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19 Cards in this Set
- Front
- Back
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What are the normals |
SaO2 greater than 85% CaO2 16 to 20 ml/dl of blood PvO2 38 to 42 mmhg P(A-a)O2 10 to 25 mm Hg on room air is normal(25 to 65 torr on 100% fio2 is normal for a vent patient) (the difference between the alveous and the artery) smaller the better CaO2 normall 20%, CvO2 is 15%, normal Ca-v02 is 5% Formaula for CaO2 is (Hb x 1.34 x SaO2) + (PaO2 x 0.003) Qs/Qt = Cc -Ca /Cc-Cv
PaO2 decreases 1 torr per year over age of 60 up to age 90
Base Excess, normal is + or -2, also we dont care unless its more than -10, then patient needs IV bicarb |
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Interpreting |
Clinical assessment of oxygen :hypoxemia noted by low PaO2, SaO2, CaO2 Differentiate between causes of hypoemia by adding PaO2 +PaCO2 while breathing fiO2 of .21% If total is between 110 and 130 Hg then simple hypoventilation exists If total is less than 110 mmHg, then usually lung dysfunction like shunt, V/Q mismatch, diffusion defect |
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Two situations of normal P(A-a) difference with hypoxemia |
Primary hypoventilation: is a state in which there is a reduced amount of air entering the pulmonary alveoli :Elevated alveolar and arterial pCO2 cause a decrease in PAo2 ::Hypoxemia occurs but A-a difference WNL High altitudes: reduced partial pressures of oxygen in inspired gas (PiO2) :Decreased PAO2 cause hypoxemia but A-a different WNL |
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V/Q mismatch |
Condition in which the ventilation (exchange of air between lungs and environment) does not match up with perfusion (pasage of blood through the lungs) Most common cause of hypoxemia is V/Q mismatch in patients with lung disease leading to resp fialure, usually in COPD Causes, bronchospasm, mucous plugs = inadequate ventilation Look at P(A-a) O2 difference Normal predicted dependent on FIO2 and patients age |
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PaO2 relationship |
10 to 25 mmHg on Ra and 25 to 65 mmHg on FiO2 100 Quick estimation of A-a gradient (age / 4) +4 so a 40 yr old 40/4 = 1-+4= 14 Large P(A-a) means severe abnormality
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PAO2 is (Pb - 47)xFiO2 - (1.25 x PaCO2) is the PAO2, the amount of oxygen in the alveolus Then minus PaO2, the amount of oxygen in the artery |
PAO2-PaO2 |
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COntinued interpretation |
PvO2 sample obtained from the pulmonary artery reflects tissue oxygenation :PvO2 reflects balance between oxygen delivery and oxygen consumption :PvO2 less than 35 mmHg is strong evidence of poor tissue oxygenation Sudden drop in PvO2 is most often caused by impaired circulation
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Base excess |
Reflects the bodies ability to compensate for a respiratory issue Has to due with buffering capabilities This is a calculation, not a measurement Normal is + or - 2 Positive values indicate either addition of buffer (pt given Bicarb) or acid has been removed Negative values (a deficit) indicate the opposite, acid has been added or base has been removed |
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Co oximetry/ hemoximetry |
Spectrophotometer: works on the principle of light absorbptions Lambert, beer law, each substances pattern of light absorptions varies with the amount present Different froms of HB absorb light differently at different wavelengths
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Values obtained from CO oximetry |
O2Hb; oxygemoglobin (O2 saturation) (>95%) COHb: carbody hemoglobin and methemoglobin less than 1.5% is normal, mehemoglobin. will be high when people eat silver CaO2 is 16 to 20% Nitric oxide is a vasodilator, changes ferrous to ferric within the hemoglobin and methemoglobin is the result
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METHB |
Blood loses ability to carry oxygen Most common cause is nitrite poisoning other causes, lidocaine spray, hurricane spray Blod turns brown, cyanosis (slate: blue skin color) dyspnea, SpO2 of 85 to 89% Treatment: methylene blue or ascorbic acid
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Sources of error in co oximeters |
Failure to mix the sample before analysis Blood clots in the sample Insufficient sample Interfering substances, fetal hemoglobin (may give erroneous values if forms of Hb that the instrument does not recognize are present) |
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Whats in a name |
Determine acid base status (acidosis/alkalosis) Respiratory system compensates immediately Metabolic system takes 24 to 48 hours to compensate
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Steps for interpretation |
Base excess Normal 0 to - or +2 Positive (excess would be a loss of acid or gain of base) Negative (deficit) gain of acid or loss of base The larger the value the more severe the deviation in the metabolic component |
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Base excess/deficit |
Adminitration of bicarb should be reserved for HCO3 less than 10 to 12 mEq/L and pH of less than 7.2, this would be for a patient with base deficint of -10 When we have the metabolic treatment, you must fix the problem Usually calcium or chrolide that cause the issue |
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Henderson hasselbalch equation |
the equation that calculates the pH pH = pK(6.1 always) + log (HCO3- (renal) / (Paco2 x 0.03) (lungs) Bicarb to Co2 ratio of less than 20:1 is an acid pH More than 20:1 is a base pH to get a pH of 7.4, you need a Bicarb to PaCo2 ratio of 20:1 |
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Simple disorders |
Respiratory acidosis :Decreased alveolar ventilation :May be causeed by ::upper airway obstruction, massive PE, drug OD, head trauma, Neuromuscular disease :PaCO2 rises causing fall in pH :Compensation = renal retention of HCO3 Respiratory alkalosis :Alveolar ventilation exceeds CO2 production :PaCO2 falls, causing a rise in pH :May be caused by ::Pain, moderate hypoxemia, acidosis, anxiety :Compensation occurs by renal loss of HCO3 ::Fully compensated if pH returns to normal ::Partial compensation: pH returns toward normal |
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Metabolic simple disorders |
Acidosis :Plasma HCO3 or E falls below normal :Conditions ::diarrhea, detoacidosis, lactic acidosis :Caused by ::Decreaseed production or excess loss of buffers ::Increased production of acids or decreased ability to excrete acids :Compensation occurs by hyperventilation ::This occurs rapidly ::Lack of compensation indicates a concurrent respiratory defect or respiratory acidosis Alkalosis :Elevated levels of plasma HCO3 or BE :Conditions ::Hypokalemia or hypochloremia ::Nasogastric suctioning ::Diuretic steroid therapy :Caused by ::Accumulation of buffers in blood/ significant acid loss :Compensation occurs by hypoventilation ::Seldom significant compensation in alert patient ::Comatose patients may have a significant response with a very high PaCO2 :::May require supplemental oxygen |
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Mixed disorders |
Respiratory/metabolic acidosis :Low HCO3 and high PaCo2 :Could bec caused by cardiopulmonary resuscitation, COPD with hypoxia, poisoning and drug overdose
Resp/Meta alkalosis :Critically ill patients in ICU, ventilatior induced alkalosis in the face of chronic hypercapnia
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