Which of the following signs and symptoms would indicate respiratory distress?

Respiratory Failure

Respiratory failure occurs when oxygenation and ventilation are insufficient to meet the metabolic demands of the body. Respiratory failure may result from an abnormality in (1) lung and airways, (2) chest wall and muscles of breathing, or (3) central and peripheral chemoreceptors. Clinical manifestations depend largely on the site of pathology. Although respiratory failure is traditionally defined as respiratory dysfunction resulting in arterial partial pressure of oxygen (Pao2) <60 mm Hg when breathing room air and Paco2 >50 mm Hg resulting in acidosis, the patient's general state, respiratory effort, and potential for impending exhaustion are more important indicators than ABG values.

The Berlin definition of ARDS was once used to describe pediatric patients with ARDS, even though the pathophysiology is different between children and adults. The current pediatric definition differs in chest imaging findings, definition of oxygenation, consideration of both noninvasive and invasive mechanical ventilation, and consideration of special populations (Table 89.7 andFig. 89.1).

Age

Respiratory distress in younger patients (under the age of 10) most commonly is related to asthma (usually allergic asthma). Hyperventilation and heart failure are significantly less common in this age group (children with severe, uncorrected, congenital heart defects may demonstrate respiratory distress, but their medical history will have provided the doctor with this information). Hyperventilation is more likely to be the cause of respiratory distress for individuals between 12 and 40 years of age. Asthma may also occur in this age group, but in most instances patients already know that they suffer from this condition. Clinically significant heart failure is rarely seen before the age of 40 years. The peak incidence of heart failure in men is between 50 and 60 years; in women, the peak falls between 60 and 70 years.

Respiratory Distress

The differential diagnosis and subsequent management of the infant with respiratory distress are the most frequent challenges encountered by the practitioner of newborn medicine. Problems posed by prematurity, the failure of the necessary transition to extrauterine existence, infectious complications, metabolic derangements, and various congenital and acquired abnormalities of the cardiopulmonary system may all lead to a similar presentation in the newborn period.

Infants with respiratory distress may present with tachypnea or cyanosis, or both, and varying degrees of a triad of signs, which includegrunting, flaring, andretractions. Grunting is a characteristic involuntary guttural expiratory sound made by infants as they exhale against a closed glottis in an attempt to maintain expiratory lung volume.Flaring refers to the reflexive opening of the nares during inspiration.Retractions are the result of increased respiratory effort with high negative intrathoracic pressures leading to an inward collapse of the relatively compliant chest wall of the newborn during inspiration.

Classic respiratory distress syndrome (RDS) is caused by a combination of lung immaturity secondary to preterm delivery and surfactant deficiency. The radiographic findings (Fig. 2.43) in such infants consist of low lung volumes, a ground-glass appearance (small airway and alveolar atelectasis), and “air bronchograms” (an outline of the large airways superimposed on the relatively airless lung parenchyma). Infants with RDS usually need supplemental oxygen therapy and surfactant replacement and often require mechanical ventilatory assistance.

Most infants with RDS recover without sequelae. However, a small proportion develops a chronic lung condition known asbronchopulmonary dysplasia. Histologically, this condition is characterized by varying degrees of inflammation and fibrosis (Fig. 2.44), and the chest x-rays exhibit areas of hyperinflation alternating with atelectasis (Fig. 2.45).

The most common cause of respiratory distress in term infants is transient tachypnea of the newborn (TTN). Thought to be related to the delayed removal of fetal lung fluid, this condition is more common in infants born by cesarean section. Radiographic findings may include streaky perihilar shadows caused by dilated lymphatics or visible fluid densities within the intralobar fissures (Fig. 2.46), or both. As its name implies, TTN resolves within hours to days, usually with minimal supportive care.

Unfortunately for the clinician, the early clinical and radiographic findings in infants with potentially life-threatening congenital pneumonias may mimic those seen in RDS or TTN (Fig. 2.47). This diagnostic uncertainty leads to early treatment with antibiotics until bacterial cultures, serial chest radiographs, and clinical improvements reassure the practitioner that the discontinuation of such antibiotics is warranted.

Summary and Red Flags

Respiratory distress may be a result of disorders of the extrathoracic or intrathoracic airways (intrinsic or extrinsic compression-obstruction), alveoli, pulmonary vasculature, pleural spaces, or thorax. The distress may be secondary to respiratory, cardiovascular, hematologic, or central nervous system diseases. The most important aspect of the evaluation of a child with respiratory distress is observation of the child's breathing pattern and a brief, directed history and physical examination. Once the cause is identified, treatment should be started quickly to avoid progression to respiratory failure.

Red flags for impending respiratory failure include sudden onset of distress (epiglottitis, foreign body aspiration), hemoptysis, severe retractions, lethargy, a sitting up–leaning forward posture, dysphagia, drooling, or aphonia. It is imperative to identify the symptoms of impending respiratory failure and not delay treatment with unnecessary clinical or radiologic studies. Epiglottitis should be recognized quickly, and treatment initiated promptly. It is also important not to miss a foreign body, which with time may produce chronic respiratory disease that is often confused with pneumonia or asthma.

Signs of a more chronic process include lack of resolution with normal therapy, chronicity of symptoms, positive family history, digital clubbing, weight loss, and/or failure to thrive. These signs should prompt further work-up and consultation with a pulmonary specialist as needed. Asthma will rarely cause digital clubbing, so its presence should raise concern for another primary lung disease process.

Differential Diagnosis

Thehyperoxia test is one method of distinguishing cyanotic CHD from pulmonary disease. Neonates with cyanotic CHD usually are unable to significantly raise their arterial blood partial pressure of oxygen (Pao2) during administration of 100% oxygen. This test is usually performed using a hood rather than nasal cannula or face mask, to best guarantee delivery of almost 100% oxygen to the patient. False-positive tests can occur if this is not done correctly. If the Pao2 rises above 150 mm Hg during 100% oxygen administration, an intracardiac right-to-left shunt can usually be excluded. This is not 100% confirmative, however, because some patients with cyanotic CHD may be able to increase their Pao2 to >150 mm Hg because of favorable intracardiac streaming patterns. In patients with pulmonary disease, Pao2 generally increases significantly with 100% oxygen as ventilation-perfusion inequalities are overcome. In infants with cyanosis from a central nervous system disorder, the Pao2 usually normalizes completely during artificial ventilation. Hypoxia in many heart lesions is profound and constant, whereas in respiratory disorders and in PPHN, Pao2 often varies with time or changes in ventilator management. Hyperventilation may improve the hypoxia in neonates with PPHN and only occasionally in those with cyanotic CHD.

Although a significant heart murmur usually suggests a cardiac basis for the cyanosis, several of the more severe cardiac defects (e.g., transposition of the great vessels) may not initially be associated with a murmur. The chest radiograph may be helpful in the differentiation of pulmonary and cardiac disease; in the latter, it indicates whether pulmonary blood flow is increased, normal, or decreased (Fig. 456.1).

Two-dimensional echocardiography with Doppler is the definitive noninvasive test to determine the presence of CHD. Cardiac catheterization is less often used for diagnostic purposes and is usually performed to examine structures that are sometime less well visualized by echocardiography, such as distal branch pulmonary arteries or aortopulmonary collateral arteries in patients with tetralogy of Fallot with pulmonary atresia (seeChapter 457.2), or coronary arteries and right ventricular sinusoids in patients with pulmonary atresia and intact ventricular septum (seeChapter 457.3). If echocardiography is not immediately available to confirm a diagnosis of cyanotic CHD, the clinician caring for a newborn with possible cyanotic CHD should not hesitate to start a prostaglandin infusion (for a possible ductal-dependent lesion). Because of the risk of hypoventilation associated with prostaglandins, a practitioner skilled in neonatal endotracheal intubation must be available.

Management

Definitive management of respiratory distress depends on the doctor’s prompt recognition of the problem and a determination of its probable cause (Box 10-2). This chapter focuses on the basic steps common to the management of most cases of respiratory distress.

INITIAL STABILIZATION

The first priority in evaluating a child with respiratory distress is to assess the airway, breathing, and circulation (ABCs). Rapid assessment and intervention can prevent the progression from respiratory compromise to respiratory failure. To assess the airway, determine whether it is patent, stable, and maintainable. If not, such an airway must be established (e.g., repositioning, instrumentation). Once these three criteria are met, the breathing process is evaluated by determining the respiratory rate, oxygen saturation, adequacy of breath sounds, and quality of respiratory effort (e.g., labored, use of accessory muscles). Determination of arterial blood gas levels may be needed if there is evidence of respiratory insufficiency or failure. If spontaneous ventilation is inadequate, assisted breathing with positive pressure, initially via a bag-mask device, is indicated. Assessment of the patient's circulation and mental status are other key aspects of the initial evaluation. Based on this rapid assessment, the clinician obtains information about the severity of the patient's condition and how rapidly interventions must be performed.

Providing supplemental oxygen is an important first step for a child presenting in distress, especially with hypoxemia demonstrated by oximetry. Oxygen can be delivered by multiple devices, and the choice depends on the child's clinical status and oxygen needs (see Chapter 38). Some of these devices can agitate a child further, worsening respiratory compromise. Allow the child to remain with the parent as much as possible, and use the least noxious form of oxygen delivery necessary. In a small number of children, airway adjuncts such as a nasopharyngeal airway, oropharyngeal airway, or assisted ventilation are needed. An oropharyngeal airway holds the tongue forward to prevent airway obstruction, so it will not be tolerated in a conscious or semiconscious patient with an intact gag reflex, and it may induce vomiting. A nasopharyngeal airway can be used in a conscious or unconscious patient but should be avoided in those with facial trauma. Continuous positive airway pressure may assist inspiratory efforts as well as provide positive end-expiratory pressure (PEEP). PEEP provides resistance to expiration, which may help expand atelectatic portions of the lung and thereby reduce ventilation-perfusion mismatch. Bilevel positive airway pressure provides inspiratory and expiratory pressure via a firmly fitting facemask, which may be uncomfortable and not well tolerated in infants or young children (see Chapter 209).

Careful reevaluation after every intervention is critical to the care of a child with respiratory compromise. This confirms proper application of the intervention and monitors the patient's response.

Respiratory Distress

Respiratory distress manifesting as deep breathing or tachypnea is associated with poor outcome in children with severe malaria.44 There may be intercostal recession, use of the accessory muscles of respiration and flaring of the alae nasi. Respiratory distress is often present as respiratory compensation for a profound metabolic acidosis, but can also be caused by the presence of severe anemia or a concomitant lung infection. Pulmonary edema is rare in children. Respiratory depression can be caused by an overuse of anticonvulsants, particularly phenobarbital in combination with benzodiazepines. Identification of these different causes of respiratory distress is important as each requires a different treatment modality.

In adults with severe falciparum malaria, but occasionally in severe vivax infections, ARDS with increased pulmonary capillary permeability can develop, which has a high mortality rate. Pregnant women are especially prone to this complication. Overhydration aggravates the condition, but is not the cause of the respiratory distress; the pulmonary capillary wedge pressure is usually normal.

Surgical Management of the Neonatal Airway

Respiratory distress in the neonate has a variety of causes (Box 36-1), and pediatric surgeons and otolaryngologists are increasingly becoming involved in the care of these patients. The ability to intubate, mechanically ventilate, and thereby prolong the lives of children with neonatal asphyxia, congenital anomalies, or other causes of respiratory distress redefines the role of the surgeon as part of the neonatal management team.

The role of the surgeon is twofold: (1) as a diagnostician and therapist for those infants who manifest respiratory distress from an anatomic problem or who present with congenital airway obstruction (i.e., congenital stridor [Box 36-2]) and (2) as a consultant for neonates undergoing medical treatment requiring long-term intubation of their airways.

10 What are the red flag physical exam findings after chest and abdominal trauma?

Respiratory distress in a child after trauma is a red flag for serious injury and potential for decompensation. Chest pain with neck discomfort is concerning for mediastinal free air; and distended neck veins are associated with pericardial tamponade. Children should be transferred to the emergency department for further evaluation with any abnormalities of lung auscultation, respiratory rate, chest rise pattern, and oxygen saturation.

In abdominal trauma, focal tenderness, distension, vomiting, and bruising are red flags for injury. Any sign of rigidity or rebound tenderness is a late finding and concerning for severe abdominal injury.