Respiratory Failure Flashcards
Gas parameters in hypoxemic respiratory failure?
PaO2 decreased; PaCO2 normal or decreased.
What is the management of hypoxemic respiratory failure?
- Reverse underlying pathology
- Oxygen therapy / ventilation
- Improve CO: +/- haemodynamic supports, reduction of O2 requirements
What are the causes of hypoxemia?
- Low FiO2 (altitude, fires)
- Hypoventilation (as pCO2 rises, pO2 must fall)
- Shunting
- Low mixed venous O2 content
- V/Q mismatch (PE, pneumonia)
- Diffusion impairment (pulmonary fibrosis, COPD)
In what settings does low FiO2 occur?
- Post op
- High altitude
What are the causes of a shunt?
- ARDS
- Pneumonia
- Pulmonary HTN
What are the causes of hypercapnia?
- High inspired CO2
- Low total ventilation
- High dead space ventilation
- High CO2 production
What are the causes of increased CO2 production?
- Fever
- Sepsis
- Seizure
- Acidosis
- Carbohydrate load
What is alveolar hypoventilation?
Inefficient gas exchange results in inadequate CO2 removal in spite of normal or increased minute volume
What are the causes of alveolar hypoventilation?
- COPD
- Asthma
- CF
- Chest wall disorder
- Dead space ventilation (rapid shallow breathing)
What are the causes of hypoventilation?
- > CENTRAL: brainstem stroke, hypothyroidism, severe metabolic alkalosis, drugs (opiates, benzos)
- > NM: Myasthenia gravis, Guillain Barre, phrenic nerve injury, muscular dystrophy, polymyositis, kyphoscoliosis
- > Muscle fatigue
What does surfactant do?
Improves lung compliance by reducing surface tension of fluid lining alveoli and preventing alveoli collapse
What is the A-a gradient?
The difference between the arterial (a) and alveolar (A) concentration of oxygen.
What does A-a gradient suggest if elevated?
A problem with diffusion or a V/Q mismatch (less commonly, shunt).
What is respiratory failure?
Impairment of gas exchange between ambient air and circulating blood, occurring in intrapulmonary gas exchange or in the movement of gases in and out of the lungs.
Which form of respiratory failure is generally precipitated by impaired gas exchange?
Impaired gas exchange generally results in hypoxemia (TYPE I).
PaO2
