35_36_Respiratory failure and NIV Flashcards
What is respiratory failure?
The acute or chronic inability of the respiratory system to maintain adequate gas exchange.
Is respiratory failure a disease?
No, it is a consequence of a disease and the underlying disease needs to be identified.
What is Type 1 or partial respiratory failure?
It is induced by pulmonary diseases (damaged lung tissue) and is characterized by arterial pO2 < 60mmHg and pCO2 < 46mmHg.
What is Type 2 or global respiratory failure?
It is induced by pump failure and is characterized by arterial pO2 46mmHg, and a numerical reduction of pO2 close to numerical increase of pCO2.
What is Type 3 or mixed respiratory failure?
It is induced by pulmonary diseases and hypoventilation and is characterized by arterial pO2 46mmHg, and hypoxemia being numerically more severe than hypercapnia.
What is the most common cause of hypoxemia?
Ventilation-perfusion (V/Q) mismatch.
What is V/Q mismatch?
It is an imbalance between total lung ventilation (airflow: V) and total lung perfusion (blood flow: Q) that occurs when either ventilation or perfusion or both changes in a way that the two parameters no longer match.
What is the increased V/Q ratio (dead space)?
It is caused by blood flow obstruction, exercise, or other factors and can lead to hypercapnia.
What is the decreased V/Q ratio (shunt)?
It is caused by poor perfusion by ventilated alveoli and can lead to hypoxemia that cannot be improved by 100% oxygen.
What is reduced diffusion?
Reduced diffusion is a condition where oxygenation is not impaired at rest but exercise induces impaired oxygenation due to reduced transit time. It may be a major cause of effort dyspnea/syncope. Increasing the FiO2 (fraction of inspired O2) can correct diffusion-related hypoxemia.
What is a right-to-left shunt?
A right-to-left shunt is a condition where the blood is shunted away from the lung, making it unable to become oxygenated. In a shunt situation, e.g. 50% of the blood is shunted away, pulmonary hypoxemia occurs. 100% oxygen therapy will not help because the shunt will still not become oxygenated. An example of this is ARDS.
What is acute respiratory failure?
A condition that develops over minutes to hours due to an acute illness or insult.
What are the clinical features of hypoxemia?
Dyspnea, tachypnea, cyanosis, pleuritic chest pain, tachycardia, arrhythmia, altered mental status (e.g. confusion, agitation).
What are the clinical features of hypercapnia?
Hypopnea, anxiety, headache, daytime sleepiness, warm extremities, coma.
What are the causes of type 1 (hypoxemia) respiratory failure?
Impaired diffusion (pulmonary edema, pneumonia, pulmonary hemorrhage, IPF), V/Q mismatch (pulmonary edema, pulmonary embolism), right-to-left shunt (ARDS, hemorrhage, lung collapse, Eisenmenger syndrome).
