Gas Exchange and Transport

hypoxia

when the tissues are deprived of oxygen (general)

hypercapnia

when the blood has too much CO2 (general)

O2, CO2, pH

There are sensors in the body for —, —, and —

O2

there is a larger gradient of which gas in the blood?

CO2, O2

We are very sensitive to small increases in —, but we can tolerate large drops in —

hypoxic hypoxia

Low arterial O2; low oxygen in the blood entering tissues

anemic hypoxia

decreased total amount of O2 bound to hemoglobin

ischemic hypoxia

hypoxia caused by reduced blood flow

histotoxic hypoxia

failure of cells to use O2 because cells have been poisoned

greater

PO2 of alveolar air is — than the PO2 of the blood

greater

PO2 of blood is — than the PO2 of the tissues

less

PCO2 of alveolar air is — than the PCO2 of the blood

greater

PCO2 of tissue is — than the PCO2 of the blood

CO2

— flows from the blood to the alveoli

O2

— flows from the alveoli to the blood

CO2

— flows from the tissues to the blood

decreases

Higher altitude — PO2

concentration gradient

— is the primary factor affecting gas exchange

inversely

Diffusion is — proportional to distance²

emphysema

the air sacs in the lungs (alveoli) become damaged. Over time, they lose their elasticity and break down, making it hard to breathe.

• The result is a high-compliance/low-elastic recoil lung with fewer and larger alveoli and less surface area for gas exchange.

fibrotic lung disease

• scar tissue thickens the alveolar wall

• Diffusion of gases through this scar tissue is much slower than normal.

  • This scarring makes the lungs stiff, reduces their ability to expand, and limits the ability to transfer oxygen into the bloodstream.

pulmonary edema

fluid backs up in the pulmonary circulation as a result of congestive heart failure

• Fluid leaves pulmonary capillaries as a result of hydrostatic pressure and pool between the capillaries and the alveoli

• excess fluid increases the diffusion distance between the alveolar air space and the blood.

decreases

increased airway resistance — alveolar ventilation

asthma

increased airway resistance decreases alveolar ventilation

large

If a gas is very soluble, — numbers of gas molecules go into solution at a low gas partial pressure.

oxygen

— is not very soluble in water

CO2

— is much more soluble in water

normal, lower

• Oxygen’s low solubility also means oxygen is slower to cross the increased diffusion distance present in pulmonary edema.

  • Diffusion of oxygen into alveolar capillaries does not have time to come to equilibrium before the blood has left the capillaries.

    • Therefore, even though alveolar PO2 is — in those with pulmonary edema, the arterial PO2 is —

2%

— of oxygen in the body is dissolved in the blood

98%

— of oxygen is bound to hemoglobin

oxyhemoglobin

Hemoglobin bound to oxygen (HbO2)

7%

Only about — of the CO2 carried by venous blood is dissolved in the plasma.

23%, 70%

 93% of CO2 diffuses into red blood cells, where — binds to hemoglobin (HbCO2) while the remaining — is converted to bicarbonate ion (HCO3-)

respiratory acidosis

when blood PCO2 is elevated so Hb can’t take up H+ and blood pH falls

bicarbonate ions

Most of CO2 the that enters the blood is transported to the lungs as — dissolved in the plasma.

buffer

HCO3- is available to act as a — for metabolic acids, thereby helping stabilize the body’s pH

H+

Hemoglobin within the red blood cell acts as a buffer and binds —

carbonic anhydrase

Enzyme that catalyzes the conversion of carbon dioxide and water into carbonic acid

HCO3−, Cl−

Chloride shift: Process in which red blood cells exchange — for —

amino groups, carbaminohemoglobin

CO2 binds with free hemoglobin at exposed — forming —

surface area

Emphysema reduces respiratory gas exchange by changing

__________.

simple diffusion

What is the main mechanism by which gases move from the alveoli into the blood and cells and back?

hypoventilation

Low alveolar PO2 can be caused by one of two mechanisms. One of them is that the inspired air has low oxygen content. What is the other reason?

pulmonary edema

Which disorder would usually result in a normal alveolar PO2

but a decreased arterial PO2 because of fluid increasing diffusion distance?

Decreased, increased

— carbon dioxide and — oxygen would stimulate decreased respiration

adult respiratory distress syndrome

Hypoxia resulting from fluid accumulation in the alveoli that cannot be corrected by oxygen therapy can lead to

hypercapnia

High carbon dioxide concentration in body fluids is called

98%

Approximately what percentage of the total blood oxygen is bound to hemoglobin instead of dissolved in plasma?

low, high, high, high

greatest oxygen unloading from hemoglobin results from — pH, — temperature,. — PCO2, and — 2,3-BPG

23

About —% of the carbon dioxide in blood is carried by hemoglobin, bound to amino groups

Increased, decreased

A patient with an opioid overdose has a decreased ventilation rate. Which of the following would you expect?

— carbon dioxide in the blood and — pH

bicarbonate ion

In which form is most carbon dioxide transported in the

blood?

lower

For maximum efficiency in loading oxygen at the lungs, the temperature should be slightly — than normal body temperature.

increases, anemia

Chronic hypoxia — 2,3 PG production in blood and can result from —

sigmoidal

what is the shape of the oxygen-hemoglobin dissociation curve?

altitude

composition of inspired air is influenced by —

CNS depression

— causes decreased rate and depth of breathing

obstructive

— lung disease increases airway resistance

restrictive

— lung disease decreases lung compliance

decreases

increased airway resistance — alveolar ventilation

surface area

emphysema decreases — of alveoli

decreased, normal

hypoventilation is when air moving into alveoli is — and O2 content of air is —

emphysema

— decreases elastance of the lungs

permeability

fibrotic lung disease decreases — of the lungs

lower

the more soluble a gas is, the — the partial pressure required to force the gas into solution

20

CO2 is — times more soluble than O2

CO x (arterial O2 - venous O2)

oxygen consumption can be calculated by:

amount of O2 bound / max that could be bound x 100

% saturation of hemoglobin = 

RBC

carbonic anhydrase can be found in the —

3 mL O2/L blood

without hemoglobin, the O2 carrying capacity is

200 mL O2/L blood

with hemoglobin, the O2 carrying capacity is

type I alveolar cells, capillary endothelium

The transfer of oxygen from alveoli to blood requires diffusion across the barrier created by — and the —

decrease, increase, increase

Pathological changes that adversely affect gas exchange include

(1) a — in the amount of alveolar surface area available for gas exchange

(2) an — in the thickness of the alveolar-capillary exchange barrier

(3) an — in the diffusion distance between the alveolar air space and the blood.

emphysema

The irritating effect of smoke chemicals and tar in the alveoli activates alveolar macrophages that release elastase and other proteolytic enzymes.

- Less elastance and surface area

what condition???

alveolar flooding

In severe cases, if edema exceeds the tissue’s ability to retain it, fluid leaks from the interstitial space into the alveolar air space, flooding the alveoli.

adult respiratory distress syndrome

alveolar flooding can cause —

bound to hemoglobin

Where is most of the arterial O2 found?

weakly

Hemoglobin molecules are composed of 4 protein subunits. Each subunit contains a heme group that can bind — to oxygen.

right

Hb + O2 ↔ HbO2

When O2 increases, the reaction shifts —

left

Hb + O2 ↔ HbO2 

When O2 decreases, the reaction shifts —

large

Below PO2 of 40 mm Hg, where the curve is steeper, small changes in PO2 cause relatively — releases of O2 from hemoglobin.

decreases

An increase in pH — Hb’s affinity for oxygen.

decreases

An increase in temperature — Hb’s affinity for oxygen

decreases

An increase in PCO2 — Hb’s affinity for oxygen

decreases

The metabolite 2,3-BPG — Hb’s affinity for oxygen.

increased

A left shift in the curve indicates — binding affinity

decreased

A right shift in the curve indicates — binding affinity.

in, out

the chloride shift transports bicarbonate — and the Cl- — of the RBC in the venous blood