Respiratory Failure is an Insidious Syndrome and has Many Causes…..

Imagine if you have a baseline respiratory rate at rest which is very slow in health or very fast in health. Too slow or too fast baseline breathing rate means that you are more at risk for respiratory failure from any of the conditions listed below. You need an arterial blood gas test to be sure of whether the cause of someone’s altered mental status or neuropsychiatric symptoms are due to respiratory failure. Outside the intensive care unit, I do not think that anyone does arterial blood gas tests [ABG’s] and so this diagnosis is often missed.

The article below is excellent at explaining what respiratory failure is.

The Pediatric Patient with Acute Respiratory Failure: Clinical Diagnosis and Pathophysiology https://www.reliasmedia.com/articles/68532- the-pediatric-patient-with-acute-respiratory-failure-clinical-diagnosis-and-pathophysiology.

Causes of Respiratory Failure

The etiology of respiratory failure is more diverse than just lung or airway disorders. Respiratory failure can occur from an abnormality in any component of the respiratory system from the CNS to the pulmonary capillary bed where gas exchange occurs,14 and to the tissues and cells where cellular uptake and utilization of oxygen occur. Nervous system disorders (from the respiratory control center in the medulla and pons via the spinal nerve pathways to the peripheral nerves and the neuromuscular junction), chest wall/pleura disorders, airway disease (e.g., obstruction), pulmonary diseases, and even cellular uptake/utilization disorders all can lead to respiratory failure. 

CNS disorders that lead to respiratory failure are control abnormalities that cause Type II (hypercapnic) respiratory failure and usually present without signs and symptoms of respiratory distress (such as dyspnea, retractions, or tachypnea).15 Common causes of respiratory failure from CNS disorders include: drug overdoses; anesthesia; sedation; seizures; and CNS infections, injuries, and malformations (i.e., meningitis, encephalitis, brain abscesses, congenital malformations, encephalopathy, ischemia, infarcts, tumors, and trauma). These disorders all exert their effect by depressing the respiratory center in the brainstem. 

Disorders of the upper motor neurons or spinal nerves also can cause Type II hypercapnic respiratory failure.16 This may occur with several disorders, including: cervical spinal cord trauma, demyelinating diseases, myelitis (poliomyelitis, transverse myelitis), and Werdnig-Hoffman syndrome. Diseases of the peripheral nerves (i.e., Guillain-Barré syndrome, post-thoracotomy phrenic nerve damage, or a peripheral neuropathy) also can lead to hypercapnic respiratory failure. 

Diseases affecting the neuromuscular junction may cause hypercapnic respiratory failure. These diseases include: myasthenia gravis, botulism, tetanus, organophosphate poisoning, and neuromuscular blocking drugs/anesthetics (i.e., pancuronium and succinylcholine). Fatigue of the respiratory muscles also can lead to ARF.17,18

Chest wall/pleura disorders lead to respiratory failure by decreasing chest wall compliance, as with flail chest, severe kyphoscoliosis, congenital or genetic deformities of the chest (e.g., severe dwarfism), or by disruption of the pleural space (e.g., pneumothorax or pleural effusion).19 These disorders cause respiratory failure by mechanical abnormalities and decreased alveolar ventilation, which result in hypercapnia. 

Airway obstruction causes increased airway resistance.3 Airway obstruction can be in the upper airway (e.g., above the vocal cords) or in the lower airway from the larynx distally. The upper airway includes the nose, paranasal sinuses, and the pharynx. The lower airway includes the larynx, bronchi, bronchioles, and the alveoli. Obstruction in children is commonly due to foreign bodies, or infection, and infrequently due to congenital abnormalities such as a laryngeal web or tracheomalacia. Causes of upper airway obstruction include: 

• Foreign bodies;

• Infections (epiglottitis, retropharyngeal abscess, or croup);

• Edema (as with anaphylaxis or laryngoedema);

• Congenital defects (web, stenosis, tracheomalacia, etc.);

• Tumors;

• Adenotonsilar hypertrophy; and

• Subglottic stenosis. 

Lower airway obstructions include similar etiologies as with upper airway obstruction (e.g. foreign body, edema, congenital defects, and infections), but also reactive airway disease (asthma and bronchiolitis) secondary to bronchospasm. 

In children, respiratory failure most often is due to diseases of the lungs.15 Pulmonary diseases include: pneumonia, near drowning, adult respiratory distress syndrome (ARDS), pneumonitis, vasculitis, pulmonary edema, cystic fibrosis, and tuberculosis. Respiratory failure also may be caused by control abnormalities or by abnormalities in the mechanical function of the lungs. Control abnormalities are the result of decreased respiratory drive and, thus, there are few or no signs of respiratory distress even when there is significant hypercapnia and/or hypoxemia.

Respiratory failure caused by abnormalities in the mechanical function of the lungs and/or chest wall generally raise the ventilatory requirements and increase the work of breathing so the patient has to expend more physical effort to breathe. The patient will have air hunger; complain of dyspnea (secondary to chemoreceptor stimulation); and have an increased respiratory drive with physical signs and symptoms of respiratory distress such as tachypnea, retractions, etc. In children, respiratory failure more commonly is caused by mechanical abnormalities than by control abnormalities.11″

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