC20). After 4 wk of budesonide treatment, mean MFEV1 decreased from 41.6 to 33.7% fall (p = 0.0004). The changes in MFEV1 were significantly different between placebo and budesonide (p = 0.03). The geometric mean PC20 increased from 3.4 to 6.3 mg/ml (p = 0.02), but the changes in PC20 were not different between the two groups (p = 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of an inhaled leukotriene antagonist, L-648,051, on early and late asthmatic reactions and subsequent increase in airway responsiveness in man

We have investigated the protective effects of the inhaled cysteinyl leukotriene antagonist, L-648,051, on allergen-induced early asthmatic response (EAR) and late asthmatic response (LAR) and the subsequent changes in bronchial responsiveness to methacholine. Ten atopic men with asthma participated in a double-blind, crossover, placebo-controlled trial. All subjects had documented EAR and LAR to house dust-mite extract. Responsiveness to methacholine was measured the day before and the day after a standardized allergen-challenge test. L-648,051 was inhaled in two doses of 12 mg 20 minutes before and 3 hours after the allergen challenge. The response was obtained from FEV1 and flows from maximal (V40m) and partial (V40p) expiratory flow-volume curves. All subjects had an EAR and LAR during placebo therapy, but only a minority demonstrated an increase in methacholine responsiveness of more than one doubling dose. The ratio of V40m to V40p during methacholine challenge was higher than during both EAR and LAR (p less than 0.05). There was no difference between drug- and placebo-therapy periods in baseline function, EAR, LAR, ratio of V40m to V40p, and the allergen-induced hyperresponsiveness (p greater than 0.1). These results indicate that an effective aerosolized leukotriene antagonist in man does not protect against allergen-induced airflow obstruction, despite the evidence of an inflammatory response to allergen challenge. This suggests that either the potency or duration of activity of L-648,051 is limited or that leukotrienes C4 and D4 do not play a causative role in human allergic asthma.

Relation between small airways disease and parenchymal destruction in surgical lung specimens

The relation between small airways disease and parenchymal destruction was investigated in lungs and lobes removed at surgery from 27 patients aged 15-70 years. Eight of the 27 patients were life-long non-smokers. The degree of small airways disease was assessed by semi-quantitative grading (SAD score) and by measuring diameter and wall thickness of membranous bronchioles. Parenchymal destruction was measured in three ways. Firstly, the number of alveolar attachments on membranous bronchioles per millimetre of circumference (AA/mm) was counted; the number of broken attachments was subtracted from the total AA/mm to give the numbers of intact attachments (normal AA/mm). Secondly, a point counting technique was used to give a destructive index (DI). Thirdly, the mean linear intercept (Lm) was determined. Total and normal AA/mm correlated negatively with the SAD score of membranous bronchioles (rs = -0.48 and -0.51) and with wall thickness (rs = -0.37 and -0.45) and DI correlated with wall thickness (rs = 0.5) and with the SAD score of respiratory bronchioles (rs = 0.53). Lm did not correlate with indices of small airway disease and total and normal AA/mm did not correlate with diameter. Multiple regression analyses showed that the correlation of total AA/mm with the SAD score of membranous and respiratory bronchioles and with wall thickness were not confounded by age or smoking. It is concluded that small airways disease is related to destruction of peribronchiolar alveoli, and it is postulated that small airways disease has a direct role in the causation of centrilobular emphysema.

The long-term effects of nedocromil sodium and beclomethasone dipropionate on bronchial responsiveness to methacholine in nonatopic asthmatic subjects

We investigated the effects of long-term treatment with two anti-inflammatory drugs, nedocromil sodium and beclomethasone dipropionate, on airway hyperresponsiveness to methacholine (PC20), on baseline FEV1 and on the bronchodilating effect of a deep breath in 25 nonsteroid-dependent nonatopic asthmatic adults. In all subjects the prestudy PC20 was less than 8 mg/ml, the postbronchodilator FEV1 was greater than 75% predicted, and skin prick tests and RAST to 13 common allergens were negative. After 2 months run-in, the subjects were randomly allocated into 3 parallel treatment groups to inhale double-blind either 4 mg nedocromil (n = 9) or 100 micrograms beclomethasone (n = 8) or placebo (n = 8) 4 times daily for 4 months. PC20 was measured using the 2-min tidal breathing method. The effect of a deep breath was measured during methacholine-induced bronchoconstriction by standardized maximal and partial expiratory flow-volume curves and was expressed as a flow ratio (M/P ratio). Pretreatment values of FEV1, PC20, and M/P ratio were not different between the 3 groups. PC20 did not change in the placebo group, but increased significantly by a factor of 3 after 8 wk of treatment with beclomethasone or nedocromil (p less than 0.001). FEV1 did not change after treatment with placebo or nedocromil (p greater than 0.2), but increased (mean change 0.2 L, SD 0.2) after 4 wk of treatment with beclomethasone (p less than 0.05). Geometric mean M/P ratio increased from 1.98 to 2.66 after 4 wk of beclomethasone (p less than 0.01), but not after nedocromil or placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Antileukoprotease-containing bronchiolar cells. Relationship with morphologic disease of small airways and parenchyma

Twenty-seven surgically removed lungs and lobes were studied to assess the relation between the abundance of bronchiolar epithelial cells containing antileukoprotease (ALP) (ALP-pos/mm) and the degree of small airways disease (SADscore) and emphysema (destructive index = DI, and number of normal alveolar attachments on membranous bronchioles = normal AA/min). Between subjects, ALPpos/mm correlated with SADscore in membranous bronchioles (rs = 0.75; p less than 0.001) and with normal AA/mm (rs = -0.38; p = 0.05). Evaluation within each subject revealed significant correlations of ALPpos/mm with SADscore in membranous as well as in respiratory bronchioles (p less than 0.001), and also with normal AA/mm (p = 0.005). In membranous and in respiratory bronchioles, ALPpos/mm correlated significantly with the ALP concentration in homogenized tissue, as measured by ELISA (rs = 0.55 and 0.57, respectively; p less than 0.01). It is concluded that disease in small airways and destruction of their alveolar attachments are associated with a rise of the number of ALP-containing epithelial cells. We hypothesize that this cellular increase is part of the general defense against inflammatory and destructive processes in distal human airways, leading to higher levels of proteinase inhibitor in order to minimize tissue damage.

Bronchial hyperresponsiveness: the need for a distinction between hypersensitivity and excessive airway narrowing

Bronchial hyperresponsiveness is currently defined as an increase in sensitivity to a wide variety of airway narrowing stimuli. Most patients with asthma and chronic obstructive pulmonary disease (COPD) exhibit such an enhanced sensitivity. In asthma, in particular, this hypersensitivity is accompanied by excessive degrees of airway narrowing. This raises the question as to whether measures of sensitivity, e.g. the provocative concentration or dose producing 20% fall in FEV1 (PC20 or PD20), comprise all the relevant information in bronchial hyperresponsiveness. In adjunct to model studies, there is experimental evidence in man that the potential mechanisms of bronchial hyperresponsiveness can be divided into those causing hypersensitivity and those responsible for the increase in the maximal attainable degree of airway narrowing. The recognition and distinction of these components of hyperresponsiveness have clinical implications in the diagnosis and therapy of asthma and COPD. Bronchial hyperresponsiveness is a composite functional disorder, which requires treatment of each of its components.

Effects of a high-protein diet in acid maltase deficiency

The effects of a high-protein diet were studied in 5 adult cases of acid maltase deficiency. Measurements of muscle strength, pulmonary function and 3-methylhistidine excretion revealed no improvement consistently attributable to the diet.

Bronchial hyperresponsiveness: the need for a distinction between hypersensitivity and excessive airway narrowing

Bronchial hyperresponsiveness is currently defined as an increase in sensitivity to a wide variety of airway narrowing stimuli. Most patients with asthma and chronic obstructive pulmonary disease (COPD) exhibit such an enhanced sensitivity. In asthma, in particular, this hypersensitivity is accompanied by excessive degrees of airway narrowing. This raises the question as to whether measures of sensitivity, e.g. the provocative concentration or dose producing 20% fall in FEV1 (PC20 or PD20), comprise all the relevant information in bronchial hyperresponsiveness. In adjunct to model studies, there is experimental evidence in man that the potential mechanisms of bronchial hyperresponsiveness can be divided into those causing hypersensitivity and those responsible for the increase in the maximal attainable degree of airway narrowing. The recognition and distinction of these components of hyperresponsiveness have clinical implications in the diagnosis and therapy of asthma and COPD. Bronchial hyperresponsiveness is a composite functional disorder, which requires treatment of each of its components.

The effect of inhaled budesonide on the maximal degree of airway narrowing to leukotriene D4 and methacholine in normal subjects in vivo

In normal humans in vivo, maximal airway narrowing to LTD4 is more severe than to methacholine. Moreover, LTD4 heightens the maximal response to methacholine for several days. To investigate whether or not this is due to inflammatory changes in the airway wall, we studied the effects of the corticosteroid budesonide on the dose-response curves to inhaled LTD4 and to methacholine. In a two-period, double-blind, placebo-controlled design, budesonide (400 micrograms twice a day) or placebo was inhaled by eight normal subjects on six consecutive days, with a 3-wk washout. Complete dose-response curves to LTD4 (0.36 to 43 nmol) were performed on Day 5, and to methacholine (1.28 to 655 mumol) on Days 4 and 6 of each period using a validated method. The response was measured by FEV1 and standardized partial expiratory flow-volume curves (V40p), and was expressed as the percent fall from baseline. A maximal response plateau was considered if more than two doses fell within a 5% response range. All subjects reached plateaus to methacholine and to LTD4. Budesonide reduced the maximal response to LTD4 (mean difference with placebo, 7.9% fall for FEV1, and 8.4% fall for V40p; p less than 0.05). During placebo the maximal response to methacholine 24 h after LTD4 was higher than 24 h before (mean change, 2.7% fall in FEV1 and 5.5% fall in V40p; p less than 0.05), but not during budesonide (mean change, -2.5% fall in FEV1 and -0.1% fall in V40p; p greater than 0.2), the changes being significantly different between the two periods (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of maximal bronchoconstriction in vivo and airway smooth muscle responses in vitro in nonasthmatic humans

We tested the hypothesis that maximal bronchoconstriction in humans in vivo is limited by the maximal contractility of airway smooth muscle by comparison of complete in vivo and in vitro dose-response curves to methacholine in 10 nonasthmatic subjects who were scheduled for thoracotomy because of malignancies. The provocative dose of methacholine that produced a 10 and 20% decrease of baseline FEV1 (PD10,20 FEV1) and the maximal fall in FEV1 (MFEV1) at the response plateau to inhaled methacholine were determined prior to surgery. Small airway smooth muscle preparations, obtained from the 10 resected lung tissue specimens, were examined in vitro to determine the sensitivity (-log EC50) and maximal isotonic shortening (Smax) to methacholine. In addition, the relaxation responses to the beta-agonist I-isoproterenol were measured. The degree of small airways disease (SAD) was examined histologically. Nine subjects showed a maximal response plateau to inhaled methacholine in vivo. The maximal fall in FEV1 at the plateau was 26 +/- 3%. All airway smooth muscle preparations (n = 30) contracted to methacholine (-log EC50, 5.94 +/- 0.09; Smax, 1320 +/- 219 micron) and relaxed to I-isoproterenol (-log EC50, 7.60 +/- 0.11; maximal relaxation [Rmax], 87 +/- 3%). No significant correlations were found between Smax or Rmax of the airway smooth muscle in vitro and the MFEV1 in vivo, and between -log EC50 for methacholine or I-isoproterenol in vitro and PD10 or PD20 FEV1 for methacholine in vivo. The severity of SAD was significantly correlated with the degree of baseline airflow limitation (p less than 0.05), but not with in vivo or in vitro responses to methacholine.(ABSTRACT TRUNCATED AT 250 WORDS)

The combined effects of histamine and methacholine on the maximal degree of airway narrowing in normal humans in vivo

In normal subjects in vivo the dose-response curve to inhaled nonsensitizing stimuli reaches a plateau at mild degrees of airway narrowing. We investigated whether the limitation of the response is due to non-optimal smooth muscle activation, by administering high doses of histamine and methacholine together. In fifteen normal subjects a complete dose-response curve to methacholine was recorded by a tidal breathing method on three randomized days. On a separate day a complete histamine inhalation test was carried out. Each methacholine test was directly followed by double blind inhalation of the highest dose of either histamine or methacholine, or a dose of saline. The response was measured by flows from partial flow-volume curves (V 40p), and was expressed in % fall from baseline. Twelve subjects reached a maximal response plateau to methacholine which was reproducible. The addition of saline or extra methacholine did not change the response from its methacholine plateau value. Histamine caused a small increase in the response on top of the methacholine plateau (+ 9.0% fall; p less than 0.001). However, the response to the combined histamine and methacholine was not significantly larger than the maximal response to histamine alone. We conclude that there is no interaction between histamine and methacholine on the maximal degree of airway narrowing. This suggests that the plateau of the dose-response curve in normal subjects in vivo is due to other factors than limited smooth muscle activation.

The combined effects of histamine and methacholine on the maximal degree of airway narrowing in normal humans in vivo

In normal subjects in vivo the dose-response curve to inhaled nonsensitizing stimuli reaches a plateau at mild degrees of airway narrowing. We investigated whether the limitation of the response is due to non-optimal smooth muscle activation, by administering high doses of histamine and methacholine together. In fifteen normal subjects a complete dose-response curve to methacholine was recorded by a tidal breathing method on three randomized days. On a separate day a complete histamine inhalation test was carried out. Each methacholine test was directly followed by double blind inhalation of the highest dose of either histamine or methacholine, or a dose of saline. The response was measured by flows from partial flow-volume curves (V 40p), and was expressed in % fall from baseline. Twelve subjects reached a maximal response plateau to methacholine which was reproducible. The addition of saline or extra methacholine did not change the response from its methacholine plateau value. Histamine caused a small increase in the response on top of the methacholine plateau (+ 9.0% fall; p less than 0.001). However, the response to the combined histamine and methacholine was not significantly larger than the maximal response to histamine alone. We conclude that there is no interaction between histamine and methacholine on the maximal degree of airway narrowing. This suggests that the plateau of the dose-response curve in normal subjects in vivo is due to other factors than limited smooth muscle activation.

The excretion of leukotriene E4 into urine following inhalation of leukotriene D4 by human individuals

Healthy volunteers underwent bronchial challenge with increasing doses of nebulized leukotriene D4 (0.007 - 200 nmol) at 15 min intervals. Total amounts of 200 nmol (females) and 400 nmol (males) were inhaled, corresponding to approximately 100 nmol and 200 nmol deposited in the lung, respectively. Of the latter amounts 3 +/- 1% (mean +/- S.E.M., n = 5) was found to be excreted as leukotriene E4 into the urine within 12 h. No further excretion after this period was observed. Approximately 50% of the total urinary leukotriene E4 was excreted during the first 2 h. These results suggest that a possible formation of sulfidopeptide leukotrienes in the lung in vivo can be monitored by measuring leukotriene E4 excretion into the urine.

Maximal airway narrowing to inhaled leukotriene D4 in normal subjects. Comparison and interaction with methacholine

We investigated whether or not leukotriene D4 can influence the maximal degree of airway narrowing in normal humans by comparing the maximal responses to inhaled methacholine and LTD4, and evaluating the interaction between both agonists. In 8 normal subjects, methacholine challenges were performed 24 h before and 24 and 72 h after a LTD4 challenge. Doubling doses of methacholine (1.3 to 655 mumol) or LTD4 (0.007 to 192 nmol) were inhaled by using a recently validated method. The highest dose of LTD4 was followed by the maximal dose of methacholine. The response was measured by FEV1 and volume history standardized partial expiratory flow-volume curves (V40p), and was expressed as percent fall from baseline. All subjects reached a maximal response plateau to both agonists. The maximal response plateau to LTD4 was systematically higher than to methacholine on the preceding day (mean difference, 13.4 and 12.7% fall for FEV1 and V40p, respectively) (p less than 0.01). Addition of methacholine on top of the LTD4 plateau caused a further increase in the response (mean, 6.6 and 4.8% fall, respectively) (p less than 0.005). The maximal responses to methacholine at 24 and 72 h after the LTD4 challenge were higher than at 24 h before (mean difference at 24 h, 4.0 and 8.5% fall for FEV1 and V40p, respectively, and at 72 h 5.7 and 9.3% fall) (p less than 0.05). However, the provocative dose of methacholine causing a 10% fall in FEV1 (PD10) or a 40% fall in V40p (PD40) was not altered by the previous LTD4 challenge test.(ABSTRACT TRUNCATED AT 250 WORDS)

Maximal airway narrowing in humans in vivo. Histamine compared with methacholine

Maximal airway narrowing to inhaled nonsensitizing stimuli is limited to a mild degree in nonasthmatic and mildly asthmatic subjects. We investigated whether this limitation is due to a nonspecific inhibitory mechanism (with regard to the agonist) by comparing the maximal response plateaus of histamine and methacholine dose-response curves. Twenty subjects (15 nonasthmatics, 5 asthmatics) were selected in order to cover a wide distribution of airway responsiveness from the normal into the mildly asthmatic range. The subjects inhaled doubling doses of either histamine (up to 54 mumol) or methacholine (up to 340 mumol), delivered to the mouth during tidal breathing, on 2 separate days. The response was measured from volume-history-standardized, partial expiratory flow-volume curves as the flow at 40% of the control vital capacity (V40p), and expressed as the percentage fall from baseline value. Sixteen subjects demonstrated a plateau for both histamine and methacholine. The maximal response on the plateau was not significantly different between the 2 agonists, nor was there a difference in the provocative dose causing a 40% fall in V40p (PD40). The slope of the dose-response curve was significantly steeper for histamine than for methacholine (p less than 0.001), whereby the histamine plateau was reached at relatively lower doses (p less than 0.01). The maximal response was inversely related to logPD40, and this relationship did not differ between histamine and methacholine. We conclude that maximal airway narrowing in vivo is limited by an inhibitory mechanism that is not dependent on the pharmacodynamic properties of the agonist. The results suggest that the extent of inhibition and the degree of airway responsiveness are determined by related mechanisms.

The value of the forced expiration technique with and without postural drainage in adults with cystic fibrosis

The effect of the Forced Expiration Technique (FET) with or without Postural Drainage (PD) was examined in eight adults with cystic fibrosis. On four mornings the patients followed a 30-min physiotherapy session consisting in a randomized order of either FET in a sitting position following a night of horizontal sleep ("FET"), or FET in a postural drainage position following sleep including postural drainage ("FET/PD"). The lung function parameters studied did not change during either of the two treatments. Sputum yield over 22.5 h before the physiotherapy sessions and over 24 h increased with PD during sleep in patients with more than 30 g of sputum per 24 h (p less than 0.05). PD during the treatment sessions did not further increase sputum production. This study indicates that sleeping head-down improves expectoration in patients with copious sputum. PD during FET is not needed after sleeping in the head-down position.

Limited maximal airway narrowing in nonasthmatic subjects. Role of neural control and prostaglandin release

In nonasthmatic subjects with normal airway responsiveness to methacholine, maximal airway narrowing is limited to a mild or moderate degree. We investigated whether the maximal response plateau or the position of the dose-response curve is due to functional inhibition by neurogenic mechanisms or to prostaglandin release. Four nonasthmatics inhaled doubling concentrations of methacholine up to 256 mg/ml (67 mg delivered during tidal breathing), followed by 4-fold-increasing doses of salbutamol up to 80 mg/ml (24 mg during tidal breathing) on 5 separate days. On each day 30 min before the test, the subjects inhaled (using a dosimeter) saline, propranolol (11 mg), or hexamethonium (910 mg) or, 2 h before the test, ingested indomethacin (75 mg) or placebo. The response to methacholine was measured from volume history standardized partial and complete maximal expiratory flow-volume curves, as FEV1 and the flows at 40% of the control FVC (V40p and V40c). Compared with saline, on average, baseline V40p was 18% lower after propranolol and 18% higher after hexamethonium. Indomethacin did not affect baseline values. There was no systematic difference between the 5 days in the dose of methacholine to cause a 10% fall in FEV1 or a 40% fall in V40p, or in the maximal response with FEV1, V40p, and V40c, or in V40p/V40c at 256 mg/ml methacholine. We conclude that limited maximal airway narrowing to methacholine in nonasthmatics is not due to a change in adrenergic, cholinergic, or ganglion-transmitted-nonadrenergic inhibitory activity nor to the release of prostaglandins.(ABSTRACT TRUNCATED AT 250 WORDS)