1. The Respiratory System
Lec 1 By
Dr. Athal Humo

2. Upper Airway Obstruction (UAO)
UAO, is defined as blockage of any part of the airway located above the thoracic inlet, can range from nasal obstruction due to the common cold to life-threatening obstruction of the larynx or upper trachea (subglottic space).

3. ETIOLOGY
The differential diagnosis of airway obstruction varies with patient age and can also be subdivided into supraglottic and subglottic causes

4. Age-Related Differential Diagnosis of Upper Airway Obstruction
NEWBORN
Congenital subglottic stenosis (uncommon)
Choanal atresia
Micrognathia (Pierre Robin syndrome, DiGeorge syndrome)
Macroglossia (Beckwith-Wiedemann syndrome, Down, hypothyroidism)
Laryngeal web, clefts, atresia
Laryngospasm (intubation, aspiration, transient)
Vocal cord paralysis/paresis
Pharyngeal collapse
Dislocated nasal cartilage

5. INFANCY Laryngomalacia (most common etiologic disorder)
Subglottic stenosis (congenital, acquired, e.g., after intubation)
Airway hemangioma
Tongue (macroglossia, tumor (dermoid, teratoma, ectopic thyroid)
Laryngeal papillomatosis
Vascular rings/slings
Rhinitis

6. TODDLERS Viral croup Spasmodic/recurrent croup
Bacterial tracheitis (toxic, high fever)
Foreign body (airway or esophageal)
Laryngeal papillomatosis
Retropharyngeal abscess
Hypertrophied tonsils and adenoids

7. OLDER CHILDREN Epiglottitis
Inhalation injury (burns, toxic gas, hydrocarbons)
Foreign bodies
Angioedema (familial history, cutaneous angioedema)
Anaphylaxis (allergic history, wheezing, hypotension)
Trauma (tracheal or laryngeal fracture)
Peritonsillar abscess (adolescents)
Mononucleosis

8. CLINICAL MANIFESTATIONS
Upper airway obstruction is more pronounced during inspiration.
The respiratory noise most commonly associated with upper airway obstruction is stridor, a harsh sound caused by the vibration of the airway structures mainly in inspiration. Occasionally stridor may also be present on exhalation.
Stridor often decreases during sleep due to lower inspiratory flow rates and increase during feeding , excitement, & agitation.
Hoarseness suggests vocal cord involvement.

9. DIAGNOSTIC STUDIES
Radiographic evaluation of a child with stridor may not be helpful. However,
Lateral views of the neck and nasopharynx can assess for adenoid hypertrophy & airway swelling.
AP views of the neck taken with the head in extension, the subglottic space should be symmetrical and the lateral walls of the airway should fall away steeply. Asymmetry suggests subglottic stenosis or a mass lesion, while tapering suggests subglottic edema. However, these findings may be subtle.
Computed tomography (CT) scans of the upper airway can help delineate the site of the obstruction but may require sedation in younger children.
Flexible nasopharyngoscopy, which can be done without sedation, is extremely useful in assessing airway patency, the presence of adenoid tissue, vocal cord, laryngomalacia and other airway lesions,.
Bronchoscopy can be useful in assessing the subglottic space and intrathoracic large airways, but this procedure requires deep sedation.

10. The Common Cold
The common cold is a viral illness in which the symptoms of rhinorrhea and nasal obstruction are prominent; systemic symptoms and signs such as myalgia and fever are absent or mild. It is often termed rhinitis but includes self-limited involvement of the sinus mucosa and is more correctly termed rhinosinusitis.
Most common pathogens associated with the common cold are the rhinoviruses. Rarely it is caused by influenza, PIV, RSV ,or adenovirus.

11. Clinical Manifestations:
The onset of common cold symptoms typically occurs 1–3 days after viral infection.
The 1st symptom noted is frequently sore or “scratchy” throat, followed closely by nasal obstruction and rhinorrhea. Cough is associated with ≈30% of colds and usually begins after the onset of nasal symptoms. The usual cold persists for about 1 wk., although 10% last for 2 wk.
A change in the color or consistency of the secretions is common during the course of the illness and is not indicative of sinusitis or bacterial super infection.

12. TREATMENT COMPLICATIONS:
The management of the common cold consists primarily of symptomatic treatment.
COMPLICATIONS:
Otitis media.
Sinusitis.
Exacerbations of asthma.

13. Adenoidal and Tonsillar Hypertrophy
The most common cause of chronic upper airway obstruction in children is hypertrophy of the adenoids and tonsils. The adenoids are lymphoid tissue arising from the posterior and superior walls of the nasopharynx in the region of the choanae. Adenoid and tonsillar hyperplasia may be aggravated by recurrent infection, allergy, and inhaled irritants.

14. Clinical Manifestations:
Mouth breathing.
Snoring.
In some patients, obstructive sleep apnea.
Recurrent or persistent otitis media, because the eustachian tubes enter the nasopharynx at the choanae and can be obstructed by enlarged adenoids.
Diagnostic Studies:
Adenoidal hypertrophy is assessed by a lateral radiograph of the nasopharynx or by flexible nasopharyngoscopy.

15. Treatment
If the adenoids or tonsils are large and thought to be significantly contributing to upper airway obstruction, then the most effective treatment is removal.
Because the adenoids are not a discrete organ but rather consist of lymphoid tissue, regrowth after adenoidectomy is possible.
If the tonsils are large and the obstruction is severe, then removing the tonsils in addition to the adenoids may be necessary.

16. Acute Pharyngitis & Tonsillitis
Etiology
Viruses: (adenoviruses, coronaviruses, enteroviruses, rhinoviruses, respiratory syncytial virus [RSV], Epstein-Barr virus [EBV], herpes simplex virus [HSV],) .
Bacteria : (GABHS)

17. CLINICAL MANIFESTATIONS
Streptococcal pharyngitis: onset is often rapid with prominent sore throat, fever, and absence of cough. Headache and gastrointestinal symptoms (abdominal pain, vomiting) are frequent. The pharynx is red, and the tonsils are enlarged and classically covered with a yellow, blood-tinged exudate. There may be petechiae on the soft palate and posterior pharynx, and the uvula may be red, and swollen. The anterior cervical lymph nodes are enlarged and tender. The incubation period is 2–5 days. Some patients demonstrate the additional stigmata of scarlet fever.

19. Viral pharyngitis: onset is more gradual, and symptoms more often include rhinorrhea, cough, and diarrhea. A viral etiology is suggested by the presence of conjunctivitis, coryza, hoarseness, and cough.

20. Diagnosis
The goal of specific diagnosis is to identify GABHS infection
Throat culture.
Antistreptococcal antibodies.

21. Treatment
Early antibiotic therapy hastens clinical recovery by 12–24 hr The primary benefit of treatment is the prevention of acute rheumatic fever, which is almost completely successful if antibiotic treatment is instituted within 9 days of illness.
Penicillin V: given bid or tid for 10 days: 250 mg/dose for children and 500 mg/dose for adolescents and adults.
Oral amoxicillin: once-daily 50mg/kg dose of amoxicillin given orally for 10 days.
Single intramuscular dose of benzathine penicillin (600,000 U for children <27 kg [60 lb]; 1.2 million U for larger children and adults) ensures compliance and provides adequate blood levels for more than 10 days.
Erythromycin: 40 mg/kg/day divided bid, tid, or qid orally for 10 days is recommended for patients allergic to β-lactam antibiotics .

22. Complications and Prognosis :
Viral: otitis media.
GABHS:
Early local suppuration (e.g. parapharyngeal abscess).
Late non suppurative (RF&GN)

23. Choanal Stenosis (Atresia)
Choanal stenosis/atresia is a congenital problem that presents in the neonatal period. It may be bilateral or unilateral and is a relatively rare cause of respiratory distress in newborns.
Neonates are generally obligate nose breathers, so obstruction of nasal passages can cause significant respiratory distress.
Inability to easily pass a small catheter through the nostrils should raise the suspicion of choanal atresia.
The diagnosis is confirmed by CT scan and by inspecting the area directly with a flexible nasopharyngoscope.
An oral airway may be useful in the short term, but the definitive treatment is surgery

24. Acute Epiglottitis
It is a medical emergency because of the risk of sudden supraglottic airway obstruction.
This illness is now rare and usually caused by group A streptococcal or staphylococcus aureus infections or H. influenza type B in unimmunized patients.

25. Clinical Manifestation
Characterized by an acute rapidly progressive course.
Often, the otherwise healthy child suddenly develops a sore throat and fever. Within a matter of hours, the patient appears toxic, swallowing is difficult, and breathing is labored.
Drooling is usually present and the neck is hyperextended in an attempt to maintain the airway. The patients typically have a preference for sitting, often with the head held forward, the mouth open, and the jaw thrust forward (sniffing position).
A brief period of air hunger with restlessness may be followed by rapidly increasing cyanosis and coma.
Stridor is a late finding and suggests near-complete airway obstruction.
Complete obstruction of the airway and death can ensue unless adequate treatment is provided.
The barking cough typical of croup is rare. Usually, no other family members are ill with acute respiratory symptoms.

26. Diagnosis
Lateral radiograph reveals thickened and bulging epiglottis (thumb sign) and swelling of the aryepiglottic folds.
Anxiety-provoking interventions such as phlebotomy, intravenous line placement, placing the child supine, or direct inspection of the oral cavity should be avoided until the airway is secure.
The diagnosis is confirmed by direct observation of the inflamed and swollen supraglottic structures and swollen, cherry-red epiglottitis, which should be performed only in prepared operating room to place an endotracheal tube or perform a tracheostomy if needed.

27. Treatment
Antibiotic therapy: as 3rd generation cephalosporine & chloramphenicol.
Endotracheal intubation: to maintain the airway. Clinical recovery is rapid, and most children can be extubated safely within 48 to 72 hours.

28. Croup (Laryngotracheobronchitis)
Croup, or laryngotracheobronchitis, is the most common infection of the middle respiratory tract.
The most common causes of croup are parainfluenza viruses (types 1, 2, and 3) and respiratory syncytial virus.
Croup is most common in children 6 months to 3 years of age, with a peak in fall and early winter. It typically follows a common cold.

29. CLINICAL MANIFESTATIONS
The manifestations of croup are a harsh barking cough, hoarseness, inspiratory stridor, low-grade fever, and respiratory distress that may develop slowly or quickly.
Signs of upper airway obstruction, such as labored breathing and marked suprasternal, intercostal, and subcostal retractions, may be evident on examination.
Wheezing may be present if there is associated lower airway involvement.

30. LABORATORY AND IMAGING STUDIES
Anteroposterior radiographs of the neck show the diagnostic subglottic narrowing of croup known as the steeple sign.
Many rapid tests (PCR or antigen) are available for parainfluenza viruses and RSV.

31. PA view of the upper airway shows the so-called steeple sign, the tapered narrowing of the immediate subglottic airway (arrows)

32. TREATMENT
Oral or intramuscular dexamethasone reduces symptoms, the need for hospitalization, and shortens hospital stays. Dexamethasone phosphate (0.6 to 1 mg/kg) may be given once intramuscularly or dexamethasone (0.6 to 1 mg/kg) once orally. Alternatively, prednisolone (2 mg/kg per day) may be given orally in two to three divided doses.
For significant airway compromise, administration of aerosolized racemic epinephrine reduces subglottic edema by vasoconstriction, temporarily producing marked clinical improvement. Aerosol treatment may need to be repeated every 20 minutes (for no more than 1 to 2 hours) in severe cases.

33. Hospitalization is often required for:
Children should be kept as calm as possible to minimize forceful inspiration. One useful calming method is for a child with croup to sit in the parent's lap. Sedatives should be used cautiously and only in the intensive care unit. Cool mist administered by face mask may help prevent drying of the secretions around the larynx.
Hospitalization is often required for:
Children with stridor at rest.
Children receiving aerosol treatment should be hospitalized or observed for at least 2 to 3 hours because of the risk of rebound airway obstruction.

34. Bacterial Tracheitis
It is a rare but serious superinfection of the trachea that may follow viral croup and is most commonly caused by S. aureus.

35. Laryngomalacia (Floppy Larynx)
Laryngomalacia is most common cause of stridor in infants. It is due to exaggerated collapse of the glottic structures, especially the epiglottis and arytenoid cartilages, during inspiration, but its precise cause is not known.
It may be due to decreased muscular tone of the larynx and surrounding structures or to immature cartilaginous structures.
Inspiratory stridor beginning at or shortly after birth should raise the suspicion of laryngomalacia. It usually does not result in much respiratory distress, but occasionally it is severe enough to cause hypoventilation (CO2 retention), hypoxemia, and difficulty with feeding.

36. Clinical Manifestations
The primary sign of laryngomalacia is inspiratory stridor with little to no expiratory component. The stridor is typically loudest when the infant is feeding or active and decreases when the infant is relaxed, supine, or the neck is flexed. Exacerbated by viral respiratory infections & GERD.
Laryngomalacia normally peaks by 3 to 5 months of age and resolves between 6 and 12 months of age.

37. Diagnostic Studies In typical cases, no need for investigation.
In severe or atypical cases, the patient should undergo flexible nasopharyngoscopy/laryngoscopy to assess the patency and dynamic movement (collapse) of the larynx and surrounding structures.

38. Treatment
In most cases, no therapy is required for laryngomalacia. The infant should be observed closely during times of respiratory infection for evidence of respiratory compromise, although most infants with laryngomalacia tolerate infections fairly well.
Infants with severe laryngomalacia that results in hypoventilation, hypoxia, or growth failure may benefit from a surgical procedure (aryoepiglottoplasty) or, in extreme cases, a tracheostomy to bypass the upper airway.

39. Subglottic Stenosis
Subglottic stenosis is the narrowing of trachea immediately below the vocal cords.
It may be:
Congenital
Acquired: due to prolonged or repeated endotracheal intubation.

40. Clinical Manifestations
Subglottic stenosis can present as stridor that is frequently biphasic (on both expiration and inspiration). However, the stridor is usually more prominent on inspiration.
Subglottic stenosis may also be associated with a barky cough similar to that noted with croup.
Respiratory infections can cause subglottic edema, exacerbating the clinical manifestations of subglottic stenosis.

41. Diagnostic Studies Treatment
Definitive diagnosis requires endoscopic evaluation, either by flexible or rigid bronchoscopy.
Treatment
Mild subglottic stenosis can be managed conservatively and may improve sufficiently with airway growth alone.
Severe cases require surgical intervention.

42. Others causes of UAO
hemangioma, usually presents before 6 months of age. The treatment of hemangiomas is controversial, but laser therapy and corticosteroids (both direct injection and systemic) have been used with moderate success. If the obstruction is severe, tracheostomy tube is needed.
Juvenile laryngeal papillomatosis .
Vocal Cord Paralysis, Paralysis may be unilateral or bilateral and is more often caused by damage to the recurrent laryngeal nerve than by a central lesion. Peripheral nerve injury can be caused by trauma (neck traction during delivery of infants or thoracic surgical procedures). Central causes as hydrocephalus.
Foreign body, should considered in any infant or child capable of ingesting small objects who develops acute onset of stridor.

43. Differentiating Supraglottic from Subglottic Causes of Airway Obstruction