Acute Respiratory Failure (Case 41)

Chapter 83 Acute Respiratory Failure (Case 41)

Christine M. Schlichting, MD

Case

A 2-year-old with tachypnea and increased work of breathing

Differential Diagnosis

Pneumonia Bronchiolitis
Croup Status asthmaticus
Pediatric acute respiratory distress syndrome (ARDS)

Speaking Intelligently

When presented with an infant or child in respiratory distress, I think of the respiratory system and its components, why each component may fail, and how this presents clinically: central control of breathing, blockage in the upper airway, lower airways dysfunction, alveolar disease, and neuromuscular failure or “bellows dysfunction.” It is important to note that respiratory failure may also occur in a patient who presents with multiple organ failure, such as septic shock, and this respiratory failure may involve many levels of the respiratory system all at once. Thinking through the cause of the distress helps me with my next interventions, which may involve taking control of the child’s work of breathing with an artificial airway or supporting the child with oxygen and medications.

The end result of respiratory failure is ventilatory failure (hypercarbia or elevation of PCO2) and/or hypoxemia (decrease in PO2), both of which can be life threatening.

Patient Care

Clinical Thinking

• It is helpful to take a stepwise approach to support of a patient in respiratory distress:
• Oxygen should be administered while an evaluation is in progress. Oxygenation improves with the delivery of supplemental oxygen or with the delivery of positive pressure, which recruits closed/collapsed airways and alveoli and in so doing decreases image mismatch. Oxygen can be delivered by nasal cannula (delivers up to 32%), simple face mask (maximum delivery 35%), and a nonrebreather mask (maximum 60%). Because of poor mask fit and room air entrainment oxygen delivery by these simple devices may not approach these levels. Improvement of ventilation can be accomplished by improving the image match so positive pressure systems such as continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) are beneficial. Finally, patients may need the support that can only be delivered via tracheal intubation and use of mechanical ventilation.
• Although it is tempting to treat the symptomatic patient reactively, it is essential, whenever possible, to gather full information, including history and appropriate tests, before interventions.
• Support of a patient in severe respiratory failure will necessitate tracheal intubation and ventilator support. The guiding principle is support with the least morbidity. Ventilators damage lungs and should be used with settings that are as low as can deliver the desired level of support. Mean airway pressures below 20 cm H2O reduce pressure injury to the alveoli (barotrauma). Permissive hypercapnia (allowing increased carbon dioxide) and subsequent respiratory acidosis is safer (if pH >7.25) than using higher airway pressures. Positive end-expiratory pressure (PEEP) should be set at a level that maintains open airways and effectively recruits collapsed lung units without decreasing cardiac output. Oxygen exposure should also be minimized: in general, inspired oxygen less than 60% is considered “safe.”

History

• What are the presenting symptoms?
• Cough indicates irritation in the airways with or without increased mucous (sputum) production. Where the secretions seem to originate is also helpful: copious nasal secretions in young children almost always indicate a viral illness, and a primary bacterial pneumonia usually has a cough producing sputum. The quality of the cough may also suggest a diagnosis
• Fever is usually a sign of infection.
• Anxiety or “air hunger” is not uncommon in patients with hypoxemia.
• Agitation occurs in both hypoxemia and in patients with hypercarbia before the onset of lethargy and coma.
• Lethargy demands careful evaluation because it can occur in many clinical scenarios of respiratory failure possibly suggesting hypercarbia.
• What is the time course of the illness? Was it sudden in onset, or had it been going on for some time and gradually worsened?
• Did the caretakers notice rapid breathing, retractions, or increased work of breathing?
• Does the patient have pertinent past medical history?

Physical Examination

• Evaluation of signs:
• Tachycardia is not a specific sign; but it may indicate hypercarbia.
• Increased respiratory rate may indicate the degree of respiratory failure, although it may be a sign of increased respiratory demand (e.g., the patient who is acidotic or with fever).
• Decreased respiratory rate may indicate failure of central control that occurs in central nervous system diseases, metabolic diseases, and drug effects, but also occurs in severe status asthmaticus and hypothermia.
• Prolonged exhalation usually indicates lower airways obstruction such as asthma but can be present in congestive heart failure (CHF) as well.
• Use of accessory muscles, nasal flaring, and retractions (suprasternal, intercostal, subcostal, and sternal) is an indication of increased respiratory effort.
• Breath sounds:
• Rales or crackles are indicative of air fluid interface in the alveoli.

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Jul 18, 2016 | Posted by in PEDIATRICS | Comments Off on Acute Respiratory Failure (Case 41)

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