ABG test

pH Normals

7.35-7.45

PaCO2 normal

35-45 mmHg

PaO2 normal

80-100mmHg

HCO3

22-26

BE normal

-2 to +2

Hypoxemia levels

Normal 80-100mmHg

Mild 60-80mmHg

Moderate 40-60mmHg

Severe <40mmHg

Anion Gap normal

9-14 mEq/L

Henderson-Hasselbach

The pH is always influenced by the relationship between the kidneys and lungs.

Renal system

Filters. Only the renal system can get rid of phosphoric and uric acids, and lactic and ketone acids. The renal system regulates bicarb through reabsorption of bicarb from the urine back to the bloodstream. And the kidneys secrete hydrogen ions into the urine which helps neutralize excess acid in the blood. The renal system is the most effective acid-base regulator.

Acute ventilatory failure

Also known as respiratory acidosis, is caused by CO2 buildup, drug overdose, head trauma, COPD, neurological disorders.

Metabolic acidosis causes

pH is low and HCO3 is low, causes- lactic acidosis, ketoacidosis, renal failure, severe diarrhea, aspirin overdose.

Acute alveolar hyperventilation causes

Aka respiratory alkalosis. Happens when too much CO2 is blown off. Most common cause is hypoxia/hypoxemia. Other causes include pain/anxiety, brain inflammation, stimulant drugs.

CO2 transport and diffusion

Diffuses across the alveolar capillary membrane 20 times faster than oxygen. At rest, metabolizing tissue cells consume approximately 250 mL of O2 and produce approximately 200 mL of carbon dioxide each minute. Newly formed Carbon dioxide is transported from tissue cells to lungs by six different mechanisms, 3 in plasma and 3 in RBC. Most of CO2 is produced at tissue cells is carried to the lungs in forms of HCO3.

pH-acid base concentration: Acids

Donates H+ and decreases pH

pH-acid base concentration: Bases (Alkaline)

Accepts H+ and increases pH

What happens during renal compensation in respiratory alkalosis

Hyperventilation= high pH

Excretes excess HCO3 into urine

Respiratory system and acid-base balance

Body adjusts automatically to fix the pH problems (Acidosis or alkalosis), induces hyperventilation or hypoventilation. For example, when pH declines, the respiratory system responds by increasing breathing depth and rate (low pH=hyperventilation), which causes more CO2 to be eliminated from the lungs reducing H+ concentration to pull acidic pH back to normal.

If the pH is increased, the respiratory system responds by decreasing breathing depth and rate (High pH= hypoventilation), which causes less CO2 to be eliminated from the lungs, which increases H+ concentration to pull alkalotic pH back to normal.

What does a high and normal anion gap mean

A high anion gap means that acids are responsible, so the gap is high in metabolic acidosis. A normal gap means the bicarb is responsible.

Diffusion

The passive movement of O2 from the alveoli into the blood and carbon dioxide from the blood into the alveoli, driven by concentrations and partial pressure gradients.

Basically, diffusion is the process by which gases move from an area of higher concentration or partial pressure to an area of lower concentration without requiring energy.

Compensated

If the ABG pH is WNL than it is compensated

Uncompensated

If the ABG pH is not WNL it is uncompensated

Partially compensated

If the pH and CO2 are the same (both Alka or both acid) it is partially compensated. But only these two values are used for determining this.

If the CO2 is alkalotic and the bicarb is acidotic, it is always what

It is always metabolic

If both the CO2 and bicarb is low, it’s always

respiratory alkalosis

If all the values are ALL acidotic or alkalotic it’s what

Mixed respiratory and metabolic acidosis or alkalosis.

Alka and Acid for values

pH- Increased is alka, decreased is acid

CO2- Decreased is alka, increased is acid

Bicarb- Increased is alka, decreased is acid

If bicarb is normal, it’s

Uncompensated

If the pH and HCO3 move in the same direction, increase or decrease, it’s

metabolic

If the pH and PaCO2 move in OPPOSITE directions, it’s

respiratory

If you have a normal pH and the PaCO2 and HCO3 are different, how do you determine if it’s alka or acid.

Whichever the pH falls closer too, alka or acid, determines if the answer is alkalosis or acidosis.

If the HCO3 is decreased, then the interpretation is a respiratory alkalosis if what is also decreased

PaCO2

If the HCO3 is increased than the interpretation is a metabolic alkalosis if what is decreased also

Metabolic alkalosis