Respiratory Airway Infections Infections
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RESPIRATORY AIRWAY INFECTIONS

General Goal: To know the cause(s) of these diseases, the most common modes of transmission, and the major manifestations of these diseases.

Specific Educational Objectives: The student should be able to:

1. recite the common cause(s), the common means of transmission, and identify the major disease manifestations.

2. determine based on clinical manifestations if a patient has one of these diseases as well as determine which disease they have acquired.

3. explain what is in the vaccines and why it is important to give the vaccines to people.

4. explain the 4 D's of epiglottitis. Know how to obtain the "thumb" and "steeple" signs and know what diseases these signs are present in.

5. describe how to avoid getting the various diseases if any prevention means are possible.

Reading:

Lecture: Dr. Neal R. Chamberlain

References:
Childhood vaccination schedule: http://www.immunize.org/cdc/schedules/

I. Croup (Epiglottitis, Laryngitis and Laryngotracheobronchitis)

Overview

The respiratory airways discussed in this section of the handout include the airways from the epiglottis to the bronchioles. The infections discussed are croup (which includes acute laryngitis, laryngotracheobronchitis, and epiglottitis), acute bronchitis, bronchiolitis, influenza, and pertussis (Figure AI-1). All of the diseases discussed in this chapter, with the exception of epiglottitis and pertussis, are usually caused by viruses; epiglottitis and pertussis are caused by bacteria.

CROUP

Acute laryngitis, laryngotracheobronchitis (viral croup), and epiglottitis (bacterial croup) are acute inflammatory diseases, collectively called croup, and involve the upper airways. The most common and most serious risk of this group of diseases is obstruction of the airway. This risk is particularly important to remember when treating very young children because the airways of young child are narrower than the airways of older children and adults.

Etiology

Parainfluenza virus type I is the most common cause of viral croup (Table AI-1 for a list of other causes of viral croup and laryngitis).

Table AI-1. Other Causes of Viral Croup
Viruses	Parainfluenza virus type II, influenza virus types A and B, adenovirus, respiratory syncytial virus, herpes simplex virus, rhinovirus, coxsackievirus A and B, echovirus

Haemophilus influenzae type b is the most common cause of epiglottitis (bacterial croup; S pyogenes is second) (see Table AI-2 for a list of other causes of epiglottitis).

Table AI-2. Other Causes of Epiglottitis
Bacteria	Streptococcus groups A, B, and C , Nontypeable Haemophilus influenzae, Streptococcus pneumoniae, Klebsiella pneumoniae, Staphylococcus aureus, Haemophilus parainfluenza, Neisseria meningitidis
Viruses	Varicella zoster virus
Fungi	Candida albicans

Manifestations

Acute laryngitis

Acute laryngitis usually begins as an upper respiratory infection, followed by dysphonia (hoarseness) and reduced vocal pitch or aphonia. Other symptoms may include odynophonia (pain when speaking), dysphagia (difficulty swallowing), odynophagia (pain when swallowing), sore throat, congestion, fatigue, and malaise. Direct examination reveals diffuse laryngeal erythema and edema and vascular engorgement of the vocal folds.

Viral croup

Patients with viral croup or laryngotracheobronchitis have a fever (38–39°C), which is higher than occurs in laryngitis, restlessness and air hunger, which is more severe than occurs in laryngitis. Croup begins with a prodromal mild upper respiratory infection with coryza, nasal congestion, sore throat, and cough that lasts 2–3 days; this is followed by hoarseness and a harsh, brassy, “bark-like” cough. Respiratory stridor usually occurs at night, often awakening the child from sleep.

Physical examination of the patient with croup may reveal minimal distress to severe respiratory failure due to airway obstruction. In mild cases, the results of the lung examination at rest usually are normal; however, mild expiratory wheezing may he heard during auscultation. Children with severe croup have primarily inspiratory stridor at rest with nasal flaring and suprasternal and intercostal retractions. Lethargy or agitation may be a result of hypoxemia. Other warning signs of severe respiratory disease are tachypnea, tachycardia out of proportion to the presence of fever, lethargy, pallor, and hypotonia (decreased muscle tone). The child may be unable to maintain adequate oral intake and may become dehydrated. Cyanosis is a late and ominous sign. Croup symptoms usually peak over 3–5 days and resolve within 4–7 days.

Epiglottitis

Epiglottitis is a medical emergency and risk of mortality is extremely high. Signs and symptoms include acute onset and fever, sore throat, and hoarseness. There is retraction of the suprasternal notch and stridor with every breath. The throat is inflamed, and the epiglottis is swollen, stiff, and a beefy red color. The disease can progress rapidly resulting in toxicity, prostration, severe dyspnea, and cyanosis. The physician should be watchful for dysphagia, dysphonia, drooling, and distress—the four D’s.

Epidemiology

Person-to-person contact is the usual means of spread of all types of croup.

Viral croup and acute laryngitis

Young children are most susceptible to viral croup, which typically occurs in children 6 months to 3 years of age, with the mean age being 18 months. Boys are more likely to develop croup than are girls.
Viral croup has an annual peak incidence during the second year of life of 50 new cases per 1000 children. The incidence of viral croup decreases dramatically by 6 years of age.
Viral croup occurs in late fall and early winter. The recurrence rate is 5%.
Outcomes of viral croup depend of how ill the patient is, the age of the patient, and the adequacy of the treatment. Complications in severe cases include crusty exudates resulting in obstruction of the airways, segmental atelectasis, pneumothorax, obstructive mediastinal emphysema, and bronchopneumonia.
Parainfluenza infections can cause viral croup anytime during the year. Influenza virus and respiratory syncytial virus infections tend to occur more frequently during the winter and early spring.
Acute laryngitis usually occurs in persons aged 18–40 years of age. Although children are less likely to contract acute laryngitis, they can acquire the disease and are usually 3 years of age or older.
Acute laryngitis is usually a mild self-limiting disease lasting 7–10 days.

Epiglottitis

The Haemophilus influenzae type b (Hib) vaccine has significantly reduced the incidence of the disease from 10.9 per 10,000 to 0.63 cases per 100,000.
H influenzae type b is still the most common cause of epiglottitis. This is believed to be due to the lack of vaccination or vaccine failure.
The median age of patients with epiglottitis has increased from 35 months of age to 80 months of age. Prior to 1994, the disease was usually seen in children 2–7 years of age.
The prevalence of epiglottitis in adults now surpasses the prevalence in children, which is due to the success of Hib vaccination of children.
The morbidity and mortality of epiglottitis can be very high, with bacteremia often resulting in meningitis, septic arthritis, or osteomyelitis.

Pathogenesis

Children have narrower airways than adults, which results in an increased number of complications associated with viral croup and epiglottitis.

Viral infection of the upper airways causes inflammation and edema of the larynx in acute laryngitis, and viral infection in the larynx, trachea, and bronchi causes viral croup. Mucus is produced by the host and causes partial obstruction of the airway in both viral croup and acute laryngitis. Swelling of the vocal cords results in dysphonia. In viral croup, narrowing of the subglottic trachea in a child’s airway results in audible inspiratory stridor. As viral croup progresses, the lumen of the trachea becomes obstructed further by fibrous exudates. The barking cough that occurs in patients with viral croup is caused by inflammation in the larynx and trachea.

Epiglottitis is a cellulitis of the epiglottis and the surrounding tissues. H influenzae type b colonizes the pharynx. The type b capsule prevents phagocytosis of the bacterial invaders. The organisms then colonize the epiglottitis and enter the tissues of the epiglottitis through minor breaks in the mucosal surface. The organisms grow in the tissues and cause an inflammatory response that result in erythema and edema. A sore throat rapidly progresses to difficulty breathing, stridor, obstruction of the airways, and respiratory arrest. Local extension from the colonized nasopharynx through soft tissues is likely to be the cause of epiglottitis.

Diagnosis

Diagnosis of acute laryngitis is based on the clinical signs and symptoms of the patient (see manifestations). Viral croup is diagnosed by hoarseness, barking cough, and inspiratory stridor and retractions, which indicate airway obstruction (Table AI-3). A patient with viral croup will usually experience less restlessness and air hunger following treatment with racemic epinephrine or water-saturated air. These treatments do not have any affect on a patient with bacterial epiglottitis. The steeple sign seen in an anteroposterior neck radiograph is characteristic of viral croup. Viral cultures usually are not obtained.

Table AI-3. Comparison of the Clinical and Radiologic Features of Viral Croup and Epiglottitis
Clinical Features	Viral Croup	Epiglottitis
Etiology	Parainfluenza virus	Haemophilus influenzae type b
Age of patient	6 month–3 years	2–7 years
Onset of disease	Gradual	Sudden
Fever	Mild	> 38°C
Abnormal chest sounds	Bark-like cough, stridor	Muffled, guttural cough
Swallowing	Normal	Difficult, with drooling
Facies	Normal	Anxious, distressed, toxic
Response to racemic epinephrine or water-saturated air	Usually good; Less air hunger and restlessness	Usually poor; Little to no effect on air hunger and restlessness
Radiology	Steeple sign in anteroposterior neck radiograph	Thumb sign in lateral radiograph

Epiglottitis- Stridor is a late sign - Act on clinical suspicion based on the history. Once stridor develops, you may only have minutes to act.

The “epiglottitis triad”: 1) Severe sore throat with aphagia or severe dysphagia (drooling etc.), usually of rapid onset, 2) Croaky or hoarse voice (like laryngitis rather than hot potato voice), 3) Pyrexia, generally unwell, dehydrated.

Suspect epiglottitis in children with a sore throat and unusual symptoms (e,g., noisy breathing, drooling or any of the symptoms above). Suspect any patient with a severe sore throat and no evidence of tonsillitis or pharyngitis on examination.

The patient with epiglottitis should be handled with extreme care because airway closure can occur simply by placing a tongue depressor in the patient’s mouth to examine the throat. Examination of the larynx can irritate the patient and cause airway closure and asphyxiation. Equipment for an emergency tracheostomy should be available during examination of a patient suspected of having epiglottitis. If the patient has bacterial epiglottitis, the etiologic agent should be determined. H influenzae type b, the most common cause of epiglottis, does not grow on blood agar, therefore, throat swabs and smears should be cultured on blood agar and chocolate agar plates. In epiglottitis, H influenzae is often in the bloodstream; therefore blood cultures are helpful. A leukocytosis can be seen in the complete blood count (CBC). A positive thumb sign on lateral radiographs of the neck is diagnostic of epiglottitis.

Therapy and Prevention

Acute laryngitis is a self-limiting infection, and symptomatic therapy usually is all that is necessary. Treatment of viral croup requires maintenance of an adequate airway as follows.

Humidification of air provides water droplets that penetrate the area of inflammation and add moisture to the mucosa. Methods used to deliver high humidity include croup tents, masks, and blow-by oxygen.
Racemic epinephrine is effective in reducing stridor in children with stridor at rest or in children with more severe symptoms who are not responding to humidified oxygen.
Dexamethasone, prednisone, or budesonide may help patients who have severe viral croup and are hospitalized or treated in the emergency department.
Oxygen may be necessary if respiratory distress occurs.
Patients should be kept in a quiet, calm environment; any treatment that separates the child from the parents should be avoided because separation can increase anxiety.
If the patient is experiencing lack of air, tracheostomy should be considered.

Proper care and handling of the patient with epiglottitis can determine whether the patient lives or dies. Treatment of epiglottitis involves securing the patient’s airway by intubation in surgery and antibiotic therapy with ampicillin/sulbactam, ceftriaxone, cefotaxime, or cefuroxime. Children should be sedated when being intubated to prevent them from pulling out the tube.

The Hib vaccine is the capsular type b polysaccharide conjugated to the diphtheria toxoid, and it has drastically reduced the incidence of epiglottitis in the US. A child who has not received the Hib vaccine and who is exposed to a patient with epiglottitis should receive chemoprophylaxis with rifampin.