Respiratory 2 Flashcards by Wadhha Alajmi

Characteristics of pulmonary circulation

Low resistance
High compliance
Low pressure (compared to systemic circulation)

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What is the significance of the low perfusion pressure in the pulmonary circulation?

Low perfusion pressure = low filtration pressure = reducing the possibility of developing pulmonary edema and helps keep the alveoli dry

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What is the normal cardiac output

5 L/min

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Describe the distribution of pulmonary blood flow in supine position

MAP is the same all over the lungs = uniform perfusion pressure in lungs

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Describe the distribution of pulmonary blood flow in standing position

Gravity changes the hydrostatic pressure and divides the lung into 3 zones:
- low flow (apex)
- moderate flow
- maximal flow (base)

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Lowest blood flow is at the ______ of the lung

Apex

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Highest blood flow is at the _______ of the lung

Base

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How is pulmonary blood flow regulated

Systemic arteries dilate (when tissue P02 is low)

to increase the blood flow and oxygen delivery to that hypoxic tissue

Pulmonary arteries constrict (when alveolar PO2 is low)

to divert the blood to better ventilated regions

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When would systemic arteries dilate to regulate pulmonary blood flow

When tissue PO2 is low

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When would Pulmonary arteries constrict to regulate pulmonary blood flow

When alveolar PO2 is low

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What is the driving force for both O2 diffusion and CO2 diffusion ?

Partial pressure differences

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Hypoxia at high altitudes :

Why is it so important to put on your own oxygen mask before assisting others in the case of depressurization at high altitudes?

To stay conscious

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How to calculate partial pressure of inspired oxygen PIO2 ?

PIO2 (trachea) =
( barometric pressure - partial pressure of water) x fraction of inspired oxygen

So….
PIO2 = (PB - PH2O) x FIO2

Constants:
PB = 760 mmHg
PH2O = 47 mmHg
FIO2 = 0.21 (21% of air is made of O2)

NOTE: PB is also known as atmospheric pressure

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PIO2 = (253 - 47) x 0.21 = 43 mmHg

LOW pressure cannot live without oxygen tank

(Normal level around 149-150)

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What is the alveolar air equation for ?

Calculation of partial pressure of O2 in the alveoli

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The alveolar partial pressure of oxygen is about

100 mmHg

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Factors that control transfer of gases across the alveolar capillary membrane

Alveolar surface area (A)
Diffusion constant (D)
Partial pressure difference (P1-P2)
Thickness of membrane (T)

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How to calculate gas diffusion Vgas

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Gas diffusion across the respiratory membrane is directly proportional to

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Gas diffusion across the respiratory membrane is inversely proportional to the ________________.

Thickness (T) of the membrane

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Oxygen is carried in the blood in 2 forms

Dissolved O2
O2 bound to hemoglobin (oxyhemoglobin)

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How is dissolved O2 measured

It is measured clinically in an arterial blood gas sample as PAO2

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Oxygen is carried in the blood in 2 forms : Which form carries the majority of oxygen

Dissolved O2 (MINOR)
- carries 3 mlO2/L of blood
O2 bound to hemoglobin (MAJOR)
- carries 196 mlO2/L of blood

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What color is oxyhemoglobin

Red

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What color is deoxyhemoglobin

Blue

Normal hemoglobin concentration

14-16 gm/dL (Or 150 gm/L)

How to calculate O2 content ?

O2 content = dissolved O2 + O2 hemoglobin

What is cyanosis

Bluish color of skin occurs when blood concentration of deoxyhemoglobin is more than 6 - 8 gm/dL

Two types of cyanosis

Central cyanosis Peripheral cyanosis

Central cyanosis indicates….

Ventilatory problem Low O2 saturation Low cardiac output

Peripheral cyanosis indicates⁣⁣⁣⁣⁣….

Poor circulation in the small peripheral vessels

Explain Hemoglobin – oxygen association/saturation curve

The hemoglobin- oxygen dissociation/saturation curve will shift to the RIGHT at which capillaries ??

Systemic capillaries

When the curve shifts to the RIGHT at systemic capillaries what does that mean

Decreased affinity of hemoglobin to O2 = release of O2 to the tissues

The hemoglobin- oxygen dissociation/saturation curve will shift to the LEFT at which capillaries ??

Pulmonary capillaries

When the curve shifts to the LEFT at pulmonary capillaries what does that mean

Increased affinity of hemoglobin to O2 = faster saturation of hemoglobin

Factors that decrease hemoglobin affinity

(Hint: increase in everything BUT decrease in pH)

Factors that increase hemoglobin affinity

(Hint: decrease in everything BUT increase in pH)

Explain Bohr Effect

Reduced affinity causes __________ shift and ________ O2 saturation

Right Low

Increased affinity causes __________ shift and ________ O2 saturation

Left High

Carbon dioxide is transported in the blood in 3 forms ; what are they and give percentages

Carbon dioxide is transported in the blood mainly as :

Bicarbonate ion (HCO3-) 80-90%

How is CO2 chemically modified as bicarbonate ion?

At the alveoli : bicarbonate is converted to CO2 and H2O At the tissue: CO2 and H2O are converted into HCO3-

Which enzyme converts CO2 and H2O to H2CO3 and the other way around?

Carbon anhydrase

Cellular gas exchange formula

Is the same as gas diffusion formula

What is tissue uptake of O2 at rest

50 mlO2/L

Why does tissue oxygen uptake increase during exercise?

Due to higher internal respiration by the mitochondria to produce ATP for the active tissue

What is hypoxia

A condition in which the tissue was deprived of adequate oxygen supply

There are 4 types of hypoxia

Hypoxemic hypoxia Anemic hypoxia Stagnant hypoxia Histotoxic hypoxia

What is hypoxemic hypoxia

The oxygen pressure in the blood going to the tissues is too low to saturate the hemoglobin

What causes hypoxemic hypoxia

Problems in ventilation, gas diffusion or high altitude

Which type of hypoxia can occur due to high altitude

Hypoxemic hypoxia

What is anemic hypoxia

The amount of functional hemoglobin is too low, and hence the capacity of the blood to carry oxygen is too low

What is stagnant hypoxia

The flow of blood to the tissues is reduced or unevenly distributed

What can cause stagnant hypoxia

Heart failure

What is histotoxic hypoxia

The tissue cells are poisoned by cyanide or sodium azide (pesticides) and are therefore unable to utilize oxygen

What 2 poisons can cause histotoxic hypoxia

Cyanide Sodium azide (pesticides)

The INVOLUNTARY control of breathing involves which components?

- receptors - brain stem control of breathing - respiratory muscles

What type of receptors are involved in involuntary control of breathing

Chemoreceptors for O2, CO2, and pH Mechanoreceptors in the lungs and joints

What part of the brain stem controls involuntary breathing

Medulla oblongata and pons

The VOLUNTARY control of breathing involves what?

Commands from cerebral cortex DIRECTLY to the respiratory muscles

Examples of voluntary breathing

Breath holding Voluntary hyperventilation

Central chemoreceptors are found in

Ventral surface of the Medulla oblongata

Central chemoreceptors sense what?

Hydrogen H+ As it is sensitive to changes in pH of CSF , which indirectly reflects changes in PaCO2 So it responds INDIRECTLY to CO2

Peripheral chemoreceptors are found in

Aortic body and carotid body

Peripheral chemoreceptors sense

Low O2 High CO2 High H+

Mechanoreceptors for breathing include

Stretch receptors Irritant receptors

Which tract is for voluntary control of breathing from the cerebral cortex directly to resp muscles?

Corticospinal tract

Which tract is for involuntary control of breathing from respiratory centers to resp muscles?

Ventrolateral tract

What are the medullary respiratory centers ?

Dorsal respiratory group DRG Ventral respiratory group VRG Pre-Botzinger complex

Dorsal respiratory group DRG is responsible for

Primarily inspiratory

Ventral respiratory group VRG is responsible for

Active in forced breathing (insp. + expir.)

Pre-Botzinger complex is responsible for

Central pattern generator Has pacemaker activity

Pontine respiratory centers

Apneustic center Pnumotaxic center

Function of apneustic center

Excites medullary inspiratory center It’s stimulation causes apneusis (Prolonged inspiration followed by brief expiration)

Function of pneumotaxic Center

Inhibits inspiration and regulates respiratory rate

When it comes to central chemoreceptors, what happens if PaCO2 is high

( high H+ in CSF and low pH) Hyperventilation = PaCO2 decreases back to normal

When it comes to central chemoreceptors, what happens if PaCO2 is low

( low H+ in CSF and high pH) Hypoventilation = PaCO2 increases back to normal

Peripheral chemoreceptors respond to changes in

Arterial PO2, PCO2, and pH

Peripheral chemoreceptors send signals through sensory afferents via which nerves

Glossopharyngeal (CN IX) Vagus (CN X)

An increase in the breathing rate occurs due to

-Decreases in arterial PO2 -increases in arterial PCO2 -Decreases in arterial pH

Effect of hypoventilation on PCO2 and PO2

increases PCO2 Decreases PO2

Effect of hyperventilation on PCO2 and PO2

decreases PCO2 Increases PO2

Respiratory 2 Flashcards

(84 cards)