ABG

-Carbon Monoxide affinity for hemoglobin

217 times higher than oxygen

STPD 1 mole

22.4L, Temperature 273 K and Pressure 760 mmHg.

At rest normal PvO2 =

35 to 45 mm Hg

Normal cardiac output

5 L/min

Oxyhemoglobin Dissociation Curve: Upper portion.

80 & 100 mm Hg (flat part) at the alveolar level increases in PO2 rapidly saturate the hemoglobin.

Calculate Amount of oxygen bound to hemoglobin:

Hemoglobin g/dl X 1.34 ml/g X So2 = ml O2 bound to hemoglobin

P50: Shift to the Right

Hemoglobin has decrease affinity for oxygen

P50: Shift to the Left

Hemoglobin has increase affinity for oxygen

Peripheral Chemoreceptors Located

Carotid and Aorta

PO2 Electrode: Also called Calibration gases used to calibrate the analyzing machine Consists of

Clark electrode two point calibration Gas mixtures of O2 concentrations of 0% and 12 % or 20% 1. 5% CO2 and 12% or 20% and nitrogen 2. 10 % CO2 and 90 % nitrogen Consists of: Platinum cathode-Negative charge Silver Anode-Positive charge O2 permeable membrane Potassium Chloride solution surrounding the electrode

Alveolar-Arterial Oxygen Tension Gradient

Difference between the PAO2 and the PaO2.

compare what is dissolved and carried by the heart with our cardiac output

Dissolved oxygen 1.34 x CO x Hb x So2 0.003 x PaO2 (Page 1143)

Main Function of ventilation:

Exchange oxygen and carbon dioxide between blood and alveolar gas and thus maintain an optimal level of PaO2 and PaCO2.

permits maximal oxygen extraction from the small amounts that cross the placental barrier

Fetal hemoglobin

Alveolar-Arterial Oxygen Tension Gradient :Assists to determine a new FiO2:

FiO2 [Desired PaO2/(PaO2/PAO2)] +(PACO 2/R) (Рв - 47)

Arterial/Alveolar oxygen Tension Ratio: Varies as

FiO2 changes.

Mixed venous PO2 (PvO2) is the measurement of

PO2 in blood withdrawn for a central venous or pulmonary artery catheter

Most important factor is the control of ventilation under normal condition is

PaCO2

Oximeter: What it uses Type of light and why

Use a light to measure the amount of oxygen in the sample Light can be used in different colors to determine Methemoglobin and carboxyhemoglobin

Most common cause of hypoxemia

VIQ Mismatch Alveoli not ventilated or Capillary has less or no blood flow Examples include Bronchospasm Mucoid obstruction of airway - result in atelectasis Chronic obstruction

Boyles Law:

Ventilation Increasing Volume reduces pressure.

ventilation- alveoli perfusion- capillary problem.

a problem in the lung in the capillaries and gas exchange can not occur

If PaO2 improves with the introduction of PEEP, but PvO2 decreases, this means

a worsening of tissue oxygenation has occurred, most likely resulting in a shunt. Blood is bypassing The lungs to be oxygenated.

continuously added to alveolar gas by diffusion

carbon dioxide

Central Chemoreceptors respond to

changes in H ion concentration Increase H stimulates the respiratory center Decrease in H concentration inhibits it.

Oxygen that is inspired starts to decrease as soon as it enters the

conducting airways.

Almost all the alveolar carbon dioxide comes from

diffusion as capillary blood equilibrates and dumps it off

Hemoglobin: -Molecule found in

erythrocytes / red blood cells

hemoglobin can carry how many molecules of oxygen.

four

As the oxygen enters the terminal airways

gas exchange occurs.

Blood doesn't have to carry large amounts of oxygen because

hemoglobin

The amount of 2,3 DPG can also affect

hemoglobin affinity.

Peripheral Chemoreceptors responsible for increase in ventilatory rate that occurs due to

low Oxygen concentration / Hypoxemia

Нурохemia: Refers to Should not be confused with

low oxygen concentration in the blood Tissue hypoxia

Respiration is maintained by the activity of the respiratory center which is the

medulla

Oxyhemoglobin Dissociation Curve: Upper Portion PO2 is more sensitive indicator of

mild hypoxemia than is Sat.

Oxygen content is reported as

ml of oxygen per 100 ml of whole blood or as volume percent.

-Each of the four hemigroups can combine with

one molecule of oxygen

The sum of the PaO2 and the PaCO2. If on room air is between 110 and 130 mmHg -the cause of hypoxemia is If the Sum is less than 110 mmHg with room air or oxygen - the cause is If the Sum is more than 130 mmHg in adults

overall hypoventilation Mismatch, diffusion or shunt. one should suspect an error

Fetal hemoglobin has a high affinity for

oxygen

PvO2 less than 35 mm Hg in a critically ill patient suggests that

oxygen extraction is increased or tissue oxygen delivery may be inadequate.

name the Blood Gas Analyzers and their electrode type

pH Electrode: Sanz Electrode PCO2 Electrode: Severinghaus Electrode PO2 Electrode: Clark electrode Oximeter

Daltons Law

partial pressure

PaO2 and PaCO2 dissolved in the

plasma of the blood.

When does the alveolar oxygen pressure decreases

pulmonary blood takes up alveoli's oxygen

fair exchange that occurs due to pressure gradients.

pulmonary blood that is returning takes up oxygen in the alveoli alveoli takes up the carbon dioxide from the blood.

Oxyhemoglobin Dissociation Curve: The exercising muscle Shifts curve to

right

Increase in 2, 3, DPG binding with hemoglobin causes

shift to the right. This shift allows blood to deliver more oxygen to the tissues

Mixed venous PO2 (PvO2) Determines

tissue oxygenation

Oxygen Consumption: Looking at oxygen consumed in

venous and arterial blood.

What is P50

where hemoglobin is 50% saturated pH 7.40, PCO2 40, Temp. 37 C

Daltons Law: Oxygen In dry air eequation

PIO2= 760 x .21 = 159.6

Amount of oxygen dissolved in plasma

PO2 X 0.003 ml of oxygen dissolved per 100 ml whole blood

Peripheral Chemoreceptors respond to

decreases in PaO2 increases in hydrogen ions increases in PaCO2

COHb

-Carbon Monoxide binds with hemoglobin

continuously removed from alveolar gas

-Oxygen

Oxyhemoglobin is formed when

-Oxygen attaches to the binding sites and Hydrogen ions are released.

Causes of Hypoxemia:

1. Altitude: 2. Overall Hypoventilation 3. VIQ Mismatch 4. Diffusion Defect 5. Shunt Anatomic right to left shunts (Blood doesn't come in contact with ventilated alveoli)

Numerical value used for oxygen content is

1.39 ml/g

Oxyhemoglobin Dissociation Curve: S shaped curve lower portion indicates

10 & 40 mm Hg (steep part) tissue levels where PO2's are low. Small changes in PO2= large changes in SO2.

Oxygen begins in the atmosphere at

160mmHg

Alveolar-Arterial Oxygen Tension Gradient: what will affect PaO2

Age

Where is oxygen is taken up and Carbon dioxide is excreted.

Lungs

Central Chemoreceptors Located

Medulla

Purpose of ABG

Monitor Oxygenation, Ventilation ,Acid-Base Status

Can be more important indicator of oxygen then either the Pa02 or SO2 when a patient is anemic or when high concentrations of dyshemoglobins are present in the blood

Oxygen content

Alveolar-Air Equation:

PAO2 = PIO2 (PaCO2 X 1.25) Remember the equation for PIO2 (PB- PH20) X FiO2 PAO2 =[(Pb -PH20) FIO2- (PaCO2 X 1.25)

Inaccurate measurement of P50

Patients who received whole blood or packed cells within 2 months before testing Patients who smoke must refrain for 8 -12 hours before testing so COHb will be normal

medulla is Constantly stimulated by

Peripheral Chemoreceptors Central Chemoreceptors

Sanz Electrode, also called Measures Type of device, what theyre made of, how they measure, calibration

Ph electrode Measures: PH on the RELATIONSHIPS between two pH across a MEMBRANE that is SENSITIVE to PH Contains: reference electrode: made of mercury-mercurous chloride measuring electrode: made of silver-silver chloride Each of these electrodes is exposed to a BATH containing POTASSIUM CHLORIDE measures a voltage difference in the solutions two point calibration: 6.840 and 7.384

PCO2 Electrode, other name Calibration Sits in what kind of bath Covered with

Severinghaus Electrode two point calibration Gas mixtures of CO2 concentrations of 5% and 10 % mix Sodium BICARBONATE and SODIUM bath or a POTASSIUM chloride bath Covered with a permeable membrane to CO2

Oxygen and CO2 exchange amoung

Slightly more oxygen is exchanged from the alveoli then the carbon dioxide is given to the alveoli..

P50: pH & PCO2 can affect

affect hemoglobin affinity and shift the curve

Cardiac Output is defined as

amount of blood ejected from the heart during each beat, multiplied by the heart rate.

Saturation defined as

amount of hemoglobin that is bound to oxygen divided by the amount of total hemoglobin that is available to bind with oxygen

Oxygen content quantifies the

amount of oxygen present in the blood.

curve: In the lungs oxygen is taken up and Carbon dioxide is excreted. The decrease in blood acid causes

an increase hemoglobin affinity for oxygen and results in oxygen uptake at a maxiumum. But will not readily let it off the hemoglobin at the tissue.

In PaO2 and PaCO2 give partial pressure of Oxygen and Carbon dioxide in

arterial Blood