Intro to resp

Question 1

what is the function of the respiratory system?

Answer 1

1) Gas exchange

2) Acid-base balance

3) Metabolic function

4) Blood filter and reservoir (like blood clots, foreign materials)

5) Body temperature (not major in humans)

6) Elimination of volatile substances

7) Phonation

Question 2

How do we measure the gas exchange?

Answer 2

Respiration exchange ration = Rate of CO2 production (V co2 L/min) / Rate of oxygen consumption (Vo2 L/min)

FYI:

• RER of 0.7: Primarily fat is being used as the fuel source.
  RER of 0.85: This indicates a mixed use of fats and carbohydrates.
  RER of 1.0: Carbohydrates are the primary energy source.
  RER above 1.0: This may indicate anaerobic metabolism, where lactate production is increasing, commonly seen during high-intensity exercise.

Question 3

What are the metabolic functions of the respiratory system?

Answer 3

• It occurs mainly in the endothelium

1) Conversion of angiotensin 1 to angiotensin 2

2) Inactivation of bradykinin

3) Removal of the prostaglandins

4) Uptake of biogenic amines like (serotonin and norepinephrine)

Question 4

what are the two functional zones of the respiratory system?

Answer 4

1) Conducting zone

• they warm, humidify, and purify incoming air, remove any foreign bodies

2) Respiratory zone

• gas exchange particularly at their thin wall site (capillary and type-1 alveolar cell “squamous”)

Question 5

at what age will we have the maximum number of alveoli (300)?

Answer 5

8 years old

Question 6

What is the function of Kohn’s pore?

Answer 6

They are small pores between the septum of adjacent alveoli to equalize the pressure between adjacent alveoli

Question 7

what is the importance of the macrophages in the alveoli?

Answer 7

1) Dust cells

• Phagocytizing particles that are not trapped by the mucus layer

2) Heart failure cells

• During heart failure, RBC might enter the alveoli which are phagocytized by the macrophages

Question 8

What is the interstitial space?

Answer 8

It is the fused basement membrane of the alveolar epithelium and capillary endothelium (the site of interstitial fluid)

• If fluid accumulates here it will result in pulmonary edema which will hinder the diffusion leading to hypoxia

Question 9

Where does pulmonary edema occur?

Answer 9

In the fused basement membrane between the alveolar epithelium and capillary endothelium

Question 10

What are the three processes of respiration?

Answer 10

1) Ventilation (bringing air into the lungs)

2) Perfusion (bringing the blood close to the alveoli)

3) Diffusion (exchange of air)

Question 11

What is meant by ventilation?

Answer 11

It is the mechanical process by which air is supplied to the lungs

Question 12

What is meant by perfusion?

Answer 12

It is the process by which blood is supplied to the alveoli

• A portion of the perfused blood bypasses the ventilated alveoli and is said to be shunted (into the bronchial circulation, thebesian veins)

Question 13

What is Dalton’s law of partial pressure?

Answer 13

It states that the total pressure in a gas mixture (the total barometric pressure) is equal to the sum of the partial pressures of the individual gases

• Pb (total barometric pressure “total atmospheric pressure” =760 mmHg at sea level) = PN2 + PO2 + PH2O + PCO2

Question 14

What is meant by partial pressure?

Answer 14

• Partial pressure refers to the pressure that a specific gas in a mixture of gases contributes to the total pressure.
• In a mixture, each gas exerts pressure independently, as if it were the only gas present. The partial pressure of a gas is directly proportional to its concentration in the mixture.

Question 15

How to calculate the partial pressure of specific gases?

Answer 15

For example for oxygen

• PO2 (partial pressure of oxygen) = Pb (barometric pressure) * FO2 (fractional concentration of oxygen)

Po2 = 761 mmHg * 0.21 = 160 mmHg

Question 16

What is the reason behind that the Partial pressure of gases is lower in the lungs?

Answer 16

Because in the lungs at 37 degrees Celsius, the inspired air will become saturated with water vapor thus lowering their fractional concentration

Question 17

What are the different partial pressures of oxygen in different settings?

Answer 17

1) Air = 160 mmHg

2) Trachea = 150 mmHg

3) Alveoli = 100 mmHg

4) Artery = 100 mmHg

5) Mixed venous = 40 mmHg

Question 18

What is the different partial pressure of carbon dioxide in different settings?

Answer 18

1) Air = 0 mmHg

2) Alveoli = 40 mmHg

3) Artery = 40 mmHg

4) Mixed venous = 46 mmHg

Question 19

What is meant by minute ventilation?

Answer 19

• The total volume of air that is moved in and out of the lungs in one minute

MinuteVentilation(VE)=TidalVolume(VT) × RespiratoryRate(RR)

Question 20

What is meant by alveolar ventilation?

Answer 20

• The volume of air that actually reaches the alveoli

Alveolar Ventilation (Va) = (Tidal Volume “Vt” - Dead Space Volume “Vd”) * breathing frequency

Question 21

What is meant by the ventilation-perfusion ratio?

Answer 21

• It is the relationship between the amount of air reaching the alveoli (ventilation, V) and the amount of blood reaching the alveoli via the capillaries (perfusion, Q)

V/P ration = (alveolar ventilation “(Vt - Vd) * F” / pulmonary blood flow)

• The normal value is 0.8 if this value, if it was more it could indicate excess ventilation (like in pulmonary embolism) or poor perfusion. if the number was lower than 0.8 when the alveoli are perfused but not well ventilated like in COPD or asthma resulting in a lower ventilation to certain alveoli

Question 22

What is meant by the anatomic dead space?

Answer 22

• It is the volume of air that remains in the conducting airways and it is not used in gas exchange, it represents the size of the conducting zone

Vt = Vd + Va (volume of fresh air in the alveoli)

• This forms the anatomic dead space

Question 23

What is meant by the alveolar dead space?

Answer 23

• This occurs when there is no blood flow to an alveolar region, or There is reduced blood flow

Question 24

what is meant by the physiological dead space?

Answer 24

• The total wasted air in the lungs when you add both the anatomic dead space with the alveolar dead space
• Physiological Vd = Anatomic Vd + Alveolar Vd
• In a normal person the physiological dead space is usually equal to the anatomical dead space

Question 25

What is the effect of the breathing patterns on the alveolar ventilation?

Answer 25

Okay so in the case of Tachypnea all of the air will be lost in the dead space and the alveolar ventilation would be 0 at the end in Bradypnea the alveolar ventilation number would increase to calculate it:

• (Vt - Vd) * F (breath frequency)
• Increasing the depth of breathing is far more effective in elevating the alveolar ventilation than increasing the frequency of breath

Question 26

How to calculate the dead space volume?

Answer 26

1) Bohr Equation

2) Fowler’s Equation

Question 27

What is the Bohr equation?

Answer 27

• CO2 in the exhaled air comes from the alveoli which were previously ventilated
• Enghoff then modified the Bohr equation using arterial CO2 instead of alveolar CO2

To measure the volume of dead space using their equation:

Vd (volume in dead space) = Tidal Volume * (partial pressure of CO2 in the arterial blood - partial pressure of CO2 in the expired air) / partial pressure of CO2 in the arterial blood

Question 28

How to measure the volume of the anatomical dead space using the Fowlers test?

Answer 28

1) A subject takes a single breath of 100% oxygen and exhales it into a nitrogen detector

2) The last air in is the first air out and thus the air that occupied the anatomical dead space is 100% oxygen and 0% nitrogen

3) The alveoli that are poorly ventilated will have the highest nitrogen concentration

Question 29

Describe the cough reflex

Answer 29

• IN THE BRONCHI AND TRACHEA

1) Trigger:

• The bronchi and trachea are sensitive to light touch with foreign matters or other irritations which will initiate a cough reflex
• The larynx, carina, and terminal bronchi are sensitive to gases and chemicals

2) Afferent nerve

• Vagus nerve

3) Central control

• Medulla in the brain

4) Efferent effect

1) up to 2.5L of air is inspired

2) The epiglottis and the vocal cords shut down to entrap the air within the lungs

3) Abdominal muscles contract forcefully along with the intercostal muscles raising the pressure in the lungs to 100 mmHg

4) The vocal cords and the epiglottis suddenly open exploding a high velocity of air (75-100 miles/hour)

5) The strong compression of the lungs collapses the trachea and bronchi (non-cartilaginous parts) to invaginate inwards taking the air through narrow slits with high speed

Question 30

Describe the sneeze reflex

Answer 30

• IN THE NASAL CAVITY
  1) Trigger:
• Irritations to the nasal passageways, not the lower respiratory

2) Afferent nerve

• 5th cranial nerve

3) Effect:
1) The uvula is depressed

2) Large amounts of air pass rapidly through the nose clearing out the nasal passages

• the mechanism is similar to the cough mechanism