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RT220 > Module 5- ABG Physiology > Flashcards

Module 5- ABG Physiology Flashcards

1
Q

What is homeostasis?

A

A state of balance or equilibrium.

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2
Q

What is the primary goal of acid base homeostasis?

A

To maintain a normal pH

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3
Q

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

A

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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4
Q

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

A

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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5
Q

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?

A

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

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6
Q

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

A

Metabolic acidosis

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7
Q

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

A

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

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8
Q

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

A

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

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9
Q

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

A

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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10
Q

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

A 
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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11
Q

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

A

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

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12
Q

What does Compensated(Chronic) mean?

A

One component adjusted to balance the pH to a normal value

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13
Q

What does uncompensated(acute) mean?

A

The pH is outside the acceptable range

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14
Q

What does partially compensated mean?

A

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

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15
Q

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

A

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

Decreased tidal volume and f , and a increased dead space

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16
Q

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

T or F?

A

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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17
Q

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

A

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

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18
Q

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

T or F?

A

True!

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19
Q

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

A

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

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20
Q

Respiratory alkalosis is always caused by what?

A

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

Increased: VT, f
Decreased: VD

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21
Q

What physiological causes can stimulate an increased VA?

A

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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22
Q

Food for thought!

A

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

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23
Q

Metabolic acidosis is caused primarily by what disease?

A

Kidney disease

24
Q

What are some physiologic causes of metabolic acidosis?

A

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

25
Q

Food for Thought!

A

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.

26
Q

What are some physiological causes of metabolic alkalosis?

A

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

27
Q

How does the body compensate for metabolic alkalosis?

A

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

28
Q

How is Combined (mixed) acid base balances identified?

A

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

29
Q

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

A

Cardiac arrest, COPD, and poisoning and drug overdose.

30
Q

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

A

Critically Ill patients and ventilator-induced alkalosis

31
Q

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

A

Normal is + or - 2 mEq/L

32
Q

A BE > +or- 2 indicates what?

A

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

33
Q

A BE < + or - 2 indicates what?

A

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

34
Q

List the types of hypoxemia?

A

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

35
Q

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

A

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

36
Q

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

A

normal hb: 12-18 g/dL

Normal SaO2/SpO2: > 95%

37
Q

What is the primary factor that determines SaO2?

A

PaO2

38
Q

Numerical relationship of PaO2 to SaO2

A

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

39
Q

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)

A

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

40
Q

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

A

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

41
Q

What are the 3 dyshemoglobins(abnormal hemoglobin)?

A

Carboxyhemoglobin, methemoglobin, and sickle cell hemoglobin

42
Q

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

A

16-20 ml/dl

CaO2= (0.003 x PaO2) + (1.34 x Hb x SaO2)

43
Q

What does the Arterial O2 Content represent?

A

The total O2 in arterial blood

44
Q

In what two ways is O2 carried?

A

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

45
Q

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

A

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

46
Q

What is hypoxia?

A

O2 available to tissues falls short of metabolic needs

47
Q

How much oxygen HB Carries depends on what two factors?

A

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

48
Q

What does the A-a Gradient measure?

A

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

49
Q

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

A

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

50
Q

During Metabolic Alkalosis, what does the respiratory system do?

A

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

51
Q

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

A

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

52
Q

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

A

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

53
Q

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

A

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

54
Q

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

A

pH, PaCO2, and HCO3

55
Q

What internal organs come into play during compensation?

A

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

RT220 (3 decks)

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