Respiratory Physiology

Question 1

What are the 5 functions of the respiratory tract?

Answer 1

1. Gas exchange
2. Heat exchange
3. Blood reservoir
4. Immunological functions
5. Hormone/enzyme functions

Question 2

Name area of the URT and the LRT system

Answer 2

URT: goes down to the glottis - nasal cavity, mouth, sinuses, pharynx
- functions to increase humidity/filter/warm inspired air

LRT: from glottis to alveoli

Question 3

What are the mechanics of respiration

Answer 3

Inspiration is independent on

Question 4

What are the controls of respiration?

Answer 4

1. Central : in the medulla
   2.chemoreceptors :
   - central chemoreceptors - proiamry control is CO2, located in the medulla on floor of 4th ventricle, detects changes in PaCo2 via change of PH in CSF
   - peripheral chemoreceptors - in the aorta and carotid bulb, reponds to PAO2 <55mmHg, results in intense sympathoadrenal activation
   - involves in HVR
2. Lung receptors:
   irritant - causes cough response
   Stretch receptors - prevents lung over inflation, becomes active during exercise - Herring Breuer reflex
3. Peripheral : muscle spindles - will stim respiratory response before CO2 rises
4. Hormonal:

Question 5

Explain the hypoxic ventilator response

Answer 5

With decreasing PAO2, this is detected by the peripheral chcemoreceptors. When PAO2 < 55mmHg (equiv to alt at 10kft), stimulation of sympathetic response causes automatic hyperventilation

Question 6

What is Fick’s Law

Answer 6

Law that states the rate of gas transfer is £ SA of the membrane that it is diffusing across & PP gradient and 1/£ to the thickness of the membrane

Vgas = A/T . D(P1-P2)

D = sol/ MW sq rt

Decrease in Vgas:
Decrease SA : emphysema, pneumonia
Increased thickness : pulmonary odena

Question 7

What is the Haldane effect

Answer 7

Describes how with offloading of O2 at the tissues, deoxygenated blood is a better carrier of CO2 as deoxyhaemoglobin, has a higher affinity for CO2 is a better acid buffer

Question 8

What is Pasteur point?

Answer 8

Is the cellular PO2 below which aerobic metabolism cannot occur (~1mmHg)

Question 9

What is ACBC and when is it used?

Answer 9

Aircrew controlled breathing cycle

Used to reduce atelectasis and hypocapnia

Used as part of G warm up, at completion of high G enegaement, after removing chest garments, every hour during long transits, with PE recovery action - use w mask