Pulmonary Atelectasis

The pathophysiologic mechanisms of atelectasis include[1, 2] :

• Resorption or obstructive atelectasis due to intrinsic or extrinsic airway obstruction

• Passive atelectasis from diaphragmatic dysfunction and hypoventilation

• Compressive atelectasis from lung tissue compression and ineffective alveolar expansion from intra or thoracic forces

• Adhesive atelectasis due to increased surface tension

Because the right middle lobe orifice is the narrowest of the lobar orifices and because it is surrounded by lymphoid tissue, it is the most common lobe to become atelectatic. This is referred to as right middle lobe syndrome.

Intrinsic airway obstruction is the most common cause of atelectasis in children, and asthma is the most common underlying disorder that predisposes patients to atelectasis. Other causes include bronchiolitis, aspiration due to a swallowing disorder, endobronchial tuberculosis, aspiration from gastroesophageal reflux, airway foreign bodies, cystic fibrosis, and increased or abnormal airway secretions for other reasons. Children younger than 10 years are less likely to have developed the interairway canals of Lambert or the interalveolar pores of Kohn. Thus, young children depend more on the feeding airways to move air into the alveoli. When their airways become obstructed, they are more likely to develop atelectasis than older children who have developed those communications.

Extrinsic compression on the airways is most likely to come from enlarged lymph nodes (such as those due to tuberculosis infection), lymphoma and other tumors in the chest, an enlarged heart that compresses the left main or left lower lobe bronchus, and left-to-right intracardiac shunts that increase blood flow through the pulmonary arteries.

In children with hypoventilation for a protracted period, the alveoli may collapse. This may occur in children with neuromuscular disease, those who have had recent thoracic or upper abdominal surgery, those on medications that decrease their minute ventilation (such as narcotics), and those with abnormally small or dysmorphic chest walls, which may be less compliant than the normal chest wall. Atelectasis is also often seen in children who undergo sedation for CT or MRI. A chest study often shows dependent atelectasis in these children. One study[3] suggested that children who are sedated with propofol infusion were less likely to develop atelectasis than children who have positive pressure ventilation anesthesia for MRI. However, the former group was older. Such children may also be predisposed to atelectasis because of poor clearance of airway secretions. An ineffective cough allows these secretions to obstruct the airway.

Atelectasis due to compressed lung tissue occurs most commonly when air, blood, pus, or chyle is present in the pleural space. Intrathoracic abdominal contents, chest wall masses, cardiomegaly, and an abnormal chest wall can all compress adjacent lung tissue. If a portion of lung enlarges, such as with congenital emphysema, or if focal overinflation occurs for any other reason, it may compress the adjacent lung, causing atelectasis.

Lack of surfactant coating on the alveolar surface from pus, fluid or cell, debris can cause increased surface tension and subsequent alveolar collapse. Some examples include respiratory distress of the preterm newborn, meconium aspiration, pneumonia, and acute respiratory distress syndrome.

Obstruction of an airway or diminished distention of alveoli may cause atelectasis. Depending on the causative mechanism, atelectasis may be acute or chronic

The most common causes involving airway obstruction include the following:

• Airway obstruction due to a mucous plug or other airway secretions, such as with bronchiolitis

• Bronchospasm airway secretions and airway inflammation in patients with asthma

• Abnormal airway secretions in cystic fibrosis

• Abnormal airway clearance, such as with ciliary dyskinesia syndrome

• Airway foreign body

• Extrinsic compression on an airway (eg, compression due to an enlarged or aberrant vessel)

• Enlarged lymph nodes that compress the airway

• Masses in the chest that compress the airway or alveoli

• Cardiomegaly or enlarged pulmonary vessels that compress adjacent airways

Causes of diminished alveolar distention include the following:

• Small or dysmorphic chest wall

• Severe scoliosis

• Neuromuscular diseases

• Anesthesia or sedation

• Pain from upper abdominal surgery

• Abdominal distention

• Chest wall or upper abdominal pain

United States statistics

Incidence of atelectasis is reported to occur in 8% to 15% of children during mechanical ventilation.[4, 5]

Race-, sex-, and age-related demographics

Race

Other than any racial predilections for the underlying disorders, no racial predilection for atelectasis has been reported (see Cystic Fibrosis and Asthma).

Sex

Atelectasis has no sex predilection.

Age

Atelectasis is probably more common in children younger than 10 years because their airways are typically narrower and are more likely to become obstructed by secretions, airway inflammation, or both. In addition, these smaller airways are more easily compressed. These children are also less likely to have collateral ventilation.

In most cases, the prognosis for the atelectasis is the same as the prognosis for the underlying disorder. If caused by a readily reversible disorder, the atelectasis should be reversible as well.

In children with significant neuromuscular disease and lower lobe atelectasis, the atelectasis may be very difficult to resolve.

Morbidity/mortality

Most of the morbidity and any mortality is due to the underlying disorder. The primary complication of atelectasis is hypoxemia, which is usually transient. Within 24-48 hours, the lung is able to decrease or shut off blood flow to the atelectatic area. This is probably caused by factors such as serotonin that reacts to the local hypoxia in the alveoli and causes an intense vasoconstriction. If the atelectasis is massive enough, it may cause enough hypoxemia acutely to require supplemental oxygen or ventilatory support.

Atelectasis is a suggested cause of fever; however, no known physiologic reason supports this. Recent data dispute this old dogma. A study of adults after open-heart surgery showed no correlation between atelectasis and fever and found that incidence of fever actually rose as the atelectasis was resolving.[6]  Patients with temperatures of more than 38.5°C were less likely to have atelectasis on radiography findings than those patients who were afebrile and undergoing radiography as part of the postoperative routine.

Another concern is the likelihood of infection in the atelectatic portion of the lung. Although the clearance in this portion of the lung is abnormal, the lung is normally a sterile environment. In the otherwise healthy child with atelectasis, infection is unlikely. However, if the child has abnormal secretions or is prone to aspiration, secondary infection of the atelectatic lung may occur. In children with chronically infected lungs, the atelectatic portion is likely to be similarly infected, with decreased ability to clear the infection. This sets up the possibility of bronchiectasis developing in that portion of the lung. Children who remain on assisted ventilation with atelectasis are at risk of developing infection, including infection in the atelectatic portion of the lung. This portion has less intrinsic clearance, which increases the risk of significant infection if organisms enter this portion.

Complications

Potential complications include the following:

• Complications arising from the underlying disorder

• Hypoxemia

• Secondary infection of the atelectatic lung

• Bronchiectasis in the atelectatic portion of a chronically infected lung

Educating the patient and the parents about the underlying disorders and the need to prevent complications is crucial.

Most symptoms of pulmonary atelectasis are nonspecific and related to the underlying disorder. The clinical presentation depends on the underlying cause and the degree of volume loss of lung.

Atelectasis alone only causes tachypnea as the child attempts to compensate for decreased tidal volume by increasing the frequency of respiration.

If the atelectasis is large enough, the child may grunt in an attempt to create auto–positive end-expiratory pressure (PEEP), both to improve oxygenation and to attempt to open the atelectatic areas.

If a child has underlying cardiopulmonary or neuromuscular disease and is on a monitor, sudden decreases in oxygen desaturation may be a sign of atelectasis. Atelectasis is one of the most common causes of sudden decreases in oxygen saturation in children.

Most findings upon physical examination are related to the underlying disorder. In one study comparing physical examination to chest radiography in children,[7]  out of 35 children with radiographically proven atelectasis, the atelectasis was detected by physical examination in only 8.

Breath sounds may be decreased in the atelectatic portion of the lung, although the segment involved may be so small that the changes cannot be perceived. Also, the atelectatic portion may be in a segment inaccessible to the stethoscope.

If the atelectatic portion and chest wall are large enough, dullness to percussion may be detected.

The atelectasis may also occur in the right middle lobe or lingula in an adolescent girl. Because both are anteriorly located, the physician must listen to the anterior chest of the patient to hear these lobes. If the physician feels awkward about examining this area and fails to do so, the lobes are not correctly evaluated, and any corresponding abnormalities are not heard.

Laboratory studies in pulmonary atelectasis should include measurement of oxygenation, either by oximetry or ABG.

Microbiological tests to detect underlying infection.

Pulmonary function studies may detect unrecognized airflow obstruction, restrictive disease, or decreased respiratory muscle pressures.

CT scanning: Chest CT scanning may help evaluate for compression of the airway. CT scanning may also detect any underlying pathology that predisposes to atelectasis. It may also reveal diffuse disease not suggested by plain radiography.

Chest radiography: Plain chest radiography is often the first study to reveal atelectasis but may fail to detect small areas of atelectasis.

A study that evaluated the usefulness of lung ultrasonography for the diagnosis of neonatal pulmonary atelectasis reported that lung ultrasonography is an accurate and reliable method for diagnosing neonatal pulmonary atelectasis. The authors also added that lung ultrasonography can find concealed lung atelectasis that could not be detected on a chest radiograph. The advantages of lung ultrasound include avoiding transport, easy to control body position, no radiation exposure, and it is available at bedside.[8]

Evidence based studies to guide therapy in pediatric atelectasis are lacking.[9] The following treatment modalities are described in the literature:

• Chest physiotherapy
• Medications including inhaled bronchodilators, DNase and surfactant
• Fiberoptic bronchoscopy
• Positive end-expiratory pressure
• Treatment of underlying infections
• Treatment of underlying condition

Bedside chest physiotherapy has been used for children on mechanical ventilation. A four-step procedure for treatment of various degree of lung collapse is described in literature.[10] The technique involves bagging with 100% oxygen, instillation of 0.25-0.5 mL/kg sterile saline endotracheally, followed by bagging with momentary inspiratory hold, then release of the hold and simultaneous forced exhalation and vibration to simulate cough, and endotracheal suctioning. In this study 84% of ventilated children had successful improvement in lung expansion.

Medications including inhaled bronchodilators, DNase, and surfactant (see Medications section).

Dornase alfa (DNase) is a mucolytic therapy and can be administered as nebulized or direct tracheal application. DNase fragments extracellular DNA molecules in tracheobronchial secretions and improves flow properties and clearance of mucus.[11] DNase has been successfully used in patients with cystic fibrosis and others with acute atelectasis. In a retrospective case series involving 25 non-cystic fibrosis children with infectious atelectasis, the administration of DNase showed clinical and radiologic improvement. However, the success of the medication depends on the amount of DNA in the secretions, and neutrophil counts in the affected area.[12]

 Although N-acetyl cysteine has been used as a mucolytic both in nebulizer and bronchoscope forms, success has not been validated in controlled studies. Furthermore, it has the potential to cause significant bronchospasm.

If the patient is severely affected by the atelectasis and response to therapy of the underlying disorder is suboptimal, bronchoscopic removal of secretions, mucous plugs, or both may be helpful.

A pediatric pulmonologist may help diagnose and treat the underlying disorder and may also be helpful if bronchoscopy is necessary.

Bronchoscopy has both a diagnostic and therapeutic value. Flexible bronchoscopy may help distinguish intrinsic obstruction from extrinsic compression. Direct bronchoscopic inspection can also better define the nature of any intrinsic obstructing lesion. A retrospective study by Bar-Zohar et al in one hundred consecutive infants and children hospitalized in a PICU showed that treatment of atelectasis by flexible fiber optic bronchoscopy was successful in 26 of 35 cases (74.3%) without any procedure-related mortality or life-threatening complications.[13] Repeat bronchoscopic examination can be performed for removal of secretions reexpansion of atelectatic segment.[14]

Rigid bronchoscopy  has been used for treatment of pediatric pulmonary atelectasis for removal of mucus plugs, thick secretions  and removal of a foreign body. Rigid bronchoscope is safe but requires general anesthesia.[15]

Bronchoscopy should be used with caution in patients in a pediatric intensive care unit, who may not be able to tolerate the changes in partial pressure of oxygen and partial pressure of carbon dioxide in arterial blood that often accompany the procedure. Caution is also warranted in patients with traumatic brain injury because of the increase in intracranial pressure that can be associated with bronchoscopy, despite the use of adequate sedation.[16]

Bronchoscopic surfactant administration was found to be successful in opening the areas of atelectasis and helping wean children from mechanical ventilation.[17]

Mechanical ventilation of pediatric patients is discussed elsewhere.

A randomized controlled trial by Roncin et al showed that continuous positive airway pressure delivered via a nasal cannula or facemask is effective in improving oxygenation and re-expanding the collapsed lung.[18]

Antibiotics are not necessary in patients with asthma. Oral corticosteroids, together with frequent inhaled bronchodilators and  inhaled corticosteroids, would address any underlying inflammation and bronchospasm.

If the child with atelectasis has cystic fibrosis, aggressive antibiotic therapy is indicated in conjunction with chest physical therapy and postural drainage. A mucus plug from other causes may respond to chest physical therapy and postural drainage. See Cystic Fibrosis for a more detailed discussion of the therapy for this disorder. Instillation of DNase (see above) and N-acetyl cysteine and rhDNase have been used with some success in facilitating the removal of mucus plugs in the airways. Both have been used in patients with cystic fibrosis and have had some success in patients without cystic fibrosis as well.

Children with neuromuscular disease, children who have undergone surgery, and children with chest pain benefit from chest physical therapy to reduce the likelihood of developing further atelectasis; whether these procedures treat the existing atelectasis is not clear. In children with neuromuscular disease, the mechanical ex-insufflator (Cough Assist Device) is helpful in preventing atelectasis and produces enough of a cough to adequately clear the airways.

If pain is causing the atelectasis, adequate pain therapy is mandatory.

If the patient is severely affected by the atelectasis and response to therapy of the underlying disorder is suboptimal, bronchoscopic removal of secretions, mucous plugs, or both may be helpful. Both N-acetyl cysteine and rhDNase have been used with some success in facilitating the removal of mucous plugs in the airways. Both have been used in patients with cystic fibrosis and have had some success in patients without cystic fibrosis as well.

DNAse has been used in cystic fibrosis to facilitate transport of the abnormal secretions. DNAse has been successfully used in other patients with acute atelectasis. However, the success of the medication depends on the amount of DNA in the secretions, which is generally not known beforehand. In mechanically ventilated children who had undergone cardiac surgery,[12] nebulized DNAse was able to ameliorate atelectasis after 10 doses. It was more effective in children with high neutrophil counts in the affected area. Bronchoscopic installation of surfactant[17] was successful in opening the areas of atelectasis and helping wean children from mechanical ventilation. Although N -acetyl cysteine has been used as a mucolytic both in nebulizer and bronchoscope forms, success has not been validated in controlled studies. Furthermore, it has the potential to cause significant bronchospasm.

The appropriate long-term management of asthma should reduce the likelihood of the child developing atelectasis.

In children with cystic fibrosis, adequate use of the airway clearance mechanisms, sometimes in conjunction with antibiotics, can reduce the likelihood of atelectasis developing.

In children with neuromuscular disease, using a mechanical ex-insufflator (CoughAssist Device) can mobilize those secretions that predispose to atelectasis.

Routine use of chest physical therapy and postural drainage after extubation has not been shown to reduce the incidence of atelectasis.

Tailor therapy to the underlying disorder whenever possible. Antibiotics are not necessary if the child has asthma and uses oral corticosteroids, frequent inhaled bronchodilators, or high-dose inhaled corticosteroids to address the underlying inflammation and bronchospasm. For more information, see Asthma. The National Asthma Education and Prevention Program (NAEPP) provides detailed information regarding managing children or adults with asthma. For more information see the NAEPP guidelines.[19]

If the child has cystic fibrosis, aggressive antibiotic therapy is indicated in conjunction with chest physical therapy and postural drainage. In children with cystic fibrosis, reducing the load of Pseudomonas species in airways facilitates airway clearance. See Cystic Fibrosis for a more complete discussion on the indications for antibiotics, antibiotics used, and dosing schedule in these patients.

Class Summary

These agents decrease muscle tone in the small and large airways in the lungs, thereby increasing ventilation. They are used in children with asthma and are potentially helpful in children with cystic fibrosis.

Albuterol (Ventolin HFA, Proventil HFA, ProAir HFA)

Relaxes bronchial smooth muscle by action on beta2-receptors with little effect on cardiac muscle contractility. First-line bronchodilator that should be used with spacer if using metered dose inhaler.

Class Summary

These agents effectively reduce airway inflammation in asthma and cystic fibrosis, which allows easier mobilization of secretions. These also reduce airway reactivity, which might increase propensity to atelectasis.

Prednisone (Deltasone, Prednisone Intensol, Rayos)

Prednisone may decrease inflammation by reversing increased capillary permeability and suppressing PMN activity. It may also cause profound and varied metabolic effects, particularly in relation to salt, water, and glucose tolerance, in addition to their modification of the immune response of the body.

Prednisolone (Orapred ODT, Millipred, Millipred DP, Veripred 20)

Prednisolone blocks release of inflammatory mediators by inhibiting phospholipase A2. Decreases inflammation by suppressing production of leukotrienes, migration of polymorphonuclear leukocytes and reducing capillary permeability. Corticosteroids may also cause profound and varied metabolic effects, particularly in relation to salt, water, and glucose tolerance, in addition to their modification of the immune response of the body.

Class Summary

These agents elicit long-acting beta2-adrenergic agonistic and anti-inflammatory effects for persistent asthma.

Fluticasone and salmeterol (Advair HFA, Advair Diskus, RespiClick)

Indicated to treat chronic persistent asthma. Salmeterol component elicits long-acting beta2-adrenergic agonist activity, resulting in bronchiole smooth muscle relaxation. Fluticasone is a corticosteroid that provides anti-inflammatory effects.

Available as dry powder inhalant containing fluticasone (100 mcg, 250 mcg, or 500 mcg) with salmeterol (50 mcg) or containing 55 mcg, 113 mcg, or 232 mcg fluticasone with salmeterol 14 mcg. HFA preparation in metered dose inhalers has 45, 115 or 230 mcg per puff, each with 21 mcg of salmeterol.

Budesonide/formoterol (Symbicort)

Formoterol relieves bronchospasm by relaxing the smooth muscles of the bronchioles in conditions associated with asthma.

Budesonide is an inhaled corticosteroid that alters level of inflammation in airways by inhibiting multiple types of inflammatory cells and decreasing production of cytokines and other mediators involved in the asthmatic response. Available as MDI in 2 strengths; each actuation delivers formoterol 4.5 mcg with either 80 mcg or 160 mcg.

Beclomethasone, inhaled (Qvar)

Decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing capillary permeability. Available as 40 mcg/actuation or 80 mcg/actuation.

Fluticasone inhaled (Flovent Diskus, Flovent HFA, Arnuity Ellipta, ArmonAir RespiClick)

Fluticasone decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing capillary permeability. Available as aerosol, Flovent HFA (44 mcg/actuation, 110 mcg/actuation, or 220 mcg/actuation), also available as Flovent Powder for Inhalation (Diskus) that delivers 50 mcg/actuation, 100 mcg/actuation, or 250 mcg/actuation

Budesonide inhaled (Pulmicort Flexhaler, Pulmicort)

Budesonide is relatively new to US market but has been extensively used in Europe. It has recently been released in a nebulizer solution approved for use in children as young as 12 mo.

Budesonide decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing capillary permeability. Available as Pulmicort Flexhaler, powder for inhalation (90 mcg/actuation and 180 mcg/actuation, each actuation delivers 80 mcg/actuation and 160 mcg respectively). Nebulization has been used in children aged 1-8 y.

Continued therapy is necessary to attempt to eliminate the atelectasis and to prevent further episodes.

If the child has asthma, prolonged taper of systemic steroids may help eliminate the airway swelling that predisposed the patient to atelectasis. Inhaled corticosteroids help control the asthma and prevent further episodes. Early recognitions of exacerbations of asthma and early therapy also prevent future problems.

If the child has cystic fibrosis, see Cystic Fibrosis for a more detailed discussion of the therapy of the disease.

If the child has neuromuscular disease or an abnormal chest wall, attempts to clear the airways, such as with chest physical therapy and postural drainage, help prevent atelectasis. The mechanical ex-insufflator is very helpful in mobilizing secretions in children with an ineffective cough. Some children benefit from positive pressure ventilation to maintain airway and alveolar patency. This should be performed in conjunction with a pediatric pulmonologist.

If aspiration due to gastroesophageal reflux or swallowing dysfunction predisposes to atelectasis, these causes should be addressed. Pharmacotherapy of gastroesophageal reflux is available. Speech therapists and occupational therapists can often assist with swallowing dysfunction.

As long as the child's oxygenation status is not compromised, activity should not be limited.

The child with atelectasis should be kept in the hospital while in need of supplemental oxygen and therapy that cannot be adequately or appropriately administered at home.

Treatment may include antibiotics and chest physical therapy.

Children with neuromuscular disease may benefit from using a mechanical ex-insufflator, which is often part of their long-term home management.

Patients should be transferred to a tertiary care facility if they require a level of support that the referring institution is unequipped for or does not frequently perform in children.

Therapy should be geared to the underlying disorder whenever possible.

If the child has asthma, then oral steroids, frequent inhaled bronchodilators, and high-dose inhaled steroids may help the underlying inflammation and bronchospasm. Antibiotics are not necessary.

If the child has cystic fibrosis, see Cystic Fibrosis for a discussion of appropriate therapy.