CCNM Phys - Respiratory

Question 1

Describe, compare and contrast the solubility of oxygen and carbon dioxide in plasma.

Answer 1

CO2 has a greater solubility than O2.

Question 2

Describe the pressure gradients at the sites of gas exchange and the direction of oxygen and carbon dioxide movement.

Answer 2

Oxygen moves “downhill” from the air to the alveoli to the blood to the tissues.
CO2 moves “downhill” from the tissues tot he blood to the alveoli to be exhaled into the air.

Question 3

Differentiate between compliance and resistance in the lung.

Answer 3

Compliance in the lung is the ability of the tissue to stretch. Compliance is developed due to the tendency for tissue to resume its original position after an applied force has been removed. Lungs tend to collaose and chest wall to expand

Resistance is increased as the lung volume is reduced. the change of pressure from alveoli to the mouth divided by the change in flow rate.

Question 4

Differentiate between type I and type II alveolar cells

Answer 4

Type I cells are flat cells with large cytoplasmic extensions and they are the primary lining of the cells of the alveoli ~ 95%

Type II cells are thicker than type one and contain numerous lamellar inclusion bodies. They represent ~5% of alveoli surface area and are important in alveoli repair. They also function in surfanctant production

Question 5

discuss the physiological significance of surfactant production.

Answer 5

Surfactant reduces surface tension, otherwise the alveoli would collapse.
Surfactant also helps prevent edema. unopposed surface tension produces 20mmHg force favouring transdilation of fluid from blood into the alveoli.

Question 6

Describe the factors determining total blood oxygen content.

Answer 6

Factors effecting blood oxygen content include amount of O2 dissolved in plasma, amount of Hb in blood and affinity of Hb for O2

Question 7

Describe the structure of hemoglobin

Answer 7

Hb is a protein with 4 subunits. each subunit contains a heme moiety attached to a polypeptide chain. there are 2 alpha and 2 beta chains. the heme is a porphyrin ring complex containing one atom of ferrous iron

Question 8

the factors that affect hemoglobin affinity for oxygen?

Answer 8

pH
temperature
[2,3-DPG]

Question 9

Predict the direction of shift of the oxyhemoglobin affinity curves in response to changes in pH, temperature, 2,3-DPG, carbon monoxide, and carbon dioxide.

Answer 9

increased pH - shift curve left

increased temp - shift curve right

increased [2,3-DPG] - shift curve right –>oxygen is liberated

decreased pH - shift right –>increased CO2 pressure, Bohr effct - deoxy Hb binds H+ more actively than oxyHb

decreased temp - shift left

increased CO2 - decrease in pH - shift curve right

CO - affinity of Hb is 210x affinity for O2 - curve rises more quickly at first, but the overall end saturation is much lower.

if the curve is shifted right a higher PO2 is required for Hb to bind to a given amount of O2 (opposite for left)

Question 10

Compare and contrast fetal hemoglobin and adult hemoglobin.

Answer 10

Fetal
-gamma instead of beta chains
-O2 content at given PO2 is greater
-binds 2,3-DPG less avidly
all of these facilitate the delivery of O2 from the mother to her fetus

Question 11

Differentiate between anatomical dead space and pulmonary dead space.

Answer 11

Anatomical dead space is the gas taht occupies the rest of the respiratory tract system, not available for gas exchange (ie. in the trachea, bronchi, bronchioles etc)

Physiological dead space is the volume of gas not equilibrating with the blood - wasted ventilation.
These two dead spaces are identical in healthy individuals.
In disease, some of the alveoli may have no gas exchange with blood and some alveoli may be over ventilated
-the volume of gas in non-perfused alveoi and only volume of air in alveoli in excess of that necessary to arterialize blood in alveolar capillaries is part of anatomical dead space

Question 12

Describe the metabolic functions of the lung.

Answer 12

produce surfactant for local use
contain fibronolytic system that lyses clots in pulmonary vessels
release a variety of substances that enter the systemic arterial blood
remove substances from the systemic venous blood
prosaglandins removed from blood & produced/synthesized in lungs & released into blood when lung tissue stretched

Question 13

Describe endocrine functions of the lung.

Answer 13

important role in activating angiotensin

converts angiotensin I to angiotensin II

Question 14

Describe immune functions of the lung.

Answer 14

first line of defense to air pathogens… (nothing in text or notes)

Question 15

Describe the four main classifications of hypoxia and be able to provide an example for each.

Answer 15

Hypoxia is an oxygen deficiency.

1) hypoxemia (hypoxic hypoxia) - PO2 of arterial blood reduced. Ex) high altitudes
2) Anemic hypoxia - normal arterial PO2, reduced Hb. Ex) anemia
3) Ischemic hypoxia - blood flow to tissues so low that adequate O2 is not delivered despite normal PO2 & Hb levels. Ex) slow circulation. congestive heart failure if to liver and brain. shock if to heart and kidneys
4) histotoxic hypoxia - delivered O2 is adequate but because of toxin tissues can’t make use of O2. ex) cyanide poisoning

Question 16

Predict and explain the respiratory compensation mechanisms that would occur in a state of metabolic acidosis or alkalosis based on the carbonic acid equilibrium.

Answer 16

Metabolic acidosis
-strong acids added to blood - H2CO3 is formed - converted to H2O and CO2 - CO2 exhaled rapidly = hyperventilation

Metabolic alkalosis
-addition of alkali to blood or removal of acids free [H+] falls - results in metabolic alkalosis - hypoventilation

Question 17

Respiratory acidosis? effects on the carbonic acid equilibrium?

Answer 17

inability of lung to remove CO2 from blood fully
excess CO2 in blood forms acid in blood
->shifts equilibrium
–>becomes more acidic (lower pH)

Question 18

respiratory alkalosis? effects on the carbonic acid equilibrium?

Answer 18

excessive breathing leads to low blood CO2 levels
->increase CO2
_increase PCO2 to bicarbonate ration
…hypocapnia –> lungs expel more CO2 than that produced by the tissue

Question 19

Explain how the carbonic acid system, proteins and hemoglobin function as physiological buffers.

Answer 19

Carbonic acid system
H2O + CO2H2CO3H+ + HCO3-
These are in equilibrium so the concentration of any particular substance does not get too high. increased H+ and CO2 both stimulate increased ventilation

Proteins?
free carbonyl and free amino acid groups dissociate (provide binding for H+)

Hb?
dissociation of the imidazole groups of the histidine residues in Hb (38 histidine residues). each individual has little contribution, but it adds up and Hb has 6x the buffering effect that plasma proteins do. Hb is a weaker acid and therefore a better buffer than HbO2

Question 20

Describe and explain the transport mechanisms for oxygen and carbon dioxide from tissues to lungs and vice versa.

Answer 20

99% of oxygen in the blood coombines with Hb to travel to the tissues and 1% is dissolved in the plasma

94.5% of CO2 is formed into carbamino compounds with plasma proteins, hydration into H+ and HCO3-, and carbamino-Hb. 5.5% is dissolved in the plasma/RBCs to travel from the tissues to the lungs.

Question 21

Describe the regulatory mechanisms that exist for the automatic control of breathing.

Answer 21

Breathing is driven by pacemaker cells in the medulla (pre-BOTC - rhythmic discharge)
impulses from these cells activate motor neurons in the cervical and thoracic spinal cord that innervate inspiratory muscles
-cervical activate the diaphragm via the phrenic nerve
thoracic activate external intercostal muscles and other respiratory muscles.

Question 22

Describe the chemical signals that trigger changes in breathing and discuss the physiological mechanisms that exist that translate that signal into a neurological response (carotid and aortic bodies, medullary chemoreceptors)

Answer 22

receptors in the carotid and aortic bodies are stimulate by a rise in PCO2 or H+ concentration of arteriol blood or decline in its PO2
Chemoreceptors are also present in the medulla oblongata - sensitive to [H+] in the CSF (CO2 crosses BBB and dissociates, increasing [H+], stimulating ventilation)

an increase in PCO2, H= or a decrease in PO2 increase respiration
a decrease in PCO2, H+ or an increase in PO2 result in a lower respiration rate

Question 23

Predict the ventilatory changes that would occur in response to excess carbon dioxide or oxygen deficiency.

Answer 23

excess CO2 or deficient O2 would result in an increase in ventilation
for O2 deficiency, marked changes in ventilation do not occur until PO2 in inspired air falls below 60mmHg or when arterial PO2 falls below 100mmHg

Question 24

Describe the effects of norepinephrine on beta adrenergic receptors in relation to the effect on breathing.

Answer 24

norepinephrine stimulates beta adrenergic receptors and results in increased respiration

Question 25

Describe the various respiratory volumes and capacities that are measured during a slow vital capacity (SVC) and calculate the volumes and capacities not directly measured (tidal volume, inspiratory and expiratory reserve volume, vital capacity, inspiratory capacity, functional residual capacity, total lung capacity).

Answer 25

tidal volume - amount of air inhaled or exhaled in one breath during relaxed, quiet brething
Inspiratory reserve volume - amount of air in excess of tidal inspiration that can be inhaled with max effort
Expiratory reserve volume - amount of air in excess of tidal inspiration that can be exhaled with mas effort
vital capacity - amount of air that can be exhaled with max effort after max inspiration (ERV+TV+IRV) - used to assess strength of thoracic muscles as well as pulmonary function
Inspiratory capacity - max amount of air that can be inhaled after a normal tidal expiration (TV+IRV)
Functional reserve capacity - amount of air remaining in the lungs after a normal tidal expiration (RV+ERV)
Total lung capacity - max amount of air the lungs can contain (RV+VC)

Question 26

When given a normal vol. vs. time or flow vs. vol. FVC graph
Predict and diagram the changes in the FVC graph’s shape in the presence of obstructive, restrictive and mixed respiratory disorders.
Explain the underlying physiological mechanisms for the change in graph shape

Answer 26

Look at lab…

Question 27

Provide appropriate instructions and perform spirometry measurements (FVC and SVC) on another group member. – Laboratory practical skill

Answer 27

Patient instructions for SVC effort:

1. Ensure the SVC tab is selected for this procedure
2. Have the patient hold on to the transducer and click the “record” button. Ensure that the patient holds the transducer still.
3. Once the computer is ready, have the patient plug their nose with two fingers with one hand, and have them put the transducer in their mouth and form a tight seal with their lips around it (don’t bite the transducer).
4. Keeping the nose plugged, have the patient breathe quietly for4-6 tidal breaths.
5. At the end of a normal inspiration, tell the patient to breathe in as long and as deep as possible (over 3-4 seconds) and exhale as long and as deep as possible (over 3-4 seconds).
6. Resume normal tidal breathing for 2-3 cycles
7. Click the “stop” button to end the effort.
8. Repeat the above procedure to get 2 measurements
9. Print out “Best SVC” to hand in as part of your lab.

Question 28

Provide appropriate instructions and perform forced expiratory measurements using a peak flow meter. – Laboratory practical skill

Answer 28

Patient instructions for FVC effort:

1. Attach flow transducer to sensor tubing and have patient hold on to it.
2. Ensure the FVC tab is selected on the computer
3. Press record button
4. Ensure the sensor is held steady away from the patient’s mouth
5. Once the computer is ready, have the patient plug their nose with two fingers with one hand, and have them put the transducer in their mouth and form a tight seal with their lips around it (don’t bite the transducer)
6. Have the patient take a deep breath in and at the peak of the full inspiration have them blow out as fast, as hard and as long as they can. Continue to encourage the patient to exhale until you hit the 6 second mark, or until the red line starts to waver, indicating that the patient is inhaling some air.
7. At that point, as the patient to inhale as fast as hard and as long as they can.
8. Click the stop button and the end of the inhalation
9. Repeat the above steps so that three good measurements are recorded.
10. Print out “Best FVC” to hand in as part of your lab.