Re,s/)irari~~rl Physiology (1975) 25, l-7;

THE EFFECT

Publishing Company, Amsterdam

North-Holland

OF ANAPHYLACTIC SHOCK IN RABBITS

MAtGORZATA

ON LARYNGEAL

SZEREDA-PRZESTASZEWSKA

Laboratory of Neurophysiology, Polish Academy of Scierlces Medical Research 00-784 Warsaw, Poland

Laryngeal

Abstract.

groups

with superior

laryngeal

In the intact anaphylactic

animals

constriction

even more pronounced lessened

resistance

of spontaneously

to airflow

breathing

CALIBRE

has

rabbits:

been

measured

(1) intact,

during

Centre,

anaphylactic

(2) vagotomized

and

Dworkowa 3,

shock

in three

(3) vagotomized

and

nerves cut. anaphylaxis

elicited

of the larynx

in the vagotomized

the size of the increase

animals.

in laryngeal

Afferent laryngeal

increases

resistance.

The

on reflexes from the lungs as the responses

were

Cutting

expiratory

denervation

Anaphylaxis Laryngeal

large

did not depend

in expiratory

the superior

laryngeal

laryngeal

nerves with vagotomy

resistance.

Laryngeal

resistance

Larynx constriction

Vagotomy

Detailed descriptions of anaphylactic shock in the rabbit emphasize the respiratory deterioration: “The manner of the death, too, with gasping, convulsive attempts at respiration suggests strongly that it is of a suffocative character” (Scott, 1911). Although the main shock organ in this species is the smooth muscle of the pulmonary artery and its branches (Doerr, 1950; Melli et al., 1963), respiratory failure and several other responses including bronchoconstriction have been studied (Troquet, 1964; Carillo and Aviado, 1968; Colinet-Lagneaux et al., 1969; Karczewski and Widdicombe, 1969; Szereda-Przestaszewska, 1973). The part of the increase in total airway resistance contributed by the lower airways in anaphylactic shock is important. However, in view of Scott’s (1911) description of the rabbit’s death in the course of anaphylactic shock, the contribution of an increase in laryngeal resistance should be taken into account. There is some indirect information on this since, in anaphylaxis in rabbits, there is increased activity of both inspiratory and expiratory laryngeal motor fibres (Szereda-Przestaszewska, 1971). These observations have been extended by measuring the mechanical changes in Accepted for publication 2 May 1975.

2

M. SZEREDA-PRZESTASZEWSKA

laryngeal resistance to airflow in rabbits undergoing anaphylactic shock. A preliminary summary ofsome ofthe results has been published (Szereda-Przestaszewska, 1974). Methods Twenty-one adult male rabbits weighing 2.6-3.6 kg were anaesthetized with urethanechloralose (0.8 g/kg+35 mg/kg of body weight i.v. and i.m.); they breathed spontaneously through a cannula inserted into the lower cervical trachea. The upper part of the trachea was cannulated rostrally for measurement of translaryngeal pressure. The recurrent laryngeal nerves were spared. A large right suprahyoid pharyngotomy was performed and the epiglottis was pulled ventrally with a suture. A stream of humidified warm air was passed through the upper cannula and the larynx at a constant flow rate (usually 2 I/min) continuously measured by a rotameter. Inflow (translaryngeal) pressure was recorded by means of a differential capacitance manometer (Hilger I.R.D. Ltd.), and its ratio to laryngeal airflow was regarded as an index of laryngeal resistance. Blood pressure was recorded from a catheter in the right femoral artery by a strain gauge transducer (type S.E. 4-82. S.E. Laboratories) and carrier amplifier (type 3C 66, Tektronix). The electrical activity of the C3 root of the right phrenic nerve was amplified (Tektronix 3A 3 amplifier) and ‘integrated’ with a diode-pump and smoothing circuit (Huszczuk, 1971). End-tidal CO, “ii, was measured using a rapid infra-red absorption meter (Godart capnograph KK), although rapid breathing patterns often prevented accurate measurements. All the variables were displayed on an oscilloscope (Tektronix 565) and photographed. TABLE Laryngeal Control

resistance

values

Vagi

and respiratory Expiratory

S.L.N.

1 rate changes

laryngeal

due to anaphylaxis

resistance

Breathing

(cm HZO~l~‘.sec~‘)

(breaths/min)

frequency

N ~___~~

intact

intact

7

20.9 k 5.86

31.2k4.2

cut cut

intact cut

7 7

29.0+ 9.3 13.9i 2.9

23.7 + 2.63 28.2 + 3.15

intact intact

7 I

+297.1

f 106.3*

+ 352.4

?c 126.0*

cut

7

+ 208.55 + 59.2X**

Anaphylaxis intact cut cut Values

are means

mean change

and standard

compared

errors,

+ 36.

N gives number

with zero effect by Student’s

t test,

I _+6.39*

+2.1 +2.25 +4.04+ 1.32** of experiments.

* P i 0.05. ** P < 0.01 for

CONTROL

OF LARYNGEAL

3

CALIBRE

To abolish lung vagal reflexes, leaving laryngeal motor innervation intact, in 14 of the 21 rabbits bilateral intrathoracic vagotomy was performed in the chest just below the origins of the recurrent laryngeal nerves. For this purpose the chest was opened on both sides, then subsequently closed and spontaneous breathing restored. In 7 of the vagotomized rabbits the superior laryngeal nerves were also cut to abolish the main afferent innervation of the larynx. Rabbits were sensitized with three intraperitoneal injections of 0.2 ml of 2% aqueous egg albumen solution, and anaphylactic shock was induced after 3 weeks with an intravenous injection of 0.5 ml of the antigen solution. Changes in laryngeal resistance and breathing frequency are expressed as comparisons of control values with the peak maximum responses, usually about 0.5-3 min after the challenging injection of antigen. All results are given as means and S.E. Results

Control values for laryngeal expiratory resistance are given in table 1. In the ‘intact’ rabbits expiratory laryngeal resistance was 20.9 f. 5.86 cm H,O . l- ’ . set- 1; this is higher than previously published control values for rabbits, possibly because airflow was greater and the pressure-flow relationship of the larynx is alinear (Stransky er ul., 1973). The control value for respiratory rate was 37.2k4.2 breaths/min. Injection of the antigen into a sensitized animal caused an increase in breathing frequency ( + 36.1 k 6.39 breaths/min) and a drop in blood pressure. There was a simultaneous increase in laryngeal resistance (+297.1+ 106.3 cm H,O. 1-l .sec-i) in all the rabbits. The increases in laryngeal resistance were observed throughout the expiratory phase of the respiratory cycle. Inspiratory laryngeal resistance also usually increased, but to a more variable and smaller degree (fig. 1). The increase in breathing frequency seemed to be associated with a decrease in endtidal COZ (Karczewski and Widdicombe, 1969; Szereda-Przestaszewska, 1973)

B

Fig. 1. Changes

in laryngeal

B, 30 set after injection end-tidal

resistance

of the antigen.

CO2 and increase integrated

in anaphylactic Note increase

in expiratory phrenic

laryngeal

nerve, end-tidal

shock

in the ‘intact’

in breathing resistance. CO,

frequency, From

rabbit.

top to bottom:

and translaryngeal

A, control

fall in blood pressure.

record;

pressure

blood

and

pressure,

4

M. SZEREDA-PRZESTASZEWSKA

although rapid breathing patterns often made accurate measurement impossible. There was an increase in the frequency of phrenic discharge, shown by the steeper slope of the integrated phrenic nerve activity.

Fig. 2. Changes record;

in laryngeal

resistance

B, 1 min 30 set after

no change

in blood

pressure,

in anaphylactic

injection drop

of the antigen,

shock

in the vagotomized

Note

slight

in end-tidal CO2 and increase Traces as for fig. 1.

increase

rabbit.

A, control

in breathing

frequency,

in expiratory

laryngeal

resistance.

Vagotomized rabbits had higher control values for laryngeal expiratory resistance (29.0 19.3 cm H,O l- 1. see- ‘) and lower for respiratory frequency (23.7 & 2.63 breaths/min). Anaphylactic shock caused variable changes in breathing frequency with an insignificant mean change ( + 2.1 f 2.25 breaths/min). Expiratory laryngeal resistance increased even more than in the intact animals (+352.4&- 126.0 cm HzO. l- l. xx-‘). Ho.wever, in this group of animals the increases in expiratory laryngeal resistance were larger at the beginning of the expiratory phase and then decreased towards the end of the phase (fig. 2). A decrease in end-tidal CO, and an

B.P 100 h-rmHgl o* A

Int. Flmmic

_

% co2

100 B

0 5

15

0

0

(1 rsec

Fig. 3. Changes superior breathing

in laryngeal

laryngeal frequency,

nerves.

resistance

A, control

in anaphylactic

record;

fall in blood pressure

shock

in the vagotomized

B, 45 set after injection

and end-tidal

CO,,

increase

of the antigen, in laryngeal

rabbit Note

expiratory

with increase

cut in

resistance.

CONTROL

OF LARYNGEAL

CALIBRE

5

increase in integrated phrenic slope were also observed; blood pressure changes were variable (fig. 2). Vagotomized rabbits with cut superior laryngeal nerves showed lower control values of the expiratory laryngeal resistance (13.9 + 2.9 cm H,O l- ’ . set- ‘) and of breathing frequency (28.2+ 3.75 breaths/min) than the intact rabbits. Anaphylaxis increased the expiratory laryngeal resistance in these animals ( + 208.55& 59.28 cm H,O . l- ’ *set- ‘) but had little action on respiratory rate ( + 4.04 + 1.32 breaths/min). The other variables changed in the same way as in the vagotomized group (fig. 3). Discussion

In eupnoeic breathing in the anaesthetized rabbit laryngeal calibre varies, showing dilatation in inspiration and constriction in expiration. This is usually only apparent in translaryngeal pressure records with high amplifier gain (Stransky et al., 1973) and therefore is not seen in the control records of figs. 1 and 3. During anaphylactic tachypnoea laryngeal expiratory resistance increases. Constrictions of the laryngeal lumen have been described in other types of tachypnoea such as those induced by phenyl diguanide, histamine or pneumothorax. However, these, unlike that due to anaphylaxis, were lessened or abolished by bilateral intrathoracic vagotomy (Stransky et al., 1973; Dixon et al., 1974). Vagal denervation of the lungs lessened the increase in respiratory rate due to anaphylaxis in rabbits (Dziewanowska and Szereda-Przestaszewska, 1973); but the laryngeal expiratory responses were even more pronounced, although the mean increase was not statistically significant compared to the changes in the intact animals (P > 0.05). These results are consistent with recordings from laryngeal motor nerve libres in anaphylactic rabbits; the increase in motor nerve activity was not abolished by cervical bilateral vagotomy (Szereda-Przestaszewska, 197 1). Although lung anaphylaxis stimulates lung irritant receptors which can cause tachypnoea and expiratory laryngeal constrictions (Mills et al., 1969) in the experiments described here any pulmonary reflex laryngoconstriction must have been outweighed by constriction mediated otherwise. The main afferent innervation of the larynx is via the superior laryngeal nerves (Suzuki and Kirchner, 1968; Murakami and Kirchner, 1971). Rabbits which had undergone bilateral intrathoracic vagotomy and cutting of the superior laryngeal nerves showed the smallest increases in expiratory laryngeal resistance on anaphylaxis. The size of the mean change compared with that for vagotomized animals is not, however, statistically significant (P > 0.05). Possibly abolition of the main afferent pathway from the laryngeal mucosa cuts off a source of information from laryngeal tissues undergoing the anaphylactic process. Afferent stimuli from the laryngeal mucosa can constrict the larynx (Szereda-Przestaszewska and Widdicombe, 1973). Electrical stimulation of the internal branch of the superior laryngeal nerve inhibits abductor and excites adductor motor libre activity (Suzuki and Kirchner, 1969; Sherrey and Megirian, 1974). It also provokes short-latency discharges in the recurrent laryngeal nerve but inhibits on-going inspiratory activity in the phrenic nerve and in the external intercostal muscles (Larrabee and Hodes, 1948; Irani et al., 1972).

6

M. SZEREDA-PRZESTASZEWSKA

It should also be remembered that cutting the superior laryngeal nerves denervates the crico-thyroid muscle (which is an adductor) which could decrease tension in the vocal folds, and change quantitatively the laryngeal constrictor responses in anaphylaxis. The origin of the laryngeal constriction in rabbits after vagotomy and section of the superior laryngeal nerves is not known. It could be situated in the central nervous system, since coagulation of the hypothalamus can depress anaphylactic reactions in guinea-pigs by stimulating the release of adrenocortical hormones and depressing thyroid activity (Fillip, 1973; Fillip and Mess. 1969a,b). Acknowledgements It is with great pleasure that I express my thanks to Prof. W. Karczewski for his advice and guidance. I am particularly grateful to Prof. J. Widdicombe for most helpful discussion and encouragement. The untiring and highly competent technical assistance of Mrs. Elzbieta Jedrychowska is gratefully acknowledged.

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au tours

du choc