69. Physiology - Acid Base II Compensation
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Questions and Answers

What is the most closely regulated pH range in the human body?

  • 7.35 - 7.45
  • 7.40 - 7.50
  • 7.30 - 7.35
  • 7.38 - 7.42 (correct)

Which of the following statements is true regarding normal arterial pCO2 levels at sea level?

  • Normal pCO2 levels remain unaffected by altitude.
  • Normal pCO2 is strictly 35 mmHg.
  • Normal pCO2 ranges from 30 to 35 mmHg.
  • Normal pCO2 is between 35 and 45 mmHg. (correct)

What is the definition of acidemia?

  • A condition resulting in a decrease of arterial pCO2.
  • A condition where pH is less than 7.35. (correct)
  • A situation with increased bicarbonate concentration.
  • A condition where pH is greater than 7.45.

Which organs are primarily involved in maintaining acid-base balance in the body?

<p>Lungs and kidneys (C)</p> Signup and view all the answers

Which of the following is a common consequence of decreased excretion processes in acid-base balance?

<p>Hypercapnia (A)</p> Signup and view all the answers

What distinguishes simple acid-base disorders from combined disorders?

<p>Presence of a single primary disorder. (C)</p> Signup and view all the answers

Which of the following represents metabolic acidosis?

<p>Decreased bicarbonate concentration. (C)</p> Signup and view all the answers

What indicates a primary disorder when pH is down and both pCO2 and [HCO3-] are down?

<p>The primary disorder is metabolic acidosis. (A)</p> Signup and view all the answers

Which arrows represent compensation in acid-base physiology?

<p>Dotted arrows (C)</p> Signup and view all the answers

In respiratory acidosis, what is the primary problem related to acid-base balance?

<p>Excess of carbonic acid. (B)</p> Signup and view all the answers

What is the normal range for [HCO3-] in acid-base values?

<p>24 mEq/L (D)</p> Signup and view all the answers

Which condition occurs when the body attempts to counteract acidosis?

<p>Increased pH levels. (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of simple acid-base disorders?

<p>They have multiple primary processes. (C)</p> Signup and view all the answers

Which biochemical response occurs rapidly in respiratory acidosis due to elevated pCO2?

<p>Increase in [HCO3-] for buffering. (C)</p> Signup and view all the answers

What does a solid arrow signify in the context of acid-base disorders?

<p>It represents the primary disorder. (C)</p> Signup and view all the answers

Which factors are important for understanding HCO3- reabsorption from the kidneys?

<p>Hormonal regulation and blood flow to kidneys. (A)</p> Signup and view all the answers

What occurs in the kidney when metabolic acidosis is developing?

<p>Increased secretion of H+ as NH4+ (D)</p> Signup and view all the answers

What characterizes the respiratory compensation in response to a metabolic acidosis?

<p>It leads to a rapid decrease in pCO2. (B)</p> Signup and view all the answers

During the recovery phase after metabolic acidosis, what happens to the acid in the body?

<p>It is excreted by the kidneys over a prolonged period. (A)</p> Signup and view all the answers

What characterizes the condition known as compensated hypercapnia?

<p>pCO2 rises initially, then stabilizes as HCO3- increases (A)</p> Signup and view all the answers

What is the effect of a lower pCO2 on respiratory compensation during metabolic acidosis?

<p>It inhibits the respiratory center's activity. (A)</p> Signup and view all the answers

Which of the following statements about renal compensation for chronic hypercapnia is true?

<p>There is an upper limit to HCO3- reabsorption rates in the kidneys. (A)</p> Signup and view all the answers

Which of the following best explains the loss of buffering capacity during metabolic acidosis?

<p>Approximately half of the strong acid is taken up by muscles and cells. (D)</p> Signup and view all the answers

What is incorrect regarding the definitions of compensated respiratory acidosis?

<p>It implies two distinct primary diseases affecting respiratory function. (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of compensated hypercapnia?

<p>The pCO2 can exceed 70 mmHg without consequences. (A)</p> Signup and view all the answers

In the context of respiratory alkalosis, what is primarily affected?

<p>A decrease in pCO2 leading to lowered HCO3- levels. (B)</p> Signup and view all the answers

What does the reaction $CO_2 + H_2O ightleftharpoons H_2CO_3$ primarily illustrate?

<p>The mass action effect following changes in carbon dioxide levels. (B)</p> Signup and view all the answers

What physiological change is immediate in response to decreased pCO2 in respiratory alkalosis?

<p>Rapid decreases in bicarbonate concentration. (D)</p> Signup and view all the answers

Which area of assessment would suggest improper compensation in chronic hypercapnia?

<p>Stable pH levels exceeding the alkalemic range. (B)</p> Signup and view all the answers

What defines hypocapnia in the context of acid-base balance?

<p>A decrease in pCO2 leading to abnormal acid-base ratios. (A)</p> Signup and view all the answers

What role does lactic acid play in the body's response to decreased pCO2?

<p>It generates more CO2 and helps normalize pH. (C)</p> Signup and view all the answers

What physiological change occurs in the kidneys as a compensation mechanism during respiratory alkalosis?

<p>Decreased HCO3- reabsorption and reduced NH4+ secretion. (B)</p> Signup and view all the answers

In a patient with chronic hypocapnia, what is expected to happen to pH levels over time?

<p>pH will approach normal but not overshoot. (C)</p> Signup and view all the answers

Which condition is associated with excessive removal of CO2 from the lungs?

<p>Respiratory alkalosis. (B)</p> Signup and view all the answers

What is the primary problem in metabolic acidosis?

<p>Accrual of non-carbonic acids. (C)</p> Signup and view all the answers

What initial change occurs in arterial blood values during a state of acute hypocapnia?

<p>Decrease in pCO2. (D)</p> Signup and view all the answers

How does increased ventilation due to aspirin intoxication initially affect blood gas levels?

<p>It causes respiratory alkalosis. (D)</p> Signup and view all the answers

During the compensation for chronic hypocapnia, what happens to HCO3- levels?

<p>They decrease over time. (C)</p> Signup and view all the answers

What type of acids primarily contribute to metabolic acidosis?

<p>Non-carbonic acids. (A)</p> Signup and view all the answers

What is a common characteristic of conditions causing respiratory alkalosis?

<p>Increased ventilatory rate. (A)</p> Signup and view all the answers

Flashcards

Normal pH range

Blood pH should be maintained between 7.35 and 7.45, although more precisely within 7.38 - 7.42

Normal pCO2 range

Blood pCO2 (partial pressure of carbon dioxide) should be in the range of 35 - 45 mmHg, but realistically the range is more closely regulated to 37 - 42 mmHg.

Normal [HCO3-] range

The normal range for bicarbonate concentration ([HCO3-]) in the blood is 22 - 26 mEq/L.

Respiratory acidosis

A condition characterized by excessive CO2 in the blood due to inadequate lung function.

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Respiratory alkalosis

A condition where the body has too little CO2 in the blood, often due to hyperventilation.

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Acid-base compensation

The body's physiological mechanisms to maintain a balance between acids and bases.

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Acid load daily

Daily acid formation is about 13,000 mmol/day of CO2 and 70-100 mmol/day of non-volatile acid.

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Primary Disorder

The initial event causing the acid-base imbalance (e.g., a change in bicarbonate levels).

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Metabolic Acidosis

An acid-base imbalance caused by a decrease in bicarbonate levels.

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Compensation (Acid-base)

Physiological response to counteract the acid-base imbalance; NOT a chemical buffering reaction, but rather a biological response.

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Normal Acid-Base Range

pH 7.40, pCO2 40 mmHg, and HCO3- 24 mM.

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Hypercapnia

A high level of carbon dioxide in the blood.

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Simple Acid-Base Disorder

An acid-base disturbance with only one primary problem.

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Buffering (Acid-Base)

A chemical reaction that neutralizes an acid or a base.

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Chronic Hypocapnia Compensation

The body's long-term response to persistently low pCO2, involving reduced HCO3- reabsorption by the kidneys.

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Non-Carbonic Acid Sources

The main sources of non-carbonic acids in the body include metabolic byproducts like lactic acid and organic molecules containing phosphorus or sulfur.

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Lactic Acidosis

A metabolic acidosis condition caused by excessive buildup of lactic acid in the blood.

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Ketoacidosis

Metabolic acidosis caused by ketones (like acetoacetate and b-hydroxybutyrate) accumulating in the blood.

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Respiratory Alkalosis Compensation

The body's response to high pH and low pCO2, often triggered by hyperventilation.

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Kidney Compensation

The kidney's role in restoring acid-base balance by adjusting HCO3- reabsorption and NH4+ secretion.

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Buffering Role of Hemoglobin

Hemoglobin in red blood cells can bind and release H+ ions, helping to buffer changes in blood pH.

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Renal Compensation Limit

The kidneys' maximum capacity for bicarbonate reabsorption prevents complete compensation for severe chronic hypercapnia (high CO2), causing a 'bend' in the compensation graph.

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Respiratory Acidosis Compensation

The body's response to respiratory acidosis (lower pH due to elevated CO2), involving an increase in bicarbonate to buffer the acidic condition, with a limit due to renal function.

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Metabolic Alkalosis

A condition where blood pH is excessively high due to insufficient CO2 or excess bicarbonate in blood.

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Respiratory Alkalosis (Hypocapnia)

A condition where decreased CO2 (low pCO2) causes a decrease in carbonic acid, thereby leading to a decrease in buffered bicarbonate.

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pCO2

Partial pressure of carbon dioxide in the blood; a measure of CO2 concentration.

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Compensation

Physiological adjustments the body makes to counteract a primary acid-base disturbance and maintain pH homeostasis.

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Bicarbonate Reabsorption

The process by which the kidneys conserve bicarbonate ions, which are crucial in maintaining acid-base balance in the blood.

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Acid-Base Balance

The maintenance of a stable pH in the body fluids. This is necessary for all metabolic processes and cellular function.

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Metabolic Acidosis: Immediate Response

When metabolic acidosis occurs, the body initially uses bicarbonate (HCO3-) in the extracellular fluid (ECF) to buffer the excess acid. This leads to a decrease in HCO3- levels.

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Metabolic Acidosis: Cellular Buffering

Over time, cells take up hydrogen ions (H+) to help buffer the acidosis. This involves proteins like hemoglobin and other cellular proteins.

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Metabolic Acidosis: Bone Buffering

In chronic acidosis, bone releases carbonate (CO3-) to help neutralize the excess acid. This is a slower process.

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Metabolic Acidosis: Respiratory Compensation

The body increases breathing rate and depth to expel more carbon dioxide (CO2), thereby reducing the acidity of the blood. This is a rapid response.

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Metabolic Acidosis: Renal Compensation

The kidneys increase the excretion of hydrogen ions (H+) in the urine, primarily in the form of ammonium (NH4+). This is a slower process but crucial for long-term correction.

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Study Notes

Acid-Base Imbalance

  • Acid-base disturbances are classified by pH
    • Acidemia: pH < 7.40
    • Alkalemia: pH > 7.40
  • Then sub-classified by carbonic acid or non-carbonic
    • Respiratory imbalances: changes in pCO2
      • Respiratory acidosis: pCO2 excess
      • Respiratory alkalosis: pCO2 deficit
    • Metabolic imbalances: changes in non-carbonic acid
      • Metabolic acidosis: base deficit
      • Metabolic alkalosis: base excess

Learning Objectives

  • Identify and classify acidemia vs alkalemia
  • Identify and classify respiratory vs metabolic imbalances
  • Define compensation for acid-base disorders
  • Learn the role of the lungs and kidneys in acid-base compensation
  • Develop proficiency in using the acid-base map to identify/categorize acid-base disorders
  • Know buffering systems involved in response to disturbance
  • Estimate expected compensatory response for acid-base disorders
  • Identify paradigm diseases associated with primary acid-base disorders

Acid-Base Definitions

  • Normal pH range: 7.35 - 7.45 (at sea level, 37°C)
  • Normal pCO2 range: 35 - 45 mmHg
  • Normal HCO3- range: 22 - 26 mEq/L

Acid-Base Regulation

  • Daily acid formation: 13,000 mmol/day CO2 + 70-100 mmol/day non-volatile acid
  • Lung excretion: 13,000 mmol/day CO2
  • Kidney excretion: 70-100 mmol/day H+ (5,000 total mmol H+)

Steps in Evaluating Acid-Base Problems

  • Obtain arterial blood sample
  • Measure pH, pCO2 and HCO3-
  • Plot values on Davenport diagram
  • Make a diagnosis based on the diagram's location.

Simple Acid-Base Disorders

  • Acidosis: pH decreases, pCO2 and/or HCO3- decrease
  • Alkalosis: pH increases, pCO2 and/or HCO3- increase
  • Primary disorder: solid arrows in diagram
  • Compensation: dotted arrows in diagram

Factors Affecting HCO3 Reabsorption

  • Carbonic anhydrase activity
  • Partial pressure CO2 (pCO2)
  • Amount filtered HCO3-
  • Amounts of filtered/secreted buffers (distal): NH3 and HPO42-

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Related Documents

Acid-Base Physiology Notes (2024) PDF

Description

Test your knowledge on acid-base disturbances classified by pH. This quiz covers various imbalances including respiratory and metabolic disorders, as well as compensation mechanisms in the body. Learn to identify and classify these disorders effectively using the acid-base map.

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