Chapter 9: Respiratory System Under Stress

Question 1

By what amount can oxygen consumption increase during exercise?

Answer 1

Ten-fold or more, from 300mL/min to 3000mL/min (6000mL/min in trained athletes!)

Question 2

What happens to the respiratory exchange ratio during exercise?

Answer 2

Instead of sitting at 0.8, it increases to 1.0 or even slightly higher

Question 3

How can the respiratory exchange ratio exceed 1.0?

Answer 3

Production of lactic acid during exercise drives the respiratory exchange ratio higher

Question 4

What level of exercise is required to raise blood lactate concentrations?

Answer 4

Severe exercise

Question 5

What is the first and best response to high altitude hypoxia?

Answer 5

Hyperventilation

Question 6

What long-term compensation does the body engage in to acclimatize to high altitude?

Answer 6

Increased RBC production (hypoxia induces erythropoietin release from the kidney)

Question 7

What is the downside of altitude-induced polycythemia?

Answer 7

Sludgy blood

Question 8

Other than hyperventilation and polycythemia, name two other physiological changes at high altitude

Answer 8

Increase the number of capillaries per unit volume in peripheral tissues and alter oxidative enzymes inside cells

Question 9

What does the combination of alveolar hypoxia-induced pulmonary vasoconstriction and polycythemia bring about?

Answer 9

Pulomonary hypertension - right ventricular hypertrophy

Question 10

What effect does breathing a helium-oxygen mixture have on a diver’s risk of decompression sickness?

Answer 10

Decreases it

Question 11

Is it easier or harder to breather a helium-oxygen mixture versus atmospheric air?

Answer 11

Easier - helium much less dense than nitrogen

Question 12

What happens to the risk of inert gas narcosis when breathing a helium-oxygen mixture?

Answer 12

Decreases it

Question 13

What happens to venous return in an astronaut experiencing 0g?

Answer 13

Increases, no pooling of blood in legs or other hydrostatic edema

Question 14

How does blood flow in the lung change in 0g?

Answer 14

More uniform perfusion of upper and lower lobes

Question 15

Where do large particles get filtered by breathing?

Answer 15

Stokes Law - large particles (>1.0 micron) traverse stream lines of uniform flow when the stream lines bend radically (such as in the back of your nose). These particles are impacted into the mucosal lining, where they stick. Some make it into the bronchi, but not very far

Question 16

Where and by what mechanism do medium-sized particles (0.1-1.0 micron) get filtered?

Answer 16

Medium sized particles sediment out of inspired air and deposit in the small airways (terminal and respiratory bronchioles), more or less at the point where flow transitions from bulk to diffuse due to exponentially increasing airway cross section

Question 17

Where does coal miner’s lung manifest?

Answer 17

Terminal and respiratory bronchioles

Question 18

Where do the smallest particles (

Answer 18

Some deposit in the alveoli by simple diffusion, others are breathed back out with expired air

Question 19

Which increases more during exercise, heart rate or alveolar ventilation?

Answer 19

Alveolar ventilation increases from 7.5 L/min to up to 120 L/min, while heart rate maybe only triples in rate.

Question 20

Why does heart rate increase so much less than ventilation during exercise?

Answer 20

Moving liquid is much harder. Also, analysis using the Fick equation shows that since you can’t increase the O2 content of inspired air, increasing O2 in the lungs has to happen through increased ventilation. Oxygen delivery to the tissues increases both by increasing O2 gradient upstream and downstream of target tissues and by increasing flow rate, a twofer.

Question 21

What happens to pulmonary vascular resistance on a newborns first breaths? Why?

Answer 21

Decreases when the smooth muscles relax

Question 22

What happens to systemic vascular resistance on a newborns first breaths? Why?

Answer 22

Increases when the parallel placental flow goes away, decreasing the number of paths around the blood flow circuit