NRSG 202- Control of Oxygenation

What is the term for high CO2 levels?

Hypercapnea

What is the term for low CO2 levels?

Hypocapnea

What is the term for high O2 levels?

Hyperoxia

What is the term for low O2 levels?

Hypoxia

In normal breathing, an individual breathes _______ mL/min

200

2 respiratory centesr in the nervous system

1. Medullary respiratory center (medulla oblongata)

2. Pontine respiratory group (pons)

2 groups of neurons in the medullary respiratory center

• Dorsal respiratory group (DRG/inspiratory area)

• Ventral respiratory group (VRG)

2 mechanisms of the DRG during normal breathing

• Neurons send impulses down the phrenic nerve towards the diaphragm

• Neurons send signals down the intercostal nerve to the external intercostal muscles

How long is the DRG's impulse on, and what does this cause?

Impulse is on for about 2 seconds → causes inspiration

How long is the DRG's impulse off, and what does this cause?

Impulse is off for about 3 seconds → causes expiration

DRG mechanism during forced inhalation

During forced inhalation, it stimulates the VRG, which triggers accessory inspiratory muscles to contract

VRG structure and function

Some neurons in the pre-Botzinger complex are pacemaker cells and set the basic rhythm of breathing by sending impulses to the DRG

VRG mechanism during forced exhalation

send impulses to accessory muscles for forced exhalation

Which respiratory group(s) is/are involved in forced inhalation?

DRG + VRG

Which respiratory group(s) is/are involved in forced exhalation?

VRG only

Pontine respiratory group function

Activated when the normal breathing rhythm must be modified

Pontine respiratory group mechanism

Transmits impulses to the DRG that helps to modify breathing rhythm

6 factors that affect the overall regulation of breathing

1. Chemoreceptors

2. Stretch receptors

3. Limbic system

4. Cortical Control

5. Temperature

6. Pain

2 types of chemoreceptors

1. Peripheral chemoreceptors

2. Central chemoreceptors

Peripheral chemoreceptors location

Located in the aortic and carotid bodies

Peripheral chemoreceptors function

monitor pCO2, pO2, and [H+]

Are peripheral chemoreceptors more sensitive to CO2 or O2?

CO2

What occurs to pH and [H+] when PCO2 is increased?

decreased pH and increased [H+]

What occurs when the peripheral chemoreceptors sense high PCO2, high [H+], and low PO2

the DRG is activated and hyperventilation occurs (the respiratory rate and depth are increased)

Effect of hyperventilation caused by stimulation by the DRG

Leads to a loss in CO2 and gain in O2

Central chemoreceptors location

located in the brainstem

Central chemoreceptors function

 respond to changes in PCO2 and [H+] in the cerebrospinal fluid (CSF)

What occurs when the central chemoreceptors sense high PCO2 and high [H+]?

the DRG is activated and hyperventilation occurs (the respiratory rate and depth are increased)

What is the general effect of high CO2 (in relation to DRG)?

High CO2 stimulates the DRG → hyperventilation → reduction in CO2

What is the general effect of low CO2 (in relation to DRG)?

Low CO2 does not stimulate the DRG → normal rhythm

How do swimmers utilize hyperventilation?

Swimmers will hyperventilate on purpose, which causes their CO2 levels to drop, so it will take longer for them to increase when holding their breath

Why could hyperventilation prior to performance be dangerous for swimmers?

if the CO2 levels are low and the O2 levels are low, the swimmer could faint or start breathing underwater

Stretch receptors location (respiratory system)

 located in the walls of the bronchi and bronchioles

Stretch receptors function (respiratory system)

work to prevent overinflation of the lungs

Hering-Breuer Reflex

as the stretch receptors in the bronchi and bronchioles are stretched, they send a signal to the vagus nerve (X), which sends an inhibitory signal to the DRG, preventing overinflation

Manifestation and use of Hering-Breuer Reflex in different ages

The Hering-Breuer Reflex is activated for normal breathing in newborn, but mostly for overexertion in adults

Limbic control of breathing

emotional stimuli cause modification in breathing (hypothalamus)

Cortical control of breathing

voluntary altering of the breathing handled by the cerebral cortex

Temperature affect on regulation of breathing

• if temperature (metabolism) increases, respiratory rate increases

• if temperature (metabolism) decreases, respiratory rate decreases

Effect of sudden drop in temperature on breathing

leads to apnea (stopping of breathing) only for a moment

Impact of sudden pain on breathing

apnea

Impact of prolonged somatic pain on breathing

increase in respiratory rate

Impact of prolonged visceral pain on breathing

decrease in respiratory rate

Hyperventilation/overventilation

a response to an increase in PCO2 that causes an increase in respiratory rate and depth

Effect of hyperventilation on gas exchange

leads to more CO2 out (main function) and more O2 in

Hyperpnea

response to a decrease in PO2 that causes an increase in respiratory depth (volume of air)

Effect of hyperpnea/deep breathing on gas exchange

leads to increased O2 in

Acclimatization

how the body responses to changes in pressure

PO2 in alveoli must be ______(lower/higher) than the PO2 in the blood for external respiration

higher

What is the effect of a larger difference between PO2 in alveoli and PO2 in blood in external respiration?

Faster rate of diffusion

PO2 at sea level is approximately ______ mmHg (______% O2)

159, 20.9

What happens to PO2 at higher elevations?

lower

PO2 at 10K and 20K feet above sea level

• 10K feet above sea level: PO2 = 110 mmHg

• 20K feet above sea level: PO2 = 73 mmHg

Immediate acclimatization to high elevations

hyperventilation

Kidneys effect on acclimatization to high elevations

decreased CO2 causes an increase in pH due to hyperventilation, and kidneys compensate to bring the pH back to normal

Hb saturation at high elevations

Hb saturation drops at first, which leads to an increase to erythropoietin → more RBCs → increase

What happens total oxygen at high elevations?

Total oxygen will drop at first, then it will increase but not to sea level levels

Why is it important to stay hydrated at high elevations?

Drinking water helps to decrease hematocrit to normal level when RBCs increase

Predict whether breathing rate would be increased, decreased, or unchanged when you are on Mont Blanc (compared to at sea level). Explain.

ncrease - chemoreceptors are stimulated by low O2, and stimulate the DRG to increase the breathing rate

Predict whether the percent saturation of hemoglobin would be increased, decreased, or unchanged when you are on Mont Blanc (compared to at sea level). Explain.

decrease - low oxygenation levels lead to low saturation

Predict whether the PO2 at high hemoglobin is 50% saturated (P50) would be increased, decreased, or unchanged when you are on Mont Blanc (compared to at sea level). Explain.

increased - more oxygenation is needed to get to full saturation

Predict what would happen to your arterial PCO2 (PaO2) when you are on Mont Blanc. Why do you expect that change?

Breathing rate increased, which causes hyperventilation → PCO2 levels drop