Chapter VXIV.3 Respiratory Failure
Paula A. Vanderford, MD
December 2013

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A former 27 week premie, now 12 months old, arrives in the emergency room diaphoretic, cyanotic, and tachypneic, with a heart rate of 220. She has bronchopulmonary dysplasia (BPD), status post tracheostomy, and is usually on (30% oxygen) by tracheostomy collar. She is on routine albuterol and fluticasone aerosols for reactive airway disease. She has had cold symptoms for two days, slight fever, and increased secretions. Today, her parents report that she has had increased work of breathing with audible wheezing. Despite giving albuterol aerosols every two hours, she has worsened over the day. She "turned blue" about 30 minutes ago, and an ambulance was called.

Exam: VS T 38.3, HR 220, RR 90, BP 86/48, oxygen saturation 80% on 100% FiO2. Her weight is 8 kg. She has a tracheostomy tube in place. She is cyanotic and has poor aeration bilaterally on auscultation. She has crackles, mild wheezing and a slightly prolonged expiratory phase. Marked retractions and nasal flaring are present.

Suspecting a plug in her tracheostomy, her tracheostomy tube is changed. Despite this, her status does not improve. She is bag ventilated via her tracheostomy and subsequently placed on mechanical ventilation. She is given IV methylprednisolone and placed on continuous albuterol via the ventilator circuit. Her saturations rise from 80% to 98% and her aeration improves. Her tachycardia improves to a HR of 160, and her RR is now 40 (on ventilator). She becomes more alert, and her flaring and retractions subside. Her chest x-ray reveals chronic changes consistent with BPD, moderate hyperaeration, scattered atelectasis and a left lower lobe infiltrate. Her nasopharyngeal RSV assay is positive for respiratory syncytial virus.

This is a case of respiratory failure due to RSV pneumonia in a patient with underlying BPD. In evaluating this child, multiple etiologies had to be considered, including problems with the tracheostomy. A plugged tracheostomy tube must always be considered as a potential cause of respiratory distress in a child with a tracheostomy.


There are multiple etiologies of respiratory distress, and the treatment obviously depends on the cause. Fortunately, the basics of airway, breathing and circulation (the "ABCs") always apply. The goal is to recognize the early signs and symptoms of respiratory problems, intervene early, and hopefully prevent progression to respiratory failure.

What is respiratory failure? Historically, emphasis was placed on arterial blood gas values in making the diagnosis of respiratory failure. A more useful definition is based on clinical findings and history. Respiratory failure is inadequate ventilation and/or oxygenation to meet the demands of the tissues, resulting in hypercarbia and/or hypoxemia. Evidence of respiratory failure includes cyanosis, tachypnea, apnea, bradypnea (slow respiratory rate), retractions, poor aeration, head bobbing, and appearance of fatigue. Depending on the etiology, the signs and symptoms will differ. A patient with pneumonia or airway obstruction likely will present with distress and tachypnea, whereas a child with respiratory failure due to multiple doses of benzodiazepines for status epilepticus may present with apnea.

Blood gases are useful if they are available and easily obtained. A blood gas obtained after multiple sticks in a dyspneic screaming, poorly perfused child may result in worsening of the child's status and provide little, if any, useful information. In the best of circumstances, an arterial blood gas (ABG) in a previously healthy child with a PaCO2 >55 mm Hg, PaO2 <60 mm Hg is consistent with respiratory failure in most instances. Note that in the above case, the diagnosis of respiratory failure was made without obtaining a blood gas. Rather, respiratory failure was based on clinical findings alone. A blood gas might have delayed treatment and would not have changed the therapy. Given her BPD, we would expect her pCO2 to be high at baseline, but with a fairly normal pH due to renal compensation (HCO3 retention). In the setting of acute respiratory failure, a low pH is important in making this diagnosis in a child with chronically elevated pCO2.

Blood gases are helpful in managing ventilator therapy. Arterial blood gases are ideal, but without an arterial line, are difficult to obtain repeatedly. A well-warmed extremity capillary blood gas is useful in following pH and pCO2 in a child with good perfusion, as are venous blood gases in certain instances. Oxygen saturation measured by pulse oximetry and end tidal CO2 monitoring (ETCO2) or transcutaneous CO2 monitoring (TCM) are also useful for monitoring during therapy and can minimize the number of blood gases needed.

There are many etiologies of respiratory failure that can generally be divided into the categories of upper airway disease, lower airway disease, parenchymal lung disease and neurologic disorders. While the specific treatment depends on the etiology, assessing and supporting the ABCs is the appropriate initial therapy. Managing the airway, supplying oxygen, and assuring adequate ventilation are the goals regardless of the etiology. Specific treatments, however, depend on determining the etiology of the respiratory distress/failure. We will review some of the more common disorders and their therapies.

Upper airway obstruction refers to obstruction to airflow that is extra-thoracic and often results in stridor. With inspiration, the diaphragm contracts and the thoracic cage expands, creating negative pressure within the airway and drawing air in. However, if there is a narrowing of the airway, and/or the airway is floppy, the negative pressure may result in further narrowing and stridor. This sound is usually high pitched and musical. Stridor is due to airflow changes within the larynx, trachea, or bronchi. Another category of noisy breathing is known as stertor, derived from the Latin word stertere meaning to snore. This is caused by obstruction of airway above the level of the larynx. It is low-pitched snoring or snuffly sound produced by vibrations of tissue of the naso-pharynx, pharynx, or soft palate.

If there is evidence of upper airway obstruction such as snoring, repositioning the airway may be useful. Suctioning the naso/oropharynx may be helpful, and in certain cases airway adjuncts such as an oral airway or nasopharyngeal tube may be necessary. Oral airways should only be used in unconscious patients. In conscious and semi-conscious patients, they may cause gagging and vomiting.

Upper airway problems include laryngomalacia, croup, epiglottitis, vocal cord problems, and airway foreign bodies.

Laryngomalacia, is a very common congenital condition of the larynx. It is one of the most common causes of noisy breathing in infants. The cartilage of the larynx with laryngomalacia is soft and floppy, resulting in the tissues collapsing inward on inspiration. This causes narrowing of the airway and results in inspiratory stridor, which worsens with agitation. This is generally present at birth, which may worsen over the first several months of life, then improves as the cartilage hardens. CXR is usually normal. Treatment is not usually necessary, but if severe and associated with cyanotic spells, poor feeding and poor weight gain, surgical repair may be needed (supraglottoplasty).

Croup (acute laryngotracheitis) is a viral process that causes mucosal swelling, and narrowing of the airway. Like laryngomalacia, this narrowing results in inspiratory stridor that worsens with agitation. The most common cause of croup is Parainfluenza virus. Croup occurs predominately in children 6 months to 3 years of age and is characterized by a barking or seal-like cough, stridor and low-grade fever. CXR in croup is usually normal with the exception of narrowing of the tracheal shadow called a “steeple sign”. Therapy includes oxygen (if hypoxic) to maintain oxygenation, and racemic epinephrine aerosols, plus systemic corticosteroids to reduce airway swelling. Only rarely is endotracheal intubation necessary to maintain the airway. If intubation is required, an endotracheal tube size 0.5 to 1.0 smaller than the appropriate size for age should be used.

Epiglottitis is swelling and inflammation of the epiglottis and surrounding tissues often due to infection with Haemophilus influenzae type B. Epiglottitis has become much less common since the introduction of the Haemophilus influenza B vaccine. Other bacteria and viruses also can cause inflammation of the epiglottis, including: Streptococcus pneumoniae (pneumococcus), and Streptococcus A, B and C. Epiglottitis is characterized by the fairly abrupt onset of high fever, a toxic appearance, drooling and a muffled voice. The patient will usually want to sit up, and tripod with head forward in efforts to keep their airway open. It is recommended that the patient be allowed to maintain their position of comfort, kept calm, and not be forced to lie down for examination, x-rays or procedures. CXR is often normal, but a lateral neck x-ray may show a thickened epiglottis. Therapy includes oxygen, endotracheal intubation and antibiotics. Intubation should be done in the OR by the most experienced clinician available since with the very swollen epiglottis, the patient may very difficult to intubate, and an emergency surgical airway may be required. If respiratory arrest occurs prior to this, bag mask ventilation in the prone position is theoretically advantageous compared to bag mask ventilation in the supine position.

Vocal cord paresis and paralysis (unilateral or bilateral) may be congenital or acquired (as a result of cardiothoracic surgery). Symptoms may include respiratory distress, hoarseness, and/or swallowing difficulties/aspiration. The treatment is dependent on the severity and the cause and may include speech therapy, injections, surgery, or tracheostomy.

Foreign body aspiration should be suspected in a previously healthy child with the acute onset of respiratory distress, especially if preceded by a history of coughing or choking. Frequently, unilateral wheezing or unequal breath sounds will be noted along with unilateral findings on CXR (atelectasis or hyperaeration). Bronchoscopy and removal of the foreign body is both diagnostic and therapeutic. In some cases where bronchospasm and airway swelling accompany the aspiration, bronchodilators, racemic epinephrine aerosols, corticosteroids and antibiotics may be indicated.

Neurologic conditions that lead to respiratory failure, in contrast to airway or pulmonary problems,are not always associated with signs/symptoms of respiratory distress. Respirations may be shallow, irregular or absent. Upper airway obstruction may be present due to altered level of consciousness with loss of pharyngeal muscle tone/coordination and lead to stertor. If the etiology is a sedative or narcotic overdose, oxygen and a reversal agent such as flumazenil or naloxone, respectively, may be all that is necessary. Note that if the sedative or narcotic has a long half-life, more than one dose or an infusion of the reversal agent may be necessary. Repositioning the airway, a jaw thrust, or nasopharyngeal tube may be useful if there is associated upper airway obstruction. Intubation and mechanical ventilation until the agent is metabolized may be necessary. Neuromuscular conditions may also lead to respiratory failure due to generalized weakness. The differential is fairly long. Clues to the diagnosis include age of onset of weakness, prior health condition, and the onset and direction of progression of the weakness. The weakness may result from a problem with the brain, the motor neurons, the neuromuscular junction, or the muscle itself. In infancy, congenital anomalies, brain injury, spinal muscular atrophy, and botulism must be considered as potential etiologies. In older children, myopathies and Guillain-Barré should be considered. Intubation and mechanical ventilation are often required until the neurologic problem resolves. Many of these conditions result in the need for tracheostomy and long-term ventilation, if desired by the patient or their family.

Diseases of the lower airways or lung parenchyma may also result in respiratory failure. Reactive airway disease, characterized by distal airway swelling, increased secretions and airway constriction, is a common cause of respiratory distress/failure. Children with asthma, bronchiolitis, and bronchopulmonary dysplasia (BPD) all have a component of reactive airways disease.

Asthma is a common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airway obstruction, and bronchospasm. The intrathoracic lower airways are narrowed, which results in expiratory wheezing. The narrowing is a result of bronchiolar smooth muscle hypertrophy/proliferation, bronchoconstriction, and narrowing due to excessive secretion of mucus. Exacerbations are often triggered by viral respiratory infections as well as allergens. CXR reveals hyperaeration and areas of atelectasis due to mucus plugging. Treatment generally includes oxygen, bronchodilators, and steroids. Bronchodilators may be inhaled intermittently, continuously, and/or with a continuous IV infusion. In severe cases high-flow nasal cannula (HFNC), continuous positive airway pressure (CPAP), bilevel positive airway pressure (BiPAP), and in patients with exhaustion/respiratory failure, intubation and mechanical ventilation may be necessary. Other controversial therapies include methylxanthines, magnesium, heliox, and inhaled anesthetics. Helium/oxygen mixtures have a lower density than nitrogen/oxygen (room air) mixtures and, therefore, flow through narrow airways with less turbulence. Magnesium is a smooth muscle relaxant and has been found to be useful for severe asthma in some studies.

Bronchiolitis is a viral illness characterized by respiratory distress, retractions, and wheezing due to airway narrowing. Multiple viruses can cause acute bronchiolitis. One of the most common is Respiratory Syncytial Virus (RSV). CXR generally shows hyperaeration and areas of atelectasis. Oxygen via nasal cannula, HFNC, CPAP, or BiPAP may be helpful and prevent the need for intubation. Bronchodilators may be helpful. Corticosteroids are most helpful in those with a prior history of reactive airway disease or chronic lung disease.

Chronic lung disease. Children with a history of prematurity and/or prior long-term mechanical ventilation will often develop chronic lung disease (CLD) or bronchopulmonary dysplasia (BPD) with scarring of the lung and hyperactive airways. CLD exacerbations may present with hyperaeration and wheezing and are often initiated by upper respiratory infections (URIs). Frequently, patients with CLD may be on home oxygen, chronic bronchodilators and/or steroid inhalers. IV or enteral corticosteroids may be useful in treating the acute airway inflammation. More frequent bronchodilators (or continuous bronchodilators) may also be helpful. See the chapter on BPD for further details.

Pneumonia reduces lung compliance and increases ventilation perfusion (V/Q) mismatching due to lung parenchymal injury, alveolar disease (alveoli filled with fluid or pus), along with decreased or inactivated surfactant. Areas of atelectasis are also common due to mucus plugging. The patient with pneumonia may have grunting respirations in addition to hypoxemia, tachypnea, rales, retractions, and nasal flaring. Grunting is a noise produced by the patient as they close the glottis prematurely with each breath. This is done unconsciously in order to increase their airway distending pressure in an effort to keep the affected alveoli open, thus increasing intrinsic PEEP. The etiology of pneumonia may be viral or bacterial, the most common organisms being RSV and pneumococcus. Aspiration of oral secretions or gastric contents may lead to aspiration pneumonia.

Viral pneumonia is usually associated with a viral upper respiratory tract prodrome, followed by increasing cough and work of breathing. Diffuse rales may be present. Fever is usually low grade, and WBC count is not significantly elevated. Viral respiratory cultures and/or rapid antigen testing techniques are useful in making the diagnosis. The CXR generally shows diffuse interstitial infiltrates. The most common organisms in children are influenza, RSV, and parainfluenza, but also include herpes (in neonates), metapneumovirus, adenovirus, and CMV (in immunosuppressed patients). Antibiotics are not indicated unless there is concern for a bacterial superinfection. Potential antivirals include oseltamivir to treat influenza, acyclovir for herpes, and gancyclovir for CMV. There are no antivirals proven to be effective for metapneumovirus, or adenovirus, but there are reports of ribavirin and cedofovir being useful in the treatment of pneumonia due to adenovirus in immunocompromised patients.

Bacterial pneumonia is characterized by high fever, cough, rales, and increased work of breathing. Leukocytosis with a left shift is often present. Decreased breath sounds may be noted if consolidation, atelectasis, or effusions occur. CXR often shows a focal infiltrate, along with effusion of various sizes. Pneumatoceles may be present especially in the case of pneumonia due to Staphylococcus aureus. The most common bacterial etiology is Streptococcus pneumoniae. Haemophilus influenza type B caused pneumonia to a modest degree prior to the development of the HIB vaccine, however it is very uncommon in immunized children. Group B Streptococcus and Gram stain negative organisms are common causes in neonates. In suspected aspiration pneumonia, therapy covering oral flora should be considered. Atypical bacteria such as Chlamydia or Mycoplasma may also cause pneumonia. The patient may be afebrile or have only low grade fever, and no leukocytosis. CXR findings are variable. Infiltrates may be unilateral, bilateral, or patchy. Lobar infiltrates are less common. Effusions may be present with Mycoplasma, but are rare with Chlamydia. Chlamydia is more common in neonates. Antibiotic therapy choice is dependent on the identified or suspected pathogen. Antibiotic coverage should have a broad-spectrum until an organism is identified. If the patient is not intubated, it may be difficult to obtain sputum for culture. Identifying the organism from the blood is uncommon. Cultures of pleural effusions may also be helpful, if present. Once an organism is identified, therapy should be tailored based on sensitivities. If no organism is identified, broad-spectrum therapy may need to be continued or narrowed based on history, immunization history, symptoms, and CXR findings.

Treatment of the child with pneumonia and respiratory failure may include oxygen, antibiotics (if a bacterial process is thought to be present), and chest physiotherapy to help open atelectatic areas and to promote coughing and mucus drainage. The provision of CPAP (or positive end-expiratory pressure in intubated patients) improves V/Q matching by improving ventilation of the involved alveoli. In some patients, HFNC or CPAP alone will be sufficient to adequately restore oxygenation, but in some cases, BiPAP or endotracheal intubation and provision of mechanical ventilation will be necessary. In cases of persistent hypoxemia, pulmonary hypertension should be considered. An echocardiogram may be warranted vs a trial of inhaled nitric oxide. Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator, and if pulmonary hypertension is present improvement with NO is fairly immediate. Due to consideration that pneumonia may result in damage to surfactant, trials of surfactant have been done. However, the results have not been consistent.

Acute respiratory distress syndrome (ARDS) is a disorder characterized by diffuse lung injury, bilateral infiltrates and a large alveolar arterial oxygen gradient (hypoxemia despite high inspired supplemental oxygen) resulting in significant hypoxemia. There are numerous etiologies for ARDS including pneumonia, near-drowning, sepsis, and burns. The disease involves alveolar filling as well as interstitial edema and infiltration with cells and fibrosis. The prognosis is variable depending on the etiology and associated morbidities (18-31% mortality rate).

Therapy for ARDS starts with treating the underlying etiology. Treatment includes endotracheal intubation and ventilation, usually with "permissive hypercapnia" techniques to attempt to reduce the trauma to the lungs caused by mechanical ventilation. Patients with ARDS have very noncompliant lungs, and using tidal volumes and rates sufficient to normalize the pCO2 often result in air leak complications (e.g., pneumothorax). Therefore, a limited TV (approximately 6 ml/kg) is used in efforts to minimize peak airway pressures, and a high pCO2 (50s to 60s) is permitted as long as the pH remains acceptable. Due to reduced lung compliance and alveolar filling, a high PEEP (10 to 15 cm H2O) is often required to maintain oxygenation in patients with ARDS. Morbidity and mortality have been shown to be reduced in patients with ARDS with this high PEEP/low tidal volume strategy. High frequency oscillatory ventilation (HFOV) is also a frequently used ventilator strategy to treat these patients. A somewhat similar mode (in theory) to HFOV called airway pressure release ventilation (APRV) is sometimes used in children with ARDS (more commonly used in adult ICUs than in pediatric ICUs). Air leaks are a common complication of ARDS regardless of mode used.

In severe cases of ARDS where it is not possible to adequately oxygenate or ventilate a patient with a reversible cause of respiratory failure, extracorporeal membrane oxygenation (ECMO) may be necessary. ECMO is a form of cardiopulmonary bypass, where a membrane oxygenator is used to ventilate and oxygenate the patient. Since the membrane oxygenator functionally does the work of the lungs, the ventilator may be reduced to “rest” (or very low settings) while the lungs heal. If the heart is functioning adequately, the patient can be placed on venovenous (VV) ECMO, where a large bore cannula with 2 lumens is placed into the right atrium, and blood is pulled from the atrium, run though the membrane oxygenator, and then the oxygenated blood (with CO2 removed) is returned to the right atrium. Once the lungs have healed (this may take 6-8 weeks), the patient is trialed off ECMO, and the cannula removed. Outcomes are poor if patients are placed on VV ECMO beyond 2 weeks of mechanical ventilation due to excessive lung injury.

Respiratory failure in neonates is covered in the neonatology section, so it will not be reviewed in this chapter.

Air leaks are another cause/contribution to respiratory failure. A discussion of air leak syndromes is found in a separate chapter in this book.

This chapter provides only a brief overview of respiratory failure; its causes, signs and symptoms, and approaches to treatment. Early recognition of respiratory distress and intervention will help prevent progression to respiratory failure and eventual cardiopulmonary arrest.


Questions

1. True/False: To diagnose respiratory failure one must obtain an ABG.

2. Etiologies of respiratory failure include:
. . . . .a. burns
. . . . .b. botulism
. . . . .c. asthma
. . . . .d. pneumonia
. . . . .e. c & d
. . . . .f. all of the above

3. Upper airway problems are generally manifest by:
. . . . .a. wheezing
. . . . .b. grunting respirations
. . . . .c. stridor
. . . . .d. tracheal deviation

4. A previously healthy child with acute onset of respiratory distress and unilateral wheezing should be suspected of having:
. . . . .a. reactive airway disease
. . . . .b. croup
. . . . .c. foreign body
. . . . .d. epiglottitis

5. Children with a central nervous system depression resulting in respiratory failure often display:
. . . . .a. retractions
. . . . .b. rapid abdominal breathing
. . . . .c. head bobbing
. . . . .d. none of the above

6. Reactive airway disease is characterized by:
. . . . .a. distal airway swelling
. . . . .b. increased secretions
. . . . .c. airway constriction
. . . . .d. wheezing
. . . . .e. all of the above

7. True/False: Respiratory distress in a child with a tracheostomy should be considered a plugged or misplaced tracheostomy tube, until proven otherwise.

8. ARDS is characterized by:
. . . . .a. large alveolar-arterial gradient
. . . . .b. reduced compliance
. . . . .c. mortality rate of 5-10%
. . . . .d. a & b


References

1.Anas N. Part II Chapter 9 – Respiratory Failure. In: Levin D, Morris FC (eds). Essentials of Pediatric Intensive Care, second Edition. 1997, St. Louis: Quality Medical Publishing, Inc., pp. 69-82.

2. Dahlem P, van Aalderen WM, Hamaker ME, et al: Prevalence and short term outcome of acute lung injury in mechanically ventilated children. Eur Respir J 2003; 22: 980-985.

3. Flori HR, Glidden DV, Rutherford GW, et al: Pediatric acute lung injury: Prospective evaluation of risk factors associated with mortality. Am J Respir Crit Care Med 2005; 171: 995-1001.

4. Li Y, Wang Q, Chen H, et al: Epidemiological features and risk factors for analysis of children with acute lung injury World J Pediatr 2012 8: 43-46.

5. Lopez-Fernandez Y, Azagra AM, De la Oliva P, et al; Pediatric Acute Lung Injury Epidemiology and Natural History (PED-ALIEN) Network: Pediatric Acute Lung Injury Epidemiology and Natural History study: Prevalence and outcome of the acute respiratory distress syndrome in children. Crit Care Med 2012; 40:3238-3245.

6. Zabrocki Luke, Brogan Tomas, Statler Kimberly, et al, Extracorporeal Membrane Oxygenation for pediatric respiratory failure: Survival and predictors of mortalit, Crit Care Med, 2011 Vol 39, No 2, pp. 364-369.

7. Zimmerman JJ, Akhtar SR, Caldwell E, et.al: Incidence and outcomes of pediatric acute lung injury. Pediatrics 2009; 124, 87-95.

8. Chapter 2-Recognition of Respiratory Failure & Shock. In: Chameides L, Hazinski MF (eds). Pediatric Advanced Life Support. 1997, American Heart Association, pp. 2.1-2.10.


Answers to questions

1. false

2. f

3. c

4. c

5. d

6. e

7. true

8. d


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