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: F.S. Southwick, Infectious Diseases in 30 Days, 1^st edition, McGraw Hill. p. 107-153.

Lecture: Dr. Neal R. Chamberlain

References: 
Childhood vaccination schedule: http://www.kcom.edu/faculty/chamberlain/Website/immune2002.htm

Hib vaccine:

http://www.cdc.gov/ncidod/EID/vol2no3/barbour.htm

Virtual Pediatric Hospital: Electric Airway

I. Croup (Epiglottitis, Laryngitis and Laryngotracheobronchitis)

The following organisms infect the upper airway:

• Haemophilus influenzae type b (capsular type), causes a very severe epiglottitis.
• Corynebacterium diphtheriae can also extend to the larynx from the pharynx.

• Parainfluenza viruses there are 4 types of virus. Types 1,3, and 4 are associated with the common cold and pharyngitis; types 1 and 3 are associated with croup; and types 1 and 3 are associated with bronchitis and bronchopneumonia.
• Adenovirus
• Echovirus
• Influenza viruses typically cause lower respiratory tract infections but may infect the upper airway.
• Respiratory Syncytial viruses can cause croup but is usually associated with bronchiolitis or bronchopneumonia in infants. These infections are worldwide in distribution.
• Mycoplasma pneumoniae

Epiglottitis - An acute onset, fever, sore throat, hoarseness, and a barking cough. Retraction of the suprasternal notch, stridor with every breath, the throat is inflamed, a beefy red swollen stiff epiglottis (movie of a "direct visualization of the epiglottis by bronchoscopy") can be seen by direct laryngoscopy, marked leukocytosis, with increased PMNs. The disease can progress very rapidly resulting in toxicity, prostration, severe dyspnea, and cyanosis. The causative agent is almost always H. influenzae. Risk of fatality is very high. This is a medical emergency. The patient should be handled with extreme care. Examination of the larynx can irritate the patient enough to cause airway closure and asphyxiation of the patient. Equipment for an emergency tracheostomy should be available during examination of a patient suspected of having epiglottitis.

Look for the 4 Ds;

1. dysphagia;
2. dysphonia (Hot potato voice);
3. drooling;
4. distress. (for a good movie showing a child in "distress".)

Laryngotracheobronchitis - Also called viral croup or just croup is a childhood infection that extends downward from the larynx to the trachea and the bronchial tree. Fever is higher, restlessness, and air hunger is more severe than in laryngitis. The patient will also demonstrate substernal and intercostal retractions in addition to suprasternal notch and supraclavicular retraction. A barky cough, bronchitic inspiratory rales and expiratory wheezes are heard on auscultation. Go to movie of "child with croup".

Diagnosis is not difficult. One looks for hoarseness, barking cough, inspiratory stridor and retractions which indicate airway obstruction (A great place go for a summary of "croup". Often times a patient with viral croup will respond to treatment with water saturated air however, a patient with bacterial epiglottitis will not). The etiological agent should be determined. Viral cultures are not usually performed and so the physician is basically getting samples for culture of H. influenzae or C. diphtheriae. Throat swabs and smears are cultured and examined. Often times in epiglottitis H. influenzae is in the blood stream therefore, blood cultures are helpful. Other airway obstructions should be considered in the differential such as acute spasmodic laryngitis, congenital laryngeal stridor, a foreign body in the larynx, and retropharyngeal abscesses. Serological tests are often performed to detect viral infections. A positive thumb sign on lateral X-ray of neck is diagnostic of epiglottitis. The "steeple sign" in an anteroposterior neck X-ray is characteristic of viral croup (acute laryngotracheobronchitis).

The morbidity and mortality of epiglottitis can be very high with bacteremia often resulting in meningitis, septic arthritis, or osteomyelitis. Airway closure can occur by just placing a tongue depressor in the patient's mouth to examine their throat. However, timely and proper treatment of this disease can save lives.

Twofold:

1. Maintenance of an adequate airway

• a. humidification of air to prevent crusty exudate formation.
• b. oxygen if respiratory distress is seen.
• c. patient should be kept quiet and handling should be avoided unless it calms the patient.
• d. if patient is still experiencing lack of air then tracheostomy should be considered.
• e. anti-inflammatory agents are not useful in maintaining the adequacy of the airway.

• H. influenzae - ampicillin or chloramphenicol.
• C. diphtheriae -antitoxin and erythromycin or penicillin G.

Vaccines are available for both diphtheria and H. influenza type b infections. The H. influenza type b vaccine (Hib vaccine) is the capsular polysaccharide conjugated to the diphtheria toxoid and is approved for immunization at 2 months with boosters at 4, 6, and 15 months. Go to this article on the Hib vaccine "Marina L. Barbour, D.Phil., M.R.C.P., (1996) Conjugate Vaccines and the Carriage of Haemophilus influenzae Type b. Volume 2, Number 3, Emerging Infectious Diseases". An article on the efficacy of the vaccine can be found here: Progress Toward Elimination of Haemophilus influenzae Type b Invasive Disease Among Infants and Children -- United States, 1998-2000.

The diphtheria toxoid is given very early in childhood and presents very little problem in the U.S.

Children exposed to someone with epiglottitis who have not received the Hib vaccine should receive chemoprophylaxis with rifampin.