Mediastinal emphysema and pneumothorax following tracheotomy for croup

MEDIASTINAL

EMPHYSEMA AND PNEUMOTHORAX

FOLLOWING

TRACHEOTOMY

FOR CROUP*

J. D. GOLDBERG, M.D., First Lieutenant,

N.

MedicaI Corps, U. S. Army

MITCHELL,

Resident in Pathology,

M.D.

Queens General Hospital

AND

A. PathoIogist, JAMAICA,

ANGRIST, LONG

INTRODUCTION

EDIASTINAL emphysema and pneumothorax have been considered rare complications foIlowing tracheotomy in croup cases. In a series at the Queens Genera1 HospitaI, both comphcations have been seen frequently. Many of the patients with comphcations present few or no symptoms and probabIy wouId have remained unrecognized without routine postoperative x-rays. Some, however, are fohowed by the we11 known respiratory and cardiovascuIar repercussions of pneumothorax, with an occasiona fata outcome. The route of entry of air into the mediastinum and pIeura1 cavities has been the subject of much debate. An evaIuation of a11possibIe mechanisms and the demonstration of the most frequent pathway in this group of cases wiII be attempted.

M

LITERATURE

MicheIs5 has reviewed the Iiterature recentIy, so that onIy a few references wiII be cited. Champney’ performed tracheotomies on stihborn infants and then subjected them to artificia1 respiration with the tracheotomy opening partiahy obstructed. He noted that mediastina1 emphysema occurred in a11 cases, and pneumothorax was Iisted as a frequent finding. Kies2 cited one case of massive mediastina1 emphysema with biIatera1 pneumothorax, foIIowing thyroidectomy. He injected air into the mediastinum through the sternum or juguIar notch in two cadavers, and noted the deveIopment of mediastina1 emphysema * From the Departments

of Pathology

M.D.

Queens General Hospital ISLAND,

N.

Y.

foIIowed by pneumothorax. MackIin3 produced mediastina1 emphysema in cats by overinffation of their Iungs under high pressures. He concluded that the air ruptured through the aIveoIar waII and dissected back to the mediastinum by way of the perivascuIar Iymphatics. Further injection of air Ied to rupture through the mediastina1 pIeura, with the production of pneumothorax, often biIatera1. The viscera1 pIeura consistentIy remained intact. He found it impossibIe to produce mediastina1 emphysema by the injection of air directIy into the pIeura1 cavity, even though extremeIy high pressures were used. Simpson4 reported a case of pneumothorax foIIowing tracheotomy and referred to the rarity of such a compIication. MicheIs5 added six case reports. He discussed possibIe mechanisms for the production of pneumothorax and suggested bronchoscopy prior to tracheotomy as a means of prevention. Barrie6 described four fata cases of pneumothorax fohowing operations on the neck. Three foIIowed thyroidectomy, and the fourth, tracheotomy for gIottic edema. AI1 were associated with mediastina1 emphysema. He postmated the route of entry of the air to be through the operative wound into the mediastinum, thence into the pIeura1 cavities. He demonstrated an intact cervica1 pIeura1 dome in each instance by methyIene bIue instaIIation into the pIeura1 sac. ANATOMY

The accompanying diagrams schematicaIIy a11 possibIe routes

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entr ‘ante of the air into the mediastinum and pIeura1 cavities invoIved in cases of obst ructive breathing. (Figs. I and 2.)

FIG.

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showed only limited mediastinal and no pneumothorax. (Fig. 3.) CASE

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FIG. I. Cervical fascia, demonstrating pathway of extension of air from neck into mediastinum. (Modified after Davis, Applied Anatomy, Figure 180.) A, Hyoid bone; B, thyroid cartilage; c, superficia1 Ieaflet of deep cervica1 fascia; D, deep Ieaffet of deep cervical fascia; E, cricoid cartilage; F, tracheotomy site; G, thyroid gland; H, space of burns; I, anterior mediastinum. ------SuperficiaI IeaAet of deep cervical fascia. PretracheaI (deep) leaflet of cervical fascia. FIG. z. PossibIe pathways of extension of air into pleura1 cavities and mediastinum. A, injury to apica pteura; B, rupture of alveolus with extension to mediastinum and rupture of mediastinal pleura; c, rupture of visceral pleura; D, extension of air through tracheotomy wound between superficia1 and deep Ieaffets of deep cervica1 fascia into mediastinum with rupture of mediastina1 pleura (usual mechanism). - + - +ParietaI pleura. -. -. -Visceral pIeura. - 0 - 0 - Mediastinal pIeura.

The variations in the route of entry of air, and in the symptomatoIogy are iIIustrated by the foIIowing case histories: CASE I. ,kfediastinal emphysema causing D. G., a two-year oId white no symptoms:

femaIe, was admitted on March 4, 1940, with a twelve-hour history of respiratory diffrcuhy foIlowing an upper respiratory infection of seven days’ duration. Examination reveaIed a restIess, paIe chiId, breathing with inspiratory stridor. ModerateIy deep supracIavicuIar and sterna1 retractions were present. On Iaryngoscopy, a marked supragIottic edema was evident. Immediate tracheotomy was performed with instantaneous and permanent relief. Check-up x-ray on March 6, rgbo

J. W., a fifteenmonth oId white maIe, was admitted on with miIdIy obstructive 3, 1940, January respiration. A diagnosis of croup was made and conservative therapy instituted. By the next day, the respiratory diffrcuIty had increased. Laryngoscopic examination reveaIed subgIottic edema, and intubation was done with marked reIief. On January IO, 1940, extubation Ied to immediate recurrence of Because the patient repeatedIy symptoms. coughed up the tube, a tracheotomy was done on January 12, 1940. The patient remained comfortabIe after that procedure. Chest x-ray taken on January I 3, 1940 revealed mediastinal on emphysema, 70 per cent pneumothorax the right, and minima1 pneumothorax on tht mothorax causing no symptoms:

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Ieft. A repeat x-ray on January 29, Ig4o showed compIete absorption of air from the mediastinum andno evidence of pneumothorax.

FIG. 3. Case

I. X-ray taken two days after tracheotomy showing air Iimited to mediastinum (a). Lateral view shows simiIar substernal Iocalization of air.

CASE III. Pneumotborax following injury to cervical pleura, causing respiratory distress, but not requiring intervention: P. D., a fourteen-

month oId white femaIe, was admitted on March I 8, I 940 with a twenty-four hour history of progressive respiratory diffIcuIty and a croupy cough. TriaI intubation gave no reIief. The child’s condition grew worse rapidly, with increasing cyanosis and dyspnea. A Iong meta suction tube was passed through the Iarynx to provide an airway and an emergency tracheotomy was done. During the procedure, the pIeura was seen to buIge high into the wound and the right pleura1 dome was injured, producing an audibIe hiss. The operative procedure was compIeted without further examination or repair of the pleura. Physica1 examination immediateIy postoperativeIy showed signs of a partia1 pneumothorax on the right. The chiId was perfectIy comfortabIe at this time. By the next day the respirations had risen from thirty to eighty per minute. X-ray at this juncture reveaIed 80 per cent pneumothorax on the right. No mediastinal empbysema was present. The chiId improved rapidIy and made an uneventfu1 recovery. CASE IV. Mediastinal empbysema and pneumotborax requiring intervention: C. J., a threemonth oId white femaIe, was admitted on December 12, 1940, with right otorrhea and a

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retropharyngea1 sweIIing. Despite chemotherapy, the swelling progressed to such an extent by the next day, that the chiId showed obvious

FIG. 4. Case IV. X-ray taken immediateIy preoperatively showing absence of air in mediastinum or pleura1 cavities.

respiratory distress. The sweIIing was incised but no pus was encountered. FoIIowing this, the obstruction to breathing progressed so rapidIy that an emergency tracheotomy was necessary five hours later. (Fig. 4.) After exposure of the fascia1 pIanes of the neck, a technica d&c&y caused considerable delay before incision into the trachea. During this interva1, air couId be heard being aspirated tbrougb the wound edges by the forcefu1 inspirations of the infant. Immediate reIief was apparent on compIetion of the tracheotomy. Two hours postoperativeIy, it was noted that the chiId was becoming increasingIy more dyspneic. The respirations were definiteIy not of the obstructive type. Physical examination suggested biIatera1 pneumothorax. A pecuIiar crepitant sound was heard over the sternum, synchronous with each heart beat. An emergency x-ray (Fig. 5) reveaIed biIatera1 pneumothorax, aImost compIete on the Ieft, and moderate mediastina1 emphysema. Immediate partia1 relief was seen after the remova of 50 cc. of air under positive pressure from the left chest. Four hours Iater, it was necessary to again tap the Ieft chest, with remova of about 60 cc. of air. On this occasion, the air was under negative pressure, and aspiration by syringe was necessary. Improvement thereafter was rapid. X-ray two weeks later reveaIed

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onIy a slight degree of mediastina1 emphysema and no pneumothorax. CASE v. hfediastinal emphysema and pneu-

Frc. +. Case 1~. X-rav taken two hours after tracheotomy sho&g bilateral pneumothorax (h) and mediastinal emphysema (a 1, the latter confirmed by IateraI view.

mothoras with f’atal termination: A. K., a fouryear old white female, was admitted at I A.M. on March 5, 1940 with a twenty-four hour history of a croupy cough and dyspnea. The patient was severely iI1, presenting marked cyanosis and deep supracIavicuIar and sternal retractions. Direct laryngoscopy reveaIed marked edema and redness of the larynx. Intubation was performed with onIy slight relief, so that tracheotomy was resorted to at noon. Immediate temporary improvement followed, but cyanosis and dyspnea soon recurred and rapidIy grew worse. At 2 P.M. the patient was bronchoscoped through the tracheotomy wound. No relief from this procedure was evident. Chest x-rays taken at 3~30 P.M. revealed 60 per cent coIlapse of the right side and 70 per cent of the left, with “pancaking of the lung.” SIight improvement was noted after aspiration of 250 cc. of air under positive pressure from the right pIeural cavity, and 75 cc. from the left. One hour later, ZOO cc. was aspirated from the right side and continuous decompression was started by connecting the needle with a rubber tubing pIaced under water. escaped from the No air, however, tuljing. The chiId died during this procedure. Postmortem examination reveaIed an extensive mediastina1 emphysema and a right tension pneumothorax. AIthough air under

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positive pressure was not found in the lett pIeura1 cavity, a partiaI coIIapse of the Ieft Iung is correIated with the x-ray findings of left

FIG. 6. X-rav taken several hours after tracheotomy. showing massive mediastina1 emphysema with considerable quantity of air following contour ot mediastinum (a).

pneumothorax. The usual method of demonstrating pneumothorax at autopsy by opening into the pIeural cavity under water and watching for the escape of air, wil1 demonstrate only positive tension pneumothoraces. A negative tension pneumothorax may exist as in Case IV, because of the shift of a IabiIe mediastinum. CASE VI. Mediastinal emphysema in a case of trauma demonstrating the pathway oj air try way of tbe cervical fascia: C. H., a twenty-year old white maIe, was injured whiIe riding on a motorcycle. He was brought to the hospital in a comatose state. Respirations were rapid and labored. MuItipIe fractures of the bones of the face were observed. There was a large perforation through the buccal mucosa in the floor of the mouth near the frenuIum. No other Iacerations in the skin of the neck were present. Death occurred two hours after admission. Autopsy discIosed marked mediastinal emphysema. Pneumothorax was not demonstrated. No rib fractures were present. Definite air bubbIes were found beneath the superficial Ieaffet of the deep cervical fascia. The air had evidentIy been aspirated through the Iaceratecl bucca1 mucosa. From this source, the air could dissect beneath the superficial IeatIet of the deep cervica1 fascia oniy if a fracture of the hyoid bone were present. On this basis, the neck organs were investigated, and muItiple

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fractures through the body and greater cornua of the hyoid bone were found. It is our impression that this confirms the essential mechanism by which mediastina1 emphysema and pneumothorax are produced following tracheotomy for croup. COMMENT

Pneumothorax can be produced by any of the mechanisms indicated in Figure I. In Case III, the air obviousIy entered the pIeural cavity through a traumatic perforation of the apica pIeura incurred at the (Route A.) In the time of operation. described instance, it must be remembered that the pneumothorax was uniIatera1 and that there was no mediastina1 emphysema. MediastinaI emphysema was demonstrated by routine postoperative x-rays on tweIve occasions in a series of eighteen tracheotomies on patients with croup. The observations extended over a period from November, 1939, to January, 1941. There were eight cases of pneumothorax, three of which were biIatera1. In all cases in wbicb there was pneumothorax, there was a coexistent mediastinal emphysema. The onIy exception is represented by Case III, in which the apica pIeura was injured. If trauma to the apica pIeura were the usua1 mechanism for the production of the coincidenta mediaspneumothorax, tina emphysema found in such cases wouId remain unexplained. To expIain the high incidence of biIatera1 pneumothorax, one wouId have to postuIate further that both pIeura1 domes were injured. It is more reasonabIe to assume that the association of mediastina1 emphysema and pneumothorax is more than coincidenta1. The frequent occurrence of mediastina1 emphysema without pneumothorax, and the rarity of pneumothorax without mediastina emphysema, strongIy suggests that the presence of air in the mediastinum is essentia1 for the production of pneumothorax. Weight to this supposition is added by MackIin’s work showing that it was impossibIe for air under positive pressure to penetrate the mediastinum from the pIeura1

cavity, but that the opposite route was quite feasibIe experimentaIIy. How then does the air reach the mediastinum? If it were by rupture of an aIveoIus (Route B), with escape of air aIong the peribronchia1 and perivascuIar Iymphatics incident to the high negative pressures deveIoped during obstructive breathing, mediastina1 emphysema shouId be more common before tracheotomy. If rupture of the aIveoIus occurred during the sudden inrush of air foIIowing reIief of the obstruction, mediastina1 emphysema shouId be as common following intubation as it is foIIowing tracheotomy. X-rays before tracheotomy faiIed to revea1 mediastina1 emphysema or pneumothorax. This negative finding wouId seem to make the rupture of an aIveoIus a Iess IikeIy mechanism. If rupture of the viscera1 pIeura (Route C) were the cause of pneumothorax, the co-existence of mediastina1 emphysema wouId stiI1 remain unexpIained. The anaIysis outIined above, eIiminating aIveoIar rupture, appIies as we11 to rupture of the viscera1 pIeura as the usua1 mechanism. With these cIinica1 data. in mind, the foIIowing experiments were undertaken to demonstrate the probabIe route of entry of air into the mediastinum and pIeura1 cavities. EXPERIMENTAL

DATA

Nine cadavers ranging in age from a stiIIbirth of six months’ gestation to a one-year oId infant were empIoyed. AI1 procedures were performed with the cadaver under water, so that any Ieakage of air was instantIy demonstrated. incision Experiment A. A IongitudinaI was made through the skin from the symphysis mentis to the upper abdomen and the skin reflected IateraIIy. The subcutaneous fat and muscIes were removed with the skin Aap over the thorax. The Costa1 cartiIages were divided cIose to the sternum and the ribs retracted so as to visuaIize the mediastina1 structures. The fascia1 pIanes of the neck were then identified by sharp dissection. A No. 20 needIe

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was inserted beneath the superficia1 Ieaffet of the deep cervica1 fascia. Air was injected under positive pressure. The pressure was measured by a mercury manometer connected with the needIe through a side-arm. Results. Injection of air under pressures of 13 to 20 mm. of mercury beneath the superficia1 Ieaflet of the deep cervica1 fascia resuIted in a dissection of the air down along the fascia1 pIanes into the anterior mediastinum. Large emphysematous bIebs formed in the mediastina1 tissues under direct observation. After injection of 20 to 50 cc. of air, no more air couId enter the mediastinum unIess the pressure was raised considerabIy. At a pressure of approximateIy 40 mm. of mercury there was a rapid faII to zero. Observation of the mediastinum invariabIy reveaIed a simuItaneous rupture of an emphysematous bIeb into the pIeural cavity. The usua1 site was at the Ieft inferoIatera1 border of the thymus gland. More air couId now be injected readily at much lower pressures, ranging from 0 to $ mm. of mercury. It is significant that a sIight change in the position of the cadaver was sufficient to cIose off this origina rupture site. Whenever this occurred, the positive pressure rose to 40 mm. of mercury again, before another site of rupture couId be seen. The new site was frequentIy on the opposite side of the mediastinum. In no case couId air be identified beneath the endothoracic fascia. Roth Iungs were reExperiment B. moved with a bIock of mediastina1 tissue. Air was injected into both main bronchi under pressure. Results. Injection of air into the main bronchus resuIted in inflation of the Iung until no more air couId be accommodated without a rise in pressure. In some cases, smal1 bubbIes of air couId be seen in the subpIeura1 Iymphatics, demonstrating a possibIe mechanism for extension to the mediastinum. The pressure then rose rapidly to IeveIs of 65 to 70 mm. of mercury, at which point rupture occurred, usuaIIy through the mediastina1 pIeura at the hiIum.

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OccasionaIIy, a point of rupture was identified in the viscera1 pIeura. Usually, IocaI pathoIogica1 conditions such as pneumonitis couId then be demonstrated. COMMENT

It is true that the experimenta conditions of forcing air into the mediastinum under positive pressures are not duplicated exactIy in a case of croup. However, an equivaIent situation does exist. During the powerfur inspiratory movements of croup, high negative intrathoracic pressures are deveIoped, and serve to draw air into the Iungs through the partiaIIy obstructed natura1 airway. With incision of the cervica1 fascia incident to tracheotomy, an initia1 pathway is estabIished for aspiration of air through the wound edges into the mediastinum. On forced expiration, positive pressures are deveIoped within the chest. The superior aperture to the mediastinum, which is widest during inspiration, is now at its narrowest diameter and tends to trap the mediastinal air. The positive pressure then forces the trapped air further down aIong the tissue pIanes. When appropriate pressure IeveIs are reached for each individua1 case, rupture through the mediastina1 pIeura into the reIat&eIy unsupported pIeura1 space occurs, with the production of pneumothorax. (Route D.) Rupture may occur on one side onIy. Now if this first route is temporariIy obstructed by change in position of the patient, corresponding to the experimental observations, a new point of rupture may appear on the same or opposite side. Once this jstulous tract is established, which must happen while the patient is struggIing for air, the usua1 intrathoracic pressures during ordinary unobstructed breathing wiI1 suffice to aspirate additional air into the pleural cavity. This accounts for the progression of the pneumothorax after the tracheotomy is completed. Thus, the usua1 Iatent period of one or more hours before the appearance of cyanosis and marked dyspnea is not surprising.

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The measures for the prevention of mediastina1 emphysema and pneumothorax are apparent, if the mechanism discussed above hoIds true. If the obstruction to breathing can be reIieved by passage of a Mosher tube, or preferabIy a bronchoscope, as first suggested by Michels, the patient’s respirations immediateIy become Iess labored. The high negative pressures essentia1 for the production of mediastinal emphysema can no Ionger occur. However, if such prophyIactic procedures are not feasibIe, it is advisabIe to reduce to a minimum, the interva1 between the division of the cervica1 fascia and the insertion of the tracheotomy tube. The treatment of the compIications of tracheotomy in patients with croup Iimits itseIf to the treatment of pneumothorax. In our experience, mediastina1 emphysema of itseIf, has never caused symptoms severe enough to warrant intervention. Absorption of air in these instances occurs spontaneousIy over a period of days or weeks. In those cases of pneumothorax in which respiratory distress is a prominent feature, simpIe aspiration of air is usuaIIy sufficient to give reIief. When the pneumothorax quickIy reforms, continuous decompression by connecting the needIe to a tube placed under water may be attempted. It must be remembered, however, that onIy air from positive tension pneumothorac& wiI1 be removed by this means. If the pneumothorax is under negative pressure,

as in Case withdrawn.

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the air must then be activeIy SUMMARY

I. Routine postoperative x-rays foIIowing tracheotomy showed mediastina1 emphysema in tweIve of eighteen cases. In eight, pneumothorax was aIso present. 2. The route of entry of air into the mediastinum and pIeura1 cavities is discussed and the most frequent mechanism is indicated. 3. The means of prevention of the compIications of mediastina1 emphysema and pneumothorax are presented.

The authors express gratefu1 appreciation to Dr. Henry Reisman for use of the cIinica1 materia1 and to Dr. Richard Grimes for permission to incIude the report of Case VI. REFERENCES I. CHAMPNEYS, F.

H. Experimental Researches in Artificial Respiration in StiIIborn ChiIdren, and Allied Subjects. Vol. VIII, p. 153, London, 1887. H. K. Lewis. z. KIES, J. Studien zur Genese d. MediastinaIemphysema u. d. Pneumothorax bei Kropfoperationen. Miincben. med. Wcbnscbr., 81: 66g, 1934. 3. MACKLIN, C. C. Pneumothorax with massive colIapse from overinffation of Iung. Canad. M. A. J., 36: 414, 1937. 4. SIMPSON, W. L. Pneumothorax

compIicating tracheotomy in ftdminating Iaryngotracheobronchitis. Arch. Otolaryngol., 26: 41 I, 1937. 5. MICHELS, M. W. Pneumothorax and mediastina1 emphysema complicating tracheotomy. Arch. Otokz~yngol., 29: 842, 1936 6. BARRIE, H. J. InterstitiaI emphysema and pneumothorax after operation on the neck. Lancer, I: 996

1940.