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83 Cards in this Set
- Front
- Back
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Oxygen content in the blood depends on 3 things |
*PO2 *RBC number *hemoglobin content |
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patients who might have low H and H? |
*post surgical due to blood loss *bone marrow transplant patients |
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Clinical signs/symptoms of anemia |
*weakness, fatigue *shortness of breath *dizziness *fast/irregular HR *pale skin *cold hands/feet |
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What is SpO2 of resting anemic patient? |
97% |
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What is SpO2 not a measure of? |
not a complete measure of circulatory sufficiency or oxygen content in blood. An anemic patient can have a normal SpO2 and still not be getting enough O2 |
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Why is <90% a critical clincal point with regards to SaO2? (correlates to 60mm Hg PO2) |
*clinical signs of hypoxemia *general cut-off point for safe exercise *CMS reimbursement (see p. 3 of packet) |
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How do you calculate systemic driving pressure? What is the normal value? |
*aortic pressure - right atrial pressure *100 - 0 = 100mm Hg |
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How do you calculate pulmonary driving pressure? What is the normal value? |
*pulmonary arteries pressure - left atrial pressure *15 - 5 = 10mm Hg |
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How do right ventricle and left ventricle have the same output (5.5L/min) but drastically different driving pressures? |
pulmonary vascular resistance has to be very low |
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What is the result of low pressure and low resistance in the pulmonary circulation? |
less filtration than in systemic capillaries no alveolar edema |
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Describe perfect gas exchange |
Ventilation would perfectly match perfusion V/Q = 1 "perfect" exchange of gas amount of blood matches amount of gas |
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Describe V/Q in the apices of the lungs |
*V/Q is increased *ventilation > perfusion *physiological dead space |
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Describe V/Q in the bases of the lungs |
*V/Q is decreased *perfusion > ventilation *shunt |
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normal V/Q value |
0.8 |
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Define autoregulation in regards to V/Q |
lungs attempt to match ventilation and perfusion by changing diameter of pulmonary arterioles |
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What do pulmonary arterioles do when PO2 is 1) high 2) low? |
1) dilate 2) constrict |
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What contributes to the 5mm Hg difference between PO2 in alveolar air and arterial blood |
V/Q mismatch V/Q = 0.8 (not quite enough air to oxygenate all blood perfectly) |
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Lung diseases cause V/Q abnormalities. What can blood going to areas not well ventilated cause? |
hypoxemia (decrease in PaO2) |
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What can a PT do therapeutically for a patient with V/Q abnormality? |
position patient to optimize V/Q (get blood away from side not ventilating well) |
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How is CO2 produced by the body? |
as a waste product of cellular respiration |
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How is CO2 removed from tissues, generically? |
diffusion out of cells, movement into the blood, and excretion by the lungs |
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In what forms is CO2 transported in the blood? |
*dissolved CO2 (5-10%) *carbamino compounds (5%) *HCO3- (80-90%) |
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What is produced when CO2 combines with water? What catalyzes this reaction? where does the reaction occur? |
*carbonic acid H2CO3 *carbonic anhydrase *Within the RBCs in systemic capillaries |
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What is the result of accumulation of carbonic acid |
dissociation into protons and bicarbonate ions (HCO3-) |
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How is the proton (H+) released by dissociation of carbonic acid buffered? |
hemoglobin |
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What affect does hemoglobin buffering of H+ ions released by carbonic acid have on O2 carrying? |
Bonding of H+ helps to offload O2 from hemoglobin |
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What happens to deoxyhemoglobin in the lungs? What effect does this have on CO2 reactions? |
*deoxyhemoglobin is converted to oxyhemoglobin *oxyhemoglobin has a weaker affinity for H+, so H+ are released within the RBCs |
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People are normally producing CO2 at a rate of 250mL/min, how does that affect CO2 equations? |
Pushes reactions toward carbonic acid creation and subsequent dissociation into proton and bicarbonate. Constant creation of acid |
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What is a normal blood pH? |
7.35-7.45 |
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What organs help maintain blood pH in such a narrow range? |
*lungs *kidneys |
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What is the equation for calculating blood pH? What is it's name? |
pH = 6.1 + log[HCO3-]/[CO2] Henderson-hasselbalch equation |
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What pH affecting compound do the lungs regulate? And the kidneys? |
*lungs regulate the respiratory component: PaCO2 *kidneys regulate the metabolic components: [H+] and [HCO3-] |
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Define volatile acids |
acids that can leave solution and enter atmosphere as a gas ex. carbonic acid |
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Define non-volatile acids. Give examples |
acids that cannot leave solution and therefor can't be exhaled and must be excreted by the kidneys. *sulfuric and phosphoric acids *byproducts from metabolism during starvation |
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What is the most important extracellular buffer? |
bicarbonate ion (as it is able to remove H+) |
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What is the definition of a buffer? |
provide or remove H+ to stabilize pH |
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How do kidneys help to buffer the blood |
excrete excessive H+ and produce HCO3- |
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Acceptable ranges of arterial blood gasses (ABGs) |
PO2: > 80mm Hg PCO2: 35-45mm Hg pH: 7.35-7.45 HCO3-: 22-26 mEq/L |
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General format for ABGs |
PO2/PCO2/pH/HCO3- |
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How, why, and when would ABGs be performed |
*arterial puncture *lung diseases, poor gas exchange, kidney diseases, electrolyte problems |
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4 "pure" acute disorders of acid-base without compensation |
*respiratory acidosis *respiratory alkalosis *metabolic acidosis *metabolic alkalosis |
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Define the compensation principle |
a change in blood pH produced either by changes in respiratory or metabolic component of acid-base balance can be partially compensated by a change in the other component. |
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Definition of and features of primary respiratory acidosis |
*reduction in pH due to primary increase in PCO2 (hypercapnia) *low pH, high PCO2, normal HCO2- |
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Common causes and symptoms of primary respiratory acidosis |
*hypoventilation, obstructive lung disorders, CNS depression *anxiety, headache > sleepiness, confusion, coma |
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Definition and key features of primary respiratory alkalosis |
*increase in pH due to primary decrease in PCO2 (hypocapnia) *high pH, low PCO2, normal HCO3- |
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Common causes and symptoms of primary respiratory alkalosis |
*hyperventilation, hypoxia, pulmonary embolus *subtle tacchycardia and cyanosis |
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What acid-base imbalance is associated with a left shift of the oxyhemoglobin dissociation curve? What does this imply? |
alkalosis shifts to the left, implying that it is harder to unload oxygen into tissue |
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what are common causes of a left shift of the oxyhemoglobin dissociation curve? |
hyperventilation, any condition causing vomitting (loss of acid), pancreatic diseases |
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How does breathing into a bag help with issues related to hyperventilation? |
Excess loss of CO2 increases blood pH and shifts oxyhemoglobin dissociation curve to the right. This makes it harder to unload oxygen into the tissues. Breathing into a paper bag shifts introduces more CO2 into the system and shifts the curve back |
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How does a pulmonary embolus result in respiratory alkalosis? |
blood flow is blocked to the lung tissue, creating a physiological dead space. V/Q increases and hypoxemia increases. This triggers increased respiration rate, leading to hyperventilation. |
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what are common causes of ketoacidosis? |
*uncontrolled type I diabetes *starvation *excessive exercise |
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Definition and key features of primary metabolic acidosis |
*decrease in pH due to primary decrease in HCO3- *low pH, normal PCO2, low HCO3- |
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Common causes and symptoms of primary metabolic acidosis |
*ketoacidosis, poisonings, renal failure, prolonged diarrhea *nausea/vomitting, lethary |
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Definition and key features of primary metabolic alkalosis |
*increase in pH due to primary increase in [HCO3-] |
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Common causes and symptoms of primary metabolic alkalosis |
*vomitting, non K+ sparing diuretic therapy, severe potassium depletion *lethargy, irritability, confusion |
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What do pH, PCO2, PO2, and HCO3- tell us? |
Acid-base balance alveolar ventilation oxygenation status buffering capacity |
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What order do you look at the 4 ABGs in order to determine respiratory/metabolic problems? |
pH to see if in balance CO2 to check respiratory function HCO3 to check metabolic function |
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What are the possible names for a patient presenting with normal pH, high CO2, and high HCO3- |
*respiratory acidosis compensation for primary metabolic alkalosis OR *metabolic alkalosis compenation for primary respiratory acidosis |
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What are the possible names for a patient presenting with normal pH, low CO2, and low HCO3- |
*respiratory alkalosis compensation for primary metabolic acidosis OR *metabolic acidosis compensation for primary respiratory alkalosis |
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3 roles of dissolved O2 in plasma |
*establishes PO2 of blood and tissue fluids *utilization by cells in tissues *determines unloading/loading of oxygen onto hemoglobin |
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What is the main anatomical structure in the CNS for breathing regulation |
brainstem, through centers in the medulla oblangata and pons |
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What is the collection of neurons involved with breathing in the medulla, and what does it do? |
*rhythmicity center *controls automatic breathing |
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What are the two centers for breathing regulation in the pons? |
*apneustic center *pneumotaxic center |
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3 nerological ways to disrupt breathing at the CNS |
*knock out the brainstem (via a stroke) *lesion above C3 *interference at the neuromuscular junction of the diaphragm |
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Where do neurons from the rhythmicity center send axons? |
directly to the innervate the diaphragm via C3, C4, C5 |
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What is a good anatomical equivalent of the rhythmicity center in the heart |
sinoatrial node: a collection of neurons that depolarize rhythmically and automatically |
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What is the role of the apneustic center? |
*promotes inspiration by stimulating rhythmicity center *provides constant stimulus for inhalation |
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What is the role of the pneumotaxic center? |
*inhibition of apneustic center (inhibits inspiration) |
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What is the result of loss of input from the pneumotaxic center (result of a common stroke)? |
*apneustic breathing *long inspiratory gasps where inspiration only stops due to natural recoil caused by lung elasticity |
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Where are chemoreceptors that regulate breathing? |
*central in the medulla *peripheral at the aortic and carotid bodies |
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What are the two types of breathing control? |
*voluntary *automatic |
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What do chemoreceptors involved in breathing monitor? |
PCO2, pH, PO2 |
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Where is the carotid body? Where, why, and how does it send information? |
*carotid body at the junction of internal and external carotid arteries *relays information to the rhythmicity center to change respiration rate and tidal volume via CNIX |
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How can input from chemoreceptors modify breathing? What kind of time frame do they do this in? |
*rate and depth (tidal volume) *fast changes that are not sustained |
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Why is PCO2 a better sampling for chemoreceptors than PO2? |
oxygen content in blood decreases slowly due to large 'reservoir' of oxygen loaded to hemoglobin. PCO2 is immediately affected by changes in ventilation. |
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What conditions increase the rate of firing from the carotid body? |
*pH decreases *arterial PCO2 increases *PO2 decreases below 60mmHg |
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Which condition provokes the strongest response? |
*PO2 decreasing below 60mm Hg (cut off point for signs of hypoxia) |
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What is the primary peripheral chemoreceptor for breathing? What is special about it? |
*carotid body *only receptors to increase ventilation in response to hypoxemia |
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What is sensed by chemoreceptors in the medulla (central chemoreceptors)? |
*falls in CSF pH directly stimulate chemoreceptors in medulla |
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What is the timeframe for changes due to central chemoreceptors? |
*responsible for 70-80% of increased ventilation that occurs in response to sustained rise in arterial PCO2 *response takes several minutes |
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What are the oxygen conditions on Mt. Everest? |
FiO2 = 21% PO2 = 42mm Hg |
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How does the body adjust to high altitude? |
Decrease in PaO2 detected by carotid body, increasing RR and tidal volume > hyperventilation > primary respiratory alkalosis. Compensation in the kidney results in decreased bicarb producation and increased H+ excretion to maintain acid-base balance. Within 15 hrs of ascent kidneys secrete EPO to trigger more RBC production. |
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How can high altitude training help athletes? |
results in more RBCs, hemoglobin, and thus oxygen carrying capacity that carries over at low altitudes |
