Day: December 2, 2019

What Causes Respiratory Failure?

Patient Presentation
A 4-year-old male came to the emergency room by ambulance with a history of increasing respiratory distress that was worsening over the past 6 hours. He had started having a runny nose in the morning and was having tachypnea by the afternoon. His mother had given him his inhaler but had not started steroid medication. He continued to worsen so she called the ambulance. He was well known to the emergency room and pulmonary staff because he had uncontrolled asthma. He had been hospitalized 3 previous times in the past year for asthma exacerbations for at least 2 days each time but had not been admitted to the intensive care unit. He was supposed to be taking a daily inhaled steroid and montelukast but his mother said she ran out of medication about 3 weeks ago.

The family and social histories revealed asthma and eczema in multiple family members, an older sibling who had been admitted to the intensive care unit for asthma and a difficult social situation. There was smoking in the household.

The pertinent physical exam showed a thin male in moderate respiratory distress on 6 liters of oxygen by facemask. His oxygen saturation was 93% but would quickly drop into the mid-85% if the mask was taken off. His heart rate was 136, respiratory rate of 48, and normal blood pressure and temperature. His weight was at the 5th percentile. HEENT revealed copious clear rhinorrhea, tympanic membranes that were dull and a slightly erythematous posterior pharynx. His respiratory examination had wheezing throughout his lung field with prolonged expiration but no obvious rales. He had tracheal tugging, intercostal retractions, nasal flaring and abdominal breathing. His skin had xerosis throughout with areas of licenification, and bright red erythema in his anticubital and popliteal fossas and adjacent areas. His overall hygiene was poor.

The diagnosis of an acute asthma exacerbation was made. The patient’s clinical course revealed he was started on continuous albuterol and given steroids in the emergency room. An initial venous blood gas showed a pH = 7.31, pCO2 = 53, pO2 = 28, and bicarbonate = 30. The radiologic evaluation of a chest radiograph showed non-specific diffuse pulmonary markings with airway trapping but no focal findings consistent with a viral process. His lung examination sounded slightly better with increased aeration after 30 minutes of continuous nebulization, but he was more sleepy and continued to have tachypnea and tachycardia and increased work of breathing. He was transferred to the intensive care unit for increased monitoring and respiratory support. He needed high flow oxygen for 36 hours and then was slowly weaned. He left the hospital 6 days after admission with the cause being respiratory syncytial virus. Additional social supports including home nursing were put into place to try to assist the family.

Discussion
The respiratory system is a complex system. The upper airways must remain patient. The lower airways must interface with the vascular system. The musculoskeletal system must provide mechanical function and the central nervous system must provide overall control. Respiratory failure occurs when the overall system cannot support the body’s necessarily ventilation, oxygenation or both. Children are at higher risk of respiratory failure. They have few intrinsic lung parenchyma problems, but have very small airways that increase the airflow resistance by themselves but then have to contend with problems such as airway edema, secretions, or bronchoconstriction which dramatically increase resistance. Remember that airflow resistance is inversely proportional to the size of the airway to the 4th power. Therefore small changes in airway size create large resistance forces. The chest wall is also more compliant which makes exerting necessary pressures for ventilation more difficult. The diaphragm also has fewer muscle fibers to exert the necessary pressure when contracting and the central nervous system is also more immature resulting in more bradypnea or apnea.

The signs and symptoms of respiratory failure include tachypnea, retractions, head bobbing, grunting, nasal flaring, tracheal tugging, belly breathing, and altered mental status (agitation is common for hypoxic patients, and somnolence with hypercarbia but either can occur). Other physical examination signs include stridor (e.g. upper airway obstruction), wheezing (e.g. lower airway disease), rales (e.g. pulmonary edema), and absent breath sounds (e.g. pulmonary consolidation, pneumothorax, pleural effusion). Laboratory testing including pulse oximetry can show hypoxia, while a blood gas testing assesses oxygen, carbon dioxide and pH values. Chest radiograph can often identify the underlying cause. Respiratory secretions are important to obtain if an infectious cause is suspected but can be helpful in other disease processes as well.

Normal ventilation provides a negative pressure gradient which causes net movement of air into the lungs. With mechanical ventilation the opposite is true as a positive gradient pushes the air into the lung. Treatment is respiratory support while the underlying cause is determined, managed or necessitates waiting until it resolves by itself. This includes potentially noninvasive methods such as continuous positive airway pressure (CPAP), bi-level positive airway pressure (BiPAP), or high flow nasal cannula oxygen (HFNCO<sub<2). Endotracheal intubation is indicated for patients who have failure of ventiliation or oxygenation despite non-invasive support methods, inability to protect their airway or a cause that necessitates endotrachael intubation (e.g. pulmonary toilet). Inhaled nitric oxide is also a treatment used for pulmonary hypertension as it selectively dilates pulmonary arterioles. Extracorporeal membrane oxygenation is used for patients who still cannot be appropriately ventilated or oxygenated with mechanical ventilation.

Learning Point
Causes of respiratory failure include:

  • Airway disorders
    • Croup
    • Congenital anomalies
    • Foreign body
    • Malacia of the airway
    • Subglottic stenosis
    • Vascular ring
    • Pulmonary edema
    • Enlarging mass
  • Lung parenchyma
    • Acute respiratory distress syndrome
    • Asthma
    • Aspiration
    • Bronchiolitis
    • Pneumonia
    • Pulmonary edema
    • Pulmonary fibrosis
    • Vascular abnormalities, e.g. pulmonary embolism
  • Neuromuscular dysfunction
    • Central nervous system disorders
    • Diaphragmatic paralysis
    • Myopathy
    • Neuropathy
    • Neuromuscular junction disorders
  • Other
    • Trauma

    Questions for Further Discussion
    1. What are some of the risks of endotracheal intubation?
    2. What are initial steps for diagnosis and management of suspected respiratory failure in your practice location?
    3. What is the definition of acute respiratory distress syndrome?
    4. What are the differences between arterial and venous blood gas measurements

    Related Cases

    To Learn More
    To view pediatric review articles on this topic from the past year check PubMed.

    Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.
    Information prescriptions for patients can be found at MedlinePlus for these topics: Respiratory Failure and Asthma.

    To view current news articles on this topic check Google News.

    To view images related to this topic check Google Images.

    To view videos related to this topic check YouTube Videos.

    Smith KA, Flori HR. Critical Care in the Pediatric Emergency Department. Pediatr Clin North Am. 2018;65(6):1119-1134. doi:10.1016/j.pcl.2018.07.004

    Friedman ML, Nitu ME. Acute Respiratory Failure in Children. Pediatr Ann. 2018;47(7):e268-e273. doi:10.3928/19382359-20180625-01

    Viscusi CD, Pacheco GS. Pediatric Emergency Noninvasive Ventilation. Emerg Med Clin North Am. 2018;36(2):387-400. doi:10.1016/j.emc.2017.12.007

    Author
    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa