Acute Respiratory Failure Flashcards
Define acute respiratory failure
The inability of the respiratory system to meet oxygen/ventilation demands
What are the two types of ARF and what is the difference?
Type One: Hypoxic RF - oxygenation failure- PaO2<60 mmhg
Type Two: Hypercapnic RF- ventilation failure w/ or w/o hypoxemia- PCO2>50mmhg
Describe the general Pathophysiology behind hypoxia
CNS >PNS > Thoracic bellows > supper airways > lungs
What are five mechanisms of hypoxemia
- Inadequate o2 at the alveolar level
- Ventilation perfusion abnormality
- Intracardiac/Intra pulmonary
- Diffusion abnormality
- Low pulmonary arterial oxygenation
What is normal air composition of O2?
21%
What is alveolar partial pressure of o2 PAO2
Driving force of O2 diffusion
O2 moves from alveolar membranes to pulmonary capillary walls to arteriolar blood flow and erythrocytes- peripheral tissues
What is the A-a gradient and what does it incite
PAO2-PaO2
The larger the gradient indicates pathology hindering O2 transfer
How much does 1l of O2 increase the inspired O2
4%
What does 2, 3 DPG do?
Stabilize hemaglobin increasing O2 at tissues
What is the Bohr effect?
O2 association with hgb is inversely affected by acidity and PCO2 concentration
What does a left shift in the oxyhemoglobin curve mean and what can cause it?
Hgb has greater affinity for O2
Causes: Alkalemia, hypothermia, hypo metabolism, abnormal hgb
What does a right shift in the oxyhemoglobin curve mean and what causes it?
Hgb has lesser affinity for O2
Causes: Acidemia, hyperthermia, hyper metabolism, chornic hypoxemia, hypercapnea
How to use PaO2 to determine if someone is oxygenating?
PaO2 = Fio2 x 5
What are the benefits and draw backs of SaO2
Reflects oxyhemaglobin but is not impacted by anemia or CO poisoning
What is the pH and CO2 in hypercapnic RF
pH <7.35
PaCO2>50
What are three general causes of increased CO2
Increased CO2 production
Deceased total tidal volume
Increased dead space ventilation
What are causes of increased CO2
Exercise, fever, sepsis, burns, trauma, excessive carb intake, hyperthyroidism
How do you determine the causes of dead space disease?
A-a gradient >10mmhg is parenchymal lung process
What are five causes of decreased tidal ventilation
Compromised neuromuscular sequence
CNS depressants
Neuromuscular transmission disorders
Abnormal respiratory mechanisms
What is the Hallmark feature of inadequate ventilation
Elevated PaCO2 w/wo hypoxemia
S/s of hypercapnic RF
Abnormal RR, irregular respirations, gasping, nasal flaring, accessory muscle use, lethargy, coma, seizures, tremors
What are risk factors for hypercapnic RF
Post-op, preexisting chronic illness, malnutrition, advanced age, morbid obesity, chronic bronchitis, cigarette smoking
