Respiratory Failure
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Introduction
Respiratory failure is an inability of the lungs to maintain oxygenation and carbon dioxide elimination.
There are two types - hypoxia (pO2 less than 90) or hypercapnea (pCO2 increased to the point of somnolence).
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes of Respiratory Failure
Hypoxemic respiratory failure |
Hypercapnea
|
acute overwhelming lung disease
- pneumonia
- pulmonary edema (congestive heart failure, ARDS)
- vascular (PE)
- inhaled toxins (ie chlorine gas)
neuromuscular problems
- respiratory centre depression (alcohol, opioids, barbiturates)
- encephalitis
- polio
- GBS
- myasthemia gravis
- ALS
- muscular dystrophy
- hypoventilation
acute on chronic lung disease
- COPD
- asthma
- cystic fibrosis
ARDS
IRDS
Pathophysiology
The five physiologic mechanisms of arterial hypoxia include:
- V/Q mismatch
- shunting (pneumonia)
- diffusion impairment
- hypoventilation
- low inspired FiO2 (altitude)
cannot breathe, too tired to breathe, will not breathe, can't breathe enough
Post-operative patients experience pain, secretions, and pain medications. The most affected patients include thoracics and upper abdominal patients.
Closing volume is the point at which lung tissue becomes atalectatic.
Secretions (pneumonia, smoking) increase closing volume.
Signs and Symptoms
- history
- physical exam
History
Symptoms include, cyanosis, tachycardia, and confusion. Hypercapnea can lead to headache, papilledema, and asterexis.
Physical Exam
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
blood gases or oxygen saturation
Diagnostic Imaging
chest X-ray
cardiogram
Differential Diagnosis
Treatments
Hypercapnic respiratory failure requires ventilation. If, with ventilation, pO2 remains low -
- sedate/paralyze the patient reduce their oxygen need
- give blood to improve peripheral oxygenation
- cool the patient to prevent fever and the attending oxygen
Treat the underlying condition.
Consequences and Course
Resources and References
Topic Development
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