Pulmonary Flashcards
a) Methodical ABG interpretation. Going to give a first, middle, and last name. (1) Always look at pH first. First name will be “compensated, non-compensated, partially-compensated, or mixed.” (2) Middle is “respiratory or metabolic.” (3) Last name is “acidosis or alkalosis.”
b) What are the 3 main values to look at for acid/base balance?
a) If the pH is out of range is it non-compensated.
*If the CO2 is the cause = respiratory
*if the HCO3 is the cause = metabolic
b) order of interpretation:
pH
CO2 (lungs are the fast compensation)
HCO3 (kidneys are slow compensation)
Normal values for:
Arterial pH
Venous pH
Arterial PaO2 (on room air)?
Venous PaO2?
Arterial PaCO2
Venous PaCO2
Arterial HCO3
Venous HCO3
Arterial SaO2
Venous SaO2
Base excess/ deficit
pH:
Arterial: 7.35 - 7.45
Venous: 7.32 - 7.42
PaO2:
Arterial: 60 - 100
Venous: 28 - 48
PaCO2:
Arterial: 35 - 45
Venous: 38 - 52
HCO3:
Arterial: 22 - 26
Venous: 19 - 25
SaO2:
Arterial: 95 - 100%
Venous: 50 - 70%
Base excess/ deficit:
Arterial: -2 to +2
- If the pH is normal but the CO2 or HCO3 isn’t, what type of compensation is this (compensated, partially compensated…)?
- If the pH is abnormal, and either the CO2 or HCO3 are abnormal, what type of compensation is this?
- If the pH is abnormal, and CO2 AND HCO3 are abnormal in different directions, what type of compensation is this?
- If the pH is abnormal and pCO2 AND HCO3 are both trending to acidosis/alkalosis, what type of compensation is this?
- Compensated.
- UNcompensated.
- Partially compensated.
- Mixed. Combined acidosis or alkalosis.
Other than anxiety or severe pain, what are some other causes of respiratory alkalosis?
Generally speaking, HYPERventilation is occurring and these are considered early respiratory failure.
- Excessive tidal volume or rate on vent
- ARDs
- HF
- Neurological disorders/ CVA (acute onset can cause cerebral vasoconstriction)
- Salicylate overdose in adults
- PE
- Decreased CO/ shock (increased RR)
- PaO2 < 60; cause and effect
Which acid/base imbalance would the following cause?
Over sedation
Drug overdose w/ respiratory depression
Brain stem dysfunction
RESPIRATORY ACIDOSIS. This is more of a late respiratory failure. Think HYPOventilation.
Others causes of resp acidosis:
- Acute pulmonary edema
- Lung diseases (asthma/ COPD/ emphysema)
- Extreme V/Q mismatch (PE, pna)
- Guillane Barre’
- Excessive CO2 production (sepsis, TPN, burns)
- Severe obesity - becomes a mechanical issue r/t weight of stomach on diaphragm.
- Muscle weakness
- Cardiac arrest
Which acid/base imbalance would the following cause?
AKI
DKA
Hyperchloremia
Toxins
Aspirin OD
METABOLIC ACIDOSIS
Other pausible causes:
- Liver failure
- Hyperkalemia
- Lactic acidosis
- Drug and alcohol OD
- Sepsis
If you don’t know the cause of the acidosis, always asses the anion gap. Either the body’s producing too much acid (DKA) or the kidneys can’t get rid of it (AKI)
Which acid/base imbalance would the following cause?
Vomiting
Diarrhea
NG tube to suction
Inadequate renal perfusion
METABOLIC ALKALOSIS
- Hypochloremia
- Hypokalemia
- Antacid abuse
- Excessive Na HCO3 infusion
- Thiazide and loop diuretics
- Excessive albuterol use
- Hyperaldosteronism (d/t RAAS activation)
Exhaled carbon dioxide = Capnography = V (ventilation)
PaCO2 = Q = Perfusion
V: Capnography: measurement of the partial pressure of carbon dioxide (CO2) in exhaled breath. aka End tidal CO2.
Both V and Q normal ranges are 35 - 45 mm Hg
- Clinically, the PaCO2 will always be higher than the end tidal CO2. In someone w/normal V/Q the Pa/PEt CO2 should be w/in 5 points of each other (mm Hg).
Always use (Class I recommended way to verify ET tube placement) during conscious sedation, etc. Also for use of CPR quality and ROSC.
When your cardiac output drops, what will that do to end tidal CO2?
Et CO2 will also drop.
d/t decreased perfusion/circulation to pick up the CO2 in the periphery.
How to calculate V/Q
PaCO2 minus PEtCO2
If they are more than 5 mm Hg difference from one another = V/Q mismatch.
If low PEtCO2 and higher PaCO2, what could be some reasons?
- PE
- PNA
- ARDS
- Overdistention of alveoli from PEEP/ TV
- ET tube in mainstem bronchus
- Mucus plug
- Low cardiac output
- Cardiac arrest
What do we call it when there is excessive blood flow in relation to ventilation?
OR
Ventilation with decreased perfusion?
Intrapulmonary Shunting.
Excessive blood flow in r/t ventilation = mucus plug, pna, ARDS
Ventilation w/decreased perfusion = PE
session 3
Does oxygen dilate or constrict vessels in the body?
Oxygen is a vasoconstrictor (except in the lungs, dilates there).
Therefore, it can be a negative inotrope on the heart. So, in the absence of hypoxemia, it can decrease the CO!
Ideally, pt’s saturation should be 90-96%
Exposure to FiO2 > 60% for over 48 hours can be toxic.
The fraction of inspired oxygen (FiO2) is the concentration of oxygen in the gas mixture.
