Acid-Base Balance and Lung Function

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Questions and Answers

Which type of chronic obstructive pulmonary disease is commonly associated with respiratory acidosis?

COPD exacerbation

Type A COPD

End-stage COPD

Type B COPD (correct)

What is the primary cause of respiratory acidosis in a patient with severe kyphoscoliosis?

Hyperventilation

Impaired neuromuscular function (correct)

Respiratory muscle fatigue

Impaired gas exchange

A patient with a severe asthma episode is likely to develop which type of respiratory disorder?

Respiratory acidosis (correct)

Metabolic alkalosis

Respiratory alkalosis

Metabolic acidosis

Which sign of respiratory acidosis is also associated with hypoxemia?

Increased neuromuscular excitability Signup and view all the answers

What is the primary cause of respiratory acidosis in a patient with Guillain-Barré syndrome?

Impaired neuromuscular function Signup and view all the answers

Which of the following is NOT a common cause of respiratory acidosis?

Hyperventilation Signup and view all the answers

A patient with acute respiratory distress syndrome is likely to develop which type of respiratory disorder?

Respiratory acidosis Signup and view all the answers

Which sign of respiratory acidosis is also associated with cardiac dysrhythmias?

Tachycardia Signup and view all the answers

What is the primary cause of respiratory acidosis in a patient with chest injury or surgery?

Pain limiting ventilation Signup and view all the answers

A patient with end-stage type A COPD is likely to develop which type of respiratory disorder?

Respiratory acidosis Signup and view all the answers

What is the primary factor that determines the partial pressure of oxygen in the blood?

The number of oxygen molecules dissolved in plasma Signup and view all the answers

What is the short-term adaptation of the human body to high altitude?

Increased breathing depth and rate (hyperpnea) Signup and view all the answers

What is the effect of hyperpnea on the body at high altitude?

It causes respiratory alkalosis and water loss Signup and view all the answers

What is the formula for calculating oxygen content in the blood?

CaO2 = Hb x 1.34 ml O2/gm Hb x SaO2 + PaO2 x (.003 ml O2/mm Hg/dl) Signup and view all the answers

What is the primary factor that determines oxygen saturation in the blood?

The percentage of all available heme binding sites saturated with oxygen Signup and view all the answers

What happens to the air in the lungs when a diver quickly swims to the surface?

It re-expands rapidly Signup and view all the answers

What is the result of a rupture of the alveoli?

Air bubbles are carried to the heart Signup and view all the answers

What is Henry's Law related to?

The solubility of gases in liquids Signup and view all the answers

What can happen to the eardrum during descent?

It can rupture due to water pressure Signup and view all the answers

What is a possible consequence of a diver not exhaling properly during ascent?

Pulmonary barotrauma Signup and view all the answers

What is the primary mechanism by which oxygen toxicity causes cellular damage?

Oxidation of polyunsaturated fatty acid components of cell membranes Signup and view all the answers

What is the primary cause of nitrogen narcosis in divers breathing air at high pressure?

Nitrogen dissolving in the neuronal membranes, changing ionic conductance Signup and view all the answers

What is the primary treatment for decompression sickness?

Gradually decreasing the pressure to normal atmospheric level Signup and view all the answers

What is the primary symptom of decompression sickness in 85-90% of people?

Pain in joints and muscles of the legs and arms Signup and view all the answers

What is the consequence of oxygen partial pressure increasing in the tissues?

Increased oxygen toxicity Signup and view all the answers

Study Notes

Acid-Base Balance: Role of the Lungs

Acid-base balance refers to the regulation of free hydrogen-ion (H+) concentration in the body fluids.

Sources of Acidity

CO2 + H2O → H2CO3 → H+ + HCO3- (source of acidity)

Regulation of H+ Balance

The Henderson-Hasselbalch equation is used to calculate how changes in CO2 and HCO3− affect pH.
pH = [HCO3-] controlled by kidney function / [CO2] controlled by lung function.

Defense Mechanisms against Changes in [H+]

Three lines of defense operate to maintain [H+] at a nearly constant level (pH 7.4):
Chemical buffer systems
Respiratory mechanism of pH control
Renal mechanism of pH control

Respiratory Mechanism of pH Control

Ventilation can compensate for pH disturbances.
Increased H+ concentration stimulates respiration, which increases alveolar ventilation and decreases H+ concentration.

Relationship between Respiration and pH

High concentrations of hydrogen trigger hyperventilation.
Respiratory system is a negative feedback mechanism.
In hypoventilation, we have increased CO2 levels.

Respiratory Acid-Base Regulation

Acts at a moderate speed.
Activated when chemical buffer systems alone are unable to minimize pH deviations.
Requires a few minutes to be initiated.
Respiratory system serves as the second line of defense.

Respiratory Compensation

Peripheric chemoreceptors and central chemoreceptors are involved in respiratory compensation.

Respiratory Acidosis

Causes:
Impaired gas exchange
Type B chronic obstructive pulmonary disease (COPD)
Bacterial pneumonia
Severe asthma episode
Pulmonary edema
Acute (adult) respiratory distress syndrome
Impaired neuromuscular function
Chest injury or surgery (pain limits ventilation)
Hypokalemic respiratory muscle weakness
Severe kyphoscoliosis
Respiratory muscle fatigue
Impaired respiratory control (brainstem)
Respiratory depressant drugs (opioids, barbiturates)
Signs and symptoms:
Headache
Tachycardia
Cardiac dysrhythmias
Neurologic abnormalities
Blurred vision
Tremors
Vertigo
Disorientation
Lethargy
Somnolence

Respiratory Alkalosis

Causes:
Hypoxemia
Signs and symptoms:
Increased neuromuscular excitability

Oxygen Pressure (pO2)

Oxygen molecules dissolved in plasma impinge on the measuring oxygen electrode, reflecting the partial pressure of oxygen
The number of O2 molecules dissolved in plasma determines how many molecules will bind to hemoglobin
PaO2 only measures free oxygen molecules, not oxygen bound to hemoglobin

Oxygen Saturation (SaO2)

Percentage of available heme binding sites saturated with oxygen
Measured as the hemoglobin oxygen saturation

Oxygen Content (CaO2)

Calculated by multiplying hemoglobin concentration, oxygen-carrying capacity of hemoglobin, and oxygen saturation
Formula: CaO2 = Hb (gm/dl) x 1.34 ml O2/gm Hb x SaO2 + PaO2 x (.003 ml O2/mm Hg/dl)

Acclimatization to High Altitude

The body adapts to high altitude through immediate and long-term acclimatization
Short-term adaptation: increased breathing depth and rate (hyperpnea) due to carotid body sensing lack of oxygen
Hyperpnea leads to respiratory alkalosis, which inhibits further respiratory rate enhancement

Oxygen Toxicity

Breathing oxygen at high pressure (4 atm) causes seizures, coma, muscle twitchings, dizziness, and other symptoms
Oxygen toxicity leads to formation of oxygen free radicals, damaging cell membranes and enzymes

Nitrogen Narcosis

High pressure causes nitrogen to dissolve in fat tissues, including neuronal membranes, reducing neuronal excitability

Decompression Sickness

When a diver surfaces too quickly, nitrogen bubbles form in body fluids, blocking blood vessels and causing tissue ischemia and death
Symptoms include pain in joints and muscles, nervous system symptoms, and shortness of breath

Treatment of Decompression Sickness

Gradual decompression in a pressurized tank to normal atmospheric pressure

Diving Problems

Descending: compression of gases causes eardrum rupture, sinus damage, lung squeeze, and eye problems
Ascending: rapid pressure change causes re-expansion of gases, leading to pulmonary barotrauma and air embolism if not exhaled properly

Henry's Law

At constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas

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Description

This quiz covers the regulation of free hydrogen-ion (H+) concentration in the body fluids, including the role of the lungs in maintaining acid-base balance and the sources of acidity.