Module 5- ABG Physiology Flashcards by Jo'esha Tate

What is homeostasis?

A state of balance or equilibrium.

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What is the primary goal of acid base homeostasis?

To maintain a normal pH

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What are 3 ways that Co2 is transported in the blood?

A small amount is dissolved in plasma, majority(80%) is ionized as Bicarbonate (HCO3), and it is also chemically bound with the protein known as carbaminohemoglobin.

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What is the Anion Gap, and what is the normal range?

The anion gap is a measurement of the difference between positive charged ions and negative charged ions.

Na+ — ([Cl-] + [HCO3-])

The normal range is 9-14mEq/L

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The normal range for the Anion Gap is 9-14mEq/L.

What occurs if the value exceeds 14, and what occurs if it is within normal range?

If >14 then acid is being added. If it is within normal range then Bicarbonate is being lost.

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Whenever there is ________ the anion gap will identify if it’s bicarbonate lost or acid added.

Metabolic acidosis

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What processes can cause a high anion gap(Acid Added)?

Lactic acidosis, ketoacidosis(DKA), renal failure, salicylate (aspirin) intoxication, methanol, and ethylene glycol.

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What processes can cause the anion gap to be normal?(Bicarb Loss!)

Diarrhea, pancreatic fistula, renal tubular acidosis(RTA), ammonium chloride, and hyperalimentation intravenous nutrition.

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Define the Henderson -Hasselbach equation, and what is the equation?

It is a equation that defines the relationship between Arterial pH, HCO3, and PaCo2. If there is a change in bicarb or PaCO2, the pH will change.

Ph= Pk + Log ( HCO3/ PaCo2 x 0.03)

Pk is always 6.1!!

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What are the normal and absolute arterial values for pH, PCO2, and HCO3?

pH= 7.35-7.45, absolute: 7.40
PCO2= 35-45, absolute: 40 torr 
HCO3= 22-26mEq/L, absolute: 24 mEq/L

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What are the values for normal, mild, moderate, and severe hypoxemia(PO2)?

Normal: 80-100
Mild: 60-79
Moderate: 40-59
Severe: < 40

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What does Compensated(Chronic) mean?

One component adjusted to balance the pH to a normal value

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What does uncompensated(acute) mean?

The pH is outside the acceptable range

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What does partially compensated mean?

One component has adjusted but the pH has not yet balanced.

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Respiratory acidosis is always caused by? If minute ventilation is decreased, then what 3 things may have occurred?

Respiratory acidosis is always caused by hypoventilation(decreased VA).

Decreased tidal volume and f , and a increased dead space

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Acute respiratory acidosis has some metabolic compensation so as a result HCO3 increases.

T or F?

False!!

Metabolic compensation only occurs in chronic(compensated) respiratory acidosis.

No compensation occurs with ACUTE respiratory acidosis so HCO3 will stay normal.

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List some factors that may cause short term (recent-hypoventilation) acute respiratory acidosis.

Drug overdose (CNS depression), neuromuscular disease, trauma, and acute bronchospasm.

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Chronic respiratory acidosis is compensated by metabolic, so HCO3 will increase.

T or F?

True!

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Long term hypoventilation (chronic respiratory acidosis) can occur as of what factors?

An increased VD(COPD)
A decreased Vt(Chronic neuromuscular disease)
A decreased Vt( extreme obesity (Pickwickian Syndrome)

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Respiratory alkalosis is always caused by what?

Respiratory alkalosis is always caused by an increased VA (hyperventilation).

Increased: VT, f
Decreased: VD

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What physiological causes can stimulate an increased VA?

Hypoxemia!(Most common cause of respiratory alkalosis), CNS stimulation(trauma,drugs,etc.), pain, anxiety, fear, and it can be mechanically induced.

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Food for thought!

Compensation for respiratory alkalosis is renal (kidney) execration of HCO3.

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Metabolic acidosis is caused primarily by what disease?

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Kidney disease

What are some physiologic causes of metabolic acidosis?

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Lactic acidemia, ketoacidosis(diabetes,starvation, alcoholic ketoacidosis), kidney failure, diarrhea(bicarb loss), and aspirin OD, or other acid-type drugs.

*Food for Thought!*

When compensation occurs for metabolic acidosis by the respiratory system, they will hyperventilate(kussmaul respirations is the most common sign) , decreasing the PaCO2 to bring the pH back to normal.

What are some physiological causes of metabolic alkalosis?

Electrolyte imbalance(hypokalemia,hypochloremia), vomiting or N-G suction, diuretics, and massive doses of steroids.

How does the body compensate for metabolic alkalosis?

It is compensated by the respiratory system to hypoventilation, increasing paCO2 to bring pH back to normal.

How is Combined (mixed) acid base balances identified?

These disorders are identified by the derangement in PaCO2 and HCO3 that both drive the pH in the same direction.

What are some factors that can cause mixed and combined respiratory AND metabolic acidosis?

Cardiac arrest, COPD, and poisoning and drug overdose.

What are some factors that can cause mixed and combined metabolic and respiratory alkalosis?

Critically Ill patients and ventilator-induced alkalosis

What is the normal value for Base excess (BE)?

Normal is + or - 2 mEq/L

A BE > +or- 2 indicates what?

It indicates a gain of base or loss of acid from non-respiratory causes

A BE < + or - 2 indicates what?

It indicates that there has been a loss of base or a gain of acid from non-respiratory causes.

List the types of hypoxemia?

Hypoventilation, V/Q mismatch, pulmonary shunting, diffusion defect, low Pio2, and dead space.

What is the alveolar air equation? And what does it do?

PaO2 = FiO2(Pb-pH2O)-(PaCO2/RQ) , it computes the partial pressure of O2 in the alveoli.

What is the normal value for Hb? What is the normal values for SaO2/SpO2?

normal hb: 12-18 g/dL | Normal SaO2/SpO2: > 95%

What is the primary factor that determines SaO2?

PaO2

Numerical relationship of PaO2 to SaO2

40-50-60/70-80-90 Rule If the PaO2 is 40, SaO2 is 70 50. 80 60. 90

The oxyhemoglobin dissociation curve quantifies the relationship between PaO2 and SaO2. If the curve shifts to the Left what occurs? Right? (FINISH THIS CARD: CARD INCOMPLETE)

If the curve shifts to the Left(REMEMBER:LOAD), affinity and pH is increased. Temperature, 2,3 DPG, carboxyhemoglobin,

What is P-50, and what is normal P-50?

P-50 is the method for expressing the position of the curve. Normal P-50 is 27.

What are the 3 dyshemoglobins(abnormal hemoglobin)?

Carboxyhemoglobin, methemoglobin, and sickle cell hemoglobin

What is the normal value for CaO2(Arterial O2 Content)? What is the formula?

16-20 ml/dl CaO2= (0.003 x PaO2) + (1.34 x Hb x SaO2)

What does the Arterial O2 Content represent?

The total O2 in arterial blood

In what two ways is O2 carried?

It is dissolved in plasma and chemically combined with Hb(majority)

What are the two major factors affecting delivery of O2 to the tissues?

A decrease in CaO2 and Cardiac output ( normal 5L/min)

What is hypoxia?

O2 available to tissues falls short of metabolic needs

How much oxygen HB Carries depends on what two factors?

It depends on the total Hb concentration (if decreased Hb=anemia) and the proportion of Hb bound to oxygen (SaO2).

What does the A-a Gradient measure?

Measures the difference between the alveolar concentration of O2 and the arterial concentration of O2. It is primarily diagnosing the source of hypoxemia(requires PaO2 and PAO2. Remember: A-a Gradient = report card of the lungs

What is the normal range of a A-a Gradient? What does a normal reading signify?

Normal range: 5-10, if it is within normal range, hypoxemia is resulting to a cause outside of the lungs. Ex: CNS disorder

During Metabolic Alkalosis, what does the respiratory system do?

The respiratory system compensates by increased PaCO2 to bring pH back to normal.

How do you identify lab errors(ABG)? What are the 6blood gas sampling pre-analytical errors?

If the pH doesn’t correlate with neither PaCO2 or HCO3, then it may be a lab error. Air in the sample, metabolic effects, venous admixture, anticoagulant effects, temperature

What will happen if you fail to ice the blood gas sample? How long will it be before the sample start to change?

Uniced samples will change within 10-15mins. CO2 will increase, pH will decrease, and PaO2 will decrease

What happens when an air bubble is left in the blood gas sample?

PaO2 will increase to above 160, and CO2 will lower.

What 3 parameters of the blood gas are effected in metabolic acidemia?

pH, PaCO2, and HCO3

What internal organs come into play during compensation?

respiratory acidosis= kidneys (renal retention of HCO3) respiratory alkalosis=kidneys (renal loss of HCO3) metabolic acidosis = lungs (hyperventilation) Metabolic alkalosis= lungs (hypoventilation)

Module 5- ABG Physiology Flashcards

(55 cards)