Bronchoconstrictor Effects of a Deep Inspiration in Patients with Asthma·3
PIERRE GAYRARD, JEAN OREHEK, CHARLES GRIMAUD, and JACQUES CHARPIN
SUMMARY __________________________________________________________ A deep inspiration from functional residual capacity to total lung capacity, performed at a low flow rate by a group of 40 unselected adult patients with asthma, yielded an immediate and transient increase (71 per cent, P < 0.001) in specific airway resistance. In 2 of the 40, deep inspiration provoked an attack of asthma. The effect of deep inspiration can be attributed to a vagal bronchoconstrictor reflex, because it was prevented or decreased in most of the cases by inhalation of an anticholinergic drug. Beta-adrenergic blockade by propranolol potentiated in a minority of subjects the bronchoconstrictor response to deep inspiration. Deep expiration also induced a bronchoconstrictor effect, which was weaker than that of deep inspiration. It follows that fmKtional studies of asthmatics may be biased if the technique requires maximal respiratory maneuvers.
Introduction Active pulmonary inflation Initiates a bronchodilator reflex in experimental animals (1). In normal man this effect is weak (2-4) and is mostly observed after a previous bronchoconstriction has been induced (5). However, a bronchoconstrictor effect was described in patients with asthma performing maximal inspiratory and expiratory maneuvers (4-9). This reaction is held responsible for exercise-induced asthma attacks by some investigators (10-12). Because the number of subjects examined in these studies was small, we have re-examined (Received in original form March 4, 1974 and in revised form December 13, 1974) 1 From the Clinique de Pneumo-Phtisiologie, Faculte de Medicine de Marseille, and Laboratoire d'Exploration Fonctionnelle Respiratoire, H6pital Salvator, Marseille. 2 Supported in part by a grant from the Institut National de Ia Sante et de Ia Recherche Medicale (INSERM). 3 Requests for reprints should be addressed to Dr. P. Gayrard, H6pital Ste-Marguerite, BP 29, 13274 Marseille Cedex 2, France.
the effects of deep inspiration on specific airway resistance (SRaw) to evaluate the frequency of occurrence and magnitude of bronchoconstriction induced by maximal respiratory maneuvers in a larger group of asthmatics. An additional study was undertaken to assess possible influences of the parasympathetic and sympathetic nervous systems. A comparison was also made between the bronchomotor effects of deep inspiration and deep expiration.
Materials and Methods The patients with asthma had a history of spontaneous attacks of dyspnea, with perceptible wheezing, occurring. usually at night. Pulmonary function tests revealed no irreversible airway obstruction. This population (34 men, 6 women; average age ± SD, 33.6 ± 11.4 years) constituted an unselected sample of adult outpatients and inpatients treated for asthma, and includes various degrees of severity of the disease. Patients did not smoke or take medication for at least 18 hours before the examination. The physical, functional, and clinical characteristics of the subjects are listed in "Subjects' Data." Measurements of SRaw were made with a constant-volume body plethysmograph (DR-8 amplifier, Electronics for Medicine, White Plains, New York) using the panting technique (7) at a frequency of
AMERICAN REVIEW OF RESPIRATORY DISEASE, VOLUME Ill, 1975
433
434
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GAYRARD, OREHEK, GRJMAUD, AND CHARPIN
(3) In 14 of the 40 patients the effects of deep inspiration were examined before and after intravenous injection of 0.2 mg of propranolol hydrochloride per kg of body weight (I mg per ml; Avlocardyl®, Laboratories Avlon, Enghien, France). Specific airway resistance was measured before and 10 min after the drug was given. (4) In 12 of the 40 patients the effects of deep expiration were compared to that of deep inspiration . Deep expiration was performed with 2 slow maximal deflations from FRC to residual volume. The data were analyzed as paired observations to minimize differences due to individual variations. Differences of means were considered not significant for P values greater than 5 per cent (P > 0.05).
50
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In all 40 asthmatics studied, deep inspiration
0 10 20 30 40 SRaw (cmH20/L/sec xVtg) before D I
Fig. I. Immediate effects of deep inspiration (DI) on specific airway resistance (SRaw) in patients with asthma (open circles), and one normal subject (X) from reference 4. Individual values. Line of identity (solid line). 2 Hz, a flow rate of I liter per sec (Flei1ch no. 2 pneumotachygraph), and a thoraCic gas volume (Vtg) close to functional residual capacity (FRC), all controlled simultaneously. The control measurement represents an average of 3 to 4 readings. Studies were carried out with 4 protocols. (1) In the 40 patients the effects of deep inspiration were measured immediately after 2 consecutive, slow maximal inflations. The inspiratory flow rate, controlled by the flow signal from the pneumotachygraph, was less than I liter per sec. Each inspiration was started and ended at FRC. The first two SRaw measurements after deep inspiration were computed separately. In 25 of the 40 patients, SRaw measurements were repeated I, 5, and 10 min after deep inspiration. (2) In these 25 patients, the effects of deep inspiration were examined after they had inhaled an anticholinergic drug (N- isopropyl-nortropine- tropate, Sch 1000 metered aerosol, 40 p,g per puff, Boehringer Laboratories, Ingelheim, Germany) with a submaximal inspiration. This maneuver was carefully controlled, i.e., performed after rehearsal and followed by a short pause at end inspiration to promote a maximal particle retention. Doses from 80 to 120 p,g were chosen according to the maximal bronchodilator effect observed in previous experiments in asthmatics (13). Measurements of SRaw were repeated, I, 5, and 10 min after deep inspiration.
produced an instantaneous bronchoconstriction (figure 1). Mean SRaw ± SD (em H 2 0 per liter per sec X Vtg) rose from 12.6 ± 5.8 t~ 21.6 ± ll.8, which is a mean increase of 71 per cent (P < 0.001). The relation between the values of SRaw before and after deep inspiration appears roughly exponential (with large individual variations). After deep inspiration the Vtg (mean ± SD) increased slightly, from 3.247 liters ± 0.683 to 3.475 liters ± 0.739 (P < 0.001). The duration of the effect of deep inspiration is shown in figure 2. Measured in 25 of the 40 patients, the bronchoconstrictor effect was maximal almost immediately, then, for a majority of
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Fig. 2. Effects of deep inspiration (DI) on specific airway resistance (SRaw) in patients with asthma, before (open circles) and after (closed circles) inhalation of an anticholinergic drug, Sch 1,000. Mean values ± I SE.
BRONCHOCONSTRICTOR EFFECTS OF DEEP
I~SPIRATIO~
IN ASTHMATICS
435
TABLE 1 EFFECTS OF DEEP INSPIRATION ON SPECIFIC AIRWAY RESISTANCE (SRaw)* WITHOUT AND WITH AN ANTICHOLINERGIC DRUG (SCH 1000), IN 25 PATIENTS WITH ASTHMA After Deep Inspiration Control Mean SE
11.8 0.9
Mean SE
16.2 1.6
After Sch 1000
First Measurement
Measurement
20.8 2.1 9.7 0.6
7.7 0.4
Second 1 Min
5 Min
10 Min
18.0 1.6
14.6 1.4
13.7 1.1
15.6 1.8
9.2 0.7
8.5 0.6
7.8 0.5
7.5 0.4
*SRaw =em H20 per liter per sec X Vtg.
the patients, decreased rapidly during the first minute (table 1). Two patients exhibited a particularly pronounced bronchoconstrictor effect, which eventually led to an actual attack of asthma, with cough. Of the 25 subjects studied, the anticholinergic drug Sch 1000 (figure 3) decreased in 19, neutralized in 3, and reversed in 2 subjects the immediate bronchoconstrictor effects of deep in~piration. In one subject, who showed a marked bronchoconstrictor effect after deep inspiration, this effect was paradoxically increased by 80 !Lg of Sch 1000 (figure 3, star), then abolished by 160 !Lg. Sch 1000 produced (table 1, figure 2) a significant decrease in SRaw baseline value (-53 per cent, P < 0.001) and a decrease in Vtg (mean ± SD) from 3.170 ± 0.610 liters to 3.030 ± 0.600 liters (P < 0.005). After Sch 1000 the mean effect of deep inspiration was significantly lessened, resulting in a 12 per cent increase in SRaw, instead of the 76 per cent increase shown in the control. The influence of the beta-blocking drug, propranolol, on the bronchial reaction to deep inspiration is shown in table 2. Ten min after injection of propranolol, baseline SRaw was increased on the average by 71 per cent (P < 0.01 ). Mean Vtg was ipcreased insignificantly. Mean (± SD) pulse rate was decreased from 83.2 ± 13.4 beats per min to 69.9 ± 12.2 beats per min (16 per cent, P < 0.001). The immediate bronchoconstrictor effect of deep inspiration was potentiated in only 4 of the 14 subjects examined. There was no significant mean increase in the effect of deep inspiration as compared to the control. The average immediate bronchoconstrictor effect of deep expiration (35 per cent increase in SRaw), which was not significantly weaker than that caused by deep inspiration (52 per cent in-
crease in SRaw), in the 12 patients examined is shown in table 3. After deep expiration the Vtg increased insignificantly. Discussion
An increase in SRaw after deep inspiration was observed in all asthmatics tested. This increase could be attributed to either bronchial or laryngeal contraction. In the present study, the possible influence of the larynx was lessened by the use of the panting technique (14). Also, the
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0 10 20 30 40 SRaw(cm H20/L/sec xVtg) before Dl
Fig. 3. Immediate effects of deep inspiration (DI) on specific airway resistance (SRaw) in patients with asthma, after inhalation of an anticholinergic drug, Sch 1000. Individual values. Line of identity (solid line). Closed circle with star (see text).
436
GAYRARD, OREHEK, GRIMAUD, AND CHARPIN
TABLE 2 EFFECTS OF DEEP INSPIRATION ON SPECIFIC AIRWAY RESISTANCE (SRaw)* WITHOUT AND WITH A BETA-BLOCKING DRUG (PROPRANOLOL), IN 14 PATIENTS WITH ASTHMA After Deep Inspiration Control Mean SE
10.8 1.3
Mean SE
11.1 1.2
After Propranolol
First Measurement
Second Measurement
1 Min
5 Min
10Min
14.3 1.6
13.0 1.2
11.8 1.4
11.7 1.2
11.1 1.2
23.1 4.0
23.3 4.6
21.7 4.4
20.2 3.7
23.3 4.8
19.0 3.1
*SRaw =em H20 per liter per sec X Vtg.
contribution of the upper airways to total airway resistance is decreased in asthma (15). Moreover, the decrease or prevention of the ef. fects of deep inspiration observed after inhalation of a beta-adrenergic drug suggest bronchial rather than laryngeal constriction (unpublished data). Airway caliber is influenced by lung elastic recoil and bronchial smooth muscle tone (3). Thus, the increase in SRaw observed could be attributed to a decrease in lung elastic recoil produced by the inspiratory maneuver. Neither change was described after deep inspiration in healthy subjects at rest (3), or in those submitted to previous bronchoconstriction (5), or in patients with asthma (7, 16). In the same subject, during inflation and deflation, pulmonary resistance was more closely related to lung volume than to elastic recoil pressure, as was observed by Colebatch and associates (16). In our experiment, the actual increase in volume noted after deep inspiration was small. Thus, the largest part of the increase in specific resistance, which is volume related, was due to an increase in the bronchial resistance itself. This change can reasonably be attributed to bronchial smooth muscle contraction. Such an
effect of deep inspiration on the smooth muscle is supported by (J) the rapid increase and disappearance of the airway obstruction observed, as opposed to the loss of elastic recoil described in asthma, which develops slowly and persists for weeks after airway obstruction is relieved (17), and (2) the marked reduction of the response to deep inspiration after bronchodilators. Deep inspiration could modify bronchial smooth muscle tone in various ways. (I) A decrease in carbon dioxide levels could occur (18); however, this possibility is still disputed as a main trigger of exercise-induced asthma (12, 19). In our experiment, the degree of hypocapnia, if any, should have been very small because the subjects performed only 2 deep inspirations and were rebreathing within an airtight box. (2) Pulmonary inflation stimulates vagal sensory receptors. In normal subjects stimulation of the bronchial stretch receptors by deep inspiration (20) initiates a bronchodilator response through inhibition of the vagal bronchoconstrictor tone (2-4). The effect becomes more marked when bronchoconstriction is already present (4, 5). In contrast, stimulation of the irritant receptors leads to a reflex bronchocon-
TABLE 3 COMPARED EFFECTS OF DEEP INSPIRATION AND DEEP EXPIRATION ON SPECIFIC AIRWAY RESISTANCE (SRaw)* IN 12 PATIENTS WITH ASTHMA After Deep Inspiration
Mean SE
Control
First Measurement
Second Measurement
11.2 1.0
17.1 2.0
16.3 2.2
1 Min
5 Min
10 Min
13.1 1.5
13.1 1.3
14.2 1.6
14.5 2.3
13.9 2.6
After Deep Expiration Mean SE
11.5 1.1
15.6 2.5
*SRaw =em H20 per liter per sec X Vtg.
14.3 2.2
15.2 2.9
437
BRONCHOCONSTRICTOR EFFECTS OF DEEP INSPIRATION IN ASTHMATICS
SUBJECTS' DATA
VC Subject No.
Sex
M
4 5 6
M M M M F M
7
F
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
M M M
2
3
33 34 35 36 37 38 39 40
F M M M M M M
F M M M M M
F M M M M M M M M M M M M M F M M
Age (years) 32 48 17 43 42 40 39 29 43 37 46 41 45 60 17 38 45 32 46 24 20 36 28 23 26 20 32
33 23 19 19 47 25 24 16
42 60 25
33 21
Weight (kg) 53 83 49 79 73 63 62 68 54 56 52 54 69 46 50 61 63 53 64
77 46 45 63 47 79 77 59 56 50 52 52 64 58 60 47 107 58
49 67 59
FEVt
Height (em)
(% predicted)
(% predicted)
SeveritY Grade*
169 167 171 174 172 166 160 165 164 169 156 162 174 153 164 168 175 158 168 176 160 166 161 148 174 176 182 170 157 173 173 166 163 171 150 183 155 155 176 170
82 111 97 73 122 97 83 96 95 91 109 107 105 109 101 80 100 85 103 91 103 98 68 95 101 112 81 72 82 82 82 92 111 75 96 100 90 116 90 77
81 100 95 45 109 91 82 89 85 69 100 91 70 72 94 71 82 87 101 70 83 98 55 87 83 93 71 50 32 70 70 59 69 60 81 83 100 124 56 61
2/3 4/Y. 2/3 4/20 3/8 3/Y. 3/14 3/10 2/14 2/3 4/4
1/1 3/20 3/15 3/Y. 3/13 2/8 4/6 3/17 2/16 2/18 3/5 1/3 2/3 4/7 1/9 3/2 4/Jr. 4/14 1/17 1/17 3/6 2/18 3/2 3/15 4/2 4/6 2/2 4/2 2/5
Smoking Habits (g per day) 20 40 13 30
Skin Testst
+ ++ +
ex•• 20 0 40 20 0 0 0
10 ex 10 0 0 0
10 0
10 20 0 0 0 5 0 0 0 0 0
10 0
ex 0
+ + + +
+ ++
+
+ + ++ ++ ++ ++ ++ +
+ + +
+ + + +
+ +
+ ++
0
ex 0
+ +
0 0
•severitY of the disease= Occurrence of attacks of asthma; (4 = 1 per day, 3 = 1 per week, 2 = 1 par month, = less than 2)/Duration in years. tcutaneous reactions: absent(-), present to one(+) or more(++) allergens. • • Ex-smoker.
stnctwn, which is also vagally mediated (20, 21). Pulmonary inflation stretches the bronchial wall that stimulates the irritant receptors (21 ). If, in asthma, the irritant receptors are "hypersensitive" (8), they will be more easily stimulated by a deep inspiration. The subsequent constrictor response would then overcome the dila.tor response arising from the stimulation of the stretch receptors. In this study our finding that the bronchoconstrictor response to deep inspiration was immediate and transient is consistent with a reflex mechanism of action. The efficiency of an anticholinergic drug such as atro-
pine (8, 18) or Sch 1000 in preventing the bronchoconstrictor effects of deep inspiration is in keeping with a reflex effect mediated by vagal pathways. The incomplete blockade of the effects of deep inspiration observed in many cases can be ascribed to the use of an insufficient quantity of drug (8). However, inhibition of the effects of deep inspiration by an anticholinergic agent might be interpreted on a mechanical basis, because it decreased Vtg and produced bronchodilation. The decrease in Vtg observed after the anticholinergic drug, although small, would tend to
438
GAYRARD, OREHEK, GRIMAUD, AND CHARPIN
counterbalance the bronchodilator effect by simultaneously reducing lung elastic recoil (3, 16). In contrast, the decrease in initial airway resistance will lessen the bronchial response to deep inspiration: For a given bronchoconstrictor effect, the lower the initial value of resistance, the smaller the absolute increase in resistance is expected (22, 23). It does not seem likely, however, that this could account for all of the change observed in our study. In one case we observed that the inhibitory effect of the anticholinergic drug was dose related regardless of baseline values. In addition, it is noticeable from the data that the range of initial SRaw from normal up to 15 em H 20 included all the SRaw values after the anticholinergic drug, and that there was no marked bronchosconstriction after deep inspiration, as opposed to the control, within the same range of initial values. In two cases, deep inspiration produced a marked and long-lasting bronchoconstriction, at variance with usual responses. This could be attributed to a positive feed-back mechanism (12, 24) if the initial bronchoconstriction initiated a permanent stimulation of the irritant receptors. (3) Deep inspiration may cause direct bronchial muscle contraction by the release of bronchoconstrictor agents, such as prostaglandin F ~· Berry and associates (25) demonstrated that prostaglandins and other factors are released by distention of the lung. This could account for the unusual responses mentioned above. Again, the anticholinergic drug might either decrease the release of the bronchoactive substance or diminish its effect on the bronchial smooth muscle by inhibiting the bronchomotor tone, because interaction between such mediators and cholinergic mechanisms have been reported (26). The beta-adrenergic blocking drug, propanolol (27), potentiated the bronchoconstrictor effects of deep inspiration in a minority of subjects, despite the increase in resting tone produced by the drug. This is further evidence against the possibility that the observed inhibitory effect of the anticholinergic drug was only due to its influence on initial airway geometry. Whatever the mechanism of action, an over-all antagonistic reaction of the adrenergic system against the bronchial parasympathetic reflex, initiated by deep inspiration, seems unlikely. In this study, deep expiration was less effective in causing a bronchoconstriction in asth-
matics than it was in the study by Simonsson and associates (8). The bronchoconstrictor effects of deep expiration could be related to the expiratory flow rate (11, 28). In the present study, expiratory flow rates lower than those by Simonsson and associates were achieved, which may explain the weaker bronchoconstriction that follows deep expiration in our cases. Previous studies (7, 8) have suggested that bronchoconstriction after deep inspiration may be a common feature of asthma, although the number of asthmatics examined were few. However, Gimeno and associates (9) found a bronchoconstrictor effect of deep inspiration in only I per cent of a large group of patients. Unfortunately, whether the patients tested had chronic bronchitis or asthma was not documented. Also, the spirometric measurements used may not have been sensitive enough to detect small changes. In conclusion, one should consider that methods requiring prior maximal inspiratory maneuvers (e.g., forced expiratory volumes, maximal expiratory flow rates, maximal flow volume cur• es) tend to reduce bronchial patency in patients with asthma. The same maneuver performed by nonasthmatic subjects results in reflex bronchodilation (3), artificially increasing differences between normal and asthmatic subjects (29). Acknowledgment
The writers thank Drs. M. B. Hughes and B. Warfield for help in translating the manuscript. References I. Widdicombe, J. G., and Nadel, J. A.: Reflex effects of lung inflation on tracheal volume, J Appl Physiol, 1963,18,681. 2. Bouhuys, A., and Jonson, B.: Alveolar pressure, airflow rate and lung inflation in man, J Appl Physiol, 1967,22, 1086. 3. Vincent, N.J., Knudson, R., Leith, D. E., Macklem, P. T., and Mead, J.: Factors influencing pulmonary resistance, J Appl Physiol, 1970, 29, 236. 4. Gayrard, P., and Orehek, J.: Effets d'une inspiration forcee sur Ia conductance des voies aeriennes, J Fr Med Chir Thorac, 1972, 26, 193. 5. Nadel, J. A., and •Tierney, D. F.: Effect of a previous deep inspiration on airway resistance in man, J Appl Physiol, 1961,16,717. 6. Herxheimer, H.: Hyperventilation asthma, Lancet, 1946, 1, 83. 7. Butler, J., Caro, C. G., Alcala, R., and Dubois, A. B.: Physiological factors affecting airway resistance in normal subjects and in patients with
"
BRONCHOCONSTRICTOR EFFECTS OF DEEP INSPIRATION IN ASTHMATICS
8.
9.
10. 11.
12.
13.
14.
15.
16.
17.
18.
obstructive respiratory disease, J Clin Invest, 1960, J9, 584. Simonsson, B. G., Jacobs, F. M., and Nadel, J. A.: Role of autonomic nervous system and the cough reflex in the increased responsiveness of airways in patients with obstructive airway disease, J Clin Invest, 1967,48, 1812. Gimeno, F., Berg, W. C., Sluiter, H. J., and Tammeling, G. J.: Spirometry-induced bronchial obstruction, Am Rev Respir Dis, 1972, 105, 68. Rebuck, A. S., and Read, J.: Exercise-induced asthma, Lancet, 1968, 2, 423. Stanescu, D. C., and Teculescu, D. B.: Exercise and cough-induced asthma, Respiration, 1970, 27,377. Simonsson, B. G., Skoogh, B. E., and Ekstrom-Jodal, B. E.: Exercise-induced airways obstruction, Thorax, 1972, 27, 169. Gayrard, P., Orehek, J., and Charpin, J.: Effets bronchodilatatcurs d'un nouvel atropinique de synthese, Sch 1000 aerosol-doseur, dans l'asthme, Rev Fr Mal Respir, 1973,1,481. Stanescu, D. C., Clement, J., Pattijn, J., and Van de Woestijne, K. P.: Glottis opening and airway resistance, J Appl Physiol, 1972, J2, 460. Blide, R. W., Kerr, H. D., and Spicer, W. S.: Measurements of upper and lower airways resistance and conductance in man, J Appl Physiol, 1964,19, 1059. Colebatch, H. J., Finucane, K. E., and Smith, M. M.: Pulmonary conductance and elastic recoil relationships in asthma and emphysema, J Appl Physiol,l973, 34,143. Gold, W. M., Kaufman, M. S., and Nadel, J. A.: Elastic recoil of the lung in chronic asthmatic patients before and after therapy, J Appl Physiol, 1967, 2J, 433. Fisher, H. K., Holton, P., Buxton, R. St. J., and
439
Nadel, J. A.: Resistance to breathing during exercise-induced asthma attacks, Am Rev Respir Dis, 1970,101, 885. 19. Vassallo, C. G., Gee, J. B., and Domm, B. M.: Exercise-induced asthma, Am Rev Respir Dis, 1912,105,42. 20. Paintal, A. S.: Vagal sensory receptors and their reflex effects, Physiol Rev, 1973, 5J, 159. 21. Widdicombe, J. G.: Regulation of tracheobronchial smooth muscle, Physiol Rev, 1963, 4J, 1.
22. Freedman, B. J.: The functional geometry of the bronchi, Bull Physiopathol Respir, (Nancy), 1972, 8, 545. 23. Pride, N. B.: Bronchial sympathetic activity in chronic bronchitis, Clin Sci, 1873,44,517. 24. Mills, J. E., Sellick, M., and Widdicombe, J. G.: Activity of lung irritant receptors in pulmonary micro-embolism, anaphylaxis and drug-induced bronchoconstriction, J Physiol (Lond), 1969, 20J, 337. 25. Berry, E. M., Edwards, J.,F., and Willie, J. M.: Release of PGF 2 and unidentified factors from ventilated lungs, Br J Surg, 1971,58, 189. 26. Douglas, J. S., Dennis, M., Ridgway, P., and Bouhuys, A.: Airway constriction in guinea-pigs: Interaction of histamine and autonomic drugs, J Pharmacal Exp Ther, 1973,184,169. 27. Grieco, M. H., and Pierson, R. N.: Mechanism of bronchoconstriction due to beta-adrenergic blockade, J Allergy Clin Immunol, 1971,48, 143. 28. Koller, E. A.: Atmung und Kreislauf in anaphylactischen Asthma bronchiale des Meersrhweinchens, Helv Physiol Acta, 1967,25,353. 29. Orehek, J., Gayrard, P., Grimaud, C., and Charpin, J.: Effect of maximal respiratory manoeuvres on bronchial sensitivity of asthmatic patients as compared to normal people, Br Med J, 1975,1, 123.
PIERRE GAYRARD, JEAN OREHEK, CHARLES GRIMAUD, and JACQUES CHARPIN
SUMMARY __________________________________________________________ A deep inspiration from functional residual capacity to total lung capacity, performed at a low flow rate by a group of 40 unselected adult patients with asthma, yielded an immediate and transient increase (71 per cent, P < 0.001) in specific airway resistance. In 2 of the 40, deep inspiration provoked an attack of asthma. The effect of deep inspiration can be attributed to a vagal bronchoconstrictor reflex, because it was prevented or decreased in most of the cases by inhalation of an anticholinergic drug. Beta-adrenergic blockade by propranolol potentiated in a minority of subjects the bronchoconstrictor response to deep inspiration. Deep expiration also induced a bronchoconstrictor effect, which was weaker than that of deep inspiration. It follows that fmKtional studies of asthmatics may be biased if the technique requires maximal respiratory maneuvers.
Introduction Active pulmonary inflation Initiates a bronchodilator reflex in experimental animals (1). In normal man this effect is weak (2-4) and is mostly observed after a previous bronchoconstriction has been induced (5). However, a bronchoconstrictor effect was described in patients with asthma performing maximal inspiratory and expiratory maneuvers (4-9). This reaction is held responsible for exercise-induced asthma attacks by some investigators (10-12). Because the number of subjects examined in these studies was small, we have re-examined (Received in original form March 4, 1974 and in revised form December 13, 1974) 1 From the Clinique de Pneumo-Phtisiologie, Faculte de Medicine de Marseille, and Laboratoire d'Exploration Fonctionnelle Respiratoire, H6pital Salvator, Marseille. 2 Supported in part by a grant from the Institut National de Ia Sante et de Ia Recherche Medicale (INSERM). 3 Requests for reprints should be addressed to Dr. P. Gayrard, H6pital Ste-Marguerite, BP 29, 13274 Marseille Cedex 2, France.
the effects of deep inspiration on specific airway resistance (SRaw) to evaluate the frequency of occurrence and magnitude of bronchoconstriction induced by maximal respiratory maneuvers in a larger group of asthmatics. An additional study was undertaken to assess possible influences of the parasympathetic and sympathetic nervous systems. A comparison was also made between the bronchomotor effects of deep inspiration and deep expiration.
Materials and Methods The patients with asthma had a history of spontaneous attacks of dyspnea, with perceptible wheezing, occurring. usually at night. Pulmonary function tests revealed no irreversible airway obstruction. This population (34 men, 6 women; average age ± SD, 33.6 ± 11.4 years) constituted an unselected sample of adult outpatients and inpatients treated for asthma, and includes various degrees of severity of the disease. Patients did not smoke or take medication for at least 18 hours before the examination. The physical, functional, and clinical characteristics of the subjects are listed in "Subjects' Data." Measurements of SRaw were made with a constant-volume body plethysmograph (DR-8 amplifier, Electronics for Medicine, White Plains, New York) using the panting technique (7) at a frequency of
AMERICAN REVIEW OF RESPIRATORY DISEASE, VOLUME Ill, 1975
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GAYRARD, OREHEK, GRJMAUD, AND CHARPIN
(3) In 14 of the 40 patients the effects of deep inspiration were examined before and after intravenous injection of 0.2 mg of propranolol hydrochloride per kg of body weight (I mg per ml; Avlocardyl®, Laboratories Avlon, Enghien, France). Specific airway resistance was measured before and 10 min after the drug was given. (4) In 12 of the 40 patients the effects of deep expiration were compared to that of deep inspiration . Deep expiration was performed with 2 slow maximal deflations from FRC to residual volume. The data were analyzed as paired observations to minimize differences due to individual variations. Differences of means were considered not significant for P values greater than 5 per cent (P > 0.05).
50
X
~
~- 40
..Jo
'~;3o I~
Eo
~
20
Results
10
0
In all 40 asthmatics studied, deep inspiration
0 10 20 30 40 SRaw (cmH20/L/sec xVtg) before D I
Fig. I. Immediate effects of deep inspiration (DI) on specific airway resistance (SRaw) in patients with asthma (open circles), and one normal subject (X) from reference 4. Individual values. Line of identity (solid line). 2 Hz, a flow rate of I liter per sec (Flei1ch no. 2 pneumotachygraph), and a thoraCic gas volume (Vtg) close to functional residual capacity (FRC), all controlled simultaneously. The control measurement represents an average of 3 to 4 readings. Studies were carried out with 4 protocols. (1) In the 40 patients the effects of deep inspiration were measured immediately after 2 consecutive, slow maximal inflations. The inspiratory flow rate, controlled by the flow signal from the pneumotachygraph, was less than I liter per sec. Each inspiration was started and ended at FRC. The first two SRaw measurements after deep inspiration were computed separately. In 25 of the 40 patients, SRaw measurements were repeated I, 5, and 10 min after deep inspiration. (2) In these 25 patients, the effects of deep inspiration were examined after they had inhaled an anticholinergic drug (N- isopropyl-nortropine- tropate, Sch 1000 metered aerosol, 40 p,g per puff, Boehringer Laboratories, Ingelheim, Germany) with a submaximal inspiration. This maneuver was carefully controlled, i.e., performed after rehearsal and followed by a short pause at end inspiration to promote a maximal particle retention. Doses from 80 to 120 p,g were chosen according to the maximal bronchodilator effect observed in previous experiments in asthmatics (13). Measurements of SRaw were repeated, I, 5, and 10 min after deep inspiration.
produced an instantaneous bronchoconstriction (figure 1). Mean SRaw ± SD (em H 2 0 per liter per sec X Vtg) rose from 12.6 ± 5.8 t~ 21.6 ± ll.8, which is a mean increase of 71 per cent (P < 0.001). The relation between the values of SRaw before and after deep inspiration appears roughly exponential (with large individual variations). After deep inspiration the Vtg (mean ± SD) increased slightly, from 3.247 liters ± 0.683 to 3.475 liters ± 0.739 (P < 0.001). The duration of the effect of deep inspiration is shown in figure 2. Measured in 25 of the 40 patients, the bronchoconstrictor effect was maximal almost immediately, then, for a majority of
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0
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20 15
JSch1000
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1o 5
C!)
0
i
Dl
Dl LJ.,..., I
0 1
5
~.
n:25
01 5 Time(min) ~0
I
10
Fig. 2. Effects of deep inspiration (DI) on specific airway resistance (SRaw) in patients with asthma, before (open circles) and after (closed circles) inhalation of an anticholinergic drug, Sch 1,000. Mean values ± I SE.
BRONCHOCONSTRICTOR EFFECTS OF DEEP
I~SPIRATIO~
IN ASTHMATICS
435
TABLE 1 EFFECTS OF DEEP INSPIRATION ON SPECIFIC AIRWAY RESISTANCE (SRaw)* WITHOUT AND WITH AN ANTICHOLINERGIC DRUG (SCH 1000), IN 25 PATIENTS WITH ASTHMA After Deep Inspiration Control Mean SE
11.8 0.9
Mean SE
16.2 1.6
After Sch 1000
First Measurement
Measurement
20.8 2.1 9.7 0.6
7.7 0.4
Second 1 Min
5 Min
10 Min
18.0 1.6
14.6 1.4
13.7 1.1
15.6 1.8
9.2 0.7
8.5 0.6
7.8 0.5
7.5 0.4
*SRaw =em H20 per liter per sec X Vtg.
the patients, decreased rapidly during the first minute (table 1). Two patients exhibited a particularly pronounced bronchoconstrictor effect, which eventually led to an actual attack of asthma, with cough. Of the 25 subjects studied, the anticholinergic drug Sch 1000 (figure 3) decreased in 19, neutralized in 3, and reversed in 2 subjects the immediate bronchoconstrictor effects of deep in~piration. In one subject, who showed a marked bronchoconstrictor effect after deep inspiration, this effect was paradoxically increased by 80 !Lg of Sch 1000 (figure 3, star), then abolished by 160 !Lg. Sch 1000 produced (table 1, figure 2) a significant decrease in SRaw baseline value (-53 per cent, P < 0.001) and a decrease in Vtg (mean ± SD) from 3.170 ± 0.610 liters to 3.030 ± 0.600 liters (P < 0.005). After Sch 1000 the mean effect of deep inspiration was significantly lessened, resulting in a 12 per cent increase in SRaw, instead of the 76 per cent increase shown in the control. The influence of the beta-blocking drug, propranolol, on the bronchial reaction to deep inspiration is shown in table 2. Ten min after injection of propranolol, baseline SRaw was increased on the average by 71 per cent (P < 0.01 ). Mean Vtg was ipcreased insignificantly. Mean (± SD) pulse rate was decreased from 83.2 ± 13.4 beats per min to 69.9 ± 12.2 beats per min (16 per cent, P < 0.001). The immediate bronchoconstrictor effect of deep inspiration was potentiated in only 4 of the 14 subjects examined. There was no significant mean increase in the effect of deep inspiration as compared to the control. The average immediate bronchoconstrictor effect of deep expiration (35 per cent increase in SRaw), which was not significantly weaker than that caused by deep inspiration (52 per cent in-
crease in SRaw), in the 12 patients examined is shown in table 3. After deep expiration the Vtg increased insignificantly. Discussion
An increase in SRaw after deep inspiration was observed in all asthmatics tested. This increase could be attributed to either bronchial or laryngeal contraction. In the present study, the possible influence of the larynx was lessened by the use of the panting technique (14). Also, the
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0 10 20 30 40 SRaw(cm H20/L/sec xVtg) before Dl
Fig. 3. Immediate effects of deep inspiration (DI) on specific airway resistance (SRaw) in patients with asthma, after inhalation of an anticholinergic drug, Sch 1000. Individual values. Line of identity (solid line). Closed circle with star (see text).
436
GAYRARD, OREHEK, GRIMAUD, AND CHARPIN
TABLE 2 EFFECTS OF DEEP INSPIRATION ON SPECIFIC AIRWAY RESISTANCE (SRaw)* WITHOUT AND WITH A BETA-BLOCKING DRUG (PROPRANOLOL), IN 14 PATIENTS WITH ASTHMA After Deep Inspiration Control Mean SE
10.8 1.3
Mean SE
11.1 1.2
After Propranolol
First Measurement
Second Measurement
1 Min
5 Min
10Min
14.3 1.6
13.0 1.2
11.8 1.4
11.7 1.2
11.1 1.2
23.1 4.0
23.3 4.6
21.7 4.4
20.2 3.7
23.3 4.8
19.0 3.1
*SRaw =em H20 per liter per sec X Vtg.
contribution of the upper airways to total airway resistance is decreased in asthma (15). Moreover, the decrease or prevention of the ef. fects of deep inspiration observed after inhalation of a beta-adrenergic drug suggest bronchial rather than laryngeal constriction (unpublished data). Airway caliber is influenced by lung elastic recoil and bronchial smooth muscle tone (3). Thus, the increase in SRaw observed could be attributed to a decrease in lung elastic recoil produced by the inspiratory maneuver. Neither change was described after deep inspiration in healthy subjects at rest (3), or in those submitted to previous bronchoconstriction (5), or in patients with asthma (7, 16). In the same subject, during inflation and deflation, pulmonary resistance was more closely related to lung volume than to elastic recoil pressure, as was observed by Colebatch and associates (16). In our experiment, the actual increase in volume noted after deep inspiration was small. Thus, the largest part of the increase in specific resistance, which is volume related, was due to an increase in the bronchial resistance itself. This change can reasonably be attributed to bronchial smooth muscle contraction. Such an
effect of deep inspiration on the smooth muscle is supported by (J) the rapid increase and disappearance of the airway obstruction observed, as opposed to the loss of elastic recoil described in asthma, which develops slowly and persists for weeks after airway obstruction is relieved (17), and (2) the marked reduction of the response to deep inspiration after bronchodilators. Deep inspiration could modify bronchial smooth muscle tone in various ways. (I) A decrease in carbon dioxide levels could occur (18); however, this possibility is still disputed as a main trigger of exercise-induced asthma (12, 19). In our experiment, the degree of hypocapnia, if any, should have been very small because the subjects performed only 2 deep inspirations and were rebreathing within an airtight box. (2) Pulmonary inflation stimulates vagal sensory receptors. In normal subjects stimulation of the bronchial stretch receptors by deep inspiration (20) initiates a bronchodilator response through inhibition of the vagal bronchoconstrictor tone (2-4). The effect becomes more marked when bronchoconstriction is already present (4, 5). In contrast, stimulation of the irritant receptors leads to a reflex bronchocon-
TABLE 3 COMPARED EFFECTS OF DEEP INSPIRATION AND DEEP EXPIRATION ON SPECIFIC AIRWAY RESISTANCE (SRaw)* IN 12 PATIENTS WITH ASTHMA After Deep Inspiration
Mean SE
Control
First Measurement
Second Measurement
11.2 1.0
17.1 2.0
16.3 2.2
1 Min
5 Min
10 Min
13.1 1.5
13.1 1.3
14.2 1.6
14.5 2.3
13.9 2.6
After Deep Expiration Mean SE
11.5 1.1
15.6 2.5
*SRaw =em H20 per liter per sec X Vtg.
14.3 2.2
15.2 2.9
437
BRONCHOCONSTRICTOR EFFECTS OF DEEP INSPIRATION IN ASTHMATICS
SUBJECTS' DATA
VC Subject No.
Sex
M
4 5 6
M M M M F M
7
F
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
M M M
2
3
33 34 35 36 37 38 39 40
F M M M M M M
F M M M M M
F M M M M M M M M M M M M M F M M
Age (years) 32 48 17 43 42 40 39 29 43 37 46 41 45 60 17 38 45 32 46 24 20 36 28 23 26 20 32
33 23 19 19 47 25 24 16
42 60 25
33 21
Weight (kg) 53 83 49 79 73 63 62 68 54 56 52 54 69 46 50 61 63 53 64
77 46 45 63 47 79 77 59 56 50 52 52 64 58 60 47 107 58
49 67 59
FEVt
Height (em)
(% predicted)
(% predicted)
SeveritY Grade*
169 167 171 174 172 166 160 165 164 169 156 162 174 153 164 168 175 158 168 176 160 166 161 148 174 176 182 170 157 173 173 166 163 171 150 183 155 155 176 170
82 111 97 73 122 97 83 96 95 91 109 107 105 109 101 80 100 85 103 91 103 98 68 95 101 112 81 72 82 82 82 92 111 75 96 100 90 116 90 77
81 100 95 45 109 91 82 89 85 69 100 91 70 72 94 71 82 87 101 70 83 98 55 87 83 93 71 50 32 70 70 59 69 60 81 83 100 124 56 61
2/3 4/Y. 2/3 4/20 3/8 3/Y. 3/14 3/10 2/14 2/3 4/4
1/1 3/20 3/15 3/Y. 3/13 2/8 4/6 3/17 2/16 2/18 3/5 1/3 2/3 4/7 1/9 3/2 4/Jr. 4/14 1/17 1/17 3/6 2/18 3/2 3/15 4/2 4/6 2/2 4/2 2/5
Smoking Habits (g per day) 20 40 13 30
Skin Testst
+ ++ +
ex•• 20 0 40 20 0 0 0
10 ex 10 0 0 0
10 0
10 20 0 0 0 5 0 0 0 0 0
10 0
ex 0
+ + + +
+ ++
+
+ + ++ ++ ++ ++ ++ +
+ + +
+ + + +
+ +
+ ++
0
ex 0
+ +
0 0
•severitY of the disease= Occurrence of attacks of asthma; (4 = 1 per day, 3 = 1 per week, 2 = 1 par month, = less than 2)/Duration in years. tcutaneous reactions: absent(-), present to one(+) or more(++) allergens. • • Ex-smoker.
stnctwn, which is also vagally mediated (20, 21). Pulmonary inflation stretches the bronchial wall that stimulates the irritant receptors (21 ). If, in asthma, the irritant receptors are "hypersensitive" (8), they will be more easily stimulated by a deep inspiration. The subsequent constrictor response would then overcome the dila.tor response arising from the stimulation of the stretch receptors. In this study our finding that the bronchoconstrictor response to deep inspiration was immediate and transient is consistent with a reflex mechanism of action. The efficiency of an anticholinergic drug such as atro-
pine (8, 18) or Sch 1000 in preventing the bronchoconstrictor effects of deep inspiration is in keeping with a reflex effect mediated by vagal pathways. The incomplete blockade of the effects of deep inspiration observed in many cases can be ascribed to the use of an insufficient quantity of drug (8). However, inhibition of the effects of deep inspiration by an anticholinergic agent might be interpreted on a mechanical basis, because it decreased Vtg and produced bronchodilation. The decrease in Vtg observed after the anticholinergic drug, although small, would tend to
438
GAYRARD, OREHEK, GRIMAUD, AND CHARPIN
counterbalance the bronchodilator effect by simultaneously reducing lung elastic recoil (3, 16). In contrast, the decrease in initial airway resistance will lessen the bronchial response to deep inspiration: For a given bronchoconstrictor effect, the lower the initial value of resistance, the smaller the absolute increase in resistance is expected (22, 23). It does not seem likely, however, that this could account for all of the change observed in our study. In one case we observed that the inhibitory effect of the anticholinergic drug was dose related regardless of baseline values. In addition, it is noticeable from the data that the range of initial SRaw from normal up to 15 em H 20 included all the SRaw values after the anticholinergic drug, and that there was no marked bronchosconstriction after deep inspiration, as opposed to the control, within the same range of initial values. In two cases, deep inspiration produced a marked and long-lasting bronchoconstriction, at variance with usual responses. This could be attributed to a positive feed-back mechanism (12, 24) if the initial bronchoconstriction initiated a permanent stimulation of the irritant receptors. (3) Deep inspiration may cause direct bronchial muscle contraction by the release of bronchoconstrictor agents, such as prostaglandin F ~· Berry and associates (25) demonstrated that prostaglandins and other factors are released by distention of the lung. This could account for the unusual responses mentioned above. Again, the anticholinergic drug might either decrease the release of the bronchoactive substance or diminish its effect on the bronchial smooth muscle by inhibiting the bronchomotor tone, because interaction between such mediators and cholinergic mechanisms have been reported (26). The beta-adrenergic blocking drug, propanolol (27), potentiated the bronchoconstrictor effects of deep inspiration in a minority of subjects, despite the increase in resting tone produced by the drug. This is further evidence against the possibility that the observed inhibitory effect of the anticholinergic drug was only due to its influence on initial airway geometry. Whatever the mechanism of action, an over-all antagonistic reaction of the adrenergic system against the bronchial parasympathetic reflex, initiated by deep inspiration, seems unlikely. In this study, deep expiration was less effective in causing a bronchoconstriction in asth-
matics than it was in the study by Simonsson and associates (8). The bronchoconstrictor effects of deep expiration could be related to the expiratory flow rate (11, 28). In the present study, expiratory flow rates lower than those by Simonsson and associates were achieved, which may explain the weaker bronchoconstriction that follows deep expiration in our cases. Previous studies (7, 8) have suggested that bronchoconstriction after deep inspiration may be a common feature of asthma, although the number of asthmatics examined were few. However, Gimeno and associates (9) found a bronchoconstrictor effect of deep inspiration in only I per cent of a large group of patients. Unfortunately, whether the patients tested had chronic bronchitis or asthma was not documented. Also, the spirometric measurements used may not have been sensitive enough to detect small changes. In conclusion, one should consider that methods requiring prior maximal inspiratory maneuvers (e.g., forced expiratory volumes, maximal expiratory flow rates, maximal flow volume cur• es) tend to reduce bronchial patency in patients with asthma. The same maneuver performed by nonasthmatic subjects results in reflex bronchodilation (3), artificially increasing differences between normal and asthmatic subjects (29). Acknowledgment
The writers thank Drs. M. B. Hughes and B. Warfield for help in translating the manuscript. References I. Widdicombe, J. G., and Nadel, J. A.: Reflex effects of lung inflation on tracheal volume, J Appl Physiol, 1963,18,681. 2. Bouhuys, A., and Jonson, B.: Alveolar pressure, airflow rate and lung inflation in man, J Appl Physiol, 1967,22, 1086. 3. Vincent, N.J., Knudson, R., Leith, D. E., Macklem, P. T., and Mead, J.: Factors influencing pulmonary resistance, J Appl Physiol, 1970, 29, 236. 4. Gayrard, P., and Orehek, J.: Effets d'une inspiration forcee sur Ia conductance des voies aeriennes, J Fr Med Chir Thorac, 1972, 26, 193. 5. Nadel, J. A., and •Tierney, D. F.: Effect of a previous deep inspiration on airway resistance in man, J Appl Physiol, 1961,16,717. 6. Herxheimer, H.: Hyperventilation asthma, Lancet, 1946, 1, 83. 7. Butler, J., Caro, C. G., Alcala, R., and Dubois, A. B.: Physiological factors affecting airway resistance in normal subjects and in patients with
"
BRONCHOCONSTRICTOR EFFECTS OF DEEP INSPIRATION IN ASTHMATICS
8.
9.
10. 11.
12.
13.
14.
15.
16.
17.
18.
obstructive respiratory disease, J Clin Invest, 1960, J9, 584. Simonsson, B. G., Jacobs, F. M., and Nadel, J. A.: Role of autonomic nervous system and the cough reflex in the increased responsiveness of airways in patients with obstructive airway disease, J Clin Invest, 1967,48, 1812. Gimeno, F., Berg, W. C., Sluiter, H. J., and Tammeling, G. J.: Spirometry-induced bronchial obstruction, Am Rev Respir Dis, 1972, 105, 68. Rebuck, A. S., and Read, J.: Exercise-induced asthma, Lancet, 1968, 2, 423. Stanescu, D. C., and Teculescu, D. B.: Exercise and cough-induced asthma, Respiration, 1970, 27,377. Simonsson, B. G., Skoogh, B. E., and Ekstrom-Jodal, B. E.: Exercise-induced airways obstruction, Thorax, 1972, 27, 169. Gayrard, P., Orehek, J., and Charpin, J.: Effets bronchodilatatcurs d'un nouvel atropinique de synthese, Sch 1000 aerosol-doseur, dans l'asthme, Rev Fr Mal Respir, 1973,1,481. Stanescu, D. C., Clement, J., Pattijn, J., and Van de Woestijne, K. P.: Glottis opening and airway resistance, J Appl Physiol, 1972, J2, 460. Blide, R. W., Kerr, H. D., and Spicer, W. S.: Measurements of upper and lower airways resistance and conductance in man, J Appl Physiol, 1964,19, 1059. Colebatch, H. J., Finucane, K. E., and Smith, M. M.: Pulmonary conductance and elastic recoil relationships in asthma and emphysema, J Appl Physiol,l973, 34,143. Gold, W. M., Kaufman, M. S., and Nadel, J. A.: Elastic recoil of the lung in chronic asthmatic patients before and after therapy, J Appl Physiol, 1967, 2J, 433. Fisher, H. K., Holton, P., Buxton, R. St. J., and
439
Nadel, J. A.: Resistance to breathing during exercise-induced asthma attacks, Am Rev Respir Dis, 1970,101, 885. 19. Vassallo, C. G., Gee, J. B., and Domm, B. M.: Exercise-induced asthma, Am Rev Respir Dis, 1912,105,42. 20. Paintal, A. S.: Vagal sensory receptors and their reflex effects, Physiol Rev, 1973, 5J, 159. 21. Widdicombe, J. G.: Regulation of tracheobronchial smooth muscle, Physiol Rev, 1963, 4J, 1.
22. Freedman, B. J.: The functional geometry of the bronchi, Bull Physiopathol Respir, (Nancy), 1972, 8, 545. 23. Pride, N. B.: Bronchial sympathetic activity in chronic bronchitis, Clin Sci, 1873,44,517. 24. Mills, J. E., Sellick, M., and Widdicombe, J. G.: Activity of lung irritant receptors in pulmonary micro-embolism, anaphylaxis and drug-induced bronchoconstriction, J Physiol (Lond), 1969, 20J, 337. 25. Berry, E. M., Edwards, J.,F., and Willie, J. M.: Release of PGF 2 and unidentified factors from ventilated lungs, Br J Surg, 1971,58, 189. 26. Douglas, J. S., Dennis, M., Ridgway, P., and Bouhuys, A.: Airway constriction in guinea-pigs: Interaction of histamine and autonomic drugs, J Pharmacal Exp Ther, 1973,184,169. 27. Grieco, M. H., and Pierson, R. N.: Mechanism of bronchoconstriction due to beta-adrenergic blockade, J Allergy Clin Immunol, 1971,48, 143. 28. Koller, E. A.: Atmung und Kreislauf in anaphylactischen Asthma bronchiale des Meersrhweinchens, Helv Physiol Acta, 1967,25,353. 29. Orehek, J., Gayrard, P., Grimaud, C., and Charpin, J.: Effect of maximal respiratory manoeuvres on bronchial sensitivity of asthmatic patients as compared to normal people, Br Med J, 1975,1, 123.
