Unit 5 - Breathing PART H-J

Question 1

Alveolar ventilation

Answer 1

Not all air that enters the respiratory tract during a tidal inspiration goes to the alveoli. Some of it fills the anatomical dead space. As a result, the alveolar ventilation is lower than the pulmonary ventilation.

Question 2

The TOTAL PULMONARY VENTILATION PER MINUTE (or minute ventilation) is

Answer 2

= tidal volume x respiratory rate
= 500 mL/breath x 12 breaths/min = 6000 mL/min

(the volume of air moved into & out of the lungs each min)

Question 3

Due to anatomical dead space,…

Answer 3

only ~350 mL of fresh air from each 500 mL tidal breath actually reaches the lungs. So TOTAL ALVEOLAR VENTILATION is

= (tidal volume – dead space volume) x respiratory rate
= (500 mL/breath – 150 mL/breath) x 12 breaths/min = 4200 mL/min

Question 4

Anatomical dead space

Answer 4

b/c the conducting airways do not exchange gases with the blood, they are known as the anatomic dead space

Question 5

B/c a sign. portion of inspired air never reaches an exchange surface, a more accurate indicator of ventilation efficiency is…

Answer 5

ALVEOLAR VENTILATION, the volume of fresh air that reaches the alveoli each min

Question 6

Alveolar ventilation

Steps:

Answer 6

1. At end of inspiration, fresh air from the atmosphere (yellow) fills the ~150 mL of the dead space and lung volume is at its maximum for a tidal breath.
2. As you expire, the ~150 mL of fresh air in the dead space is expired, along with 350 mL of low oxygen air (blue) from the alveoli. The dead space then fills with ~150 mL of low oxygen air from the alveoli.
3. As you inspire , the 150 mL of low oxygen air in the dead-space re-enters the alveolus along with 350 mL of fresh air from the tidal breadth. The other 150 mL of fresh air left from the tidal inspiration now occupies the dead space.

Question 7

Because the volume of the dead space does not change, depth of breath is…

Answer 7

far more important in increasing alveolar ventilation than respiratory rate

Question 8

Alveolar ventilation can be drastically affected by changes in the rate or depth of breathing…

Answer 8

MAXIMUM VOLUNTARY VENTILATION, which involves breathing as deeply & quickly as possible, may increase total pulmonary ventilation to as much as 170 L/min

Question 9

Increasing alveolar ventilation by…

Answer 9

increasing breathing rate and depth (hyperventilation) increases alveolar PO2 and decreases PCO2 within physiological limits.

Question 10

Decreasing alveolar ventilation by…

Answer 10

decreasing breathing rate and depth (hypoventilation) decreases alveolar PO2 and increases PCO2 within physiological limits.

Question 11

We find only v. small swings in PO2. Why?

Answer 11

1) the amount of O2 that enters the alveoli with each breath is roughly = to the amount of O2 that enters the blood, &
2) the amount of fresh air that enters the lungs with each breath is only a little more than 10% of the total lung volume at the end of inspiration

Although alveolar gases do not change much with quiet breathing, changes in alveolar ventilation can sign. affect the amount of fresh air & O2 that reach the alveoli

Question 12

Ventilation patterns

Answer 12

1. Eupnea
2. Bradypnea
3. Tachypnea
4. Hypoventilation
5. Hyperventilation
6. Dyspnea
7. Apnea

Question 13

Eupnea =

Answer 13

breathing is normal quiet (tidal) breathing; 12-20 breaths per minute.

Question 14

Bradypnea =

Answer 14

decreased respiratory rate compared to normal (<12 breaths/minute)

Question 15

Tachypnea =

Answer 15

increased respiratory rate and decreased depth compared to normal (panting). (>20 breaths/min)

Question 16

Hypoventilation =

Answer 16

decreased alveolar ventilation (due to decreased respiratory rate and depth (<12 breaths per minute).

Question 17

Hyperventilation =

Answer 17

increased alveolar ventilation (due to increased respiratory rate and depth (>20 breaths/minute).

Question 18

Dyspnea =

Answer 18

shortness of breath and difficulty breathing (a severe symptom of COVID-19, pneumonia and many other diseases).

Question 19

Apnea =

Answer 19

period of cessation of breathing. May occur in association with some breathing disorders (e.g. sleep apnea).

Question 20

Hypoventilation when

Answer 20

less fresh air enters the alveoli, alveolar PO2 ↓’s & alveolar PCO2 ↑’s

Question 21

Hyperventilation as

Answer 21

AV ↑’s, alveolar PO2 ↑’s & alveolar PCO2 falls

Question 22

Ventilation perfusion coupling

Answer 22

It is important to match the rate of air flow (VENTILATION) into groups of alveoli with the rate of blood flow (PERFUSION) past those alveoli.
- otherwise, blood draining poorly ventilated alveoli will mix with that from well-ventilated alveoli, decreasing the average PO2 of systemic arterial blood

Question 23

Ventilation/perfusion matching involves…

Answer 23

the local regulation of smooth muscle tone in BOTH the bronchioles and pulmonary arterioles in response to changes in the PCO2 and PO2 of the air, blood, or interstitial fluid (ISF) surrounding these structures.

Question 24

External respiration:

Answer 24

1) Moving O2 from the atmosphere to the alveolar exchange surface
2) Gas exchange must occur across the alveolar-capillary interface
3) BF (perfusion) past the alveoli must be high enough to pick up the avail. O2

Question 25

Bronchioles

Answer 25

PCO2 increases - dilate

PCO2 decreases - constrict

PO2 increases - (constrict)

PO2 decreases - (dilate)

Question 26

Pulmonary Arteries

Answer 26

PCO2 increases - (constrict)

PCO2 decreases - (dilate)

PO2 increases - (dilate)

PO2 decreases - constrict

Question 27

Systemic Arteries

Answer 27

PCO2 increases - dilate

PCO2 decreases - constrict

PO2 increases - constrict

PO2 decreases - dilate

Question 28

Ventilation perfusion coupling

The response of pulmonary arterioles to changes in PCO2 and PO2 is…

Answer 28

opposite to that of systemic arterioles. For example, when PCO2 is high (and PO2 is low) in an organs tissues, it indicates a need for more oxygen. So vasodilation of the systemic arterioles occurs to increase blood flow, bringing more O2 to the tissue and clearing CO2 faster. In contrast, high PCO2 (low PO2) in the lung tissue (alveoli) indicates that that section of lung will not oxygenate the blood well. So vasoconstriction occurs in order to send the blood to an area of lung tissue where adequate gas exchange can take place. See Figure 17.14 in the text for a full list of effects.

Question 29

Ventilation perfusion coupling

Example:

Decreased ventilation to area of lung

Answer 29

1. Decreased ventilation to area of lung
2. Pulmonary blood ↓ PO2 , ↑PCO2
3. Vasoconstriction of pulmonary arterioles
4. Decreases blood flow (i.e. ↓ perfusion)
5. Perfusion decreased to match decrease in ventilation
6. Diversion of blood flow away from local area of poor ventilation toward areas with better ventilation

Question 30

Ventilation perfusion coupling

Example:

Decreased blood flow to area of lung

Answer 30

1. Decreased blood flow to area of lung
2. Alveoli ↓ PCO2, ↑ PO2 (compared to normal – since blood is no longer placing CO2 into or taking O2 out of it)
3. Bronchoconstriction
4. Decreases air flow (i.e. ↓ ventilation)
5. Ventilation decreased to match decrease in perfusion
6. Diversion of air flow away from local area of poor perfusion toward areas with better perfusion

Question 31

Ventilation perfusion coupling

Conditions that cause a decrease in ventilation:

Answer 31

1. Pneumonia
2. Asthma
3. COPD (Chronic Obstructive Pulmonary Disorder).

Question 32

Ventilation perfusion coupling

Conditions that cause a decrease in perfusion:

Answer 32

1. Pulmonary embolism