Pulmonary Function Tests Flashcards
Normal blood pH range
7.35-7.45
Normal PaCO2 range
35-45 mmHg
Normal HCO3 range
22-26 mEq/L
What is compensation
if the pH imbalance is caused by the respiratory system (CO2) , the renal system (HCO3) will try to compensate and vice versa
What is metabolic acidosis
ph decreases
pCO2 stays the same
HCO3 decreases
What is metabolic alkalosis
ph increase
pCO2 stays the same
HCO3 increases
What is respiratory acidosis
ph decreases
pCO2 increases
HCO3 stays the same
What is respiratory alkalosis
ph increases
pCO2 decreases
HCO3 stays the same
6 steps to analyze Arterial blood gases
- is the pH normal
- is the CO2 normal
- Is the HCO3 normal
- Match the CO2 or the HCO3 with the pH
- Does the CO2 or the HCO3 go the opposite direction of the pH
- are the pO2 and the O2 saturation normal
What do these ABGs indicate?
pH 7.16 CO2 49 HCO3 38
Respiratory Acidosis
What do these ABGs indicate?
pH 7.58 CO2 54 HCO3 28
Metabolic Alkalosis
What does an FEV1/FVC reading 10 below predicted indicate?
Obstruction
What does a decreased FEV1 indicate
Obstruction (particularly the severity of the obstruction)
What does a decreased FVC indicate
Restriction
What does GOLD define COPD as
FEV1/FVC ratio < 70% after treatment
What test do you do prior to drawing an ABG and what artery are you taking the blood from usually?
Allen’s test to make sure there is good collateral flow to the hand, and the radial artery
Define acidosis in relationship to pathological changes occurring in the body
Acidosis is when the pH decreases <7.35, this is more common because carbon dioxide is dissolved in the blood as carbonic acid (weak acid). This occurs when there is poor pulmonary ventilation, CO2 levels rise, which leads to rise in carbonic acid and decreased pH.
Define alkalosis in relationship to the pathological changes occurring in the body.
Alkalosis is increased pH >7.45= too little CO2 in blood, due to hyperventilation or excessive breaths given via a mechanical ventilator in a cricical care setting. Try to reduce the number of breaths taken to normalize pH. Respiratory compensation pathway will try to compensate for this in 2-4 hours, if it can’t help enough the metabolic pathway compensates.
ABG findings in metabolic acidosis
pH↓, pCO2 same, bicarb ↓
ABG finding in metabolic alkalosis
pH↑, pCO2 same, bicarb ↑
ABG findings in respiratory acidosis
pH ↓, pCO2↑, bicarb same
ABG findings in respiratory akalosis
pH ↑, pCO2 ↓, bicarb same
