Pressure & Gas Exchange (Respiratory System)

Question 1

What is transpulmonary pressure?

Answer 1

Transpulmonary pressure is the Pleura difference between the intra-pulmonary pressure found within the lungs and the intrapleural pressure found in the pleura surrounding the lungs.

Question 2

Describe pleural pressure.

Answer 2

Although the pleural pressure changes slightly throughout inhalation and exhalation, it continually remains more negative than atmospheric pressure and is always negative in comparison to the intrapulmonary pressure

Question 3

What is Boyle’s Law?

Answer 3

The inverse relationship between volume and pressure where, as volume increases, pressure decreases and vice versa. The intrapulmonary pressure, or pressure inside the lungs, changes in response to the changes in the volume of the lung.

Question 4

Describe the relationship between volume and pressure during inhalation and exhalation.

Answer 4

Inhalation: increased volume, decreased pressure
Exhalation: decreased volume, increased pressure

Question 5

What is intrapleural pressure?

Answer 5

The slightly negative pressure that exists between the two plerual layers.

Question 6

Describe the pulmonary pressures during inspiration.

Answer 6

Pleural pressure becomes more negative during inspiration, as the recoil tendency for the lungs is higher, which tends to cause transpulmonary to increase as well.

Question 7

What is brinchodilation?

Answer 7

Increase in bronchiole diameter: Epinephrine and sympathetic stimulation; increased airflow

Question 8

What is bronchcontstriction?

Answer 8

Decrease in diameter: Histamine, parasympathetic nerves, cold air, and chemical irritant; Decrease airflow

Question 9

What is pulmonary compliance?

Answer 9

Ease with which the lungs can expand.

Question 10

How does surfactant affect pulmonary compliance?

Answer 10

Surfactant secreted by great cells of alveoli disrupts hydrogen bonds between water molecules and thus reduces the surface tension: increases compliance and decreases resistance.

Question 11

What is the anatomical dead space?

Answer 11

The conduction zone of the airway where there is no gas exchange. (150 mL)

Question 12

What is the physiologic (total) dead space?

Answer 12

Anatomical dead space + pathological alveolar dead space. In pulmonary disease, some alveoli unable to exchange gases.

Question 13

What is the alveolar ventilation rate (AVR)?

Answer 13

Air that ventilates alveoli (350 mL) x respiratory rate (12 bpm) =. 4,200 mL/min; measurement is relevant to the body’s ability to get oxygen to the tissues and dispose of carbon dioxide.

Question 14

What is the forced expiratory volume (FEV1)?

Answer 14

% of vital capacity that can be exhaled in a given time interval; Healthy adult reading is 75% to 85% in 1 second.

Question 15

What are obstructive disorders?

Answer 15

Airway diameter decreased due to inflammation and smooth muscle contractions, or bronchiolar secretion. Reduced FEV1

Question 16

What are restrictive disorders?

Answer 16

Reduction in pulmonary compliance and decrease in gas exchange. Reduced TLC.

Question 17

Describe the composition of air by their partial pressures?

Answer 17

PN2 = 78.6% × 760 mm Hg = 597 mm Hg
* PO2 = 20.9% × 760 mm Hg = 159 mm Hg
* PH20 = 0.5% × 760 mm Hg = 3.7 mm Hg*
* PCO2 = 0.04% × 760 mm Hg = 0.3 mm Hg
* PN2 + PO2 + PH20 + PCOz = 760 mm Hg

Question 18

Describe alveolar gas exchange.

Answer 18

Air in the alveolus is on contact with a film of water covering the alveolar epithelium, gases diffuse down their gradients until the partial pressure of each gas in the air is equal to its partial pressure.

Question 19

Describe the partial pressures in the lung during pulmonary gas exchange.

Answer 19

PO2=104 mm HG in alveolar air versus 40 mm Hg in arriving blood
PCO2 = 46 mm Hg in arriving blood versus 40 mm Hg in alveolar air.

Question 20

Describe the partial pressures in the lung during systemic gas exchange.

Answer 20

PO2 = 95 mm Hg in arriving blood versus 40 mm Hg in tissue
PCO2 = 46 mm Hg in tissue versus 40 mm Hg in arriving blood