Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Chapter 11 Egans
Gas Exchange and Transport
| Question | Answer |
|---|---|
| Respiration | process of getting O2 into the body for tissue utilization and removal of CO2 into the atmosphere |
| Oxygen must be moved into the lungs where it....... | diffuses into the pulmonary circulation and is transported into the blood to the tissues |
| Carbon dioxide builds up into the tissues because of..... | metabolism |
| Carbon dioxide diffuses into.... | capillary blood before being carried to the lung for exchange with alveolar gasses |
| Gas movement between lungs and tissues occure by? | simple diffusion |
| What is the diffusion gradient for oxygen? | normal atomospheric inspired partial pressure (PIO2) of 159 mm Hg to a low point of 40 mm Hg or less in the capillaries |
| What is the final gradient for oxygen infusion into the cell? How many mm Hg? | intracellular PO2 (5 mm Hg) |
| What is the diffusion gradient for carbon dioxide? | highest in the cells 60 mm Hg and lowest to room air 1 mm Hg |
| What is the difference of the oxygen diffusion gradient compared to the carbon dioxide diffusion gradient. | Oxygen has a cascade gradient moving from atmosphere to Intracellular. Carbon dioxide moves from intracellular to the atmosphere. |
| The carbon dioxide diffusion gradients cascade causes..... | CO2 to move from tissues into the venous blood, which is transported to the lungs and out to the atmosphere |
| Alveolar partial pressure of carbon dioxide (PACO2) | varies directly with the body's production of CO2 and inversely alveolar ventilation |
| What factor is used to convert VCO2 from STPD to BTPS? | 0.863 |
| what is the formula used to convert VCO2 from STPD to BTPS? | PACO2= VCO2 * 0.863 --------------- VA (alveolar ventilation) |
| Normally complex respiratory control mechanisms maintain the PACO2 within a range of? | 35-45mm Hg |
| If carbon dioxide production increase as with exercise or fever what happens to ventilation? | ventilation automatically increases to maintain PACO2 within normal range |
| What is the most important facto in determining the alveolar partial pressure of oxygen (PAO2)? | inspired partial pressure of oxygen (PIO2) |
| Once oxygen is in the lungs it is diluted by what 2 things? | water vapor and carbon dioxide |
| What is the alveolar air equation formula? | PAO2= FIO2*(PB -47)-(PACO2/0.8) |
| According to Dalton's law the partial pressure of alveolar nitrogen must.... | equal the pressure it would exert if it alone were present |
| What is the formula to compute the partial pressure of alveolar nitrogen (PAN2)? | PAN2= PB-(PAO2+PACO2+PH2O) |
| The only partial pressures that change int he alveolus are? Why? | oxygen and carbon dioxide. Because both water vapor tension and PAN2 remain constant. |
| Based on the alveolar air equation if the FIO2 remains constant the the PAO2 will? | vary inversely with PACO2 |
| When a patient is breathing room air what is the sum of the alveolar PO2 and alveolar PCO2? | 140 mm Hg |
| Neural control mechanisms and increased work of breathing prevent decreases in PaCO2 much below? | 15-20mm Hg |
| If patient is breathing room air at sea level the RT should or shouldn't exspect to see a PaO2 any higher that 120 mm Hg during hyperventilation? | should not exspect any higher than 120 mm Hg |
| PO2 values higher than 120 mm Hg indicate? | patient is breathing supplemental oxygen |
| Diffusion | process of gas molecules moving from an area of high partial pressure to low partial pressure |
| In order for oxygen to diffuse into and out of the lung and tissues, O2 and carbon dioxide must move through.... | barriers |
| Alveolar capillary membrane | the barrier to gaseous diffusion in the lung |
| What 3 barriers must be penetrated in order for O2 and CO2 to move btw alveoli and pulmonary capillary blood? | alveolar epithelium, intersitial space, capillary endothelium |
| Fick's first law of Diffusion | the greater the surface area, diffusion constant, and pressure gradient, the more diffusion will occur |
| Diffusion in the normal lung mainly depends on? | gass pressure gradients |
| What must exist in order for gas exchange to occure between the alveoli and pulmonary capillaries? | difference in partial pressures |
| In pulmonary diffusion Alveolar PaO2 averages how many mm Hg? | 100 mm Hg |
| In pulmonary diffusion Mean PaCO2 is approximately how many mm Hg? | 40 mm Hg |
| In pulmonary diffusion PvO2 is how many mm HG? | 40 mm Hg |
| In pulmonary diffusion PvCO2 is how many mm Hg? | 46 mm Hg |
| The pressure gradient for oxygen diffusion into the blood is approximately? | 60 mm Hg |
| Does carbon dioxide diffuse faster or slower across the alveolar-capillary membrane than oxygen? Why? | 20 times faster. Because of its much higher solubility in the plasma. |
| Diffusion time in the lungs depends on? | rate of pulmonary blood flow |
| How long does blood take to flow through the pulmonary capilary? | 0.75 seconds |
| Low concentrations of what are used more commonly to measure diffusing capacity of the lung? | carbon monoxide (0.1%-0.3%) |
| The PaO2 of healthy person breathing at sea level is approximately how much less than the calculated PaO2? | 5-10 mm Hg less |
| 2 factors that account for the 5-10 mm Hg difference in calculated PaO2 are? | 1.right to left shunts in pulmonary and cardiac circulation 2.regional differences in pulmonary ventilation and blood flow |
| What are the 2 anatomilace right to left shunts that exist in a normal human being? | 1.bronchial venous drainage 2.thebsian venous drainage |
| What does a right to left shunt cause poorly oxygenated venous blood to do? | causes it to move directly into the arterial circulation, lowering the oxygen content of the arterial blood. |
| What is the ideal ventilation and perfusion ratio? | 1.0 |
| A high ventilation/perfussion ratio indicates that? Low V/Q? | ventilation is greater than normal, perfusion is less than normal, or both. LOW- ventilation is less than normal, perfusion is greater than normal, or both. |
| In areas with low V/Q the alveolar PO2 is? PCO2 is? | alveolar PO2 lower, PCO2 higher than normal |
| Area with ventilation but no blood flow represent? | dead space |
| Alveolar shunts | V/Q ratio values of zero not normal, distinguished from true anatomical shunts. |
| Regional differences in V/Q ratios in the normal lung are caused by? | gravity and most evident in the upright position |
| Does perfusion increase or decrease farther down the lung? | increases. Bases receive nearly 20 times as much blood flow than the apexes. |
| Does ventilation increase or decrease farther down in the lung bases? | increases. Four times as much ventilation than apexes. |
| V/Q at apexes of lungs | ventilation exceeds blood flow resulting in high V/Q (3.3), high PO2 (132 mm Hg), low PCO2 (32 mm Hg). |
| V/Q at bases of lungs | blod flow increases more than ventilation due to gravity |
| (Oxygen Transport)blood carries O2 in what 2 forms? | 1.dissolved in plasma and erythrocyte fluid. 2. majority is carried in combination with hemeglobin inside the RBC |
| Formula for Dissolve oxygen in blood? | Dissolved oxygen= PO2*0.003 |
| Deoxygenated hemoglobin serves as a what in transport? | important blood buffer for hydrogen ions, important in carbon dioxide transport |
| Oxyhemoglobin | oxygen molecules bind to Hb by way of ferrous iron ion and coverted to it's oxygenated state |
| In whole blood each gram of normal Hb can carry how many ml of oxygen? | 1.34 ml |
| Hb increases the oxygen carrying capacity of the blood by how much? | 70 fold as compared to plasma alone |
| Saturation | measure of proportion of available Hb that is actually carrying oxygen |
| Hb saturation formula | SaO2=[HbO2 / Total Hb]*100 |
| HbO2 curve | relationship btw PaO2 and SaO2 is S shaped |
| How to find the total oxygen content of blood? | total oxygen content of bloo equals the sum of that dissolved and chemically combined with Hb |
| Formula for Total oxygen content of blood | CaO2=(0.003*PO2)+(Hbtot*1.34*SO2) |
| What is the normal CaO2 concentration? | 16-20 ml/dl |
| What is the difference between the arterial and venous oxygen contents? | 5 ml/dl |
| C(a-v)O2 | arteriovenous oxygen contents difference. Amount of O2 given up by every 100mL of blood on each pass through thet tissues |
| Fick equation | The C(a-v)O2 combined with total-body oxygen to calculate cardiac output |
| Normal range for cardiac output | 4-8L/min in adult |
| According to Ficks equation if the O2 consumption remains constant a decrease in cardiac ouput will do what to the arteriovenous oxygen contents difference? | increase the C(a-v)o2 |
| According to ficks equation if the cardiac output rises and oxygen consumption reamins constant what will happen to the arteriovenous oxygen contents difference? | C(a-v)O2 will decrease |
| What are some factors other than HbO2 curve that affect oxygen unloading and loading? | blood pH, body temp, erythrocyte concentration of certain organic phosphates, variations in the structure of Hb, chemical combinations of Hb with substances other than O2 |
| Bohr effect.....What does it do? | impact of changes in blood pH on Hb affinity for O2. It alters the position of the HbO2 dissociation curve. |
| A low pH shifts a curve to the? | right |
| A high pH shifts a curve to the? | left |
| When blood ph drops and shifts the curve to the right the Hb saturation for a given PO2... | falls |
| As blood pH rises and the curve shifts to the left Hb saturation for a given PO2... | rises |
| As blood in the tissue picks up CO2, pH falls and the HbO2 curve shifts to the? Does it increase or decrease the affinity of Hb for oxygen? | right. decreasing the affinity of Hb for O2. |
| With a lower of the affinity of Hb for O2 Hb readily gives up what to the tissues? | O2 |
| Venous blood returns to the lungs and the pH does what? This shifts the curve to the? Does this increase or decrease the affinity of Hb for oxygen? | Increases. left. Increasing the affinity of Hb for O2 and enhancing its uptake from the alveoli. |
| A drop in body temperature shifts the HbO2 cureve to the? | left, increasing Hb affinity for O2. |
| As body temperture rises the curve shifts to the? | right, affinity of Hb for O2 decreases. |
| At the tissues, temperature changes are directly related to? | metabolic rate |
| Organic phosphate 2,3-diphosphoglcerate | found in abundance in the RBC's and forms a loose chemical bond with the globin chains of deoxygenated Hb. |
| 2,3-DPG does what to the molecule in it's deoxygenated state? | It stablilizes the molecule and reuces it's affinity for oxygen |
| What would happen if we didn't have 2,3-DPG? | Hb affinity for O2 would be so great that normal O2 unloading would be immpossible |
| Increased 2,3 DPG concentrations shift the HbO2 curve to the? Promoting what? | right. Oxygen unloading |
| Low 2,3-DPG concentrations shift the curve to the? And does what to the Hb affinity for O2? | left. Increasing the Hb affinity of O2 |
| Alkalosis, chronic hypoxemia, and anemia all increase or decrease 2,3-DPG concentrations? | increase and promote oxygen unloading |
| Acidosis does what to 2,3-DPG? | lowers the level of DPG and a greater affinity of Hb for O2. |
| What happens to DPG in banked blood? | It decreases in concentration over time and after a week of storage there is less than 1/3 of the normal value of DPG. This shifts the HbO2 curve to the left decreasing availability of oxygen to the tissues. |
| What happens with large transfusions of banked blood that is more that a few days old? | It impairs oxygen delivery even in the presence of a normal PO2 |
| When do structural abnormalities of hemoglobins occur? | when the amino acid swquence in the molecule's polypeptide chains varies from normal. |
| What percent of the circulating hemoglobin are abnormal in a healthy individual? | 15-40% |
| Sickle Cell hemoglobin? | abnormal hemoglobin that is less soluable and causes the hemoglobin to become suceptible to polymerization and precipitation when deoxygenated |
| What events cause the hb to crystalize and the RBC to become hardened and curved like a sickle? | dehydration, hypoxia, acidosis |
| Patients with sickle cell are prone to? | vaso-occlusive disease and anemia. |
| Acute chest syndrome? Symptoms? | most common cause of death in patients with sickle cell anemia. Symptoms:acute chest pain, cough, dyspnea, infiltrate on the CXR and develops progressive anemia and hypoxemia |
| Methemoglobin | abnormal form of the molecule where the heme-complex normal ferrous iron ion loses an electron and oxidizes to its ferric state. |
| What happens in the ferric state of methemoglobin? | iron ion cannot combine with oxygen |
| What happens as a result of the iron ion not being able to combine with oxygen in the ferric state of methemoglobin? | a special form of anemia results called methhemoglobinemia |
| What is the most common cause of methemoglobinemia? | therapeutic use of medications containg nitrogen. Nitric oxide, nitroglycerine, lidocaine |
| What color is the blood of a patient who has methemoglobin? | brown, slate-gray skin coloration |
| How do we confirm that a patient has methemoglobin? | spectrophotometry |
| How is methemoglobin treated? | reducing agents such as methylene blue or absorbic acid when the blood level exceeds app. 40% |
| Carboxyhemoglobin | Hb with carbon monoxide |
| Hemeglobins affinity for carbon monoxide is how much more greter than it is for oxygen. | 200 times greater |
| The combination of carbonmonoxide shifts the HbO2 curve to the? | left. Impeding oxygen delivery to the tissues |
| What is the treatment for carbon monoxide poisoning? | giving the patient as muxh oxygen as possible because oxygen reduces the half-life of carboxyhemoglobin. Sometimes a hyperbaric chamber is used |
| Fetal Hemoglobin | blood having a high proportion of an Hb varian during fetal life and for up to 1 year after birth |
| Fetal hemoglobin causes a shift to the? | left. HbF has a greater affinity for oxygen than does normal adult Hb |
| What does the leftward shift of fetal hemoglobin aid in doing? | aids oxygen loading at the placenta |
| The PO2 values to the fetus in utero are high or low? | low |
| What happens after birth with the Fetal hemoglobin? | this enhanced oxygen affinity is less advantageous after birth. Over the first year of life HbF is gradually replaced with normal Hb. |
| P50 | partial pressure of oxygen at which the Hb is 50% saturated, standardized to a pH of 7.40 |
| What is a normal P50? | 26.6 mm Hg |
| Conditions that cause an decrease in Hb affinity for oxygen cause a shift to the? | right. |
| Conditions with an increase in affinity cause a shift to the? What happens to P50? | left. P50 decreases to lower than normal |
| How much carbon dioxide is carried in the blood? | 45-55 ml/dl |
| In what three forms is carbon dioxide carried in the blood? | dissolved in physical solution, chemically combined with protein, ionized as bicarbonate |
| Dissolved carbon dioxide plays an important role in? How much is released at the lungs? | transport. 8% |
| Carbon dioxide hasa the capacity to chemically cobine with free amino groups of protein molecules forming a? | carbamino compound |
| what is carbaminohemoglobin? what percentage does it transport? | A compound of carbon dioxide and hemoglobin, which is one of the forms in which carbon dioxide exists in the blood. 12% of the total carbon dioxide. |
| Approximately what percent of the blood carbon dioxide is transported as bicarbonate? | 80% |
| Hydrolysis | chemical process in which a molecule is cleaved into two parts by the addition of a molecule of water |
| What does the hydrolysis of CO2 form? | carbonic acid |
| What enzyme enhances the hydrolysis reaction? | carbonic anhydrase |
| Where does the majority of hydrolysis occur? | RBC |
| What happens when hydrolysis of carbon dioxide continues for a while? | Bicarbonate begins to accumulate in teh RBC |
| How is equilibrium obtained when bicarbonate accumulates in the RBC? | by the chloride shift |
| Chloride shift | The movement of chloride ions from the plasma into red blood cells as a result of the transfer of carbon dioxide from tissues to the plasma, a process that serves to maintain blood pH. |
| Haldane effect | influence of oxyhemoglobin saturation on CO2 dissociation |
| What is the Haldane effect a result of? | changes in the affinity of Hb for CO2 as a result of its buffering of Hydrogen ions |
| A high SaO2 decreases or increases the blood's capacity to hold carbon dioxide? Does this help in loading or unloading this gas at the lungs? | Decreases. unloading |
| What is the formula for oxygen delivery? | DO2=CaO2*Qt |
| Hypoxia | when oxygen delivery falls short of cellular needs |
| In what three ways will hypoxia occur? | If the arterial blood O2 content is decreased, if cardiac output or perfusion is decreased, or if abnormal cellular function prevents proper uptake of O2 |
| When does hypoxemia occur? | when partial pressure of O2 in the arterial blood (PaO2) is decreased to lower than normal. |
| What things might a decreased PaO2 be caused by? | low ambient PO2, hypoventilation, impaired diffusion, V/Q imbalances, right to left anatomical or physiological shunting, aging, altitude |
| What is the approximate PaO2 at the age of 60? | 85 mm Hg |
| Mountain sickness | traveling to high altitudes which decreases the PaO2 causing hypoxia |
| Alveolar PO2 varies directly or indirectly with alveolar PCO2? | indirectly |
| Even when alveolar PO2 is normal disorders of the alveolar capillary membrane may limit diffuion of oxygen into the pulmonary bed thereby lowering the? Diseases that do this are? | PaO2. Interstitual edema, Pulmonary fibrosis |
| What is the most common cause of hypoxemia in patients with lung disease? | Ventilation perfusion imbalances |
| What happens when ventilation is greater than perfusion? | there is wasted ventilation, alveolar dead space |
| What happens when ventilation is less than perfusion? | ventilation perfusion ratio is low and blood leaves the lungs with abnormally low oxygen content |
| What does ventilation perfusion imbalances usually occur in lung disease? Why? | both excess wated ventilation and poor oxygentation. Because the imbalance impairs O2 exchange and PaO2 is reduced |
| What does a ventilation perfusion imbalance of 0 represent? | there is blood flow but no ventilation and is equivalent to a right to left anatomical shunt |
| To differentiat between hypoxemia caused by a V/Q imbalance and hypoxemia caused by shunting what do you do? | If the O2 is more than 50% and the PaO2 is less than 50% significant shunting is present. otherwise it is a V/Q imbalance |
| Formula for estimating the expected PaO2 in older adults | Expected PaO2=100.1-(0.323*Age in years) |
| For the arterial oxygen content to be adequate there also must be? | enough normal Hb in the blood |
| Can hypoxia occur if the Hb is low even when the PaO2 is normal? Why? | Yes. Because of low oxygen content in the arterial blood |
| What are the 2 hemoglobin deficiencies? | absolute, relative |
| What is absolute hemoglobin deficiency? | occurs when Hb concentration is lower than normal due to a low blood Hb concentration by either loss from hemorrhage or inadequate erythropoesis. |
| What is relative Hb deficiency? | caused by either displacement of O2 from normal Hb or prescence of abnormal Hb variants. |
| What can a low Hb content do to the oxygen carrying capacity of the blood? | seriously impair the oxygen carrying capacity of the blood |
| Hypoxia can still occur when the CaO2 is normal if? | blood flow is reduced |
| What are the 2 types of reduced blood flow? | circulatory failure(shock), local reduction in perfusion(ishemia) |
| What happens with prolonged shock? | causes irreversible damage to the central nervous system and eventual cardiovascular collapse |
| What 3 things can result from ishemia? | anaerobic metabolism, metabolic acidosis, eventual death of tissue |
| Dysoxia | form of hypoxia in which cellular uptake of O2 is abnormally decreased |
| What is an example of dysoxia? | cyanide poisoning. It disrupts intracellular system preventing cellular use of oxygen |
| Dysoxia also may occur when... | tissue oxygen consumption becomes dependent on O2 delivery |
| What leads to lactic acid accumulation and metabolic acidosis? | tissue extraction reaches a maximum and decreases delivery of O2 resulting in a oxygen debt due to oxygen demand exceeding oxygen delivery |
| In sepsis and ARDS oxygen debt may occur at normal levels of? | oxygen delivery |
| Any disorder that lowers alveolar ventilation relative to metabolic need impairs? | carbon dioxide removal |
| What does impaired CO2 removal by the lungs cause? | hypercapnia and respiratory acidosis |
| When does a decrease in alveolar ventilation occur? | minute ventilation is inadequate, dead space ventilation per minute increases, or a ventilation perfusion imbalance exists |
| Inadequate minute ventilation is caused by? | decreased tidal volume |
| Inadequate minute ventilation occurs in what types of conditions? | restrictive conditions: atelectasis, neuromuscular disorders, or conditions that impede thoracic expansion (kyphoscoliosis) |
| A decrease in RR is less common but may be present with respiratory center depression as in? | drug overdose |
| An increased dead space ventilation is caused by either? | rapid shallow breathing, or increased physiologic dead space (V/Q 0) |
| What does increased dead space ventilation cause? | the proportion of wasted deadspace increases and lowers alveolar ventilation and impairs CO2 removal |
| IN theory V/Q imbalance should cause a rise in PACO2. However many patients who are hypoxemic because of a V/Q imbalance have a low or normal PaCO2. What does this suggest? | V/Q imbalances have a greater effect on oxygenation than on carbon dioxide removal. |
| To compensate for high PCO2 values with V/Q imbalances what must happen? | patients minute ventilation must increase |
| Patients who can increase their minute ventilation with V/Q imbalance then to have? | normal or low PaCO2 combined with hypoxemia |
| Patients with an V/Q imbalance who cannot increase their minute ventilation are? when does this occur? | hypercapnic. This occurs only when V/Q imbalance is severe and chronic like with COPD |
| When a patient is hypercapnic what must happen for them to maintain a normal PaCO2? | they must sustain a higher than normal minute ventilation |
Created by:
blh