Lab Practical Blood Buffer & Respiratory Acid-Base

What are the 2 blood buffer systems?

• bicarbonate system

• protein system

What are the 2 processes that develop in the blood buffer system?

• acidosis

• alkalosis

What are the 3 fluids used in the blood buffer system?

• complete unbuffered water

• 2% bicarbonate solution in water

• 1% albumin (protein) solution in water

What do the concentrations used in the blood buffer system represent?

the effect similar to buffer in blood plasma

What are the 3 main pH levels mentioned in the blood buffer system?

• 7.4

• 5.0

• 9.0

What is the typical pH of plasma?

7.4

What color are solutions of 7.4 pH?

light green/blue

What color are solutions of 5.0 pH?

yellow/orange

What color are solutions of 9.0 pH?

dark ink blue

What pH does severe acidosis never drop lower than?

7.2

What pH does severe alkalosis never raise higher than?

7.6

Adding drops of 0.1 M HCl does what to the pH of 7.4 in each buffer?

7.4 → 5.0

Adding drops of 0.1 M NaOH does what to the pH of 7.4 in each buffer?

7.4 → 9.0

Color change from drops of 0.1 M HCl

neutral → orange/yellow

Color change with drops of 0.1 M NaOH

neutral → dark ink blue

What is the order of general buffer strengths (weakest → strongest)?

1. water

2. albumin (protein)

3. bicarbonate

Why bicarbonate is strongest

It is part of a dynamic equilibrium system involving CO₂ and can be regulated by lungs and kidneys

How many drops did it take for water to change color?

1

How many drops did it take for the albumin to change color?

20

How many drops did it take for the bicarbonate to change color?

over 30 drops

Why does the number of drops into bicarbonate get capped at 30?

bicarbonate is a much stronger buffer so it is able to accept or donate the H+ without exhibiting the visible pH change via color

What is the general effect of a buffer on the amount of acid/base that is required to produce a given pH change?

buffers stabilize pH by absorbing added acid or base, making pH harder to change

What does blowing above the DI water with a straw for 2 deep breaths do to the CO2 concentration?

makes the CO2 concentration in the gas space about 5%

What does blowing above the DI water with a straw for 2 deep breaths represent in the body?

gas moving from the air space into liquid as seen in the alveoli

If blowing with the straw makes bubbles or goes into the DI water, what cannot be assumed?

no assumption that the gas is moving from the air space into the liquid like it would in the alveoli

What does capping the DI water/straw flash and swirling it around do?

equilibrate the dissolved gas with the liquid, the color may change

Is HCl or NaOH used in the CO2 dissolution experiment with the straw? Why?

NaOH because we are adding acid (CO2) to the systems

What buffers are used in the carbon dioxide dissolution experiment with the straw?

• water + indicator

• bicarbonate + indicator

What chemical occurrence happened when we blew air above the water with a straw? Why?

it changed to yellow by dissociating it and receiving H+

How does the observation of the water turning back to yellow despite adding NaOH fit what is known about H-H equilibrium?

The solution turns back to yellow because removing H⁺ with NaOH shifts the equilibrium to the right, generating more H⁺ from dissolved CO₂, demonstrating the dynamic nature of the Henderson–Hasselbalch system.

What happens when you add a drop of NaOH to the yellow-colored water? What happens once you add multiple?

the liquid goes from being acidic and yellow, to blue/green, then back to yellow until multiple drops turn it dark blue and alkaline

When adding lots of NaOH to the acidic water after the carbon dioxide dissolution, what chemically occurs?

the NaOH counteracts the H+ that came from the CO2

What are you doing to the H-H equilibrium as you add NaOH?

as you add NaOH, you are removing H⁺ from the system (because OH⁻ combines with H⁺ → H₂O)

What chemical occurrence happened when we blew air above the bicarbonate with a straw?

no color change occurs

Using bicarbonate, does the fact that there is no color change visible mean less CO2 was absorbed by the liquid or is there another possible explanation? Why?

the lack of color change does not mean less CO₂ was absorbed; it means the bicarbonate buffer neutralizes the added H⁺, preventing a noticeable pH change

Process of carbon dioxide dissolution experiment

1. CO2 blown into gas space

2. CO2 enters the fluid and turns it acidic

3. NaOH added directly to fluid to bring back to neutral

4. Still lots of CO2 remaining (partial pressure is higher in the air!)

5. CO2 remaining will move into the fluid repeatedly to make it acidic

What equipment is used in the evidence for CO2 dissolution experiment?

indicator pipette with 1 drop of liquid in it

What does using an indicator pipette help us see?

gas moving into a sealed container, changing the pressure and moving the bubble of liquid either in or out

What processes occur in the evidence for CO2 dissolution experiment?

• blowing air above liquid makes water acidic & yellow

• Hooking indicator pipette up through a small tube on top of a stopper & swirling the liquid will move the gas down into the liquid and push the bubble of liquid inwards

Why does the bubble move down in during the CO2 dissolution experiment?

we are decreasing the pressure in the top of the flask, making the pressure outside of the flask higher so that the bubble moves down

Simply put, how does the bubble move in the CO2 dissolution experiment?

with a difference in pressure

What does the model for metabolic “blowing off” CO2 represent?

metabolic acidosis

What is used in the model for metabolic “blowing off” CO2 experiment?

• 2% bicarbonate solution

• indicator drop (close to tip of pipette where it will be connected to the tubing)

• “acid bolus” of 40 drops of 0.1 M HCl in plastic dosage cup to be quickly added to solution

What does combining bicarbonate and HCl form?

CO2 gas

What way does the bubble move in the model for metabolic “blowing off” CO2 experiment with bicarbonate and HCl?

out away from the flask

Why does the bubble move up in the model for metabolic “blowing off” CO2 experiment?

because there is more pressure inside the flask from the production of CO2

If you had a kidney problems and were not getting rid of H+, how would they be removed?

the respiratory system by exhaling and getting rid of CO2

Explain what you see based on the H-H equilibrium. How does this relate to what is seen in patients who are producing metabolic acids into circulation, or in individuals in heavy exercise above their aerobic capacity?

Adding metabolic acid increases H⁺, which pushes the Henderson-Hasselbalch equilibrium to the left: H⁺ combines with HCO₃⁻ to form H₂CO₃, which then breaks down into CO₂ and H₂O. This causes more CO₂ gas to form, increasing pressure in the flask and moving the indicator drop. In patients with metabolic acidosis or during heavy exercise above aerobic capacity, excess acids (like lactic acid) are buffered the same way, producing extra CO₂ that must be removed by faster, deeper breathing (“blowing off” CO₂).

Henderson-Hasselbalch equation

CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃⁻

If pH decreases, what happens to H+ and what does it lead to?

H+ increases → acidosis

If pH increases, what happens to H+ and what does it lead to?

H+ decreases → alkalosis

If the shift of pH is the result of CO2 buildup/removal, what is its origin?

respiratory origin

If the shift of pH is the result of direct H+ buildup/removal, what is its origin?

metabolic origin

What describes the Henderson-Hasselbach bicarbonate buffer system?

• reversible

• very sensitive (carbonic acid in middle)

What enzyme is involved in the Henderson-Hasselbach bicarbonate buffer system?

carbonic anhydrase enzyme

When does respiratory acidosis develop?

when CO2 is not eliminated across the respiratory membrane at the rate it is produced

When CO2 is not eliminated in respiratory acidosis occurs, what happens to the equation?

the CO2 buildup on the left side of the equation pushes the reaction to the right, increasing both the H+ and bicarbonate (HCO3-) stores to the right

↑ CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻

What is the cause of respiratory acidosis?

any limitation of gas exchange across the respiratory membrane

What are examples of causes of respiratory acidosis?

• emphysema

• COPD

• atelectasis

• acute asthma

• shallow breaths not exceeding the functional dead space

• brain stem injury

• chemical depression of respiration

• Cheyne-Stokes respiration

What occurs to the bicarb stores in respiratory acidosis?

increased

Symptoms of respiratory acidosis

varying depending on cause and degree of compensation

• if respiratory control is intact and trying to compensate: deep, raid, and dyspneic

• if not intact: aberrant and shallow

• Vasodilatory flush of hypercapnia

When does respiratory alkalosis develop?

when CO2 is eliminated across the respiratory membrane at a faster rate than at which it builds up

When CO2 is eliminated in respiratory alkalosis, what happens to the equation?

CO2 loss on the left side of the equation pulls the equation to the left with a subsequent loss of both H+ and bicarbonate (HCO3-) stores

↓ CO₂ + H₂O ← H₂CO₃ ← H⁺ + HCO₃⁻

What does respiratory alkalosis cause?

always hyperventilation

What are examples of causes associated with respiratory alkalosis?

(hyperventilation)

• emotional factors

• asthmatic attack

• pneumonia

• attempt to deal with decreased O2 available at altitude

What syndrome is respiratory alkalosis most often seen clinically?

anxiety-driven hyperventilation syndrome

What occurs to the bicarb stores in respiratory alkalosis?

decreased

What are symptoms of respiratory alkalosis?

the symptom is the cause

• rapid deep breathing

• apparent dyspnea

solution = control breathing depth and rate to drive CO2 back up (ex. paper bag)

When does metabolic acidosis develop?

when H+ is introduced into the body tissues and blood at a faster rate than it is removed by the kidney or other buffering mechanisms

When H+ is introduced in metabolic acidosis, what happens to the equation?

equilibrium pushes to the left, depleting bicarbonate stores (HCO3-) and increasing the load of CO2 that must be eliminated across the respiratory membrane

CO₂ + H₂O ← H₂CO₃ ← ↑ H⁺ + HCO₃⁻

What secondarily causes metabolic acidosis?

when bicarbonate stores (HCO3-) are lost metabolically, leaving an excess of H+

What are the causes of metabolic acidosis?

• renal disease

  • limits ability of kidney to secrete H+

• diabetes

  • results in excessive utilization of fat stores and ketoacidosis

• starvation

  • same effect as untreated diabetes

• excess alcohol ingestion

• severe diarrhea

  • removes bicarbonate-rich pancreatic secretions at an excessive rate

What occurs to the bicarb stores in metabolic acidosis?

decreased

Symptoms of metabolic acidosis

variable depending on cause and acute/chronic nature

• acute: CO2 in blood is high → dyspnea and observable effects

• chronic: this is absent

When does metabolic alkalosis develop?

when H+ is removed from the body tissues and blood at a faster rate than it is produced

When H+ is removed in metabolic alkalosis, what happens to the equation?

equilibrium pushes to the right, increasing bicarbonate stores (HCO3-)

CO₂ + H₂O → H₂CO₃ → ↓ H⁺ + HCO₃⁻

What secondarily causes metabolic alkalosis?

when bicarbonate (HCO3-) is introduced excessively into the body (ex. use of baking soda as antacid) → rare in younger people, seen in geriatric medicine

What are causes of metabolic alkalosis?

• severe vomiting

  • removes gastric acid from body and leaves behind large stores of bicarbonate (HCO3-)

• kidney conditions or drug interaactions

  • cause excessive H+ secretion

• excessive intake of bicarbonate as antacid

• severe prolonged constipation

  • retains bicarbonate of pancreatic secretions

What occurs to bicarb stores in metabolic alkalosis?

increased

Symptoms of metabolic alkalosis

almost always have decreased respiratory rate that is associated with lowered blood CO2