Differential Diagnosis of the Wheezing Child: Part II, Toddlers and Children
Authors: Richard M. Ruddy, MD, Division Chief, Pediatric Emergency Medicine, Children's Hospital Medical Center, Cincinnati, Ohio, Division of Pediatric Emergency Medicine; Michael A. Gittelman, MD, Fellow, Pediatric Emergency Medicine, Children's Hospital Medical Center, Cincinnati, Ohio, Division of Pediatric Emergency Medicine.
Peer Reviewer: Steven Krug, MD, Associate Professor of Pediatrics, Northwestern University Medical School; Head, Division of Pediatric Emergency Medicine, Children's Memorial Medical Center.
In the last issue, we reviewed the differential for wheezing in the infant younger than 1 year of age. In this issue, the authors provide a comprehensive review of wheezing for older children. Older children present a greater clinical challenge because the majority of them are going to be asthmatic. It is easy to fall into a routine and fail to ask a few key questions that can easily identify the child with underlying pathology. The authors provide a clinically based algorithm that will help identify children who require a more comprehensive evaluation. This article also highlights the importance of the "history and physical examination" for evaluation of the wheezing child, an aspect of prediatric emergency medicine that is both challenging and exciting for clinicians.
-The Editor
Acute Causes of Wheezing in Children Older than 1 Year
Case # 1. A 1 and-a-half-year-old black male presented to the emergency department (ED) with an acute onset of respiratory distress and wheezing. The child has a history of asthma and he has been on steroids twice in the past year. He currently takes a steroid inhaler for prophylactic therapy and he uses a nebulizer with Albuterol as needed at home. This morning, his mother noted that the child was coughing more frequently. She states that his breathing became more labored and wheezing was appreciated later in the afternoon. Several albuterol nebulizer treatments were attempted at home. When the child did not experienc relief of his symtoms, his parents rushed him to the ED. The parents deny any fevers, URI symptoms, or ill contacts.
In the ED, the child was well-appearing, non-toxic, and in mild respiratory distress. Initial vital signs included temperature, 99°F; heart rate, 120 beats/min; respiratory rate, 36 breaths/min; blood pressure, 90/54; and pulse oximetry, 92% on room air. On lung exam, he had diffuse wheezing with exaggerated wheezes on the left side of the chest. Subcostal and suprasternal retractions were evident without any grunting or flaring. Cardiac exam was significant for a 1/6 systolic ejection murmur appreciated over the left sternal border. Extremities were warm, peripheral pulses were strong, and no clubbing or cyanosis was noted. He was awake, alert, and active in the exam room.
His WBC was 13,000 cells/mm3, with a hemoglobin of 12.3 g/dL and a hematocrit of 36%. Because of his nonfocal exam and his hypoxia by pulse oximetry, the chest radiograph below was obtained. (See Figure 1.)
Foreign Body Aspiration. The diagnosis of a foreign body aspiration always tends to be difficult. It would be easy if every child presented with a clear history of a choking event while eating, with the chief complaint of coughing and isolated wheezing. However, many patients do not have a history of a choking episode. While foreign body aspiration can occur in any aged child, they most commonly occur between 1 and 2 years of age. Since children younger than 6-9 months of age lack the mobility or hand dexterity to ingest a foreign body, its occurrence is rare in this population. Any item can be ingested and most are not radiopaque. Of the objects ingested, peanuts tend to be a common one, accounting for approximately one-third of all reported aspirations.1 Grapes, hot dogs, corn kernels, and beans are other frequently aspirated items. Their presentation can mimic many other illnesses and is often not classic. The majority of patients present with coughing or unilateral, homophonous wheezing; these symptoms may be similar whether the object is lodged in the trachea, the bronchi, or even in the esophagus. Older patients often present with wheezing isolated to the righ tlower lobe region because of the wider diameter and milder angle of the right lobe bronchus. On the other hand, younger children can have either main stem bronchus affected, causing a more homophonous wheeze.2 Other symptoms, such as dyspnea, cyanosis, stridor, or retractions, may also be present. The isolated obstruction could even trigger an irritant response and cause a diffuse heterophonous wheeze, similar to the presentation of an asthmatic. Thus, with all the varied presentations and difficult diagnostic considerations, the diagnosis of a foreign body aspiration must be considered in any child with unequal breath sounds, an acute onset of symptoms, symptoms timely associated with eating, or patients with recurrent pneumonias, isolated to one lobe of the lung.
Besides the history and physical exam, a chest radiograph may aid in the diagnosis. Although one study showed chest x-rays to be normal 25% of the time, it may demonstrate isolated atelectasis, hyperinflation, or a radiopaque foreign material.3 As in case #1, the chest radiograph manifests an abnormally over-inflated left lung compared to the right, with an exam significant for unequal, predominantly left, homophonous wheezing. In young children, the preferred inspiratory vs. expiratory films may be difficult to obtain. It is recommended to order bilateral decubitus chest films to aid in deflating the lungs and better display air trapping. Of course, if a foreign body aspiration is suspected, even with a normal chest radiograph, rigid bronchoscopy to visualize the foreign object is essential. If a foreign object is retained in the lung, complications, such as persistent wheezing, pneumonia, pneumothorax, and bronchiectasis, may result.
Anaphylaxis. Anaphylaxis is the result of mediators being released from mast cells and basophils in response to the union of antigens with immunoglobulins. This potentially life-threatening reaction can be caused by any substance that is recognized as foreign to the body. Most commonly, insect bites, foods, and medications are the inciting agents. These patients can present with myriad complaints. Usually, the first symptom described is a tingling sensation around the mouth or on the distal extremities. Then, children may describe feeling short of breath, wheezy, pruritic, flushed, and may have significant abdominal cramps. If symptoms persist, patients can become hypotensive, unconscious, and progress into full cardiopulmonary arrest. The more rapid the symptoms present, the more systemic the manifestations and worse the immediate course.
The immediate recognition of symptoms by the physician usually offers a better prognosis, as treatment may be rapidly administered. On occasion, elevated serum tryptase levels can be helpful in making the diagnosis, when the diagnosis is less clear. The mainstay of treatment remains epinephrine given either subcutaneously or intravenously. Other supportive measures may include steroids, to prevent the late phase or recurrence of the reaction; diphenhydramine, for its antihistaminic properties; and a beta-agonist aerosol, to help with bronchoconstriction.
Pulmonary Infections. Viral pneumonia in the immunocompetent host, similar to RSV in an infant, can affect children older than 1 year of age. The same pathogens are involved, such as adenovirus, parainfluenza virus, rhinovirus, and others. For wheezing to be present, a generalized infection is usually seen. Chest radiographs will commonly show diffuse disease, parenchymal consolidations, or interstitial infiltrates. In school-aged children, Mycoplasma pneumoniae or Chlamydia pneumoniae must be considered. These patients typically have symptoms and a chest radiograph that appears worse than expected by their physical appearance. Bacterial pneumonia, on the other hand, rarely presents with wheezing, unless a reactive airways component is associated with the illness.
Children with parasitic infections, particularly visceral larval migrans (toxocariasis), can present with recurrent pulmonary disease and wheezing. When the egges of this round worm parasite of dogs and cats are ingested by humans, the infection occurs. Most commonly, children between 1 and 7 years are affected, with a mean of 2 years of age.4 After the larva penetrate the gastrointestinal tract, they tend to migrate via blood and lymphatic vessels into other sites, including the liver, lungs, CNS, eyes, and heart. Clinical symptoms, such as fever, cough, wheezing, seizures, poor visual acuity, and abdominal pain, generally predominate. These complaints often last over several months and then begin to dissipate. Diagnosing visceral larval migrans is often difficult, as parasitic material is not excreted by humans and larvae are usually not found on specimen biopsy. Commonly, patients present with persistent eosinophilia, a leukocytosis, and hypergammaglobulinemia. Enzyme-linked immunosorbent assays can be used to detect Toxocara antigens. Some studies have shown ELISA to have a specificity of 90-95% and a sensitivity of 73-78% at a titer of 1:32; an even lower titer can be accepted for ocular larva migrans.4 Treatment is mainly supportive as symptoms are often mild and resolve over time. With severe pulmonary disease, steroids have been given to decrease inflammation. Larvicidal agents, like diethylcarbamazine or mebendazole, may benefit patients with severe CNS disease, yet these drugs have been shown to cause significant hypersensitivity reactions due to dying larvae.5 A balance between the risk of therapy and the severity of the disease must be made.
Inhalational/Irritant Injury. Specific gases, chemicals, and airborne molecules can cause irritation within the smaller airways and induce wheezing. Passive cigarette smoke from parental smoking has been shown to increase respiratory illnesses in children and decrease levels of small airway function on pulmonary function tests.6 According to the FDA, children are starting to smoke at a younger age, with a 30% increase in smoking by 8th grade students noted over the past five years. Other air pollutants, such as nitrogen dioxide, atmospheric ozone, sulphur dioxide, talcum powder, and carbon monoxide, have also been shown to adversely affect lung function. One study demonstrated an increase in ED visits for wheezing episodes during times of increased average concentrations of sulphur dioxide and ozone.7 Chemicals like kerosene, gasoline, and hydrocarbons can be easily aspirated due to their low viscosity and may result in a secondary pneumonitis. These patients often present with tachypnea, crackles, and, occasionally, wheezing. Finally, spores inhaled from aspergillosis has been shown to cause a hypersensitivity pneumonitis. Bronchopulmonary aspergillosis is more common in children with a history of chronic lung disease, such as asthma or cystic fibrosis. Often they present with cough, dyspnea, and wheezing, an elevated serum IgE, and Aspergillus in the sputum.
For the child in case 1, a chest radiograph was obtained because the child was significantly hypoxic for his clinical exam and had increased focal wheezing in one specific region of the chest. The chest radiograph showed hyperaeration of the left lung, arousing suspicion for a foreign body aspiration. Decubitus films were obtained that also showed hyperexpansion of the left chest. The patient was referred to pulmonology for a rigid bronchoscopy and a piece of hot dog was successfully removed. The child was observed for 24 hours in the hospital and he was continued on steroids and bronchodilators by aerosol.
Chronic Causes of Wheezing in Children Older than 1 Year
Case # 2. A 15-year-old white male is referred to the ED by his primary physician to "rule out pneumonia." His parents state that the child had been ill frequently over the past six months with multiple bouts of pneumonia. Each time he was treated with antibiotics, the symptoms resolved. He recently has been noted to wheeze at home and he has lost fifteen pounds over the last two weeks, according to his pediatrician. Sweat tests, barium swallows, HIV studies, and immunoglobulin levels done in the past week have all been normal. Over the past three days, he began to develop a fever (Tmax = 102°F), his wheezing worsened, and he began to complain of night sweats and increasing chest pains. As a result, the child was sent to the ED.
On physical exam, the child was non-toxic, ill-appearing, and in mild respiratory distress. Vital signs included a temperature of 101°F; heart rate of 110 beats/min; respiratory rate of 32 breaths/min; blood pressure of 96/54; and pulse oximetry of 92% on room air. He had a significant homophonous wheeze appreciated throughout his chest, and subcostal and suprasternal retractions. Cardiac exam was within normal limits. His abdomen was non-tender, non-distended, and no masses were evident. No clubbing or edema was seen on the extremities and peripheral pulses were strong.
Initial laboratory studies revealed a WBC count of 14,000 cells/mm3, hemoglobin of 9.8 g/dL, and a platelet count of 351,000. His chest x-ray demonstrated a large mediastinal mass compressing the distal tracheal. (See Figure 2.)
Neoplastic Diseases. Tumors anywhere within the thoracic cavity, including the lungs, mediastinum, chest wall, pleura, and diaphragm, may cause external compression on the tracheobronchial tree and result in a homophonous wheeze. Primary pulmonary tumors are rare in pediatrics, with bronchial adenomas being the most common.8 When a neoplasm is detected within the lung parenchyma, a metastatic infiltrate must be considered. Specific metastatic lesions to the lung are Wilms tumor, osteogenic sarcoma, and hepatoblastoma. Mediastinal tumors, on the other hand, are seen more commonly than any other thoracic tumor in children. This region is often divided into three compartments: the anterior or prevascular area containing the thymus and the thyroid; the middle or vascular space region containing the great vessels and the pericardium; and the posterior or post-vascular region that contains mainly nerves, the trachea, the esophagus, and the thoracic duct. Approximately 40% of mediastinal masses in children occur in the posterior compartment, with 95% being of neurogenic origin.9 Lymphomas, however, are usually located in the anterior or middle compartment, and they are the most common tumor found within the mediastinum, making up 46% of all mediastinal tumors.10
Because thoracic tumors may be of different types and may have varied locations, they differ considerably in their rapidity of onset and their clinical presentation. Children with pulmonary tumors can present with fever, hemoptysis, chest pain, dyspnea, cough, or a homophonous wheeze. The tumor may be of less than a weeks duration and still cause significant symptomatology. If the tumor is long-standing, the patient may have a history of pneumonia or persistent atelectasis due to airway obstruction. Rapidly expanding, space-occupying lesions, like a lymphoma, would cause more compression of structures and will probably have clinical symptoms at presentation. Infiltrative lesions, on the other hand, such as Langerhans Cell Histiocytosis, are often more insidious and only discovered incidentally on a chest radiograph.
Overall, the initial diagnostic study should be a plane frontal and lateral chest radiographs. If a tumor is suspected, consultation with a pediatric surgeon or radiologist is recommended in order to determine further diagnostic studies. CT scan and MRI are often the next radiographic modalities of choice; however, bronchoscopy or surgery should be performed in order to make a tissue diagnosis.
Lymph Node Enlargement. Besides neoplasms, enlarged lymph nodes located in the thoracic cavity may also cause external compression of the tracheobronchial tree and produce a homophonous wheeze. This lymphadenopathy may be the result of an infiltration by phagocytes or malignancies, or it is due to a proliferation of the normal lymphoid tissue. It may be the result of a regional problem, such as a thoracic tumor (i.e., Lymphoma) or an isolated infection (i.e., Mycobacterial or Atypical tuberculosis), or a systemic reaction, such as in patients with an autoimmune disease (i.e., Lupus erythematosus) or a lipid storage disease (i.e., Gaucher disease). Commonly, these patients have minimal or no symptoms, and regional lymphadenopathy is detected only by a routine chest radiograph. However, occasionally these children may present with dyspnea, chest pain, cough, and a homophonous wheeze. Tuberculosis, for example, causes enlarged hilar adenopathy as tuberculin reactivity develops. (See Figure 3.) As these lymph nodes enlarge, bronchial narrowing may result and produce a unilateral wheeze. With a more invasive disease process, the infected node could erode into the bronchus and deposit material into the lumen, resulting in a partial or complete bronchial obstruction. Even after treatment of tuberculosis, this lymphadenopathy may take 2-3 years to completely resolve.11 If suspected, a plain chest radiograph should be obtained. A CT scan or an MRI of the chest is indicated when the anatomy or the extent of the invasive process needs to be better delineated.
Pulmonary Hemosiderosis. Pulmonary hemosiderosis is a rare pediatric disease in which hemosiderin deposits within alveolar macrophages secondary to recurrent pulmonary bleeding. This deposition of hemosiderin usually results from a primary disease of the lungs, such as in idiopathic pulmonary hemosiderosis, pulmonary hemosiderosis with milk sensitivity (Heiner's Syndrome), or pulmonary hemosiderosis with glomerulonephritis (Goodpasture's Syndrome). However, systemic diseases, as in left-sided heart failure or collagen vascular diseases (i.e., Wegener's granulomatosis), can produce intrapulmonary bleeding and hemosiderin deposition. Most often, in children, no apparent cause for their pulmonary hemorrhage is found and they are diagnosed with idiopathic pulmonary hemosiderosis.12 Despite the underlying cause for their bleeding in the lungs, most children present with symptoms associated with their respiratory insufficiency or their iron deficiency anemia. Acute episodes of hemorrhage may result in hemoptysis, excessive coughing, dyspnea, pallor, crackles, or heterophonous wheezing. With chronic attacks, clubbing and pulmonary hypertension may be evident.
The diagnosis of pulmonary hemosiderosis should be suspected if a child presents with recurrent pneumonia or respiratory symptoms, an iron deficiency anemia, and diffuse interstitial infiltrates on chest radiograph. (See Figure 4.) In order to definitively make the diagnosis, hemosiderin must be found within macrophages on smears obtained from sputum or gastric aspirates. Occasionally, the diagnosis is difficult and an open lung biopsy is indicated.13 Once determined, other associations, like milk protein allergy or glomerulonephritis and systemic diseases, must be excluded as the cause of the pulmonary hemorrhage. Once the underlying cause is determined, the appropriate treatment may be initiated. If idiopathic pulmonary hemosiderosis is diagnosed, supportive therapy is indicated. This includes oxygen, blood transfusions, iron therapy, and, possibly, mechanical ventilation if necessary. Some studies have shown that immunosuppressive therapy with steroids or azathioprine has been beneficial for these patients.14
Alpha-1-Antitrypsin Deficiency. Alpha-1-antitrypsin is a protease inhibitor that primarily affects neutrophil elastase, an inflammatory host defense protein. The most common cause of alpha-1-antitrypsin deficiency is the homozygous inheritance of the z-type alpha-1-antitrypsin gene. This results in the normal synthesis of antitrypsin, but 85% of the inhibitor gets blocked in the terminal hepatocyte of the liver, impeding its secretion.15 Children with this deficiency may present early in life with jaundice, failure to thrive, or hepatomegaly. However, the most prevalent clinical disorder associated with alpha-1-antitrypsin deficiency is the chronic obstructive pulmonary disease (COPD) that occurs primarily in the second to third decade of life. Patients can present with dyspnea, coughing, and hyperaertion on chest radiograph. As with other people who suffer from COPD, bronchial hyper-responsiveness and heterophonous wheezing has been shown to affect approximately 20% of patients with alpha-1-antitrypsin deficiency.16 Eventually, cirrhosis of the liver and end-stage pulmonary disease occurs over time. In order to diagnose alpha-1 antitrypsin deficiency, low serum levels of alpha-1-antitrypsin should be detected. Liver biopsy will demonstrate eosinophilic cytoplasmic granules in the peripheral hepatocytes and definitively make the diagnosis.
Because of the obvious mediastinal mass on chest radiograph, the boy in case # 2 had a CT scan of the chest to further delineate its location. An anterior mediastinal mass was diagnosed and it was determined to be consistent with a non-Hodgkin's Lymphoma. As a result, the child was referred to the hematology-oncology department.
Evaluating the Wheezing Child
Initial Management. The initial evaluation of any wheezing infant must begin with assessing the child's respiratory status and the degree of respiratory distress. This assessment may only take a few seconds if the child is breathing comfortably and speaking in full sentences. However, if the child has signs of hypoxia or significant respiratory distress, emergency supportive measures should be instituted. Some of the earlier signs of hypoxia may include: tachycardia, shortness of breath, accessory muscle use, and anxiety. These early indicators should be sought before the true signs of respiratory failure (i.e., cyanosis, decreased mentation, and apnea) appear.
Besides visualizing the patient for signs of respiratory distress, the "ABCs" should be stabilized as with any patient in an emergent situation. Is the child's airway patent? Does the patient have good breath sounds bilaterally? Does the patient have adequate tissue perfusion? In the wheezing child, assessing the breath sounds may be difficult. If the patient has severe lower airway obstruction, no breath sounds may be heard or the wheezing may be quiet. Louder wheezing does not usually correlate with worse disease. Also, other respiratory noises, such as stridor, must be identified. For example, croup may present with upper airway stridor and expiratory wheezing as the virus affects both the upper and lower respiratory tract. Lastly, a noninvasive pulse oximeter should be placed for monitoring. Pulse oximetry is valuable since studies have shown that hypoxemia cannot be determined by clinical evaluation in a patient with respiratory distress.17 A pulse oximeter reading above 95% is reassuring. However, if the level is 90-95%, supplemental oxygen and further evaluation is warranted.
History. After the initial evaluation, a careful history and physical exam will aid the physician in accurately determining a cause for a child's wheezing episode, with minimal laboratory testing. As mentioned earlier, it may be helpful to begin by categorizing patients according to their age and chronicity of their symptoms. It is important to recognize that some disorders which commonly present in the first year of life may have a delayed presentation. Also, disorders that usually occur after 1 year of age could present earlier in life. Therefore, all plausible diagnoses should be considered and searched for by history and physical exam.
Algorithms can help in this decision-making process. First, it is important to distinguish between the child with an acute wheezing episode and the child who has persistent wheezing. After differentiating the chronicity of the symptoms, it is then helpful to categorize patients by their age at presentation (< or > 1 year of age). After these four classifications have been established, specific historical clues can guide the physician toward the cause of the child's wheezing. (See Figures 5 and 6.)
For the healthy child with an acute onset of wheezing, upper respiratory symptoms, and younger than 1 year of age, the diagnosis will most often be bronchiolitis. (See Figure 5.) However, it is important to inquire about other historical facts. Ask about the child's birth history-Was the child born prematurely? Did the child require mechanical ventilation? Was the child diagnosed with other anomalies (i.e., rib or radial anomalies, anal atresia, etc.)? Determine the child's feeding history-Does the child have a swallowing dysfunction or a known neurologic abnormality? Is there vomiting after feeding? Has the child been gaining weight appropriately? Ask about other systems besides the lungs-Does the child have a known cardiac murmur? Will the infant become short of breath while feeding and feed slowly? How is the child's urine output? It is important to determine if this patient is having an asthma exacerbation-Is there a family history of asthma? Does the child have atopic dermatitis? Has the child ever wheezed before?
For the child older than 1 year of age with an acute episode of wheezing, asthma and a foreign body aspiration will be the most common etiologies. It is still prudent to question whether the child has signs of anaphylaxis-upper respiratory stridor, pruritis, or urticaria? Did the child have a choking episode or did these symptoms begin after eating? Is it possible that they may have ingested something? What substances are inside the house? How much smoking is done at home? Has the child had any fever, URI symptoms, abdominal pains? Have they ever wheezed in the past and what was done for them at that time? Has the child ever been treated with "cough medicines," which ones were used, and have they helped?
Figure 6 provides an algorithm for the child with persistent or recurrent episodes of wheezing. It is initially helpful to separate these patients by their age. For the children younger than 1 year of age, historical questions should include: Has the child had multiple bouts of pneumonia in the past? Have they been diagnosed with sinusitis or recurrent bouts of otitis media? Has he/she been gaining weight appropriately? Is the wheezing persistent or episodic? Does anything make the wheezing better or worse? More questions can be asked for the child older than 1 year. These inquiries include: Has the child ever looked jaundice? Has he/she coughed blood? Is the child on any medicines, such as iron, for anemia? Does he/she have any associated nonspecific symptoms, like fever, night sweats, fatigue, or weight loss?
Finally, the emergency physician should inquire about this particular illness and why the patient was brought into the ED on this visit. Was this illness worsening or sudden in onset? How severe is the illness? Is anyone else ill at home? Is the child able to eat now or sleep at night with this respiratory difficulty? Has the child turned cyanotic, apneic, or had a change in his or her level of consciousness?
Physical Exam. After initially surveying the cardiopulmonary systems, a secondary survey along with a complete lung exam must be accomplished. Make sure air exchange is appreciated on inspiration as well as expiration. If no air movement is heard, severe bronchoconstriction must be assumed. Are the lung sounds equal bilaterally? What is the child's respiratory rate and is it appropriate for age? Does the child have any grunting, flaring of the nostrils, or subcostal or intercostal retractions? Subcostal retractions are a sign of hyperaeration and air trapping (a barrel chest is often seen on exam), while intercostal retractions are a sign of an increased work of breathing without hyperaeration. Make sure the "noisy breathing" is clearly wheezing and not just hysteria, coughing, stridor, or congestion. Because of the obstruction in the smaller airways, the expiratory phase is often prolonged. This is measured by the inspiratory to expiratory ratio, which is normally 1:2; in a child with asthma, this ratio can be prolonged to 1:4.18 If the airways become more narrowed with more serious disease, the wheezing may extend into inspiration as well. Is the expiratory wheezing different in all lung fields (heterophonous) or is it the same in all lung fields (homophonous)? Is the wheezing localized to one area of the lung, such as in a foreign body aspiration, or is it diffuse, as in pulmonary hemosiderosis? Sometimes the wheezing is difficult to appreciate, as in the case of an infant who will not voluntarily take deep breaths. In this case, forced expiration by squeezing the infant's chest will help to elicit the wheeze. Finally, can crackles be heard in one focal region, like in pulmonary sequestration, or are they diffuse, such as the patient with bronchiolitis?
In addition to the lungs, extrapulmonary physical findings may help to diagnose the child's cause for wheezing. Special attention should be paid to the child's height and weight. Has the child been growing appropriately? Make sure the child's level of consciousness is at his or her baseline. Does the child have eczema or jaundice, as in the case of asthma or alpha-1-antitrypsin deficiency? Is a murmur heard? Does the child have hepatomegaly? It is important to look for clubbing as a sign of chronic and prolonged respiratory difficulties, such as in patients with cystic fibrosis, pulmonary hemosiderosis, or other chronic problems. It is rare to see an asthmatic with clubbing.
Laboratory Data. Most children in the ED do not require any laboratory tests since their diagnosis is often made by the history and physical exam and they tend to respond nicely to bronchodilator therapy. Nevertheless, testing is generally indicated to assess the child in severe respiratory distress or to verify the underlying suspected diagnosis.
For the child in respiratory distress, the pulse oximeter is the easiest and quickest way to determine the patient's oxygenation status. Preferably, the child's oxygen saturation should be higher than 95% to show that the child is oxygenating well. One study demonstrated that a pulse oximeter higher than 95% in asthmatics, regardless of therapy, was a good indication that they can be discharged home.19 Although the pulse oximeter assesses the patient's oxygenation, it gives no information as to how well the child is ventilating. Capnometry or end tidal CO2 monitoring has been shown to be a non-invasive means for assessing ventilation. It is more easily obtained in the intubated patient; however, recent literature has shown it to be useful in the non-intubated child.20 More commonly, ventilation is evaluated by obtaining a blood gas. Since the only relevant items for ventilation are the pH and the pCO2, any form of blood gas is acceptable (i.e., capillary, venous, or arterial). A capillary blood gas is especially useful in the bronchiolitic infant who is breathing 80 breaths/min since an arterial sample may be difficult to obtain and it may give abnormal results if the patient is crying or hyperventilating during the procedure. A chest radiograph may be reasonable if the child is in moderate to severe respiratory distress in order to rule out a pneumothorax or atelectasis. As mentioned earlier, the routine use of chest x-rays in the asthmatic child or the child with his or her first onset of wheezing is often of no benefit.21 It has been shown recently that grunt or oxygen saturation lower than 93% in children presenting to the ED with bronchiolitis is a predictor of pneumonia on radiograph.22 Lastly, some physicians will advocate the use of hand-held peak flow meters within the ED to determine the patient's degree of respiratory distress; however, with these devices, it is difficult to reproduce good results in children younger than 6 years of age.
After the emergency physician suspects a diagnosis by the child's history and physical exam, laboratory data may be obtained to solidify the determination. Blood studies can be drawn, such as mycoplasma titers or cold agglutinins for mycoplasma, tryptophan levels for the presumed anaphylactic reaction, and immunoglobulins for the immune-deficient host. Viral studies and RSV rapid antigen testing may be accomplished by swabbing the nasopharynx or by deep nasopharyngeal suctioning. A PPD can be placed to diagnose tuberculosis or to display anergy in the T cell deficient patient. If a foreign body is suspected, an initial chest radiograph may show asymmetric hyperaeration, as in case # 1. Lateral decubitus films may be beneficial to show air trapping in the very young patient who cannot cooperate for inspiratory and expiratory films. Of course, rigid bronchoscopy must be performed if a foreign body is suspected, even if the chest x-ray is normal.
Finally, the emergency physician may schedule other diagnostic studies to be obtained at a later date, depending on the individual scenario. Sweat tests should be obtained on any child with chronic wheezing, failure to thrive, a poor response to therapy, or other suggestions of cystic fibrosis. Echocardiography can be used to determine any cardiac or vascular anomaly. Angiography or MRI may be arranged to detect the exact location of a vascular ring, such as a double aortic arch. A barium swallow can show aspiration syndromes (i.e., TEF or neuromuscular swallowing defects), compression by vascular structures, or normal anatomy to rule out malrotation of the gut causing gastroesophageal reflux. Scintiscans and pH probe testing can be obtained in order to confirm GER. CT scans of the chest may help to show the exact location and size of a thoracic neoplasm and lymphadenopathy. And, for older children, airway hyperreactivity can be objectively assessed by spirometry and airway challenges with exercise and cold air.
Therapeutic Management. For any child who presents to the ED with heterophonous wheezing, a trial of bronchodilator therapy is warranted. Usually, this treatment is initiated with aerosolized medicine, yet it can be given orally or by MDI. As the child's respiratory rate, retractions, and work of breathing improve, the response can be assessed clinically. Although beta-agonists primarily stimulate tachycardia, the heart rate commonly decreases as a result of therapy. It may take three or four treatments until a significant response has occurred. Occasionally, bronchodilator therapy may worsen the child's wheezing or oxygen saturation. If increased wheezing occurs with beta-agonists, either the patient is opening his or her smaller airways allowing increased turbulence of airflow or the child's central airways are collapsible, causing a more homophonous wheeze to present. When central airway collapse occurs, there should be consideration for withholding bronchodilator therapy.2 The decision to withholding bronchodilator therapy should be made cautiously. Also, some children may present to the ED dehydrated due to poor feeding with respiratory distress. However, fluid replacement must be done judiciously as increasing the patient's volume may cause interstitial edema and increase airway obstruction.
Other treatments must be geared toward the patients underlying cause for wheezing. For example, a foreign body must be removed promptly or an asthmatic may require steroids to decrease parenchymal inflammation causing airway obstruction. The rapidity of improvement commonly depends on the chronicity of the symptoms and the degree of the patient's respiratory distress.
Summary
Wheezing is a common complaint in the ED. The majority of the children who wheeze will have a diagnosis of a viral infection or asthma. However, the atypical causes of wheezing, such as foreign body aspiration, cystic fibrosis, and neoplasm, must be considered in the differential diagnosis. Laboratory tests are often of little value in making a diagnosis within the ED. A chest radiograph is of low yield unless the patient has local findings on physical exam or fails to respond to therapy. In treating the wheezing child, broncholdilators continue to be the predominate therapy; however, their use in the treatment of bronchiolitis remains controversial.
References
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