# Seminar 05: Pediatric Respiratory Disorders ## Year 3: Pediatrics Clerkship --- ## Learning Objectives By the end of this seminar, students will be able to: 1. Evaluate acute respiratory distress in children 2. Diagnose and manage croup 3. Recognize and treat bronchiolitis 4. Diagnose and manage asthma across severities 5. Describe foreign body aspiration 6. Recognize signs of respiratory failure --- ## Seminar Outline ### I. Respiratory Assessment The respiratory system in children differs anatomically and physiologically from adults in ways that significantly impact disease presentation and management. Infants have proportionally larger heads and tongues with smaller mandibles that predispose to airway obstruction when muscle tone decreases during sleep or sedation. The larynx is positioned higher (C3-C4 versus C5-C6 in adults) and more anterior, with the epiglottis more omega-shaped and the narrowest portion at the subglottic level (cricoid ring) rather than the glottis. The smaller absolute airway diameter means that even minor edema or secretions produce significant increases in resistance; one millimeter of circumferential edema reduces cross-sectional area by 75% in an infant compared to 44% in an adult. Recognition of respiratory distress requires systematic assessment of respiratory rate, effort, and adequacy. Age-appropriate respiratory rate norms must be applied, with tachypnea defined as greater than 60 breaths per minute in newborns, greater than 50 in infants two to twelve months, greater than 40 in children one to five years, and greater than 30 in older children and adolescents. Work of breathing is assessed by examining for nasal flaring (indicating recruitment of accessory muscles), subcostal, intercostal, and suprasternal retractions (reflecting increased negative intrathoracic pressure generation), head bobbing (accessory muscle use in infants), and grunting (expiratory braking to maintain positive end-expiratory pressure). Paradoxical abdominal breathing with chest wall retraction during inspiration indicates severe distress. Auscultation provides essential diagnostic information but must be interpreted in context. Wheezing (high-pitched, musical sounds during expiration) indicates lower airway narrowing from bronchospasm, inflammation, or obstruction and is the hallmark of asthma. Crackles (discontinuous, crackling sounds) suggest alveolar or small airway disease with fluid, secretions, or atelectasis. Stridor (high-pitched, harsh sound during inspiration) indicates upper airway obstruction and localizes to the larynx or proximal trachea. Decreased or absent breath sounds may indicate consolidation, effusion, pneumothorax, or severe bronchospasm with minimal air movement. The timing and quality of abnormal sounds help localize pathology and guide diagnosis. Pulse oximetry provides continuous non-invasive assessment of oxygen saturation but has important limitations. Normal saturation targets vary by altitude and clinical context but generally should exceed 94% on room air for most children. Motion artifact and poor perfusion reduce accuracy, and certain conditions (carboxyhemoglobin, methemoglobin) cause falsely normal readings despite tissue hypoxia. Oximetry detects hypoxemia but does not assess ventilation or carbon dioxide levels; a child with respiratory failure may have normal oxygen saturation on supplemental oxygen while developing significant hypercarbia. Capnography provides more complete respiratory monitoring in critically ill children and during procedural sedation. Panel A: Anatomical comparison diagram of infant versus adult airway showing higher laryngeal position, proportionally larger tongue, and narrowest point location. Panel B: Clinical photographs demonstrating signs of respiratory distress including nasal flaring, retractions (subcostal, intercostal, suprasternal), and head bobbing in an infant. Panel C: Chart of age-appropriate respiratory rate norms with zones indicating normal, tachypnea, and severe tachypnea. Panel D: Waveform comparison of normal versus abnormal capnography patterns with corresponding clinical significance. --- ### II. Croup (Laryngotracheobronchitis) Croup is the most common cause of upper airway obstruction in children, typically affecting those aged six months to three years during fall and winter viral seasons. Parainfluenza viruses (types 1, 2, and 3) cause the majority of cases, with influenza, RSV, and adenovirus also implicated. The characteristic barky, seal-like cough results from subglottic inflammation and edema narrowing the airway at its already narrowest point. Stridor, initially with agitation, progresses to stridor at rest in moderate to severe cases. The illness typically follows an upper respiratory prodrome, with symptoms often worse at night and resolving over three to seven days. Severity assessment using the Westley Croup Score guides management and disposition decisions. The score incorporates stridor (0-2 points), retractions (0-3 points), air entry (0-2 points), cyanosis (0-4 points), and level of consciousness (0-5 points), with mild disease scoring less than 2, moderate 3-7, and severe 8-11 or greater. Mild croup with occasional barky cough, no stridor at rest, and minimal retractions can be managed at home with cool mist humidification (though evidence for efficacy is limited). Moderate croup with frequent cough, stridor at rest, and visible retractions requires emergency department evaluation. Severe croup with marked stridor, significant retractions, cyanosis or pallor, and decreased air entry necessitates immediate intervention. Corticosteroids benefit all children with croup presenting for care, reducing symptom severity and return visits regardless of initial severity level. Dexamethasone 0.6 mg/kg orally as a single dose is the preferred treatment due to its long half-life eliminating the need for repeated dosing and equivalent efficacy to intramuscular or nebulized routes. Lower doses (0.15-0.3 mg/kg) may be effective for mild disease. Oral administration is preferred when tolerated, with intramuscular injection reserved for children unable to take oral medication. The steeple sign on anteroposterior neck radiograph, representing subglottic narrowing, supports the diagnosis when imaging is obtained but is not required for management. Nebulized racemic epinephrine provides rapid but temporary improvement in moderate to severe croup through mucosal vasoconstriction and reduction of subglottic edema. The effect peaks at 30 minutes and wanes by 2 hours, requiring a minimum 3-4 hour observation period after administration to ensure symptoms do not rebound before discharge. Multiple doses may be given but suggest severe disease requiring close monitoring or admission. Heliox (helium-oxygen mixture) may reduce work of breathing by improving laminar airflow through narrowed airways but is not uniformly available. Intubation is rarely needed but should employ an endotracheal tube 0.5-1 mm smaller than age-predicted size due to subglottic swelling. Panel A: Anteroposterior radiograph demonstrating the steeple sign of subglottic narrowing in croup compared to normal airway contour. Panel B: Westley Croup Score table with clinical features defining mild, moderate, and severe disease plus corresponding management for each. Panel C: Timeline of croup clinical course from URI prodrome through peak symptoms and resolution, noting characteristic nocturnal worsening. Panel D: Treatment algorithm showing dexamethasone for all patients, addition of epinephrine for moderate-severe cases, and observation requirements. --- ### III. Epiglottitis Epiglottitis, while now rare due to Haemophilus influenzae type b vaccination, remains a life-threatening emergency when it occurs. The incidence has decreased dramatically since widespread Hib vaccination, but cases still occur from other pathogens including Streptococcus pyogenes, Streptococcus pneumoniae, and Staphylococcus aureus. The disease involves rapid swelling of the epiglottis and surrounding supraglottic structures that can progress to complete airway obstruction within hours. Unlike croup, which develops gradually over days with viral prodrome, epiglottitis presents acutely with rapid progression over hours. The classic presentation includes the "4 Ds": drooling (unable to swallow secretions), dysphagia (painful swallowing), dysphonia (muffled "hot potato" voice), and distress (respiratory difficulty). The child appears toxic with high fever and sits in the tripod position (sitting forward with neck extended and chin thrust forward) to optimize airway patency. Unlike croup, there is no barky cough, and stridor may be minimal until obstruction becomes severe. The child appears anxious and resists lying down. Any agitation or disturbance may precipitate complete obstruction, making calm assessment essential. Diagnosis relies on clinical recognition, with direct visualization of the airway avoided outside a controlled setting with airway management capability. The thumbprint sign on lateral neck radiograph represents the swollen epiglottis but should only be obtained if it does not delay management or require the child to lie supine. Direct visualization showing a cherry-red, swollen epiglottis confirms the diagnosis but should be performed only in the operating room with anesthesiology and ENT prepared for immediate airway intervention. Blood cultures and epiglottic cultures should be obtained once the airway is secured. Management priorities focus on maintaining airway patency while avoiding agitation. The child should be allowed to remain in the position of comfort with a parent present, and interventions such as IV placement, blood draws, or throat examination should be deferred until the airway is controlled. Transport to the operating room for direct laryngoscopy and intubation under anesthesia with ENT backup for possible tracheostomy is the safest approach. Once intubated, broad-spectrum antibiotics covering the likely pathogens (ceftriaxone plus vancomycin for MRSA coverage) are initiated. Most children can be extubated within 24-48 hours as the swelling resolves with antibiotic therapy. Panel A: Clinical photograph showing child in tripod position with anxious appearance and drooling characteristic of epiglottitis. Panel B: Lateral neck radiograph demonstrating thumbprint sign of swollen epiglottis compared to normal epiglottic contour. Panel C: Comparison table differentiating croup from epiglottitis including onset, fever, cough, drooling, toxicity, and management. Panel D: Management algorithm emphasizing airway protection priority, avoiding agitation, and controlled intubation in operating room. --- ### IV. Bronchiolitis Bronchiolitis is the leading cause of hospitalization in infants under one year of age, characterized by inflammation and obstruction of small airways predominantly caused by respiratory syncytial virus (RSV). RSV causes approximately 70% of cases, with human metapneumovirus, parainfluenza, influenza, adenovirus, and rhinovirus causing the remainder. The disease primarily affects infants under two years, with peak severity at two to three months when maternal antibodies wane but the immune system remains immature. Seasonal epidemics occur annually in temperate climates, typically from November through March, with earlier onset in southern regions. The pathophysiology involves viral infection of bronchiolar epithelium causing inflammation, edema, increased mucus production, and sloughed epithelial cells that obstruct small airways. Unlike asthma, smooth muscle bronchospasm plays a minimal role, explaining the lack of bronchodilator efficacy. The clinical course begins with upper respiratory symptoms (rhinorrhea, cough, low-grade fever) for two to three days, followed by progressive lower respiratory involvement with tachypnea, wheezing, crackles, and respiratory distress. Most infants have mild disease managed at home, but the very young (under three months), premature infants, and those with cardiopulmonary disease or immunodeficiency are at risk for severe disease requiring hospitalization. Diagnosis of bronchiolitis is clinical, based on the characteristic presentation of a first episode of wheezing with respiratory distress in an infant during RSV season. Routine diagnostic testing is not indicated in typical cases. Chest radiography often shows hyperinflation with peribronchial thickening and patchy atelectasis that may be misinterpreted as bacterial pneumonia, leading to unnecessary antibiotic treatment; radiographs should be reserved for severe or atypical presentations. Viral testing (RSV antigen or PCR panel) may guide infection control decisions in hospitalized patients but does not change management for individual patients and is not routinely recommended. Management of bronchiolitis is primarily supportive, as no pharmacologic intervention has proven benefit. Oxygen supplementation is provided to maintain saturation above 90% (some guidelines allow intermittent desaturation to 90% during sleep), using the lowest flow necessary. Nasal suctioning relieves upper airway obstruction from secretions but deep suctioning offers no additional benefit and may cause mucosal trauma. Adequate hydration through oral or intravenous fluids prevents dehydration from increased respiratory losses and poor feeding. Bronchodilators (albuterol, epinephrine) have not shown consistent benefit in clinical trials and are not routinely recommended. Corticosteroids provide no benefit and are not indicated. High-flow nasal cannula therapy has become increasingly used for infants with moderate to severe disease, providing heated humidified oxygen with some positive airway pressure support. Panel A: Timeline of bronchiolitis clinical course from URI prodrome through peak respiratory symptoms at days 5-7 and gradual resolution over 2-3 weeks. Panel B: Clinical photograph of infant with bronchiolitis demonstrating tachypnea, subcostal retractions, and nasal flaring with vital sign abnormalities listed. Panel C: Chest radiograph appearance in bronchiolitis showing hyperinflation and peribronchial thickening, contrasted with lobar consolidation of bacterial pneumonia. Panel D: Evidence-based management showing supportive care that works (oxygen, suctioning, hydration) versus ineffective treatments (bronchodilators, steroids, antibiotics). --- ### V. Asthma Pathophysiology and Diagnosis Asthma is the most common chronic disease of childhood, affecting approximately 8% of children in the United States and characterized by chronic airway inflammation, reversible airflow obstruction, and bronchial hyperresponsiveness. The inflammatory process involves multiple cell types including mast cells, eosinophils, T lymphocytes, macrophages, and airway epithelial cells, with release of mediators causing bronchoconstriction, edema, and mucus hypersecretion. Over time, airway remodeling with smooth muscle hypertrophy, subepithelial fibrosis, and goblet cell hyperplasia leads to fixed airflow limitation. Understanding pathophysiology guides both acute management (relieving bronchoconstriction, reducing inflammation) and chronic therapy (preventing inflammation, preventing remodeling). The diagnosis of asthma in children older than five years relies on clinical history, physical examination, and spirometry demonstrating reversible airflow obstruction. Characteristic symptoms include recurrent wheezing, cough (particularly nocturnal or exercise-induced), chest tightness, and shortness of breath that vary over time and in intensity. Symptom triggers include respiratory infections (the most common trigger in children), allergen exposure, exercise, cold air, smoke, and strong emotions. A positive family history of asthma or atopy supports the diagnosis. Spirometry showing reduced FEV1/FVC ratio with at least 12% improvement in FEV1 following bronchodilator confirms reversibility; bronchoprovocation testing may be needed if baseline spirometry is normal. Diagnosing asthma in children younger than five years is challenging because spirometry cannot be reliably performed and wheezing has multiple causes in this age group. The modified Asthma Predictive Index helps identify preschoolers with recurrent wheezing likely to develop persistent asthma: major criteria include parental history of asthma, eczema in the child, or allergic sensitization to aeroallergens; minor criteria include allergic sensitization to milk, egg, or peanut, wheezing unrelated to colds, or eosinophilia greater than 4%. Two major criteria or one major plus two minor criteria predict persistent asthma with reasonable accuracy. Many young children with viral-induced wheezing ("happy wheezers") will outgrow symptoms without developing persistent asthma. Asthma severity classification guides initial therapy selection before treatment is initiated. Intermittent asthma involves symptoms two or fewer days per week, nighttime awakenings two or fewer times per month, short-acting beta-agonist use two or fewer days per week, and no interference with normal activity. Mild persistent asthma involves symptoms more than two days per week but not daily, with nighttime awakenings three to four times per month. Moderate persistent asthma involves daily symptoms, nighttime awakenings more than once per week but not nightly, and some limitation of activity. Severe persistent asthma involves symptoms throughout the day, nighttime awakenings often nightly, and extreme limitation of activity. FEV1 parameters also contribute to classification. Panel A: Cross-sectional illustration of normal versus asthmatic airway showing smooth muscle constriction, mucosal edema, mucus plugging, and inflammatory infiltrate. Panel B: Spirometry flow-volume loop demonstrating obstructive pattern with bronchodilator reversibility, including interpretation of FEV1 and FEV1/FVC ratio. Panel C: Modified Asthma Predictive Index flowchart for preschool-age children with recurrent wheezing, showing major and minor criteria. Panel D: Asthma severity classification table with symptom frequency, nighttime awakening, SABA use, and FEV1 criteria for each category. --- ### VI. Asthma Classification and Stepwise Treatment Long-term asthma management follows a stepwise approach based on severity and response to treatment, with the goal of achieving and maintaining control. Step 1 (intermittent asthma) requires only as-needed short-acting beta-agonist (SABA) for symptom relief. Step 2 adds a low-dose inhaled corticosteroid (ICS) as the preferred controller, with alternatives including leukotriene receptor antagonists or cromolyn. Step 3 increases to medium-dose ICS or adds a long-acting beta-agonist (LABA) to low-dose ICS. Step 4 involves medium-dose ICS plus LABA, with consideration of tiotropium in adolescents. Steps 5 and 6 require high-dose ICS plus LABA with possible addition of oral corticosteroids or biologics for severe uncontrolled asthma. Inhaled corticosteroids remain the cornerstone of controller therapy, reducing inflammation, preventing exacerbations, improving lung function, and potentially preventing airway remodeling when used consistently. Common ICS options include fluticasone, budesonide, beclomethasone, and mometasone, with different delivery devices (metered-dose inhaler, dry powder inhaler, nebulizer) selected based on age and ability to coordinate. Spacer devices should be used with all metered-dose inhalers to improve drug delivery and reduce oropharyngeal deposition causing local side effects (oral candidiasis, dysphonia). Long-term ICS use at standard doses has minimal systemic effects, though growth velocity may be slightly reduced in the first year; final adult height is minimally affected. Short-acting beta-agonists (albuterol, levalbuterol) provide rapid relief of acute symptoms through bronchial smooth muscle relaxation and should be available to all patients with asthma. Increasing SABA use beyond two days per week (excluding exercise pre-treatment) indicates inadequate control requiring step-up of controller therapy. Overreliance on SABA without adequate anti-inflammatory therapy increases exacerbation risk and mortality. Long-acting beta-agonists (salmeterol, formoterol) provide sustained bronchodilation over 12 hours but must always be used in combination with ICS due to increased exacerbation risk when used alone in certain populations. Leukotriene receptor antagonists (montelukast) provide modest benefit as add-on therapy or as alternative to ICS for mild disease. The asthma action plan is an essential tool for patient and family education that outlines daily management and responses to worsening symptoms. The green zone indicates good control with continuation of maintenance medications. The yellow zone is activated when symptoms increase or peak flow decreases to 50-80% of personal best, prompting increased SABA use and often doubling of ICS or adding oral corticosteroids. The red zone indicates a medical emergency when symptoms are severe or peak flow falls below 50% of personal best, requiring immediate SABA, oral corticosteroids, and seeking emergency care. Every patient with asthma should receive a written action plan reviewed at each visit. Panel A: Stepwise treatment algorithm for asthma showing medications at each step from Step 1 through Step 6 with preferred and alternative options by age group. Panel B: Comparison of inhaler devices (MDI with spacer, DPI, nebulizer) with age-appropriate selection guide and proper technique demonstration. Panel C: Asthma action plan template showing green, yellow, and red zones with corresponding symptoms, peak flow ranges, and medication instructions. Panel D: Chart showing ICS dose equivalencies across preparations (fluticasone, budesonide, beclomethasone) with low, medium, and high-dose ranges. --- ### VII. Asthma Exacerbation Management Acute asthma exacerbations range from mild episodes manageable at home to life-threatening respiratory failure requiring intensive care. Assessment includes determining exacerbation severity through clinical evaluation (mental status, ability to speak in sentences, accessory muscle use, wheezing intensity) and objective measures (oxygen saturation, peak expiratory flow if able to perform). Mild-moderate exacerbations show the patient speaking in sentences, sitting comfortably, increased respiratory rate, some accessory muscle use, oxygen saturation above 90%, and peak flow above 50% predicted. Severe exacerbation features include speaking only in words, hunched posture, agitation, respiratory rate above 30, marked accessory muscle use, oxygen saturation below 90%, and peak flow below 50%. Initial management of moderate to severe exacerbation centers on rapid administration of inhaled bronchodilators and systemic corticosteroids. Albuterol via metered-dose inhaler with spacer (4-8 puffs) or nebulizer (2.5-5 mg) is given every 20 minutes for three doses, then hourly if needed. Continuous nebulization (10-20 mg/hour) may be necessary for severe exacerbations. Ipratropium bromide added to albuterol during the first hour provides additional bronchodilation in moderate to severe exacerbations with reduction in hospitalization. Systemic corticosteroids (prednisone/prednisolone 1-2 mg/kg, maximum 60 mg, or dexamethasone 0.6 mg/kg, maximum 16 mg) should be given early, with oral route preferred unless the child cannot tolerate oral intake. Adjunctive therapies are considered when response to initial treatment is inadequate. Intravenous magnesium sulfate (25-75 mg/kg, maximum 2 g over 20 minutes) provides smooth muscle relaxation and is indicated for severe exacerbations not responding to initial therapy, with evidence supporting reduced hospitalization. Subcutaneous or intramuscular epinephrine or terbutaline may be used when inhaled beta-agonists cannot be effectively delivered due to poor air movement. High-flow nasal cannula provides humidified, heated oxygen at flows that may support respiratory effort. Heliox may reduce work of breathing by improving flow dynamics in narrowed airways. Noninvasive positive pressure ventilation (BiPAP) can provide ventilatory support while avoiding intubation in selected patients. Disposition decisions depend on response to treatment, with reassessment occurring throughout the emergency department stay. Discharge criteria include substantial symptom improvement, oxygen saturation above 94% on room air (or baseline for patient), sustained response (at least 60 minutes after last treatment), and peak flow above 70% of predicted or personal best. Discharge planning includes corticosteroid course (typically 3-5 days of prednisone or 1-2 days of dexamethasone), reliever inhaler with spacer, review of controller medication adherence, written asthma action plan, and close outpatient follow-up within one to four weeks. Admission criteria include persistent hypoxia requiring supplemental oxygen, poor response to emergency treatment, high-risk features, or inability to ensure adherence to discharge plan. Panel A: Acute asthma severity assessment table with clinical findings and objective measures differentiating mild-moderate from severe exacerbations. Panel B: Emergency department treatment algorithm showing medication dosing, timing, and decision points for escalation from initial treatment through adjunctive therapies. Panel C: Peak expiratory flow interpretation guide with green, yellow, and red zones and corresponding percentage of personal best or predicted. Panel D: Discharge criteria checklist and discharge plan components including medication prescription, action plan, and follow-up timing. --- ### VIII. Foreign Body Aspiration Foreign body aspiration is a common and potentially life-threatening event in young children, with peak incidence between one and three years when oral exploration behaviors combine with immature swallowing coordination and incomplete dentition for adequate chewing. Food items (nuts, seeds, popcorn, hot dog pieces, grapes, raw carrots) account for most aspirations, while non-food items (coins, small toys, button batteries, balloon fragments) cause significant morbidity. Button battery ingestion or aspiration is a particular emergency due to caustic injury occurring within hours of contact with mucosa. The right main bronchus is more commonly affected due to its larger diameter and more vertical angle from the trachea. Clinical presentation varies depending on the size and location of the foreign body and whether complete or partial obstruction occurs. Acute choking with witnessed aspiration is the classic presentation, with coughing, gagging, and respiratory distress; complete obstruction causes inability to cry or cough and cyanosis. Many foreign body aspirations are not witnessed, and the initial choking episode may resolve as the object lodges distally, leading to an asymptomatic interval followed by chronic symptoms. Persistent or recurrent pneumonia in the same location, unilateral wheezing, and chronic cough unresponsive to treatment should prompt consideration of foreign body even weeks to months after potential aspiration. Physical examination may reveal asymmetric breath sounds, localized wheezing, or evidence of complete obstruction. Radiographic evaluation includes chest radiograph (inspiratory and expiratory views or lateral decubitus films in young children who cannot cooperate with forced expiration) looking for the foreign body if radiopaque, or indirect signs including unilateral hyperinflation from ball-valve obstruction, atelectasis from complete obstruction, or pneumonia. Many aspirated materials (food, plastic) are radiolucent and will not be visualized on plain films. Expiratory films or lateral decubitus positioning demonstrates air trapping with the affected lung remaining hyperinflated while the normal lung deflates. Fluoroscopy can demonstrate asymmetric diaphragm movement with breathing. When clinical suspicion is high despite unremarkable imaging, rigid bronchoscopy should be performed for both diagnosis and removal. Management of acute complete airway obstruction follows basic life support guidelines. For responsive infants under one year, alternating five back blows and five chest thrusts is used until the object is expelled or the infant becomes unresponsive. For responsive children over one year, abdominal thrusts (Heimlich maneuver) are performed. If the child becomes unresponsive, CPR is initiated with airway visualization during compressions and removal of visible objects; blind finger sweeps are avoided as they may push the object deeper. Subacute and chronic foreign body aspiration requires rigid bronchoscopy for visualization and removal in the operating room, which is both diagnostic and therapeutic. Delay in diagnosis and removal increases complication risk including pneumonia, bronchiectasis, and respiratory failure. Panel A: Common aspirated objects in children including peanuts, grapes, coins, hot dogs, and small toys, with age-based risk factors and prevention strategies. Panel B: Paired chest radiographs demonstrating unilateral hyperinflation on expiratory film from ball-valve obstruction, compared to symmetric deflation in normal. Panel C: Illustrated technique for back blows and chest thrusts in infant under one year versus abdominal thrusts in older child for choking relief. Panel D: Bronchoscopic images showing foreign body lodged in bronchus with extraction instruments and post-removal findings. --- ### IX. Other Respiratory Conditions Pertussis (whooping cough) remains an important pediatric respiratory infection despite vaccination, particularly affecting incompletely immunized infants who are at highest risk for severe complications. Caused by Bordetella pertussis, the illness progresses through three stages: the catarrhal stage (1-2 weeks) resembling a common cold, the paroxysmal stage (2-8 weeks) with characteristic paroxysms of rapid coughs followed by inspiratory "whoop" and post-tussive vomiting, and the convalescent stage (weeks to months) with gradually decreasing cough. Young infants may present with apnea without classic whoop. Diagnosis is confirmed by PCR of nasopharyngeal swab, with treatment using azithromycin (or other macrolide) reducing transmission but not significantly altering the clinical course once paroxysms are established. Prevention through DTaP vaccination and Tdap boosters including maternal vaccination during pregnancy remains the primary strategy. Tuberculosis in children differs from adult disease in important ways, typically representing primary infection rather than reactivation. Children acquire TB through exposure to infected adults, with the highest risk in household contacts of active pulmonary TB. Primary pulmonary TB in children is often asymptomatic or causes mild symptoms, with chest radiograph showing hilar lymphadenopathy and possible parenchymal infiltrate. Screening uses tuberculin skin test (TST) or interferon-gamma release assay (IGRA) in children over two years, with positive results indicating infection requiring evaluation for active disease. Treatment of latent TB infection (LTBI) with isoniazid or rifampin prevents progression to active disease. Active TB requires multi-drug therapy with directly observed treatment for adherence. Obstructive sleep apnea (OSA) affects 2-4% of children, with peak incidence between two and eight years when lymphoid tissue is largest relative to airway size. Adenotonsillar hypertrophy is the primary cause in healthy children, though obesity, craniofacial abnormalities, and neuromuscular disorders contribute in specific populations. Symptoms include snoring, witnessed apneas, restless sleep, mouth breathing, enuresis, and paradoxically hyperactivity and behavioral problems rather than adult-pattern sleepiness. Polysomnography confirms the diagnosis and quantifies severity. Adenotonsillectomy is first-line treatment for most children with adenotonsillar hypertrophy, resolving OSA in approximately 75%. CPAP is second-line therapy for persistent OSA after surgery or when surgery is contraindicated. Reactive airway disease is a term sometimes used for wheezing with viral respiratory infections in infants and toddlers who have not yet met criteria for asthma diagnosis. Many young children wheeze with viral infections due to small airway caliber and may outgrow this tendency without developing persistent asthma. The Asthma Predictive Index helps identify which children with recurrent wheezing are likely to develop persistent asthma. Management during acute episodes is similar to asthma exacerbations with bronchodilators, though response may be less robust. Controller therapy is generally not initiated until a pattern of recurrent symptoms emerges consistent with asthma, though treatment trials may be considered in high-risk children. Panel A: Pertussis clinical stages timeline showing catarrhal, paroxysmal, and convalescent phases with characteristic symptoms and duration of each. Panel B: Chest radiograph of primary tuberculosis in a child showing hilar lymphadenopathy with algorithm for TB screening and evaluation. Panel C: Anatomical illustration of upper airway in child with adenotonsillar hypertrophy causing obstruction during sleep with polysomnography findings. Panel D: Comparison of reactive airway disease versus asthma features with Asthma Predictive Index criteria and management implications. --- ### X. Respiratory Failure and Support Respiratory failure occurs when the respiratory system cannot adequately oxygenate blood (type I, hypoxic failure with low PaO2) or eliminate carbon dioxide (type II, hypercapnic failure with elevated PaCO2), or both. Causes in children include severe asthma, bronchiolitis, pneumonia, croup, foreign body aspiration, neuromuscular disease, and central nervous system dysfunction. Recognition of impending respiratory failure requires vigilance for signs of deterioration including exhaustion with decreasing respiratory effort (paradoxically appearing "better"), altered mental status indicating hypoxia or hypercapnia, worsening retractions followed by decreased chest wall movement, and bradycardia as a pre-arrest sign. Supplemental oxygen is the most basic respiratory support and should be titrated to maintain target oxygen saturation. Oxygen delivery devices include nasal cannula (flows up to 2-4 L/min delivering FiO2 approximately 24-40%), simple face mask (5-10 L/min for FiO2 40-60%), non-rebreather mask with reservoir (10-15 L/min for FiO2 60-90%), and venturi mask for precise FiO2 delivery. Blow-by oxygen, with tubing held near the child's face, provides minimal supplementation but may be tolerated by infants and young children who resist devices. High-flow nasal cannula (HFNC) delivers heated, humidified oxygen at flows exceeding standard nasal cannula capacity (1-2 L/kg/min), providing washout of nasopharyngeal dead space, generation of positive airway pressure, and improved tolerance. Noninvasive positive pressure ventilation (NIPPV) provides respiratory support without endotracheal intubation. Continuous positive airway pressure (CPAP) delivers constant pressure throughout the respiratory cycle, improving oxygenation by recruiting atelectatic lung and reducing work of breathing. Bilevel positive airway pressure (BiPAP) provides higher pressure during inspiration (IPAP) for ventilatory support and lower pressure during expiration (EPAP), unloading respiratory muscles and augmenting tidal volume. Indications include respiratory failure with preserved protective reflexes and ability to protect the airway, as a bridge to avoid intubation, and for post-extubation support. Contraindications include impaired consciousness, inability to protect the airway, facial trauma, and copious secretions that cannot be cleared. Invasive mechanical ventilation through endotracheal tube is required when noninvasive support is insufficient or contraindicated. Endotracheal tube size is estimated using age-based formulas: internal diameter in millimeters equals (age in years divided by 4) plus 4 for uncuffed tubes or (age divided by 4) plus 3.5 for cuffed tubes, with cuffed tubes now preferred for all ages to improve ventilation and reduce reintubation. Depth of insertion approximates tube size times 3 in centimeters at the lip. Ventilator settings are adjusted to achieve target oxygenation (through FiO2 and PEEP) and ventilation (through tidal volume and rate). Lung-protective strategies limiting tidal volume to 6-8 mL/kg and plateau pressure reduce ventilator-induced lung injury. Panel A: Comparison of type I (hypoxic) versus type II (hypercapnic) respiratory failure with causes, blood gas findings, and treatment approach. Panel B: Oxygen delivery devices comparison showing nasal cannula, simple mask, non-rebreather, and HFNC with flow rates and approximate FiO2 delivery. Panel C: CPAP and BiPAP waveform comparison showing continuous versus bilevel pressure delivery with clinical applications for each. Panel D: Age-based endotracheal tube sizing chart with formulas for cuffed and uncuffed tubes and depth of insertion guidelines. --- ## Summary - Respiratory distress signs include tachypnea, retractions, nasal flaring, grunting, and cyanosis as a late sign - Croup presents with barky cough and stridor; treat with dexamethasone for all patients, adding nebulized epinephrine for moderate-severe disease - Epiglottitis is a medical emergency with drooling, toxic appearance, and tripod positioning; avoid throat examination and secure airway in controlled setting - Bronchiolitis management is supportive with oxygen, nasal suctioning, and hydration; bronchodilators and steroids are not effective - Asthma diagnosis in children over 5 years uses spirometry showing reversible obstruction; under 5 years relies on clinical features and Asthma Predictive Index - Asthma treatment follows stepwise approach with ICS as controller and SABA for rescue; all patients need written action plan - Asthma exacerbation requires albuterol plus ipratropium plus systemic steroids; add magnesium sulfate if severe - Foreign body aspiration presents with acute choking or chronic unilateral wheeze; rigid bronchoscopy provides diagnosis and treatment - Pertussis causes paroxysmal cough with inspiratory whoop; treat with azithromycin to reduce transmission - Signs of impending respiratory failure include exhaustion, altered mental status, and decreasing respiratory effort --- ## Key Terms | Term | Definition | |------|------------| | Stridor | High-pitched inspiratory sound from upper airway obstruction | | Wheeze | High-pitched expiratory sound from lower airway obstruction | | Croup | Viral laryngotracheobronchitis causing barky cough and stridor | | Bronchiolitis | Viral lower respiratory infection in infants causing small airway obstruction | | ICS | Inhaled corticosteroid; cornerstone controller therapy for asthma | | SABA | Short-acting beta-agonist for quick relief of bronchospasm | | Peak flow | Maximal expiratory flow rate used to monitor asthma control | | Westley score | Croup severity scoring system guiding treatment decisions | --- *This content is subject to the [MIT License](https://opensource.org/licenses/MIT). © 2024–2026 Hibbert School of Medicine.*