| Question | Answer |
| A-a Gradient: | The difference(gradient)between alveolar and arterial PO2 |
| A-a Gradient Formula: | A-aDO2=PAO2-PaO2
*PAO2 must be calculated first |
| PAO2: Alveolar Air Equation: | PAO2=(PB-Ph2O)FIO2-PaCO2
*PaCO2 is divided by .8*
PB=747
pH20=47 |
| Shortcut for Alveolar Air Equation when using it for A-a Gradient | PAO2=(7xFIO2 as whole number)-(PaCO2+10) |
| Normal A-a Gradient: | 25-65% on 100% |
| V/Q Mismatch(too much deadspace): | 66-300
Common when PE is involved |
| Shunting: | >300 |
| What is Arterial Oxygen Content? | Best measurement of oxygen delivered to the tissues, or the best index of oxygen transport. Measures Lung Function. |
| "Oxygen in RBC": | 1.34 |
| "Oxygen in Plasma": | .003 |
| Arterial Oxygen Content Formula: | CaO2=(Hbx1.34xSaO2)+(PaO2x.003) |
| What is Mixed Venous Oxygen Content? | Total amt of oxygen carried in the mixed venous blood. Measures Heart Function. |
| Mixed Venous Content Formula: | CvO2=(Hbx1.34xSvO2)+(PvO2x.003) |
| Normal CvO2: | 14%(12-16%) |
| Normal CaO2: | 17-20% |
| C(a-v)O2: | CvO2 is subtracted from CaO2.
Measures the oxygen consumption of the tissues. |
| C(a-v)O2 Norm: | 4-5 vol % |
| PaO2/FIO2 or P/F Ratio: | Used in determination of Acute Lung Injury(ALI). |
| P/F Ratio Norm: | 380 mmHg or greater |
| A P/F Ratio of less than 200 mmHg indicates what? | ARDS |
| A P/F Ratio of less than 300 indicates what? | Acute Lung Injury |
| Qs/Qt(Shunt)Equation: | Qs/Qt=(A-aDO2).003/(A-aDO2).003
+C(a-v)O2 |
| Qt(Cardiac Output)Equation: | VO2/C(a-v)O2(10)
*ALL numbers are given except 10* |
| VO2(Oxygen Consumption)Equation: | VO2=QtxC(a-v)O2x10 |
| How is PaO2 estimated from the SaO2? | Subtract 30 from SaO2 |
| Vd/Vt(deadspace to tidal vol)Ratio Formula: | PaCO2-PECO2x100/PaCO2 |
| Vd/Vt Norm: | 20-40%(Up to 60% for vent pts) |
| Most common cause for an increased Vd/Vt ratio: | Pulmonary Embolism |
| Desired Minute Volume Formula: | (VExPaCO2)=(VExPaCO2) |
| Desired PaO2 Formula: | FIO2xDesired PaO2/Current PaO2 |
| What do you do for an abnormal PCO2 with normal pH? | Don't change anything. Indicative of a chronic pt with COPD. |
| When the pH is inside the acceptable range(7.35-7.45): | It is Compensated or Chronic |
| When the pH is outside the acceptable range(7.35-7.45): | It is Non-Compensated or Acute |
| Respiratory Vs. Metabolic: Respiratory | A Respiratory Acidosis or Alkalosis is the diagnosis when the pH is abnormal b/c of a change in PCO2. |
| Respiratory Vs. Metabolic:
Metabolic | A Metabolic Acidosis or Alkalosis is the diagnosis when the pH is abnormal b/c of a change in HCO3-. |
| ABG Normal for Newborn: | pH:>7.30
PaCO2:<50
PaO2:>50 |
| COPD Pt in Acute Resp. Failure(Loss of Hypoxic drive): | pH:7.30
PaCO2:80
PaO2:80
HCO3-:38 |
