Respiratory Physiology

Question 1

McFadden et al (1968)

Answer 1

Measured minute and alveolar ventilation in relation to FEV1 and found that asthma is associated with alveolar -hyper-ventilation

Question 2

V/Q matching in asthma

Answer 2

Studies have shown V/Q mismatch in asthma

Question 3

What is type I respiratory failure also called?

What is the Co2 level?

Answer 3

Gas exchange failure

Co2 level is low or normal

Question 4

West et al (1964)

Answer 4

Characterised the distribution of blood flow in the vertical plane of the lung.
In a dog, inhaled radioactive xenon isotope, scanned the lungs(A). Then rebreathed into a bag for 2 mins and rescanned (A). Dividing A by B gives pulmonary blood flow per unit lung volume,
They showed very little blood flow at the top of the lung.

They described 3 zones, zone I at the top of the lungs where alveolar pressure is greater than arterial pressure and so there is arterial collapse. Zone II where alveolar pressure is lower than arterial but greater than venous (waterfall zone). Here, blood flows in pulses as pressure builds up in the artery due to too high a resistance at the venous end of the capillary until it is enough to overcome the alveolar pressure and then it flows.
Zone III where arterial and venous pressure are both greater than alveolar pressure. This is the biggest zone of the lung in health.

Question 5

When does zone I and II of the lung become bigger?

Answer 5

During positive airway pressure ventilation.

Question 6

Prisk et al (1994)

Answer 6

Showed that even in space where there is the absence of gravity, pulmonary blood flow remains inhomogenous.

Question 7

Grunig et al (1997)

Answer 7

Showed that during exercise, pulmonary vascular resistance falls, allowing pulmonary arterial pressure to remain relatively constant.
Pressure measured using doppler cardiography.

Question 8

Pulmonary arterial hypertension

Answer 8

Vessel walls become thickened and less compliant, flow cannot increase without an accompanying increase in pressure. Leads to pulmonary oedema. Can cause peripheral odema as the right heart cannot keep up, produces a venous backlog.

Question 9

What is Cor pulmonale?

Answer 9

It is heart problems arising from a pulmonary cause.

Question 10

Smith et al (2009)

Answer 10

Showed acute pulmonary hypertension in healthy volunteers ascending to 4300m

Question 11

Hodson et al 2016

Answer 11

Hypoxia induced proliferation in the carotid body and ventilatory acclimation to altitude is HIF-2 but not HIF-1 dependant.

Question 12

Calbet et al (2002)

Answer 12

Isovolaemic haemodilution at altitude doesn’t reduce execercise capacity at altitude. No benefit to the increased haematocrit?

Question 13

Krogh and Lindhard, 1913

Answer 13

Proposed the concept of cortical irradiation in control of breathing during exercise.
They used tasks where the power output was the same but the degree of conscious effort was greater (through partial muscle paralysis) - breathing increased in that group

Question 14

Effect of hypnosis on ventilatory response to exercise

Answer 14

Using hypnosis to reduce conscious effort reduces exercise induced hypernea.

Question 15

Eldridge et al

Answer 15

Stimulated the hypothalamic motor area in cats, produced an increase in heart rate and ventilatory rate. However, unlike exercise as blood pressure rose as well.

Question 16

Dejours

Answer 16

First person to suggest that only a neurohumoral response could account for the step change response in control of breathing during exercise.

Question 17

What are the 3 phases of the ventilatory response to excercise?

Answer 17

Phase I: initial rapid increase in ventilation, neurally mediated as so rapid

Phase II: gradual increase in breathing over several minutes, humorally mediated

Phase III: If below the AT, breathing plateaus, if above the AT, continual steady increase.

Question 18

What happens to arterial PCO2 during exercise?

Answer 18

Importantly, it remains constant. This means that there is no feedback signal from CO2 to manipulate breathing.

CO2 does rise in very high intensity exercise, by definition this is not sustainable.

Question 19

What happens PO2 and pH during exercise?

Answer 19

They remain constant

Question 20

Eldridge et al

Answer 20

Showed that fictive activity increases phrenic nerve activity. This shows the importance of the central drive to breathe during exercise.

Question 21

Neural and Humoral dog experiment (Kao 1963)

Answer 21

Vascular system of a dog re-plumbed so that the humeral demands are met by a separate dog. Stimulation of the muscles of the “neural dog” increased the ventilatory rate, showing the role for a neural feedback from muscles in control of breathing during exercise.

Question 22

Adams et al (1984)

Answer 22

Stimulation of muscles in paraplegic humans does not cause an increase in ventilation.
This is evidence against the neural muscle feedback theory, but can be explained by compensation by other mechanisms

Question 23

Mcclosky and Mitchell (1972)

Answer 23

Showed that stimulation of muscle in decorticate cats increased blood pressure and that this response was abolished by lesion at the dorsal root.

Question 24

Role for cardio dynamic hyperpnoea in control of breathing during exercise?

Answer 24

Wasserman (1974): increased cardiac output by infusion of isoproterenol, measured ventilation and found that it increased. Simultaneous infusion with propranolol (to inhibit the increase in cardiac output) inhibited the rise in breathing.

Banner et al (1988) showed a normal ventilatory response to exercise when the early rise in CO was inhibited, evidence against the theory but can be explained by redundancy in the system.

Question 25

Somjen 1992

Answer 25

Proposed that the brain has learned the adequate ventilatory response to excercise through trial and error over many years during development. Learned through comparison of ventilatory response, perceived effort and blood gas composition.

Question 26

Holdsworth et al (2020)

Answer 26

British soldiers on expedition in the Himalayas, Iron infusion to see if it affected pulmonary arterial pressure, no change seen in pulmonary pressure (but maybe because low sample size and many soldiers had to drop out of the study). Improved metrics of RV function, SpO2, index of SV

Question 27

Metabolic changes at altitude

Answer 27

• Increased angiogenesis (Wahl et al)
• Downregulation of mitochondrial oxygen consumption (Papandreou et al)
• With towards anaerobic metabolism
• Reduction in mitochondrial density, in acclimatised climbers and Tibetan Sherpas (Howald, 1990) (Kayser, 1991)

Question 28

Aragones et al (2008)

Answer 28

Phd KO mouse

Question 29

Formenti et al (2010)

Answer 29

Metabolic changes in Chuvash polycythemia.

Question 30

Ballester et al 1989

Answer 30

Demonstrated that V/Q mismatch is worsened by high flow oxygen

Question 31

Eckert 2013 (2 points)

Answer 31

Heterogeneity of OSA

PCRIT values -5 to 2

Question 32

Sutherland 2019

Answer 32

Obesity as a risk factor in OSA, most pronounced in asian population

Question 33

Sands 2014

Answer 33

Genioglossus muscle activity is protective OSA

Question 34

OSA studies

Answer 34

Sands 2014
Sutherland 2019
Eckert 2013
Eckert 2013
Loop gain
MND
PCRIT
Arousal threshold