McCance Patho Chapter 36

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Alterations of Pulmonary Function in Children

When is the branching of the bronchial tree complete during fetal life?

16th week

How many years do the number of alveoli continue to increase?

During the first 5-8 years of life.

Blunted ventilatory response

For up to 3 weeks of age, the newborn has a blunted ventilatory response to hypoxia compared with older children and adults.

Signs of acute respiratory failure

*Increased respiratory effort with retractions.
*Cyanosis or pallor
*Decreased level of consciousness
*Cardiovascular signs


typical for nasopharyngeal obstruction


harsh, vibratory sound of variable pitch caused by turbulent flow through the partially obstructed airway

Inspiratory stridor

obstruction of the extrathoracic airway (above the thoracic inlet)

Expiratory stridor

generated by an obstruction in the intrathoracic airway (the middle to lower trachea and central bronchi.

Biphasic stridor

obstruction of the glottis itself or a fixed lesion in the subglottic space

muffling of the voice

suggests supralaryngeal obstruction, such as epiglottitis or retropharyngeal abscess.

Why does airway obstruction occur sooner in infants than in older children?

Airway resistance is proportional to the inverse of the fourth power of the radius, thus decrease to half the original diameter increases resistance 16 fold.


acute laryngotracheobronchitis. Caused by a virus 85% of cases, common from 6 months to 3 years. Highest in late autumn and winter. Occurs more in boys. Caused primarily by subglottic edema from the infection. Harsh cough, stridor, low-grade fever.

Spasmodic croup

characterized by hoarseness, barking cough, and stridor, but is of sudden onset, usually at night and without viral prodrome. Often resolves as quickly as it develops and usually occurs in older children.

Acute epiglottis

Caused by Haemophilus influenzae type B (Hib). Infants less than 1 year of age are at greatest risk. Usually 2-6 years old. Inflammation of supraglottic structures. Severe sore throat, high fever, toxic appearance, muffled voice, may drool, sits erect and quietly. Life threatening emergency. Examination of the throat should NOT be attempted because it may trigger laryngospasm and respiratory collapse.

The most common potentially life-threatening upper airway infection in children. Abrupt or following viral illness. Inflammation of upper trachea. Tachypnea, stridor, hoarse voice, fever, harsh cough, toxic appearance, purulent secretions. Broad spectrum IV antibiotics

Bacterial tracheitis.

Peritonsillar abscess

unilateral swelling of the pharynx, fever, sore throat, dysphasia, trismus, and pooling of saliva. most often a complication of acute tonsillitis.

Retropharyngeal abscess

Occurs more commonly in male children about 4 years of age and as a consequence of either nasopharyngeal infection or penetrating local injury.


An allergic phenomenon causing localized edema involving the deep, subcuatneous layers of skin or mucous membranes. Causes facial swelling first. If airway is compromised, standard treatment includes epinephrine, antihistamines, and corticosteroids.


Abnormally soft laryngeal cartilages and is the most common cause of chronic stridor in infants. The epiglottis or arytenoids, or both, fold inward with inspiration. Inspiratory stridor, feeding difficulties. Usually mild and improves spontaneously over the first year of life.


Tracheobronchial cartiages are flaccid and tend to collapse during the expiratory cycle.

subglottic stenosis

subglottic airway diameter of less than 4 mm at the cricoid region in a full-term infant. (3 mm in premie) Incomplete recanalization of the laryngotracheal tube during the third month of gestation. Can be a complication of endotracheal intubation.

Obstructive Sleep apnea syndrome (OSAS)

Breathing disorder. Prolonged partial and/or intermittent complete UAO during sleep. Associated with failure to thrive, behavioral deficits, and sudden infant death. Snoring, labored breathing, restlessness, and sweating during sleep. Most common case is adenotonsillar hypertrophy.

Choanal atresia

Congenital lack of patency of the nasal cavity within the nasopharynx.

Laryngeal atresia

caused by failure of the larynx to recanalize during embryogenesis.

Tracheal stenosis

Rare malformation characterized by inspiratory and expiratory stridor whithin the first weeks of life. Assoicated with pulmonary, cardiovascular, and GI malformations.


Infection and inflammation in the terminal airways and alveoli. Usually viral in young children.

Respiratory Distress Syndrome (RDS)

Caused by surfactant deficiency, fibrin deposits in the alveoli create the appearance of hyaline membranes. Prematurity is major factor. PaO2 less than 50 mm Hg in room air, central cyanosis, classic chest film "ground glass" appearance.

Bronchopulmonary dysplasia

aka chronic lung disease of prematurity. Associated with arrested lung development. Usually premature birth before 28 weeks of gestation.

Canalicular stage

Lung development in fetus between 16-28 weeks. Critical period during which type II epithelial cells appear, capillaries grow into the future distal alveolar regions, and the interstitium begins to condense.

Saccular stage

lung development at approximately 26-28 weeks. The alveoli are vulnerable to inflammation and impaired growth during this stage.


Common viral induced lower respiratory tract infection of the small airways that occurs in children younger than 2 years of age. Most commonly caused by RSV. Peak in winter, spike in February. Airway narrowing causes obstruction of airflow that is worse with expiration.

Most common cause of viral pneumonia in infants and young children

Respiratory synctial virus (RSV)

Atypical pneumonia

caused by mycoplasma pneumoniae or chlamydophila pneumoniae. The most common cause of CAP in school aged children.

Aspiration pneumonitis

caused by a foreign substance, such as food, meconium, secretions, or environmental compounds entering the lung and causing inflammation of the lung tissue.

Bronchiolitis Obliterans (BO)

fibrotic obstruction of the respiratory bronchioles and alveolar ducts secondary to intense inflammation. Rare in children, associated with viral pulmonary infections.

Most prevalent chronic disease in children. Initiated by a type I hypersensitivity reaction primarily mediated by IgE.


Acute Lung Injury/Acute respiratory distress syndrome

ALI precedes the development of ARDS. Results from injury. Progressive respiratory distress, severe hypoxemia refractory to treatment with supplemental oxygen, decreased pulmonary compliance, bilateral infiltrates, and no evidence of heart failure.

Cystic Fibrosis

An autosomal recessive inherited disorder that is associated with defective epithelial chloride ion transport. Characterized by abnormal secretions that cause obstructive problems within the respiratory, digestive, and reproductive tracts.

Expiratory stridor is also called...

monophonic wheeze

Children have more cartilage in their airway than adults


Airway obstruction occurs earlier in infants than in children


Compared to older children, a 2 week neonate has a blunted ventilatory response to


Meconium aspiration causes pneumonitis because the _________ __________ in meconium cause inflammation.

Bile Salts

The ______________ hypothesis attempts to explain the high prevalence of asthma in westernized cultures


Up to 2-3 months, babies can only breathe through their nose.



disease of unkown cause. Most common cause of unexplained infant death in the Western countries. Low during the first month of life, peaks at 2-4 months, unusual after 6 months. Higher in winter months.

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