- Email: [email protected]
The effect of atropine and albuterol aerosols on the human bronchial response to histamine
The effect of atropine and albuterol aerosols on the human bronchial response to histamine Charlotte 1. Casterline, M.D., Richard Evans, III, M.D., and George W. Ward, Jr., M.D. Washington, D. C.
l’his study was designed to determine whether histamine-induced bronchooonstridion in human asthmatics is mediated by the parasympathetic nervous system and inuolves cholinergic pathways. Inhalation challenges were performed on 14 ad& asthmatic patients using the standardized procedure for inhalation challenge recently recommended by the Asthma and Allergic Disease Centers panel. The efeot of pretreatment with either aerosoli#ed atropine sulfate or aerosolized aibuterol, a specifio beta-l adrenergio agonist, was studied. !Che cumzt,lative units of histamine regtired for ind?.bGtiOn of a positive bronchial response (.SOqo or greater drop Cn FEV, from baseline) was used as the basis of comparison of the effects of these drugs. This value was expressed as th,e PD,-FEV, to histamine. Analysis of the data showed that aerosolization of szlficient atropine to efJ’ect a cholinergic blockade, as shown by inhibition of the bronchial response to inhaled methacholine, only minimally aspected the bronchial response to histamine (p < 0.06). However, the administration of alblsterol markedly shifted the response to histamine (p < 0.005). Although there was a statistically significant change in the mean PD,-FEV, to histamine following atropine blockade, this eflect was small in comparison to that which could be demonstrated with a beta agonist. It would thus appear that the major influence of histamine ik not through chobinergic pathways.
When presensitized tissues such as lung, bronchi, or leukocytes of asthmatic patients are exposed to specific antigens, histamine is released and induces bronchoconstriction. The way in which this bronchoconstriction occurs may be a direct effect on the bronchial smooth muscle or may be mediated through the lung irritant receptors via the vagal parasympathetic nervous system. In addition, the exact role of the sympathetic nervous system (beta receptors) is unclear, although beta adrenergic agents are known to reverse many of the effects of histamine. The purpose of this study was to further elucidate the role of the parasympathetic nervous system in histamine-induced asthma in humans. Bronchospasm was induced in a group of asthmatic patients by the inhalation of histamine. The effects of pretreatment with the anticholinergic agent atropine and an adrenergie From the Department of Allergy Washington, D. C. Received for publication Jan. 27, Accepted for publication May 3, Reprint requests to: Charlotte L. Washington, D.C. 20021.
and Clinical 1976. 1976. Casterline,
Immunology,
Walter
Reed Army
Medical
Center,
M.D., Box 191, Walter
Reed Army
Medical
Center,
Vol. 58, No. 5, pp. 607-618
Casterline,
Evans,
and Ward
J. ALLERGY CLIN. IMMUNQL. NOVEMBER 1976
agent on the bronchial response to histamine were studied. The adrenergic agent chosen was albuterol (Schering Corporation), a specific beta-2 adrenergic agonist. MATERIALS
AND
METHODS
Inhalation challenges were performed using the procedure recommended by the standardization panel of the Asthma and Allergic Disease Centers, National Institute of Allergy and Infectious Diseases.1 One milliliter of the solution to be inhaled was placed in a DeVilbiss No. 42 nebulizer which wa.s connected to an automatic air metering device. Twenty pounds per square inch (psi) of compressed air was connected to the input valve. The timing adjustment was set at 0.6 see, an interval previously found to be comfortable for adult patients. The Dosimeter, designed at Johns Hopkins University, delivers a consistent amount of solution from the connected DeVilbias nebulizer and is triggered by inhalation. All breaths of the solutions were delivered during inspiration from functional residual capacity to inspiratory capacity. The Donti pulmonary performance analyzer (Cavitron) was used to measure forced vital capacity (FVC), forced expiratory volume in one second (FEV,), and peak flow (PF). Recalibration procedure for this machine was performed daily, and frequent calibration against a positive volume displacement spirometer (Jones pulmonar) was also done. Fourteen adult asthmatic patients were studied after informed written consent was obtained. Tests were done on four consecutive or nearly consecutive days at the same hour, as described below. When possible, testing was performed when the patients were lasymptomatie and on no medications. When this was not possible and medications were required, the following modifications were made : injected or inhaled beta adrenergic stimulants were withheld at least 8 hr ; sustained-release beta adrenergic stimulants were withheld for 12 hr ; theophylline preparations were withheld for 6 hr or 12 hr (sustained-release preparations) ; cromolyn sodium was withheld for 24 hr. Patients receiving alternate-day eortieosteroid drugs were not challenged within the first 2,4 hr of the last dose administered. Patients receiving daily corticosteroid drugs were challenged prior to the daily steroid dose. None of the patients were taking antihistamines, alpha adrenergic blocking agents, or antieholinergic agents.
Expression
of data
A histamine inhalation unit is arbitrarily defined as one inhalation of 1 mg/ml of histamine base in diluent (normal saline). The cumulative units of histamine required for induction of a positive response was expressed as the PD,,-FEV, to histamine. This value was used as the basis of comparison of the effects of atropine and albuterol on the pulmonary response to histamine. A methacholine inhalation unit is arbitrarily deflned as one inhalation of 1 mg/ml of methacholine in diluent (normal saline). Data were expressed as the PD,,-FEV, to methacholine. The end point for each histamine challenge was considered to be a 20% or greater drop in FEV, from the baseline value, sustained for 10 min. On the atropine and albuterol challenge days, the end point could have been calculated as a 20% or greater drop from the highest FEV, obtained following the bronchodilator aerosol. However, analysis of the results showed the PD,-FEV, to histamine to be the same by either calculation.
Technique-day
1
Baseline determination. The patient was familiarized with the equipment and instructed as to the procedure. Three consecutive baseline determinations of FVC, FEV,, and PF were obtained. The highest FEV, was considered to represent the baseline value. Saline contToZ. Sodium chloride injection, U.S.P., the diluent for the histamine and methacholine, was administered following establishment of baseline pulmonary functions. The patients were given 5 inhalations of saline, after which FEV, was measured. If no drop in FEV, greater than 10% from baseline occurred, the inhalation challenge was performed.
Effect
VOLUME 58 NUMBER 5
TABLE I. PD,,-FEV,
of atropine
and albuterol
aerosols
to histamine Day 1 baseline histamine
Patient
R. M. R. J. D. P.
Day 2 Dostatrorke
II
II
2.05 22.30
EF. . E. M. D. C. R. P. T. F.
9.80
i3 H: ti. A. B. S. Sm. Mean SEM P
:“7 41 31 91 181
Day 3 Dostalbuterol
351
z:
Day 4 repeat histamine
II GO
534
9.80
5;; 95
4GO 9.80 9.80 20 -
5% z.30 2:.50 20 5.54 -
I Wheezed 49 13.70 <0.05
145 95 191 45 <0.005
:i 19 iii
Histamine inhalation challenge. Five breaths of serial dilutions of histamine dihydrochloride (Fisher Chemical Company) were given on successive inhalations to the patient. FESI, was measured immediately. If the test was negative, 5 breaths of the next dilution were given; if the test was borderline, less than 5 breaths of the next dilution were given. Testing was continued until the previously determined end point was reached. Dilutions of histamine used were: 6.03, 0.06, 0.12, 0.25, 1.0, 2.5, 5.0, 10.0, and 25.0 mg/ml. The PD,,-FEV, to histamine was recorded. Isoproterenol aerosol was administered following completion of the histamine challenge.
Technique-day
2
The same criteria for adequate baseline were used. Methaoholine inhakztion &alZenge. Methacholine bromide (Sigma) was prepared in the following concentrations: 0.15, 0.31, 0.62, 1.25, 2.5, 5.0, 10.0, and 25.0 mg/ml. Five breaths of these serial dilutions of methacholine were given to each patient sequentially. Pulmonary function measurements were taken immediately. The end point was considered to be a 20% or greater reduction in FEV, from the baseline value, sustained for 10 min. Administration of methacholine was continued until the end point was reached. The PD,,-FEV, to methacholine was recorded. Administration of r&opine sulfate. Following induction of a 20v0 or greater drop in baseline FEV, by methacholine, the patient was given 5 mg of atropine sulfate by inhalation, and pulmonary function tests were repeated. When maximum bronchodilatation was achieved (usually within 10 min), repeat methacholine challenge was performed as described below. Bepeat methachohe challenge. The patient was given the cumulative amount of methacholine to which he had previously responded. This was administered as a single inhalation challenge. If a 20% drop in FEV, did not occur, the patient was given 2 to 10 times the amount of methacholine to which he had responded previously, again administered as a single inhalation challenge. The FEV, was again measured. If a 20% drop in FEV, did not occur, this indicated adequate vagal blockade by atropine, and the histamine challenge was then performed. Histmine inhalation challenge. The procedure for histamine challenge was as described for day 1. The previously described criteria for establishment of the end point were used. To ensure maintenance of adequate levels of atropine in the lungs, one breath of 1 mg/ml eoncen-
610
Casterline,
J. ALLERGY CLIN. IMMUNOL. NOVEMBER 1976
Evans, and Ward
tration of atropine sulfate (approximately 0.02 mg) was inhaled prior to the administration to histamine was recorded. Isoproterenol aerosol of each dilution of histamine. The PD,,-FEV, was administered following completion of the histamine challenge.
Technique-day
3
The same criteria for adequate baseline were used. Two actuations of albuterol aerosol, 85 mcg/burst, were given prior to histamine inhalation challenge. Pulmonary functions were measured following administration of albuterol. Histamine challenge was then performed using the same technique as described for day 1. The PD,,-FEV, to histamine was recorded. Following the positive response to histamine, again calculated as a 20% or greater drop in FEV, from baseline, either isoproterenol or albuterol was administered to reverse the bronchospasm.
Technique-day
4
The same procedure was used for establishing tion challenge as described for day 1.
a baseline
and performing
histamine
inhala-
RESULTS
Fifty-four bronchial challenges were performed on 14 patients, the results of which are summarized in Table I. Eleven patients completed all four days of the study. Patient V. H. developed a severe headache following histamine inhalation on days 2 and 3, so that day 4 was omitted. Patients C. W. and R. J. could not return for repeat histamine challenge on day 4. Patient S. Sm. had a paradoxical response to atropine resulting in a 50% drop in FEV, from baseline so that day 2 could not be completed. Side effects following atropine administration included dryness of the mouth, nose, and eyes, headache, sore throat, blurred vision, raspy voice, and fatigue. One patient, as mentioned, complained of a severe headache probably induced by histamine. No side effects were reported following administration of methacholine, albuterol, or isoproterenol. The mean PD,,-FEV, to histamine on day 1 was 20 and on day 4 was 19. Individual patients varied no greater than two dilutions in their response to histamine on days 1 and 4. Since identical testing procedures were carried out on these two days, the results indicate good reproducibility of the technique. On day 2, the bronchodilatory effect of aerosolized atropine following methacholine challenge ranged from 0% to 50% increase over baseline FEV,, with an average increase of 10%. Adequate and sustained vagal blockade was achieved in 13 out of the 14 patients. The method used in this report is quite similar to a method previously reported to successfully inhibit the bronchial cholinergic response.z Furthermore, the average amount of time which elapsed from the administration of atropine to completion of the histamine challenge was 30 min. It is unlikely that the effect of the inhaled atropine would have diminished in this short period of time, especially since a large initial dose of atropine (5 mg) was administered. Following atropine administration, the mean PD,,-FEV, to histamine was 49 as compared to the baseline mean of 20. The PD,,-FEV, values before and after atropine were compared for each patient, and a paired Student t test revealed the difference to be significant but minimal (p < 0.05).
VOLUME 5% NUMBER 5
Effect
of atropine
and albuterol
aerosols
5%
On day 3, the administration of albuterol, a specific beta-2 bronchodilator, effected bronchodilatation in all except one patient. The range of percent increase over baseline FEVl was 5% to 26%, with an average of 17%. The amount of bronchodilation observed following the albuterol administration was related to each patient’s initial degree of bronchial tone. The mean I’D,,-FEV1 to histamine following the administration of albuterol was 191, as compared to the baseline mean of 20. The PD,,-FEV1 to histamine before and after albuterol were compared for each patient, and a paired Student t test showed the difference to be highly significant (p < 0,005).
The subject of autonomic control of bronchomotor tone in human subjects has been difficult to analyze quantitatively due to limitations in experimental design. It nevertheless is becoming apparent that understanding the role of the autonomic nervous system in human asthmatics is essential for the advancement of physiologic and pathophysiologic knowledge.3 Animal studies have shown that stimulation of tracheal irritant receptors by histamine phosphate, irritant gases such as ammonia, carbon dust, or other irritant substances results in bronchoconstriction. This response appears to be mediated by the parasympathetic nervous system via the vagus nerve. Blockade of the eholinergic pathway with an anticholinergic agent such as atropine sulfate inhibits the bronchoconstriction response to tracheal irritants.4+’ Whether in fact these data can be applied to humans has been debated, and attempts have been made to clarify this issue.‘3 8 In human asthmatics, atropine sulfate has been shown to be an effective bronehodilator, suggesting that cholinergic presumably vagal, nervous activity eontributes to bronchoconstriction in such patients. g-11 It has been suggested that lung irritant receptors in humans can initiate bronchoeonstriction which is mediated by the vagus nerve.7s 8 Sympathomimetics also affect bronchial smooth m.uscle tone. Adrenergie stimulants such as epinephrine, isoproterenol, and albuterol cause bronchodilatation. Blockade of the sympathetic beta receptors with propranolol causes bronchoconstriction in asthmat.ic patients. ~7 I3 These pharmacologic data suggest that the sympathetic nervous system is operative in maintaining bronchial smooth musele tone, but the extent of its influence is unclear. This study was designed to determine whether histamine-induced bronchoconstriction in human asthmatics is mediated by the parasympathetic nervous system and involves cholinergic receptors. The aerosol route of administration of substances was chosen to allow direct deposition into the tracheobronchial tree, ensuring contact with lung irritant receptors. The procedure recently recommended by the standardization panel of the Asthma and Allergic Disease Centers was used for performance of the histamine and methacholine inhalation ehallenges. The Dosimeter allowed administration of known amounts of these substances. Pulmonary function tests were able to be performed repeatedly a.nd reproducibly by the use of the Donti pulmonary performance analyzer. The metha-
61
Casterline,
Evans, and Ward
J. ALLERGY CLIN. !MMUNOL. NOWMBER 1976
choline challenge followed by reversal with atropine and rechallenge with increased amounts of methacholine was evidence that appropriate doses of atropine had been administered. Finally, each patient served as his own control. The results, as outlined previously, can be interpreted as follows. Histamineinduced bronchoconstriction in human asthmatics is reproducible by this technique. Premeditation with aerosolized atropine sulfate only minimally affected the bronchial response to histamine. Pharmacologic blockade of the methacholine response was evidence that sufficiently large doses of atropine had been administered. These data lend little or no support to the theory that aerosolized histamine acts primarily on the lung irritant receptors to induce cholinergic-mediated bronchoconstriction. The administration of albuterol prior to histamine inhalation challenge markedly shifted the response to histamine. The effect observed was much greater than that which could be demonstrated with atropine. The interpretation of this finding is less certain. Perhaps the decrease in smooth muscle tone was so great that it could only be overcome by large doses of histamine-or possibly the beta receptor stimulation overpowered the weaker vagal influence, b’eing indirect evidence that vagal input is minimal. As previousiy mentioned, inhaIed histamine may act directly on bronchial smooth muscle independent of sympathetic or parasympathetic nervous pathways. The exact nature of histamine receptor sites on bronchial smooth muscle has not been clarified by this study but deserves further investigation. In conclusion, although there was a statistically significant change in mean PD,,-FEV, to histamine following atropine blockade, this effect was small in comparison to that which could be demonstrated with a beta agonist. It thus appears that the major influence of histamine in human asthmatics is not through cholinergic pathways. The authors wish to express their appreciation to Richard Kaplan, M.D., for suggestions on experimental design.
Rosenthal,
M.D.,
and Hyman
REFERENCES 1 Chai, H., Farr, R., Froelich, L., Mathison, D., McLean, J., Rosenthal, R., Sheffer, A., Bpeetor, S., and Townley, R.: Standardization of bronchial inhalation challenge procedures, J. ALLERGY CLIN. IMMUNOL.~~: 323,1975. 2 Rosenthal, R,., Summer, W., Permutt, S., and Norman, P.: Effect of atropine on antigenmediated bronehospasm, J. ALLERGY CLIN. IMMLJXOL. 53: 73, 1974. (Abst.) 3 Widdicombe, J., and Sterling, G.: The autonomic nervous system and breathing, Arch. Intern. Med. 126: 311, 1970. 4 Sellicke, H., and Widdicombe, J. : Stimulation of lung irritant receptors by cigarette smoke, carbon dust, and histamine aerosol, J. Appl. Physiol. 31: 15, 1971. 5 Gold, W., Kessler, G., and Yu, D.: Role of vagus nerves in experimental asthma in allergic dogs, J. Appl. Physiol. 33: 719, 1972. 6 DeKock, M., Nadel, J., Zwi, S., Colebatch, H., and Olsen, C.: New method for perfusing bronchial arteries : Histamine bronchoconstriction and apnea, J. Appl. Physiol. 21: 185, 1966. 7 Simonsson, B., Jacobs, F., and Nadel, J.: Role of autonomic nervous system and the cough reflex in the increased responsiveness of airways in patients with obstructive airway disease, J. Clin. Invest. 46: 1812, 1967. 8 Yu, If., Galant, S., and Gold, W.: Iqhibition of antigen-induced bronehoconstriction by atropine in asthmatic patients, J. Appl. Physiol. 32: 823, 1972.
VOLUME 58 ?dUMBER 5
Effect
of atropine
and albuterol
aerosah
9 Herxheimer, H.: Atropine cigarettes in asthma and emphysema, Br. Med. J. 2: 1.6’7, I959. 10 Cropp, G.: The effectiveness of atropine sulphate aerosol as a bronchodilator in asthmatic children, Fourth Annual Workshop of the Asthma and Allergic Disease Centers, NIH, Bethesda, 1974, National Institutes of Health, p. 166. 11 Cropp, G.: The role of the parasympathetic nervous system in the maintenance of chronic airway obstruction in asthmatic children, Am. R,ev. Respir. Dis., p. 112, 1975. 12 McNeill, R.: Effect of a ,8-adrenergic-blocking agent, propranolol, on asthmatics, Laneet 2: 1191, 1964. 13 Zard, CT., and Beall, G.: Bronchial response to beta-adrenergic blockade, New Engl. .I. Med. 275: 580, 1966.
l’his study was designed to determine whether histamine-induced bronchooonstridion in human asthmatics is mediated by the parasympathetic nervous system and inuolves cholinergic pathways. Inhalation challenges were performed on 14 ad& asthmatic patients using the standardized procedure for inhalation challenge recently recommended by the Asthma and Allergic Disease Centers panel. The efeot of pretreatment with either aerosoli#ed atropine sulfate or aerosolized aibuterol, a specifio beta-l adrenergio agonist, was studied. !Che cumzt,lative units of histamine regtired for ind?.bGtiOn of a positive bronchial response (.SOqo or greater drop Cn FEV, from baseline) was used as the basis of comparison of the effects of these drugs. This value was expressed as th,e PD,-FEV, to histamine. Analysis of the data showed that aerosolization of szlficient atropine to efJ’ect a cholinergic blockade, as shown by inhibition of the bronchial response to inhaled methacholine, only minimally aspected the bronchial response to histamine (p < 0.06). However, the administration of alblsterol markedly shifted the response to histamine (p < 0.005). Although there was a statistically significant change in the mean PD,-FEV, to histamine following atropine blockade, this eflect was small in comparison to that which could be demonstrated with a beta agonist. It would thus appear that the major influence of histamine ik not through chobinergic pathways.
When presensitized tissues such as lung, bronchi, or leukocytes of asthmatic patients are exposed to specific antigens, histamine is released and induces bronchoconstriction. The way in which this bronchoconstriction occurs may be a direct effect on the bronchial smooth muscle or may be mediated through the lung irritant receptors via the vagal parasympathetic nervous system. In addition, the exact role of the sympathetic nervous system (beta receptors) is unclear, although beta adrenergic agents are known to reverse many of the effects of histamine. The purpose of this study was to further elucidate the role of the parasympathetic nervous system in histamine-induced asthma in humans. Bronchospasm was induced in a group of asthmatic patients by the inhalation of histamine. The effects of pretreatment with the anticholinergic agent atropine and an adrenergie From the Department of Allergy Washington, D. C. Received for publication Jan. 27, Accepted for publication May 3, Reprint requests to: Charlotte L. Washington, D.C. 20021.
and Clinical 1976. 1976. Casterline,
Immunology,
Walter
Reed Army
Medical
Center,
M.D., Box 191, Walter
Reed Army
Medical
Center,
Vol. 58, No. 5, pp. 607-618
Casterline,
Evans,
and Ward
J. ALLERGY CLIN. IMMUNQL. NOVEMBER 1976
agent on the bronchial response to histamine were studied. The adrenergic agent chosen was albuterol (Schering Corporation), a specific beta-2 adrenergic agonist. MATERIALS
AND
METHODS
Inhalation challenges were performed using the procedure recommended by the standardization panel of the Asthma and Allergic Disease Centers, National Institute of Allergy and Infectious Diseases.1 One milliliter of the solution to be inhaled was placed in a DeVilbiss No. 42 nebulizer which wa.s connected to an automatic air metering device. Twenty pounds per square inch (psi) of compressed air was connected to the input valve. The timing adjustment was set at 0.6 see, an interval previously found to be comfortable for adult patients. The Dosimeter, designed at Johns Hopkins University, delivers a consistent amount of solution from the connected DeVilbias nebulizer and is triggered by inhalation. All breaths of the solutions were delivered during inspiration from functional residual capacity to inspiratory capacity. The Donti pulmonary performance analyzer (Cavitron) was used to measure forced vital capacity (FVC), forced expiratory volume in one second (FEV,), and peak flow (PF). Recalibration procedure for this machine was performed daily, and frequent calibration against a positive volume displacement spirometer (Jones pulmonar) was also done. Fourteen adult asthmatic patients were studied after informed written consent was obtained. Tests were done on four consecutive or nearly consecutive days at the same hour, as described below. When possible, testing was performed when the patients were lasymptomatie and on no medications. When this was not possible and medications were required, the following modifications were made : injected or inhaled beta adrenergic stimulants were withheld at least 8 hr ; sustained-release beta adrenergic stimulants were withheld for 12 hr ; theophylline preparations were withheld for 6 hr or 12 hr (sustained-release preparations) ; cromolyn sodium was withheld for 24 hr. Patients receiving alternate-day eortieosteroid drugs were not challenged within the first 2,4 hr of the last dose administered. Patients receiving daily corticosteroid drugs were challenged prior to the daily steroid dose. None of the patients were taking antihistamines, alpha adrenergic blocking agents, or antieholinergic agents.
Expression
of data
A histamine inhalation unit is arbitrarily defined as one inhalation of 1 mg/ml of histamine base in diluent (normal saline). The cumulative units of histamine required for induction of a positive response was expressed as the PD,,-FEV, to histamine. This value was used as the basis of comparison of the effects of atropine and albuterol on the pulmonary response to histamine. A methacholine inhalation unit is arbitrarily deflned as one inhalation of 1 mg/ml of methacholine in diluent (normal saline). Data were expressed as the PD,,-FEV, to methacholine. The end point for each histamine challenge was considered to be a 20% or greater drop in FEV, from the baseline value, sustained for 10 min. On the atropine and albuterol challenge days, the end point could have been calculated as a 20% or greater drop from the highest FEV, obtained following the bronchodilator aerosol. However, analysis of the results showed the PD,-FEV, to histamine to be the same by either calculation.
Technique-day
1
Baseline determination. The patient was familiarized with the equipment and instructed as to the procedure. Three consecutive baseline determinations of FVC, FEV,, and PF were obtained. The highest FEV, was considered to represent the baseline value. Saline contToZ. Sodium chloride injection, U.S.P., the diluent for the histamine and methacholine, was administered following establishment of baseline pulmonary functions. The patients were given 5 inhalations of saline, after which FEV, was measured. If no drop in FEV, greater than 10% from baseline occurred, the inhalation challenge was performed.
Effect
VOLUME 58 NUMBER 5
TABLE I. PD,,-FEV,
of atropine
and albuterol
aerosols
to histamine Day 1 baseline histamine
Patient
R. M. R. J. D. P.
Day 2 Dostatrorke
II
II
2.05 22.30
EF. . E. M. D. C. R. P. T. F.
9.80
i3 H: ti. A. B. S. Sm. Mean SEM P
:“7 41 31 91 181
Day 3 Dostalbuterol
351
z:
Day 4 repeat histamine
II GO
534
9.80
5;; 95
4GO 9.80 9.80 20 -
5% z.30 2:.50 20 5.54 -
I Wheezed 49 13.70 <0.05
145 95 191 45 <0.005
:i 19 iii
Histamine inhalation challenge. Five breaths of serial dilutions of histamine dihydrochloride (Fisher Chemical Company) were given on successive inhalations to the patient. FESI, was measured immediately. If the test was negative, 5 breaths of the next dilution were given; if the test was borderline, less than 5 breaths of the next dilution were given. Testing was continued until the previously determined end point was reached. Dilutions of histamine used were: 6.03, 0.06, 0.12, 0.25, 1.0, 2.5, 5.0, 10.0, and 25.0 mg/ml. The PD,,-FEV, to histamine was recorded. Isoproterenol aerosol was administered following completion of the histamine challenge.
Technique-day
2
The same criteria for adequate baseline were used. Methaoholine inhakztion &alZenge. Methacholine bromide (Sigma) was prepared in the following concentrations: 0.15, 0.31, 0.62, 1.25, 2.5, 5.0, 10.0, and 25.0 mg/ml. Five breaths of these serial dilutions of methacholine were given to each patient sequentially. Pulmonary function measurements were taken immediately. The end point was considered to be a 20% or greater reduction in FEV, from the baseline value, sustained for 10 min. Administration of methacholine was continued until the end point was reached. The PD,,-FEV, to methacholine was recorded. Administration of r&opine sulfate. Following induction of a 20v0 or greater drop in baseline FEV, by methacholine, the patient was given 5 mg of atropine sulfate by inhalation, and pulmonary function tests were repeated. When maximum bronchodilatation was achieved (usually within 10 min), repeat methacholine challenge was performed as described below. Bepeat methachohe challenge. The patient was given the cumulative amount of methacholine to which he had previously responded. This was administered as a single inhalation challenge. If a 20% drop in FEV, did not occur, the patient was given 2 to 10 times the amount of methacholine to which he had responded previously, again administered as a single inhalation challenge. The FEV, was again measured. If a 20% drop in FEV, did not occur, this indicated adequate vagal blockade by atropine, and the histamine challenge was then performed. Histmine inhalation challenge. The procedure for histamine challenge was as described for day 1. The previously described criteria for establishment of the end point were used. To ensure maintenance of adequate levels of atropine in the lungs, one breath of 1 mg/ml eoncen-
610
Casterline,
J. ALLERGY CLIN. IMMUNOL. NOVEMBER 1976
Evans, and Ward
tration of atropine sulfate (approximately 0.02 mg) was inhaled prior to the administration to histamine was recorded. Isoproterenol aerosol of each dilution of histamine. The PD,,-FEV, was administered following completion of the histamine challenge.
Technique-day
3
The same criteria for adequate baseline were used. Two actuations of albuterol aerosol, 85 mcg/burst, were given prior to histamine inhalation challenge. Pulmonary functions were measured following administration of albuterol. Histamine challenge was then performed using the same technique as described for day 1. The PD,,-FEV, to histamine was recorded. Following the positive response to histamine, again calculated as a 20% or greater drop in FEV, from baseline, either isoproterenol or albuterol was administered to reverse the bronchospasm.
Technique-day
4
The same procedure was used for establishing tion challenge as described for day 1.
a baseline
and performing
histamine
inhala-
RESULTS
Fifty-four bronchial challenges were performed on 14 patients, the results of which are summarized in Table I. Eleven patients completed all four days of the study. Patient V. H. developed a severe headache following histamine inhalation on days 2 and 3, so that day 4 was omitted. Patients C. W. and R. J. could not return for repeat histamine challenge on day 4. Patient S. Sm. had a paradoxical response to atropine resulting in a 50% drop in FEV, from baseline so that day 2 could not be completed. Side effects following atropine administration included dryness of the mouth, nose, and eyes, headache, sore throat, blurred vision, raspy voice, and fatigue. One patient, as mentioned, complained of a severe headache probably induced by histamine. No side effects were reported following administration of methacholine, albuterol, or isoproterenol. The mean PD,,-FEV, to histamine on day 1 was 20 and on day 4 was 19. Individual patients varied no greater than two dilutions in their response to histamine on days 1 and 4. Since identical testing procedures were carried out on these two days, the results indicate good reproducibility of the technique. On day 2, the bronchodilatory effect of aerosolized atropine following methacholine challenge ranged from 0% to 50% increase over baseline FEV,, with an average increase of 10%. Adequate and sustained vagal blockade was achieved in 13 out of the 14 patients. The method used in this report is quite similar to a method previously reported to successfully inhibit the bronchial cholinergic response.z Furthermore, the average amount of time which elapsed from the administration of atropine to completion of the histamine challenge was 30 min. It is unlikely that the effect of the inhaled atropine would have diminished in this short period of time, especially since a large initial dose of atropine (5 mg) was administered. Following atropine administration, the mean PD,,-FEV, to histamine was 49 as compared to the baseline mean of 20. The PD,,-FEV, values before and after atropine were compared for each patient, and a paired Student t test revealed the difference to be significant but minimal (p < 0.05).
VOLUME 5% NUMBER 5
Effect
of atropine
and albuterol
aerosols
5%
On day 3, the administration of albuterol, a specific beta-2 bronchodilator, effected bronchodilatation in all except one patient. The range of percent increase over baseline FEVl was 5% to 26%, with an average of 17%. The amount of bronchodilation observed following the albuterol administration was related to each patient’s initial degree of bronchial tone. The mean I’D,,-FEV1 to histamine following the administration of albuterol was 191, as compared to the baseline mean of 20. The PD,,-FEV1 to histamine before and after albuterol were compared for each patient, and a paired Student t test showed the difference to be highly significant (p < 0,005).
The subject of autonomic control of bronchomotor tone in human subjects has been difficult to analyze quantitatively due to limitations in experimental design. It nevertheless is becoming apparent that understanding the role of the autonomic nervous system in human asthmatics is essential for the advancement of physiologic and pathophysiologic knowledge.3 Animal studies have shown that stimulation of tracheal irritant receptors by histamine phosphate, irritant gases such as ammonia, carbon dust, or other irritant substances results in bronchoconstriction. This response appears to be mediated by the parasympathetic nervous system via the vagus nerve. Blockade of the eholinergic pathway with an anticholinergic agent such as atropine sulfate inhibits the bronchoconstriction response to tracheal irritants.4+’ Whether in fact these data can be applied to humans has been debated, and attempts have been made to clarify this issue.‘3 8 In human asthmatics, atropine sulfate has been shown to be an effective bronehodilator, suggesting that cholinergic presumably vagal, nervous activity eontributes to bronchoconstriction in such patients. g-11 It has been suggested that lung irritant receptors in humans can initiate bronchoeonstriction which is mediated by the vagus nerve.7s 8 Sympathomimetics also affect bronchial smooth m.uscle tone. Adrenergie stimulants such as epinephrine, isoproterenol, and albuterol cause bronchodilatation. Blockade of the sympathetic beta receptors with propranolol causes bronchoconstriction in asthmat.ic patients. ~7 I3 These pharmacologic data suggest that the sympathetic nervous system is operative in maintaining bronchial smooth musele tone, but the extent of its influence is unclear. This study was designed to determine whether histamine-induced bronchoconstriction in human asthmatics is mediated by the parasympathetic nervous system and involves cholinergic receptors. The aerosol route of administration of substances was chosen to allow direct deposition into the tracheobronchial tree, ensuring contact with lung irritant receptors. The procedure recently recommended by the standardization panel of the Asthma and Allergic Disease Centers was used for performance of the histamine and methacholine inhalation ehallenges. The Dosimeter allowed administration of known amounts of these substances. Pulmonary function tests were able to be performed repeatedly a.nd reproducibly by the use of the Donti pulmonary performance analyzer. The metha-
61
Casterline,
Evans, and Ward
J. ALLERGY CLIN. !MMUNOL. NOWMBER 1976
choline challenge followed by reversal with atropine and rechallenge with increased amounts of methacholine was evidence that appropriate doses of atropine had been administered. Finally, each patient served as his own control. The results, as outlined previously, can be interpreted as follows. Histamineinduced bronchoconstriction in human asthmatics is reproducible by this technique. Premeditation with aerosolized atropine sulfate only minimally affected the bronchial response to histamine. Pharmacologic blockade of the methacholine response was evidence that sufficiently large doses of atropine had been administered. These data lend little or no support to the theory that aerosolized histamine acts primarily on the lung irritant receptors to induce cholinergic-mediated bronchoconstriction. The administration of albuterol prior to histamine inhalation challenge markedly shifted the response to histamine. The effect observed was much greater than that which could be demonstrated with atropine. The interpretation of this finding is less certain. Perhaps the decrease in smooth muscle tone was so great that it could only be overcome by large doses of histamine-or possibly the beta receptor stimulation overpowered the weaker vagal influence, b’eing indirect evidence that vagal input is minimal. As previousiy mentioned, inhaIed histamine may act directly on bronchial smooth muscle independent of sympathetic or parasympathetic nervous pathways. The exact nature of histamine receptor sites on bronchial smooth muscle has not been clarified by this study but deserves further investigation. In conclusion, although there was a statistically significant change in mean PD,,-FEV, to histamine following atropine blockade, this effect was small in comparison to that which could be demonstrated with a beta agonist. It thus appears that the major influence of histamine in human asthmatics is not through cholinergic pathways. The authors wish to express their appreciation to Richard Kaplan, M.D., for suggestions on experimental design.
Rosenthal,
M.D.,
and Hyman
REFERENCES 1 Chai, H., Farr, R., Froelich, L., Mathison, D., McLean, J., Rosenthal, R., Sheffer, A., Bpeetor, S., and Townley, R.: Standardization of bronchial inhalation challenge procedures, J. ALLERGY CLIN. IMMUNOL.~~: 323,1975. 2 Rosenthal, R,., Summer, W., Permutt, S., and Norman, P.: Effect of atropine on antigenmediated bronehospasm, J. ALLERGY CLIN. IMMLJXOL. 53: 73, 1974. (Abst.) 3 Widdicombe, J., and Sterling, G.: The autonomic nervous system and breathing, Arch. Intern. Med. 126: 311, 1970. 4 Sellicke, H., and Widdicombe, J. : Stimulation of lung irritant receptors by cigarette smoke, carbon dust, and histamine aerosol, J. Appl. Physiol. 31: 15, 1971. 5 Gold, W., Kessler, G., and Yu, D.: Role of vagus nerves in experimental asthma in allergic dogs, J. Appl. Physiol. 33: 719, 1972. 6 DeKock, M., Nadel, J., Zwi, S., Colebatch, H., and Olsen, C.: New method for perfusing bronchial arteries : Histamine bronchoconstriction and apnea, J. Appl. Physiol. 21: 185, 1966. 7 Simonsson, B., Jacobs, F., and Nadel, J.: Role of autonomic nervous system and the cough reflex in the increased responsiveness of airways in patients with obstructive airway disease, J. Clin. Invest. 46: 1812, 1967. 8 Yu, If., Galant, S., and Gold, W.: Iqhibition of antigen-induced bronehoconstriction by atropine in asthmatic patients, J. Appl. Physiol. 32: 823, 1972.
VOLUME 58 ?dUMBER 5
Effect
of atropine
and albuterol
aerosah
9 Herxheimer, H.: Atropine cigarettes in asthma and emphysema, Br. Med. J. 2: 1.6’7, I959. 10 Cropp, G.: The effectiveness of atropine sulphate aerosol as a bronchodilator in asthmatic children, Fourth Annual Workshop of the Asthma and Allergic Disease Centers, NIH, Bethesda, 1974, National Institutes of Health, p. 166. 11 Cropp, G.: The role of the parasympathetic nervous system in the maintenance of chronic airway obstruction in asthmatic children, Am. R,ev. Respir. Dis., p. 112, 1975. 12 McNeill, R.: Effect of a ,8-adrenergic-blocking agent, propranolol, on asthmatics, Laneet 2: 1191, 1964. 13 Zard, CT., and Beall, G.: Bronchial response to beta-adrenergic blockade, New Engl. .I. Med. 275: 580, 1966.