Resp 4 Flashcards
Gases, just like ions and water, move
according to the principles of
diffusion
he partial pressures of the gases
ONLY include the gases that are
dissolved in the plasma
If cells utilize more oxygen than
normal, the gradient —-
which — flow of oxygen
from the blood to the tissues
increases
increases
Tissue PO2 is a function of: (2)
(1) The rate of O2 transport to the tissues in blood (blood flow) (2) The rate at which the tissues use O2.
Increased blood flow and/or
increased metabolism will
result in
more O2 delivery to
the tissues.
Without Hemoglobin, CO would need to be --- L/min to transport sufficient oxygen to meet the needs of the tissues at rest.
83.3
–% of total oxygen content is
dissolved in plasma (PaO2 =
100 mmHg)
2
–% of O2 reversibly binds to
hemoglobin inside of the RBC
98
98% of O2 reversibly binds to
hemoglobin inside of the RBC
-does not contribute to
partial
pressure
Hemoglobin A (α2b2):
4 subunits
each of which each binds 1 O2
molecule.
Iron must be in — state
to bind O2
ferrous (Fe2+)
The amount of oxygen
bound to Hb
depends on: (2)
- Plasma PO2
- Number of binding
sites in RBCs –
depends on the Hb
amount per RBC.
(normally each
RBC contains ~1
million Hb
molecules)
CaO2 =
ml of O2 carried by oxyhemoglobin plus ml of O2
carried dissolved in plasma
skipped
equation
CaO2 =
SaO2 (Hb x 1.34) + 0.003 (PaO2)
SaO2 is the
% saturation of hemoglobin
– Average 97%
Hb represents
g of hemoglobin/100 ml blood
– Average is 15 g Hb/100 ml blood
PaO2 is the
partial pressure of oxygen in arterial blood
– Average is 95 mmHg
Average CaO2 is ~
19.782 ml O2/ 100 ml blood
Reduction in the amount of hemoglobin in the blood significantly reduces the
blood oxygen
content.
2,3-BPG binds to
Beta subunits of deoxy HB and decreases its O2 affinity. It causes more oxygen unloading. Normal Venous PvO2 Normal Arterial PaO2
At a high PO2,
hemoglobin’s
affinity for O2 is
highest.
At a high PO2,
hemoglobin’s
affinity for O2 is
highest.
POSITIVE COOPERATIVITY.
The lower the
PO2, the more
likely
O2 will
dissociate from
hemoglobin
Oxyhemoglobin Dissociation Curve
Shifts to the RIGHT is called the
bohr effect
Oxyhemoglobin Dissociation Curve
Shifts to the RIGHT
indicates:
DECREASED affinity
between hemoglobin
and oxygen
Oxyhemoglobin Dissociation Curve
Shifts to the RIGHT
in this instance,
oxygen
is MORE likely to
dissociate from
Hemoglobin.
RBCs contain 2,3-bisphosphoglycerate
– a metabolic intermediate. Levels of
2,3-BPG increase with (4)
exercise,
hypoxia from high altitude, pregnancy
and chronic lung disease.
Oxyhemoglobin Dissociation Curve
Shifts to the RIGHT
Helps match
O2 delivery to
O2 demand, advantageous
since O2 can be released at
selective tissues.
Oxyhemoglobin Dissociation Curve Shifts to
the LEFT
indicates
an INCREASED affinity between oxygen and
hemoglobin
Oxyhemoglobin Dissociation Curve Shifts to
the LEFT
In this instance,
oxygen is LESS likely to dissociate
from hemoglobin.
Oxyhemoglobin Dissociation Curve Shifts to
the LEFT
caused by (4)
– Decreased PCO2
– Increased pH (ex. 7.6)
– Decreased temperature
– Decreased 2,3-BPG
Carbon Monoxide has a —x greater affinity for
Hemoglobin than Oxygen.
250X
Only small amounts of CO can be lethal
• CO bound to hemoglobin increases
Hb’s affinity for O2 (a left-ward shift in
curve)
Even though CaO2 may be greatly
reduced,
PaO2 of blood may be normal.
Carbon Monoxide-Hemoglobin Curve
Treatment: (2)
- Pure oxygen
* 5% CO2
Presentation of CO Poisoning:
“Common in smoke inhalation,
enclosed exposure to automobile exhaust, or in the wintertime with
home furnaces. Patients present with cherry red skin (classic), flu-
like symptoms, headache, and neurologic symptoms.”
Variants of Hemoglobin (3)
Methemoglobin Hemoglobin F (Fetal Hemoglobin) Hemoglobin S (Sickle Cell)
Methemoglobin (2)
– Heme with Fe3+ does not bind O2 as readily
(reduced affinity) & also causes any heme groups in
the same Hb molecule with heme in the Fe2+ state to
have have higher affinity for bound O2 net effect
is reduced O2 delivery to the tissues
– Can occur due to G6PDH deficiency or upon
exposure to some local anesthetics (prilocaine and
benzocaine).
Hemoglobin F (Fetal Hemoglobin) (2)
– α2gamma2 (no β chains)
– Higher affinity for oxygen than HbA because it
doesn’t contain the Beta chain that binds to 2, 3-
BPG.
Hemoglobin S (Sickle Cell) (3)
– Normal α units, abnormal beta units (due to one amino
acid change)
– When deoxygenated, RBCs
form sickle shapes, obstructing small vessels
– O2 has lower affinity for HbS than Hb A
About — mL of carbon dioxide is
produced by the tissue metabolism each
minute in a resting 70-kg person and must
be carried by the — blood to the lung
for removal from the body.
200 to 250
venous
At a cardiac
output of 5 L/min, each 100 mL of blood
passing through the lungs must therefore
unload — mL of carbon dioxide
4 to 5
Carbon Dioxide Transport in the Blood
Transported as: (3)
- Dissolved CO2
- Carbamino-hemoglobin
(CO2Hgb) - Bicarbonate (HCO3-)
Carbon Dioxide Transport in the Blood
Volume of transport is
~4 ml CO2/ 100 ml blood.
Carbon Dioxide Transport Mechanisms (3)
- Dissolved CO2 ~7%
- Carbaminohemoglobin (& Carbamino Compounds) ~23%
- Bicarbonate ~70%
Dissolved CO2 ~7%
– PCO2 is 40mmHg in arterial blood, 46 mmHg in venous bl
Carbaminohemoglobin (& Carbamino Compounds) ~23% (2)
– CO2 forms a loose, reversible bond with hemoglobin (on terminal
amine groups)
– Slowest of the reactions
Bicarbonate ~70% FAST! (2)
– In RBCs, carbonic anhydrase rapidly forms carbonic acid from H2O
and CO2, which in turn dissociates to H+ and HCO3-
– H+ combines with hemoglobin for buffering and HCO3- moves into
plasma in exchange for Cl- (via band 3 protein)
Carbon Dioxide Transport Mechanisms: Systemic
Capillaries
If there were no carbonic anhydrase, PaCO2 would equal
80 mmHg
(compared to the
normal of 45
mmHg).
Carbon Dioxide Transport Mechanisms: Systemic
Capillaries
Haldane
Effect:
Deoxygenated Hb promotes increased binding of CO2 to Hb.
Carbon Dioxide Transport Mechanisms:
Pulmonary Capillaries
Note the reverse direction of the transport by band three protein, which leads to (2)
an increase in intracellular HCO3- and production of CO2 via carbonic anhydrase.
Carbon Dioxide Transport Mechanisms:
Pulmonary Capillaries
Haldane
Effect:
Oxygenated
Hb promotes
dissociation of
CO2 from Hb.
Carbon Dioxide Transport Mechanisms:
Pulmonary Capillaries
Movement of CO2 into the
alveolus will — PaCO2
decrease
