Respiratory Regulation

Question 1

Why would Oxygen Therapy worsen the condition of a patient with Chronic Respiratory Acidosis?

Answer 1

1. Increasing PO2 would Reduce HYPOXIC Drive.
2. The reduction in HYPOXIC Drive leads to Hypoventilation.
3. Hypoventilation goes increases PCO2, worsening hypercapnia and acidosis.

Question 2

What can cause the body to rely more on HYPOXIC drive rather than pCO2?

Answer 2

1. Chronic CO2 retention can lead to “Desensitization” of peripheral chemoreceptors
2. This prevents CN IX (glossopharyngeal) from sending afferent signals to the brainstem.
3. Appropriate Hyperventilation response is not done to combat the acidosis.

Question 3

Describe the functions of each pertaining to control of the respiratory system.

1. Controller
2. Effectors
3. Sensors

Answer 3

1. Pre-Botzinger complex, VRG and DRG initiate/control the respiratory rhythm from afferent info from receptors.
2. Lung and respiratory muscles carry out controller commands.
3. *Mechanoreceptors - sense stretch of lungs and upper airways
   * Chemoreceptors - sense acid, CO2 and hypoxia (if peripheral ~ carotid bodies) or just acid and CO2 (if central)

Question 4

How does the carotid body chemoreceptors sense Hypoxia? Is it able to sense CO poisoning or anemic conditions?

Answer 4

1. Hypoxia is sensed as changing PO2 or O2 tension.
2. CO and anemia will not stimulate Carotid bodies, since those are not involved with changing PO2, but SaO2 and CaO2, respectively.

Question 5

Describe the 3 classes of Vagal Mechanoreceptors (where found and function)

Answer 5

1. Stretch receptors - slow-adapting mechanoreceptors found in lungs/airways, monitor LUNG INFLATION/DEFLATION
2. Irritant Receptors - these fast-adapting receptors are found in the lungs; associated with COUGH/SNEEZE reflex
3. J-receptors - are non-myelinated nerve endings found in pulmonary vessels; linked to issues with pulmonary circulation (embolism, congestion, drugs)

Question 6

Name the muscles used for during

1. Inspiration
2. Expiration

Answer 6

1. Diaphragm - contracts; external intercostals, SCM, scalene muscles.
2. Rectus Abdominus, Transversus Abdominus, Obliques (internal and external), Internal intercostals

Question 7

How do proprioceptors relate to respiration?

Answer 7

They are activated during lung deflation and involve the accessory muscles and joints during expiration. This might cause the controllers to augment inspiration.

Question 8

Define DLCO

Answer 8

Diffusion limitation Capacity - the higher the better gas exchange
Decreased with pulmonary Fibrosis and with pulmonary edema

Question 9

Define Dynamic Airway Compression

Answer 9

Airways constrict during the Effort Independent Phase of Expiration, thus increasing resistance to flow.

Question 10

Define the significance of Alveolar Dead Space

Answer 10

1. Ventilated and non-perfused alveoli [Q=0]
2. V/Q = INFINITY
3. Pathological: low Cardiac Output, Pulmonary embolism and increases with pulmonary fibrosis.

Question 11

Describe an Absolute Shunt

Answer 11

1. Perfused and non-ventilated Alveoli [V=0]
2. V/Q = 0 (mismatch)
3. Can be increased with Pulmonary Edema

Question 12

Describe the changes in A-a(DO2) within the following scenarios.

1. Pulmonary Fibrosis
2. Increased Elevation
3. Pulmonary Edema

Answer 12

It’s a Physiologic phenomenon that describes the difference in PO2 pressures between alveoli and arteriolar blood.

1. Increased w/ Fibrosis
2. No change in altitude
3. Increased w/ Edema

Question 13

Why does FEV1 increase with pulmonary Fibrosis, a restrictive disease.

Answer 13

Although the inspiration and FVC is changed, alveolar recoil is not changed.