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), and is usually on home oxygen (30%) 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 in 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, R 90, BP 86/48, oxygen saturation 80% on an increased oxygen flow provided by paramedics. Her weight is 8 kg (25th percentile for a 9 month old, corrected post conception age). She has a tracheostomy tube in place. She is cyanotic and has poor aeration on auscultation. She has crackles, wheezing and a prolonged expiratory phase. Marked retractions and nasal flaring are present.
Suspecting a plug in her tracheostomy, her tracheostomy tube is suctioned and then changed when there is some resistance to passage of the suction catheter. Despite changing her tracheostomy, her status does not improve. She is bag ventilated via her tracheostomy and subsequently placed on mechanical ventilation. She is given IV methylprednisolone and more beta adrenergics. Her saturations rise from 80% to 98% and her aeration improves. Her tachycardia improves to 170 and her RR is now 50 (ventilator). She becomes more alert and her flaring and retractions subside. Her chest x-ray reveals chronic changes consistent with BPD, hyperaeration and scattered areas of atelectasis. 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 the 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 basic tenants 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? In the past, emphasis has been placed on arterial blood gas values. A more useful definition is based in clinical findings and history. Basically, respiratory failure is the inadequate ventilation and oxygenation, resulting in hypercarbia and hypoxemia severe enough to require ventilatory assistance. Evidence of respiratory failure includes cyanosis, tachypnea, apnea, slow respiratory rate, retractions, poor aeration, and appearance of fatigue. Depending on the etiology, the signs and symptoms will differ. 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 situations, an arterial blood gas (ABG) in a previously healthy child with a PaCO2 >55, PaO2 <60 is consistent with respiratory failure in most instances. She exhibited another common feature of respiratory failure, which is that she failed to adequately oxygenate despite maximal supplemental oxygen by mask. This can be easily assessed by monitoring the pulse oximeter readings while maximal supplemental oxygen by mask is administered. Note that in our 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. In the setting of acute respiratory failure, a low pH is important in making this diagnosis in a child with chronically elevated pCO2. Eventually in the therapy of a child with respiratory failure, blood gases will be helpful in managing therapy. Well warmed capillary blood gases are useful in following pH and pCO2 in a child with good perfusion (as an alternative to ABGs). Oxygen saturation measured by pulse oximetry and end tidal CO2 monitoring (ETCO2) or transcutaneous CO2 monitoring (TCM) are also useful for monitoring during therapy.
There are many etiologies of respiratory failure including neurologic disorders, respiratory infections and foreign bodies. Some specific conditions include: head injury, coma, status epilepticus, narcotics/sedatives, botulism, Guillain-Barre syndrome, airway foreign body, croup, asthma, tracheomalacia/tracheal stenosis, flail chest, burns, bronchiolitis, pneumothorax, pleural effusion, pneumonia, ARDS/neonatal RDS, pulmonary edema, etc.
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 location and cause of the respiratory distress. Chapters in multiple books have been written about each specific disorder. Given the limited scope of this chapter, only a few of the more common disorders will be described and their therapies outlined.
If there is evidence of upper airway obstruction, such as snoring or harsh stridor, 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. Upper airway problems are generally manifested by stridor and include epiglottitis, croup, laryngomalacia, vocal cord problems and airway foreign bodies.
Epiglottitis has become much less common since the wide spread use of the Haemophilus influenza B vaccine. Epiglottitis is characterized by high fever, a toxic appearance, drooling and a muffled voice. Therapy includes oxygen, endotracheal intubation and antibiotics.
Croup is much more common, occurs predominately in infants, and is characterized by a barking or seal-like cough, stridor and low grade temperature. Therapy includes oxygen, epinephrine aerosols and corticosteroids. Only rarely is endotracheal intubation necessary.
Laryngomalacia, vocal cord problems and foreign body aspiration are generally diagnosed by history and laryngoscopy/bronchoscopy. Oxygen is always an appropriate initial therapy, offered in the least threatening manner. Intubation may be required acutely for severe laryngomalacia and vocal cord dysfunction. Tracheostomy may be necessary for long term problems.
Foreign body aspiration should be suspected in a previously healthy child with the acute onset of respiratory distress. 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 are usually the only therapy required for aspirated objects. In some cases where bronchospasm and airway swelling accompany the aspiration, bronchodilators, epinephrine aerosols and corticosteroids may be indicated.
Neurologic conditions that lead to respiratory failure, in contrast to airway or pulmonary problems, are not usually associated with signs/symptoms of respiratory distress. Respirations may be shallow, irregular or absent. Level of consciousness may be impaired, depending on the cause, but this may be difficult to assess due to muscle weakness. If the etiology is a sedative or narcotic overdose, oxygen and a reversal agent such as naloxone or flumazenil may be all that is necessary. For longer term conditions such as Guillain-Barre or botulism, intubation and mechanical ventilation are usually required until the neurologic problem resolves. Central hypoventilation and spinal cord injuries frequently result in the need for tracheostomy and long term ventilation.
Reactive airway disease, characterized by distal airway swelling, increased secretions and airway constriction is a common cause of respiratory distress/failure. Children with bronchiolitis, bronchopulmonary dysplasia (BPD) and asthma all have a component of reactive airways disease. Bronchiolitis is a viral illness, most commonly seen in infants. Oxygen is always indicated for the child in distress. Bronchodilators may be helpful. Corticosteroids are most helpful in those with a prior history of reactive airways disease. Children with a history of prematurity and prior long term mechanical ventilation will often develop BPD with scarring of the lung and hyperactive airways. BPD exacerbations are characterized by hyperaeration and wheezing, and are often initiated by URIs. Frequently they will be on chronic bronchodilators and nebulized corticosteroids or steroid inhalers. It is important to ask this history since children on corticosteroids recently may be adrenal suppressed and require stress dose (high dose) corticosteroids with acute illnesses. Corticosteroids will also be useful in treating acute airway inflammation. More frequent bronchodilators (or continuous bronchodilators) may be helpful. The use of heliox and magnesium have been reported to be useful in some patients, but are not yet considered standard therapies. Helium/oxygen mixtures have a lower density than nitrogen/oxygen (room air) mixtures and therefore flow with less turbulence. Magnesium is a smooth muscle relaxant and has been reported to be useful for severe asthma by some investigators.
Pneumonia reduces lung compliance and increases ventilation perfusion (V/Q) mismatching due to lung injury and filling of the alveoli. Areas of atelectasis are also common due to mucus plugging. The patient with pneumonia may have grunting respirations (closing the glottis prematurely in order increase their intrinsic airway distending pressure to keep the alveoli open: PEEP), in addition to hypoxemia, tachypnea, rales, retractions, and nasal flaring. Treatment of the child with pneumonia and respiratory failure may include oxygen, antibiotics (if a bacterial process is thought to be present), chest physiotherapy to help open atelectatic areas and promote drainage, and mechanical ventilation. The provision of PEEP (positive end expiratory pressure) improves V/Q matching by improving ventilation of the involved alveoli. In some patients, continuous positive airway pressure (CPAP) alone will be sufficient to adequately restore ventilation and oxygenation, but in most cases, provision of mechanical ventilation will be necessary.
Adult 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 drownings, sepsis and burns. The disease involves alveolar filling as well as interstitial edema and infiltration with cells and fibrosis. The prognosis is poor even with intensive care. Treatment includes tracheal intubation and ventilation, usually with "permissive hypercapnia" techniques to reduce barotrauma. Patients with ARDS have very stiff noncompliant lungs and using tidal volumes and rates sufficient to normalize the pCO2 often result in air leak complications (such as pneumothorax). Therefore, a high pCO2 (50s to 60s) is permitted, as long as the pH remains acceptable (variable, depending on the center). Morbidity and mortality have been shown to be reduced in patients with ARDS with this technique. Due to reduced lung compliance and alveolar filling, high PEEP is generally required to maintain oxygenation in patients with ARDS. High frequency oscillation ventilation is also frequently used. Air leaks are a common complication.
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.
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 neurologic conditions 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. low morbidity & mortality
. . . . . d. a & b
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. Aoki B, McClosky K. Chapter 2-Respiratory System. In: Aoki B, McClosky K (eds). Evaluation, Stabilization & Transport of the Critically Ill Child. 1992, St. Louis: Mosby Yearbook, pp. 17-56.
3. 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