Arterial blood gases Flashcards
What is arterial blood gas analysis
Refers to the measurement of pH and the partial pressure of oxygen and CO2 in arterial blood
What do ABGs help us assess?
effectiveness of gas exchange by providing measurements of the partial pressures of O2 and CO2
what is paCO2 controlled by
ventillation
what does pO2 measure
only free unbound O2 molecules
What does the amount of O2 in the blood depend on
- Hb concentration: the capacity to carry
- sO 2:
What is SO2
saturation of Hb with O2 - how much of the carrying capacity is being used
PO2 is the driving force for…
saturating Hb with O2
What dictates PaO
- Alveolar ventilation
- Ventilation/perfusion
- FiO2
When and why do you analyze arterial blood gases
- Establish a diagnosis
- To assess illness severity
- To guide and monitor treatment
What are normal ranges for pH
7.35-7.45
what are normal ranges for PaCO2
35-45 mmHg
What are normal ranges of HCO3
22-28 mEq/l
what is the order of analysis for uncompensated ABG
Analyze pH
Analyze PaCo2
Analyze HCO3-
If you have a change in only PaCo2 what does this indicate?
Primary disorder is respiratory
What does a change in only HCO3- indicate
primary disorder is metabolic
If both PaCo2 and HCO3 are off what does this mean?
compensated
If only one of PaCo2 and HCO3 is off what does this mean?
uncompensated
What is the time period for respiratory compensation? for renal compensation?
minutes to hours
1-5 days
what are mixed disorders
when more than one primary acid-base disorder is occurring at the same time
What are some causes of metabolic acidosis
- Ketoacidosis
- Poisoning
- Renal failure
What are some causes of metabolic alkalosis
- Sodium base overload
- potassium depletion
- Vomiting
- Coshing’s syndrome
- Conns syndrome
- Nasogastric suction
- Some medications
What are some causes of respiratory acidosis
- CO2 retention secondary to hypoventilation
- COPD, flail chest injury, neuromuscular disorders, sleep apnea
What are some causes of respiratory alkalosis
- Secondary to alveolar hyperventilation
- pain, anxiety, fever, breathlessness, hypoxia
Do PTs primarily help with respiratory or metabolic conditions
respiratory
5 causes of impaired oxygenation
- Decrease inspired oxygen
- alveolar hypoventilation
- Diffusion impairment
- Shunt
- Ventilation/perfusion mismatch
What is the major mechanism for hypoxemia
hypoventilation
If hypoventilation is causing hypoxemia, PaO2 should decrease ___ for every ___ in PaCO2
1mmHg
1mmHg increase
Hypoventilation leads to _____
respiratory acidosis
hyperventilation leads to ____
respiratory alkalosis
