The Respiratory System PDF

THE RESPIRATORY SYSTEM Prof. Dr. Raid M R Umran Pediatrics Block ANATOMY OF THE RESPIRATORY SYSTEM The large surface area of the nasal turbinates, warm, humidify, and filter the inspired air. Secretions draining from the paranasal sinuses are carr...

THE RESPIRATORY SYSTEM Prof. Dr. Raid M R Umran Pediatrics Block ANATOMY OF THE RESPIRATORY SYSTEM The large surface area of the nasal turbinates, warm, humidify, and filter the inspired air. Secretions draining from the paranasal sinuses are carried to the pharynx by the mucociliary action of the ciliated respiratory epithelium. The epiglottis protects the larynx during swallowing by deflecting material toward the esophagus. The posterior wall of the trachea is membranous, allowing airway caliber to change during inspiration and expiration. Beyond the lobar bronchi, cartilaginous support of the airways becomes discontinuous but persists until the terminal bronchioles. Airway formation and branching is complete at birth, although length and caliber continue to increase until final adult height is achieved. The lung parenchyma, where gas exchange occurs, is composed of the respiratory bronchioles, alveolar ducts, and alveoli. A full-term infant has approximately 25 million alveoli; an adult nearly 300 million alveoli. The growth of new alveoli occurs during the first 2 years of life and is complete by 8 years of age.  PULMONARY PHYSIOLOGY The major function of the lungs is to exchange O2 and CO2. Negative intrathoracic pressure is generated by contraction and lowering of the diaphragm during normal inspiration, exhalation is normally passive. Tidal volume (TV): is the amount of air inspired with each relaxed breath. Functional residual capacity (FRC): The volume of gas retained in the lung at the end of a relaxed exhalation. Total lung capacity (TLC) is the volume of gas in the lungs at the end of maximal inhalation. Residual volume (RV) is the volume of gas left in the lungs at the end of a maximal exhalation. Vital capacity (VC) is the maximal amount of air that can be forcibly expelled from the lungs and is the difference between TLC and RV. Lung compliance (change in volume for a given change in pressure) is a measure of the ease with which the lung can be inflated. Airway resistance is influenced by the diameter and length of the conducting airways, the viscosity of gas, and the nature of the airflow  Obstructive airways disease that impact airway resistance, particularly lower airway resistance. Restrictive lung disease is the processes that decrease lung compliance (surfactant deficiency, pulmonary fibrosis, pulmonary edema) can also result from respiratory muscle weakness, pleural disease (effusion, inflammation, or mass), thoracic stiffness (scoliosis), and abdominal distention. The nose, Ciliated epithelium lining the airways, Alveolar macrophages and polymorphonuclear cells and Cough are important mechanism for protecting the lungs from infection.  Gas exchange depends on alveolar ventilation, pulmonary capillary blood flow, and the diffusion of gases across the alveolar-capillary membrane. Exchange of CO2 is determined by alveolar ventilation, whereas the exchange of O2 is influenced primarily by the regional matching of ventilation (V) with pulmonary blood flow (Q) (V/Q matching). Hypoxemia resulting from V/Q mismatching. Causes of Hypoxemia:  Any factor that impairs respiratory mechanics is likely to increase the respiratory rate. Normal respiratory rate by age: Clinical assessment: History: Examination: Physical Signs of Pulmonary Disease:  Cough is a rapid, forceful expiration intended to clear the airways of debris and secretions Grunting (forced expiration against a partially closed glottis) Stridor is a harsh, monophonic sound caused by a partially obstructed large airway, more commonly heard on inspiration and localized to the neck. Wheezing is produced by partial obstruction of the smaller lower airways, more commonly heard during exhalation and localized to the chest. Rhonchi, crackles or rales. DIAGNOSTIC MEASURES Imaging techniques Chest radiographs Computed tomography (CT) of the chest Magnetic resonance imaging (MRI) Ultrasonography Arterial blood gas Pulse oximetry Pulmonary function testing Endoscopic evaluation of the airways Examination of sputum Lung biopsy THERAPEUTIC MEASURES Oxygen Administration Aerosol Therapy Intubation Tracheostomy Mechanical Ventilation Sinusitis Only the maxillary and ethmoid sinuses are present at birth, whereas the sphenoid sinuses are present by 5 years of age. Frontal sinuses begin to develop at 7 years of age and are not completely developed until adolescence. Sinusitis is a suppurative infection of the paranasal sinuses and most commonly occurs as a complication of an upper respiratory tract infection (URI). Mainly due to viral and bacterial. The bacterial causes of most cases of acute sinusitis are Streptococcus pneumoniae, nontypable Haemophilus influenzae, and Moraxella catarrhalis. Staphylococcus aureus and anaerobes emerge as important pathogens in subacute and chronic sinusitis. Fungal sinusitis can occur in immunocompromised patients, especially those with prolonged and/or profound neutropenia. The most common presentation of acute bacterial sinusitis is persistent rhinorrhea, nasal congestion, and cough, especially at night, headache, high fever and purulent nasal discharge Routine imaging is not recommended in uncomplicated infections. Plain x-ray, computed tomography (CT), and magnetic resonance imaging (MRI) may reveal sinus clouding. Amoxicillin for 10–14 days can be used as first-line therapy of uncomplicated sinusitis in children. Broadening therapy to amoxicillin-clavulanate is appropriate if there is no clinical response to amoxicillin within 2–3 days Otitis Media OM is a suppurative infection of the middle ear cavity. Bacteria gain access to the middle ear when the normal patency of the eustachian tube is blocked by upper airway infection or hypertrophied adenoids. The common bacterial pathogens are Streptococcus pneumoniae, nontypable Haemophilus influenzae, Moraxella catarrhalis, and less frequently, group A streptococcus. In infants, the most frequent symptoms of OM are nonspecific and include fever, irritability, and poor feeding. In older children and adolescents, OM usually is associated with fever and otalgia (acute ear pain). OM also may present with otorrhea (ear drainage) after spontaneous rupture of the tympanic membrane. Routine laboratory studies are not useful in the evaluation of OM and depend on clinical evaluation. First-line therapy for most children is amoxicillin (80–90mg/kg/day in two divided doses). Recommended nextstep treatments include high-dose amoxicillin-clavulanate (amoxicillin 80–90mg/kg/day), cefdinir, or ceftriaxone (50mg/kg intramuscularly in daily doses for 3 days). Intramuscular ceftriaxone is especially appropriate for children with vomiting that precludes oral treatment. Tympanocentesis may be required for patients who are difficult to treat or who do not respond to therapy. Acetaminophen and ibuprofen are recommended for fever or pain. Decongestants or antihistamines are not effective.  Croup (Laryngotracheobronchitis) 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. An inflammation of laryngotracheal airway with increases airway resistance and the work of breathing. During inspiration, the walls of the subglottic space are drawn together, aggravating the obstruction and producing the stridor characteristic of croup. The most common causes of croup are parainfluenza viruses (types 1, 2, and 3), respiratory syncytial virus (RSV), influenza, and adenovirus. Clinical manifestations of croup are a harsh cough; barking or brassy, hoarseness, inspiratory stridor, low-grade fever, and respiratory distress. Symptoms worse at night and are exacerbated with crying or agitation. Croup is a clinical diagnosis and does not require routine radiology or laboratory studies. Anteroposterior radiographs of the neck often show the diagnostic subglottic narrowing of croup known as the steeple sign. Dexamethasone (0.6mg/kg) may be given once intramuscularly or orally. Alternatively, prednisolone (2mg/kg/day) may be given orally for 3 days. For significant airway compromise, administration of aerosolized racemic epinephrine reduces subglottic and producing marked clinical improvement. Hospitalization is often required for children with cyanosis or stridor at rest. Epiglottitis Is a medical emergency because of the risk of sudden airway obstruction. usually caused by group A streptococcus or Staphylococcus aureus or H. influenzae type b. Patients typically prefer sitting, often with the head held forward, the mouth open and drooling saliva, and the jaw thrust forward (sniffing position, tripod position), and they may appear distressed and toxic. Lateral radiograph reveals thickened and bulging epiglottis (thumb sign) and swelling of the aryepiglottic folds. The diagnosis is confirmed by direct observation of the inflamed and swollen supraglottic structures and swollen, cherry red epiglottis. Direct observation of the larynx should only be performed in the operating room. Epiglottitis requires antibiotic therapy and may be endotracheal intubation to maintain the airway. Pertussis Pertussis is an acute respiratory tract infection; Pertussis (whooping cough) is caused by Bordetella pertussis, a gram-negative pleomorphic bacillus with fastidious growth requirements. B. pertussis infects only humans and is transmitted person to person by coughing. The typical incubation period is 7–10 days but can range between 5 and 21 days. Patients are most contagious during the first 2 weeks of cough. The progression of the disease is divided into catarrhal, paroxysmal, and convalescent stages. The catarrhal stage is marked by nonspecific signs (increased nasal secretions and low-grade fever) lasting 1–2 weeks. The paroxysmal stage is the most distinctive stage of pertussis and lasts 2–4 weeks. Coughing occurs in paroxysms during expiration, causing young children to lose their breath. The forceful inhalation against a narrowed glottis that follows this paroxysm of cough produces the characteristic whoop. The convalescent stage is marked by gradual resolution of symptoms over 1–2 weeks. Coughing becomes less severe, and the paroxysms and whoops slowly disappear. The diagnosis depends on isolation of B. pertussis or detection of its nucleic acids. Culture on specialized media. Polymerase chain reaction. Lymphocytosis is present in 75–85% of infants and young children but is not diagnostic. The white blood cell count may increase from 20,000/mm3 to more than 50,000/mm3. Treatment Macrolide antibiotics (azithromycin, clarithromycin, or erythromycin) are recommended for treatment. Azithromycin is preferred in neonates due to the association between erythromycin treatment and the development of pyloric stenosis. Treatment during the catarrhal phase eradicates nasopharyngeal carriage of organisms within 3–4 days and may lessen symptom severity. Treatment in the paroxysmal stage does not alter the course of illness but decreases the potential for spread to others. Complications and prognosis Major complications are most common among infants and young children and include hypoxia, apnea, pneumonia, seizures, encephalopathy, malnutrition, and death. Most children recover normal pulmonary function with complete healing of the respiratory epithelium. Bronchiolitis Bronchiolitis is a disease of small bronchioles with increased mucus production and occasional bronchospasm, and airway obstruction. It is commonly caused by a viral lower respiratory tract infection. Bronchiolitis is most commonly seen in infants and young children. Respiratory syncytial virus (RSV) is a primary cause of bronchiolitis, followed in frequency by human metapneumovirus, parainfluenza viruses, influenza viruses, adenoviruses, rhinoviruses, coronaviruses, and, infrequently, Mycoplasma pneumoniae. Bronchiolitis is a leading cause of hospitalization of infants. Bronchiolitis occurs almost exclusively during the first 2 years of life, with a peak age at 2–6 months. Many healthy children with bronchiolitis can be managed as outpatients. premature infants and children with chronic lung disease of prematurity, hemodynamically significant congenital heart disease, neuromuscular weakness, or immunodeficiency are at increased risk of severe, potentially fatal disease. CLINICAL MANIFESTATIONS Incubation period of 4–6 days. Progressive respiratory illness similar to the common cold Cough and rhinorrhea. Over 3–7 days to noisy, raspy breathing and audible wheezing. Low-grade fever accompanied by irritability Increased work of breathing. Physical signs of bronchiolar obstruction include prolongation of the expiratory phase of breathing, nasal flaring, intercostal retractions, suprasternal retractions, and air trapping with hyperexpansion of the lungs. grunting and cyanosis may be present in sever cases. LABORATORY AND IMAGING STUDIES Routine laboratory tests are not required to confirm the diagnosis. It is important to assess oxygenation in severe cases of bronchiolitis by Pulse oximetry. Frequent, regular assessments and cardiorespiratory monitoring of infants are necessary Rapid viral diagnosis of nasopharyngeal secretions performed by polymerase chain reactions for RSV, human metapneumovirus, parainfluenza viruses, influenza viruses, coronaviruses, and adenoviruses are sensitive tests to confirm the infection. Chest radiographs are not always necessary but frequently show signs of lung hyperinflation, including increased lung lucency and flattened or depressed diaphragms. Areas of increased density may represent either viral pneumonia or localized atelectasis. Treatment Supportive therapy, including respiratory monitoring, control of fever, hydration, upper airway suctioning, and, if needed, oxygen administration. Indications for hospitalization include moderate to marked respiratory distress, hypoxemia, apnea, inability to tolerate oral feeding, and lack of appropriate care available at home. Hospitalization of high-risk children with bronchiolitis should be considered. Among hospitalized infants, supplemental oxygen by nasal cannula is often necessary, but intubation and ventilatory assistance for respiratory failure or apnea are required in less than 10% of these infants. Bronchodilators, corticosteroids, chest physiotherapy, and hypertonic saline are seldom effective and are not generally recommended. Likewise, antibiotics should be avoided unless there is strong suspicion for concomitant bacterial infection. RIBAVIRIN, Not routinely recommended. May be useful in infants with confirmed RSV at risk for more severe disease Prognosis: Most cases of bronchiolitis resolve. Recurrence is common but tends to be mild. The incidence of asthma seems to be higher in children hospitalized for bronchiolitis as infants. There is a 1–2% mortality rate, highest among infants with pre-existing cardiopulmonary or immunologic impairment. PREVENTION Monthly injections of palivizumab, an RSV-specific monoclonal antibody, initiated just before the onset of the RSV season Palivizumab is indicated for infants with prematurity (born before 29 weeks, 0 days gestation), chronic lung disease of prematurity, and those with hemodynamically significant cyanotic and acyanotic congenital heart disease. Pneumonia Is an infection of the lower respiratory tract that involves the airways and parenchyma, with consolidation of the alveolar spaces. Lobar pneumonia describes pneumonia localized to one or more lobes of the lung. Bronchopneumonia refers to inflammation of the lung that is centered in the bronchioles and leads to the production of a mucopurulent exudate that obstructs some of these small airways and causes patchy consolidation of the adjacent lobules. Interstitial pneumonitis refers to inflammation of the interstitium, which is composed of the walls of the alveoli, the alveolar sacs and ducts, and the bronchioles. Pneumonia is the single largest contributor of childhood mortality worldwide, killing an estimated 1 million children under 5 years of age annually Causes: Infectious agents that commonly cause community-acquired pneumonia vary by age: Additional agents occasionally cause pneumonia. Severe acute respiratory syndrome (SARS) is due to SARS associated coronavirus (SARS-CoV) or SARS-CoV-2, the cause of the coronavirus infectious disease (COVID-19) pandemic. SARS-CoV-2 is an emerging pathogen but appears to cause less mortality in children than in adults; Avian influenza (bird flu) is a highly contagious viral disease of poultry and other birds caused by influenza A (H5N1). CLINICAL MANIFESTATIONS Neonates may have fever or hypoxia. Fever, chills, tachypnea, cough, malaise, pleuritic chest pain, retractions, and shortness of breath—are common in older infants and children. COVID-19 include cough, fever, dyspnea, and myalgias. Other include abdominal pain and diarrhea, headache, sore throat, as well as loss of taste or smell sensations. Severe involvement includes worsening dyspnea, hypoxia, and greater than 50% lung infiltrates on imaging. Critical illness includes respiratory failure requiring mechanical ventilation or extracorporeal membrane oxygenation (ECMO) and multiorgan system dysfunction (myocarditis, hypercoagulability, acute kidney injury). Viral pneumonias are generally associated more often with cough, wheezing, or stridor; fever is less prominent than with bacterial pneumonia. Bacterial pneumonias are typically associated with higher fever, chills, cough, dyspnea, and auscultatory findings of lung consolidation. Other signs of respiratory distress include nasal flaring, intercostal and subcostal retractions, and grunting. LABORATORY AND IMAGING STUDIES CBC: WBC with viral pneumonias is often normal or mildly elevated, with a predominance of lymphocytes. whereas with bacterial pneumonias, the WBC count can be elevated (>15,000–20,000/mm3) and with a predominance of neutrophils. Mild eosinophilia is characteristic of infant C. trachomatis pneumonia. Blood cultures should be performed on moderately to severely ill (5–10%). (PCR) or rapid viral antigen detection can be used forto confirme viral, M. pneumoniae and CMV pneumonitis. Frontal and lateral radiographs CXR are required to localize disease and adequately visualize retrocardiac infiltrates; they are recommended for diagnosis among hospitalized. Bacterial pneumonia characteristically shows lobar consolidation or a round pneumonia, with pleural effusion in 10–30% of cases. Viral pneumonia characteristically shows diffuse, streaky infiltrates of bronchopneumonia and hyperinflation. Atypical pneumonia, as with M. pneumoniae and C. pneumoniae, shows increased interstitial markings or bronchopneumonia. Ultrasound should be used to assess the size of pleural effusions and whether they are freely mobile. Computed tomography (CT) is used to evaluate serious disease, lung abscesses, bronchiectasis, and effusion characteristics. DIFFERENTIAL DIAGNOSIS allergic hypersensitivity pneumonitis, asthma, cystic fibrosis; cardiac diseases, such as pulmonary edema caused by heart failure; and autoimmune diseases, such as certain vasculitides and systemic lupus erythematosus. lung trauma and contusion, hemorrhage, foreign body aspiration. TREATMENT Therapy for pneumonia includes supportive (intravenous fluids, oxygen, or even assisted ventilation) and specific treatment. Depends on the degree of illness, complications, and the infectious agent. Hospitalization should be considered in infants under 6 months with suspected bacterial pneumonia Pneumococcal Pneumonia S. pneumoniae is still the most common cause of bacterial infection of the lungs. one or more lobes, lobar pneumonia diffuse disease that follows a bronchial distribution and that is characterized by many limited areas of consolidation around the smaller airways Permanent injury is rare. ali alfaydawi 2020 29 ali alfaydawi 2020 30 CLINICAL MANIFESTATIONS. Abrupt onset of fever of 39º O/E Respiratory distress the chest is often unrevealing. Auscultation may reveal Cyanosis diminished breath sounds and fine, Grunting; crackling rales on the affected side, Flaring of the alae nasi; and there may be localized dullness Retractions of the supraclavicular, to percussion Intercostal, and subcostal areas; pleuritic pain Tachypnea; and Tachycardia 31 Radiographic findings Lobar consolidation Bronchopneumonia Pleural reaction Empyema( complication ) COMPLICATIONS metastatic infection Empyema pleural effusion ali alfaydawi 2020 32 ali alfaydawi 2020 33 ali alfaydawi 2020 34 ali alfaydawi 2020 35 ali alfaydawi 2020 36 Staphylococcal Pneumonia a serious and rapidly progressive infection associated with prolonged morbidity and high mortality. less frequently than pneumococcal or viral pneumonia more common in infants than in children. Most cases occur between October and May staphylococcal pneumonia is frequently preceded by a viral upper respiratory tract infection 30% of all patients are under 3 mo of age and 70% are under 1 yr ali alfaydawi 2020 37 PATHOGENICITY AND PATHOLOGY confluent bronchopneumonia often unilateral or more prominent on one side than the other presence of extensive areas of hemorrhagic necrosis pleural surface is usually covered by a thick layer of fibrinopurulent exudate Multiple abscesses Rupture of a small subpleural abscess may result in pyopneumothorax may erode into a bronchus, producing a bronchopleural fistula. ali alfaydawi 2020 38 CLINICAL MANIFESTATIONS Abruptly with the onset of high fever, cough, and evidence of respiratory distress Signs and symptoms include tachypnea, grunting respirations, sternal and subcostal retractions, nasal flaring, cyanosis, lethargic toxic Severe dyspnea and a shocklike state may be present gastrointestinal disturbances, characterized by vomiting, anorexia, diarrhea abdominal distention secondary to a paralytic ileus. ali alfaydawi 2020 39 Physical findings depend on the stage of pneumonia. Early……diminished breath sounds, scattered rales, and rhonchi With the development of effusion, empyema, or pyopneumothorax, dullness on percussion is noted, and breath sounds and vocal fremitus are markedly diminished ali alfaydawi 2020 40 LABORATORY MANIFESTATIONS In the older infant and child a leukocytosis of ³{greater than or equal}20,000 cells/mm3 usually occurs, young infant the white blood cell count may remain within the normal range. a count