Spontaneous Expulsion of Foreign Body Bronchus: Understanding the Mechanism

Abstract

Foreign Body (FB) aspiration pose a challenge to the otolaryngologist of its early diagnosis along with safe removal. Almost all airway foreign bodies require bronchoscopy and removal. Very rarely, spontaneous expulsion of bronchial FB may happen. We are reporting one such case of spontaneous expulsion of a metallic FB from right main bronchus in a fourteen-year-old boy. The mainstay of treatment for FB bronchus is bronchoscopic removal. Spontaneous expulsion occurs very rarely & may be associated with life threatening complications. Impaction of FB in sub glottis may lead to sudden choking & death. In this report we also have tried to provide insight into the physics and physiological mechanism facilitating spontaneous expulsion of a bronchial foreign body.

Introduction

Foreign Body (FB) aspiration commonly occurs in children. It may present with life threatening emergency, requiring urgent intervention. Usually there is a history of foreign body aspiration or of initial choking episode followed by cough, difficulty in breathing due to partial or total blockage of the airway. On examination of the chest there can be added sounds along with diminished air entry, which can probably guides to the side of lodgment. This typical presentation can only be seen in few patients, while sometimes it can be symptomless and can be missed. Most frequently aspirated foreign bodies are food items or their parts or non-organic objects like parts of toys, pebbles, plastic piece, coins or organic like plants, bones, nuts and seeds. Metallic FB which are sharp pose a danger of perforation and can cause complication. Rigid bronchoscopy and removal of foreign body is the standard of care for these cases with spontaneous expulsion reported in fortunate few.

Case Report

A fourteen-year-old boy was brought to the emergency department with the complaints of accidental aspiration of a metallic FB, screw. He presented with throat pain and cough while swallowing. Examination of chest revealed slightly decreased air entry on right side of the chest. On X-ray chest, a metallic FB (screw) was noted in the right bronchus (Fig. 1). Rigid bronchoscopy and FB removal were planned and patient was kept on broad spectrum antibiotics along with steroids. While preparing the patient for bronchoscopy, patient had a sudden bout of cough and he expectorated the metallic FB screw spontaneously (Fig. 2). On auscultation of the chest, right side air entry had improved post expulsion. A repeat chest x-ray confirmed the expulsion of the foreign body (Fig. 3) with an overall improvement of symptoms.

Fig. 1.

Chest radiograph with foreign body (metallic screw) in right main bronchus

Fig. 2.

Expectorated foreign body (metallic screw)

Fig. 3.

Chest radiograph following expectoration of foreign body

Discussion

Foreign body inhalation or aspiration in the airway is a common ENT emergency, with high morbidity and mortality if not managed early and appropriately.

In 1921, Jackson suggested that spontaneous expulsion of intrapulmonary FB occurs so rarely that removal should be performed early to avoid subsequent complication [1].

The length of trachea is 10–11 cm and its external diameter is 2 cm in males and 1.5 cm in females. The right main bronchus is about 5 cm in length and aligned more vertically as compared to the left. The diameter of right main bronchus is about 1.7 cm in men and 1.5 cm in women [2]. It is aligned at an angulation of 25–30 degrees with respect to trachea.

When a FB enters the lower airway, it usually follows a more vertical and the gravity gradient course. Hence it would more commonly get lodged in the right main bronchus which is relatively straighter, wider, shorter and is closer to trachea, as compared to the left main bronchus. Rarer instances of lodgment of FB in left bronchus can be explained by Bernoulli’s effect. Due to smaller diameter of left main bronchus as compared to right, more negative suction pressure is attained during coughing, laughing or speaking leading to aspiration of foreign body to left side [3].

Protective airway defense mechanisms, like cough that expels the FB which comes in contact with the respiratory mucosa. Another mechanism is at the level of the larynx which protects the lower airway by sphincteric closure of laryngeal inlet, false cord and true cord, thus making it difficult for FB to be inhaled [4].

Expulsion or expectoration is an act of coughing out the foreign body or material from the airway. Cough is mediated via a reflex arc made of sensory receptors which are myelinated, rapidly adapting receptors, located in carina, trachea, and large bronchi. They are stimulated by mechanical or chemical irritants in response to obstruction, through substance like histamine, substance P,capsaicin and bradykinin. Mechanical laryngeal stimulation initiates vigorous expiratory efforts to prevent aspiration. Stimulation distal to larynx generates inspiratory phase to produce airflow necessary to remove the stimulus [5].

The cough reflex has three phases: 1. Inspiratory phase, 2. Compressive phase, 3. Expiratory phase. In Inspiratory phase large amount of air is inhaled to attain adequate volume to produce cough. Inhaling large volumes of air also causes greater lengthening of expiratory muscles to generate positive intrathoracic pressure [6].

In Compressive phase glottis closes for 0.2 s and vocal cords adduct tightly to entrap the air in the lungs. Glottic closure helps in maintaining the lung volume as intrathoracic pressure builds up by forceful contraction of abdominal muscles and expiratory muscles. It generates a positive pressure which may be as high as 300 mmHg [3].

In Expiratory phase, the vocal cords abduct and glottis opens up, promoting high expiratory flow rates of 75 to 100miles/hrs. Initially there is a short blast of turbulent flow lasting for 0.3–0.5 s. Here the flow rates may be 12L/s [6]with maximum velocity up to500mph and intrathoracic energy 25 J [7]. This blast of air is because of release of compressed air from distal airways as well as central airway due to high intrathoracic pressure [6]. This rapidly moving airstream carries with it any foreign matter which is present in the airway.

There exists a relationship between expiratory flow and airstream velocity which depends on cross sectional area (Velocity = flow/ cross sectional area). So, as the cross-sectional area decreases the velocity increases. Velocity of air is more in central airway which is further enhanced by dynamic compression of these airway. As the kinetic energy of airstream is proportional to the square of the velocity of airstream (Energy = Mass × Volume²), this degree of dynamic compression also increases the kinetic energy which in turn may enhance the spontaneous expulsion [6].

In our case, the metallic FB screw was lodged in right bronchus. To reduce infection and inflammation patient was on antibiotics and steroids. As the oedema reduced, the presence of FB acted as an irritant stimulus initiating severe bout of cough strong enough to cause the expulsion of FB from the bronchus.

Airway FB should be removed once the diagnosis is made by bronchoscopy. Spontaneous expulsion of airway FB may increase the chances of its lodgment in sub glottis as it is the narrowest part of the upper airway in children. This can impose a life-threatening emergency during forceful expulsion [8]. Hence a watchful eye must be kept for forceful bout of cough while preparing the patient for bronchoscopic removal.

The standard treatment for airway foreign body is rigid bronchoscopic removal. Spontaneous expulsion of FB bronchus is rare. Though it saves the patient from an invasive procedure (bronchoscopy) and its potential complications but it also poses a real risk of lodgment of the foreign body in the sub glottis and sudden respiratory arrest.

Funding

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Declarations

Conflict of interest

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Human and Animal Rights

This research does not involve human participants and/or animals.

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