Chapter 6 - C02 Transport (PDF)

Module 6 Chapter 6 – 02 Dissociation Curve – C02 Transport Chapter 7 – Acid-Base Balance © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Oxyhem...

Module 6 Chapter 6 – 02 Dissociation Curve – C02 Transport Chapter 7 – Acid-Base Balance © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Oxyhemoglobin (HbO2) Dissociation Curve Also known as HbO2 equilibrium curve Part of nomogram that graphically illustrates percentage of hemoglobin chemically bound to oxygen at each oxygen pressure © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Clinical Significance of the Flat Portion of the Curve PO2 can fall from 60 As Hb moves through to 100 torr and A-C system, significant hemoglobin will still partial pressure be 90 percent difference continues to saturated with exist between alveolar oxygen gas and blood – Excellent safety zone – Even after most O2 has transferred – Enhances diffusion of O2 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Plateau = safety zone – Starting from Pa02 up to Pa02 level? Steep = danger zone – Begin when Pa02 = ? © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Clinical Significance of the Flat Portion of the Curve Increasing PO2 beyond 100 torr adds very little O2 to blood – Dissolved O2 only (PO2 x 0.003 = dissolved O2) Reduction of PO2 below 60 torr causes rapid decrease in amount of O2 bound to hemoglobin – However, diffusion of oxygen from hemoglobin to tissue cells enhanced © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  P50 Point of reference on oxyhemoglobin dissociation curve Represents partial pressure at which hemoglobin is 50 percent saturated with oxygen Normally, approximately 27 torr © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Oxyhemoglobin Dissociation Curve © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 6-6.  Factors that Shift Oxygen Dissociation Curve pH Temperature Carbon dioxide 2,3-bisphosphoglycerate (2,3-BPG) – RBC anaerobic glycolysis – Hypoxia - ↑ – Anemia - ↑ PH ↑ then ↑ – Stored Blood - ↓ Fetal hemoglobin (Hb F) Carbon monoxide hemoglobin (affinity?) (carboxyhemoglobin or COHb) © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Factors that Shift Oxygen Dissociation Curve When curve shifts to right, P50 increases – 02 Affinity to Hb decrease When curve shifts to left, P50 decreases – 02 Affinity to Hb increases © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Carbon Dioxide Transport To fully comprehend this subject, need basic understanding of: – How carbon dioxide is transported from tissues to lungs – Understanding of carbon dioxide (CO2) transport to study of pulmonary physiology and to clinical interpretation of arterial blood gases – Acid–base balance – PCO2/ HCO3–/pH relationship in respiratory acid- base imbalances – Also…PCO2 /HCO3–/pH relationship in metabolic acid–base imbalances © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Carbon Dioxide Transport At rest, each minute, Newly formed carbon metabolizing tissue dioxide is transported cells from tissue cells to – consume lungs by six different approximately 250 mL mechanisms of oxygen – Three in plasma – produce approximately – Three in RBCs 200 mL of carbon dioxide © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Carbon Dioxide (CO2) Transport Mechanisms © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 6-13.  C02 in Plasma 1. Carbamino compound (protein) 2. Bicarbonate C02 + H20 →slow hydration→H2C03→H + HC03 - HC03 will combine with Na to form Sodium Bicarbonate - HC03 + Na → NaHC03 3. Dissolved C02 C02 + H20 →H2C03 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  CO2 Is Converted to HCO3 How CO2 is converted to HCO2 at tissue sites Most of CO2 produced at tissue cells is carried to lungs in form of HCO3 Ratio? HC03 to H2C03 ? © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 6-17.  C02 inside RBC 1. Carbamino Hb C02 + Hb02 →HbC02 2. Bicarbonate C02 + H20 →fast hydration?→H2C03→H + HC03 - Carbonic Anhydrase – enzyme causes fast hydration - HC03 will leave RBC to combine with Na to form Sodium Bicarbonate - HC03 + Na → NaHC03 - As HC03 leaves RBC, replace with Chloride. Why? -Also water enters RBC, increase size 3. Dissolved C02 C02 + H20 →H2C03 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  CO2 Is Converted to HCO3 How CO2 is converted to HCO2 at tissue sites Most of CO2 produced at tissue cells is carried to lungs in form of HCO3 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 6-17. In plasma In RBCs Carbamino compound (1%) Carbamino-Hb (21% – Bound to protein – Bound to Hb Bicarbonate (5%) Bicarbonate (63%) Dissolved CO2 (5%) Dissolved CO2 (5%) © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Carbon Dioxide Elimination at the Lungs How HCO3 is transformed back into CO2 and eliminated in alveoli © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 6-18. Carbon Dioxide Dissociation Curve Similar to oxygen dissociation curve, loading and unloading of CO2 in blood can be illustrated in graphic form Shape vs 02 curve? © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Carbon Dioxide Dissociation Curve Increase in PCO2 from 40 to 46 mmHg raise CO2 content by approximately 5 vol% PCO2 changes have greater effect on CO2 content levels than PO2 changes on O2 levels © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 6-20.  Carbon Dioxide Dissociation Curve At two different oxygen/hemoglobin saturation levels (SaO2 of 97 and 75 percent) When saturation of O2 increases in blood, CO2 content decreases at any given PCO2 – Known as Haldane effect – Vs 02 on 02 curve (Bohr effect – Hb 02 binding affinity is inversely related to acidity and C02 concentration (02 curve shift) © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 6-21. Carbon Dioxide Dissociation Curve Comparison of oxygen and carbon dioxide dissociation curves in terms of partial pressure, content, and shape Linear vs S-shape © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 6-22. Bohr effect Haldane effect The effect of PC02 and pH Phenomenon, on the oxyhemoglobin curve deoxygenated blood is known as Bohr effect enhances loading of C02 PC02 ↑ (H+ ↑), 02 curve (onto Hb) and will desaturation oxygenation of blood – 02 curve shifts right enhances unloading of C02 (leaves Hb) during C02 transport Saturation? © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Chapter 7 Acid-Base Balance and Regulation Under normal conditions, both H+ and HCO3– ion concentrations in blood regulated by three major (buffer) systems: 1. Chemical buffer system (weakest & fastest) 2. Respiratory system ( 1 to 3 minutes) - 2x buffer power of All chemical buffer systems 3. Renal system (Strongest but slowest) © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Chemical Buffer System Responds within fraction of a second to resist pH changes – Also known as first line of defense Chemical Buffer System composed of 3: 1.Carbonic acid-bicarbonate buffer system 2.Phosphate buffer system 3.Protein buffer system 1. Body’s most abundant and influential supply of buffers (75%) © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Protein Buffer System and Acid- Base Balance Hemoglobin in RBCs – Good example of protein that works as intracellular buffer CO2 released at tissue cells quickly forms H2CO3 and then dissociates into H+ and HCO3– ions © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Protein Buffer System and Acid-Base Balance Simultaneously, Because reduced hemoglobin is hemoglobin carries unloading oxygen at negative charge, free H+ tissue sites and ions quickly bond to becoming reduced hemoglobin anions hemoglobin – Reduces acidic effects of H+ on pH – H2CO3 (weak acid) is buffered by even weaker acid (hemoglobin protein) © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Respiratory System Acts within one to three minutes by increasing or decreasing breathing depth and rate to offset acidosis or alkalosis, respectively © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Respiratory System and Acid-Base Balance Respiratory system does not respond as fast (1-3 minutes) as chemical buffer systems. – However, has up to two times the buffering power of all chemical buffer systems combined CO2 produced by tissue cells enters RBCs and is converted to HCO3– ions © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Respiratory System and Acid-Base Balance Under normal When CO2 is unloaded conditions, volume of at lungs, preceding CO2 eliminated at lungs is equal to equation flows to left amount of CO2 and causes H+ produced at tissues generated from When respiratory carbonic acid to system is impaired for transform back to water any reason, serious acid-base imbalance can develop © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Renal System Body’s most effective acid-base balance monitor and regulator Requires one day or more to correct abnormal pH concentrations © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Renal System and Acid-Base Balance Even though Similarly, although chemical buffer respiratory system can systems can expel volatile carbonic inactivate excess acid by eliminating acids and bases CO2, it cannot expel momentarily, they are other acids unable to eliminate generated by cellular them from the body metabolism © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Renal System and Acid-Base Balance Only renal system can rid body of acids such as phosphoric acids, uric acids, lactic acids, and ketone acids – Also known as fixed acids © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Renal System and Acid-Base Balance Basically, when Conversely, when extracellular fluids extracellular fluids become alkaline, renal become acidic, renal system retains H+ and system retains HCO3– excretes basic and excretes H+ ions substances primarily into urine HCO3– into urine – Causes blood pH to – Causes blood pH to increase decrease – But increase H+ in – But increase HC03 in urine will increase pH in urine will decrease pH urine in urine © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  CHAPTER 7 THE BASIC PRINCIPLES OF ACID-BASE REACTIONS AND PH © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Acids and Bases Electrolytes – Similar to salts Both can: – Ionize and dissociate in water – Conduct electrical current © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Acids Defined as proton donors – Because hydrogen ion is only a hydrogen nucleus proton Thus, when acids dissolve in water solution, they release hydrogen ions (protons) and anions Acidity of solution directly related to concentration of protons – Reflects only free hydrogen ions Not those bound to anions © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Acid-Base Balance and Regulation Most H+ ions in body originate from: 1) Breakdown of phosphorous-containing proteins Phosphoric acid 2) Anaerobic metabolism of glucose Lactic acid 3) Metabolism of body fats Fatty and ketone acids 4)Transport of CO2 in blood as HCO3– liberates H+ ions © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Acids For example, hydrochloric acid (HCl) found in stomach works to aid digestion and dissociates into a proton and a chloride ion: HCl H+ Cl- proton anion © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Acids Other acids in body: – Acetic acid (HC2H3O2) Often abbreviated as [HAc] – Carbonic acid (H2CO3) Molecular formula for common acids easy to identify – Begins with hydrogen ion…but not always © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Bases Proton acceptors Hydroxyl ion or OH- Taste bitter Feel slippery Substance that takes up hydrogen ions [H+] in measurable amounts Bicarbonate ion (HCO3–) – Important base in body – Especially abundant in blood © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Bases NaOH Na+ + OH- cation hydroxide ion and then OH- + H+ H2O water © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  pH: Acid-Base Concentration As concentration of hydrogen ions in solution increase, the more acidic solution becomes As level of hydroxide ions increases, the more basic, or alkaline, solution becomes © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Acid – Base Balance pH: © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Henderson-Hasselbalch (H-H) Equation Mathematically pK derived from illustrates how pH of dissociation constant solution is influenced of acid portion of by HCO3– to H2CO3 buffer combination ratio pK is 6.1 and HCO3– – Base to acid ratio to H2CO3 ratio is 20:1 – Under normal conditions – Ratio range is 18:1 to 22:1 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  H-H Equation Clinically, dissolved CO2 (PCO2 x 0.03) can be used for denominator of H-H equations instead of H2CO3 – Possible since dissolved carbon dioxide is in equilibrium with and directly proportional to blood [H2CO3] Can be written as follows: © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  H-H Equation Applied During Normal Conditions When HCO3– is 24 mEq/L, and PaCO2 is 40 mmHg, base to acid ratio is 20:1 and pH is 7.4 (normal) H-H equation confirms 20:1 ratio and pH of 7.4 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. H-H Equation Applied During Normal Conditions © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  H-H Equation Applied During Abnormal Conditions When HCO3– is 29 mEq/L, and PaCO2 is 80 mmHg, base to acid ratio decreases to 12:1 and pH is 7.18 (acidic) H-H equation confirms 12:1 ratio and pH of 7.18 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. H-H Equation Applied During Abnormal Conditions © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  H-H Equation Applied During Abnormal Conditions Conversely, when HCO3– is 20 mEq/L, and PaCO2 is 20 mmHg, base to acid ratio increases to 33:1 and pH is 7.62 (alkalotic) H-H equation confirms 33:1 ratio and pH of 7.62 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. H-H Equation Applied During Abnormal Conditions © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Clinical Application of H-H Equation H-H equation may be helpful in cross checking validity of blood gas reports when pH, PCO2, and [HCO3–] values appear out of line May also be useful in estimating what changes to expect when any one of H-H equation components is altered © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Acid-Base Balance and Regulation Nearly all Normal arterial pH range: biochemical – 7.34 to 7.45 reactions in body Alkalosis or Alkalemia influenced by – pH > 7.45 acid-base balance Acidosis or Acidemia of their fluid – pH < 7.35 environment © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Relationships ↑ CO2 will ↓ pH ↑ HC03 will ↑ pH – Why C02 rising? – Pattern? – Hypoventilation – HC03 is Bicarbonate, ↓ CO2 will ↑ pH it is a base! More base, more alkalotic – Why? – Hyperventilation ↓ HC03 will ↓ pH © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Normal Values pH 7.35 – 7.45 PCO2 35 - 45 HCO3 22 - 26 PO2 80 – 100 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  pH 7.40 is alkalosis PCO2 >45 is acidosis PCO2 100 mmHg = Hyperoxia © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Basic Blood Gas Terminology Uncompensated = Acute Respiratory = Alveolar Hyperventilation = ↓ PC02 Hypoventilation = ↑ PC02 Fully Compensated = Chronic w/ pH back within normal range (does not overcompensate) Partially compensated = pH not back to normal range, but identify the other(good) system is working to help (compensate) – Attempts/Brings pH back to normal range – Does NOT Over-compensate 7.40 serves as crossing lane Combined = Mixed = Respiratory + Metabolic © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Step by Step Interpretation Look at the pH: is it normal, normal acidotic or alkalotic? acidotic, alkalotic Look at the PaCO2: is it normal, normal acidotic or alkalotic? acidotic, alkalotic Look at the HCO3-: is it normal, normal acidotic or alkalotic? acidotic, alkalotic Once you have determined the state of each parameter, you simply match them up. Lastly, look at Pa02 to determine if 1) normal 2) Hypoxemia – mild, moderate, or severe 3) Hyperoxia (too much 02) © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Interpretation pH = 7.40 N PaCO2 = 42 mmHg N HCO3 = 22 mEq/L N Pa02 = 82 mmHg N Normal Blood Gas © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Interpretation pH 7.40 N PaCO2 = 42 mmHg N HCO3 = 22 mEq/L N Pa02 62 mmHg ?? Normal Blood Gas w/ Mild Hypoxemia © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Interpretation pH 7.30 Acidosis PCO2 55 Acidosis HCO3 22 Normal Uncompensated Respiratory Acidosis Acute Respiratory Acidosis Acute alveolar hypoventilation Acute Respiratory Failure © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Respiratory Acidosis (Acute Respiratory Failure) (Uncompensated Alveolar Hypoventilation) Example: – pH is 7.18 ↓ Acidosis – PCO2 is 80 ↑ Acidosis – HCO3– is 26 mEq/L Normal range – no compensation – acute ventilatory failure confirmed – Uncompensated Respiratory Acidosis – 3rd name? © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 7-5.  Interpretation pH 7.30 Acidosis PCO2 = 55 mmHg Acidosis HCO3 = 22 mEq/L Normal Pa02 = 35 mmHg ?? ( < 40 mmHg = Severe) Uncompensated Respiratory Acidosis w/ Severe Hypoxemia Acute Respiratory Acidosis w/ Severe Hypoxemia Acute alveolar hypoventilation w/ Severe Hypoxemia Respiratory Failure w/ Severe Hypoxemia © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Renal Compensation In patient who hypoventilates for long period of time, kidneys will work to correct decreased pH by retaining HCO3– in blood – E.g., COPD © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Example: Renal Compensation – pH is 7.30 ↓ – PCO is 80 torr 2 ↑ – HCO is 37 mEq/L 3 ↑ – pH & C02 is true relationship, so it is a respiratory problem. HC03 is trying to help, compensation. How much ? Look at pH, it is within range ? – Yes – fully compensated, if No – partially compensated – ventilatory failure with partial renal compensation confirmed © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 7-6.  Acute Ventilatory Failure with Partial Renal Compensation Example: – pH is 7.30 ↓ – PCO2 is 80 torr ↑ – HCO3– is 37 mEq/L ↑ – ventilatory failure with partial renal compensation confirmed – Partially compensated Alveolar Hypoventilation © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 7-6.  Acute Ventilatory Failure with Partial Renal Compensation (Partially Compensated Respiratory Acidosis) Acute ventilatory failure with partial renal compensation present when: – Reported pH and HCO3– are both above normal red- colored PCO2 blood buffer bar (in purple-colored area), but pH is still less than normal – Also known as partially compensated respiratory acidosis See Figure 7-6 Partial – trying to bring back pH to normal limits, but the pH is still NOT within normal limits © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  5 Common Causes of Acute Ventilatory Failure 1) Chronic obstructive 3) General anesthesia – Generally, anesthetics pulmonary disorders cause ventilatory failure – Pulmonary disorders can 4) Head trauma lead to acute ventilatory – Severe trauma to the brain failure can cause acute E.g., chronic ventilatory failure emphysema, chronic 5) Neurologic disorders bronchitis – Neurologic disorders can 2) Drug overdose lead to acute ventilatory failure – Can depress ventilation – E.g., Guillain-Barré – E.g., narcotics or Syndrome, Myasthenia barbiturates Gravis © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 7-2.  Interpretation pH = 7.59 alkalosis PCO2 = 24 alkalosis (why?) HCO3- = 20 Normal Uncompensated Respiratory Alkalosis Acute Respiratory Alkalosis Acute alveolar hyperventilation © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Interpretation pH = 7.59 alkalosis PaCO2 = 24 mmHg alkalosis (why?) HCO3 = 23 mEq/L Normal Pa02 = 110 mm Hg ?? Uncompensated Respiratory Alkalosis w/Hyperoxia Acute Respiratory Alkalosis w/Hyperoxia Acute Alveolar Hyperventilation w/Hyperoxia © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Common Causes of Acute Alveolar Hyperventilation (Uncompensated Respiratory Alkalosis) 1) Hypoxia – Any cause of hypoxia can cause acute alveolar hyperventilation E.g., lung disorders, high altitudes, heart disease 2) Pain, anxiety, and fever – Relative to the degree of pain, anxiety, and fever, may see hyperventilation 3) Brain inflammation – Relative to the degree of cerebral inflammation, may see hyperventilation 4) Stimulant drugs – Agents can cause alveolar hyperventilation E.g., amphetamines © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 7-3.  Acute Alveolar Hyperventilation (Uncompensated Respiratory Alkalosis) Example: – pH is 7.55 ↑ – PCO2 is 25 torr ↓ – HCO3– is 22 mEq/L Normal, no comp – acute alveolar hyperventilation confirmed © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 7-7.  Renal Compensation In patient who hyperventilates for long period of time, kidneys will work to correct increased pH by excreting excess HCO3– in urine – E.g., patient who has been overly mechanically hyperventilated for more than 24 to 48 hours – Also known as partially compensated respiratory alkalosis © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Alveolar Hyperventilation with Partial Renal Compensation Example: – pH is 7.50 ↑ – PCO2 is 20 torr ↓ – HCO3– is 15 mEq/L ↓ – alveolar hyperventilation with partial renal compensation confirmed – Other name? © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 7-8.  General Comments: Compensation As a general rule, kidneys do not overcompensate for abnormal pH If patient’s blood pH becomes acidic for long period of time due to hypoventilation, kidneys will not retain enough HCO3– for pH to climb higher than 7.40 The kidneys help bring the pH back to within its normal limit. To reach it ! © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  General Comments Opposite also true One important – Should blood pH exception: become alkalotic for – In people who long period of time due chronically hypoventilate to hyperventilation, for long period of time, kidneys will not excrete not uncommon to find enough HCO3– for pH pH greater than 7.40 to fall below 7.40 (e.g., 7.43 or 7.44) E.g., patients with chronic emphysema or chronic bronchitis © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  General Comments Exception due to water and chloride ion (Cl-) shifts that occur between intercellular and extracellular spaces when renal system works to compensate for decreased blood pH (retains HC03-) – E.g. Respiratory Failure – Causes overall loss of blood chloride Hypochloremia – Will increases blood pH © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  To Summarize Lungs play important role in maintaining PCO2, HCO3–, and pH levels on moment- to-moment basis Kidneys play important role in balancing HCO3– and pH levels during long periods of hyperventilation or hypoventilation © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. METABOLIC ACID-BASE IMBALANCES © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Interpretation pH 7.25 Acidosis PCO2 41 Normal HCO3 12 Acidosis Uncompensated Metabolic Acidosis Acute Metabolic Acidosis © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Common Causes of Metabolic Acidosis 1. Lactic acidosis - Fixed acids 2. Ketoacidosis - Fixed acids 3. Salicylate intoxication - Aspirin overdose - Fixed acids 4. Renal failure 5. Uncontrolled diarrhea © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 7-4.  Interpretation pH =7.25 Acidosis PCO2 = 41 mmHg ?? Normal HCO3 = 12 mmHg Acidosis Pa02 = 50 mmHg ?? Uncompensated Metabolic Acidosis w/ Moderate Hypoxemia Acute Metabolic Acidosis w/ Moderate Hypoxemia © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Metabolic Acidosis with Partial Respiratory Compensation Example: – pH is 7.30 ↓ – PCO2 is 25 ↓ – HCO3– is 12 mEq/L ↓ – metabolic acidosis with partial respiratory compensation confirmed © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 7-10.  Common Causes of Metabolic Alkalosis 1) Hypokalemia 5) Excessive 2) Hypochloremia administration of 3) Gastric suctioning sodium bicarbonate or vomiting 6) Diuretic therapy 4) Excessive 7) Hypovolemia administration of corticosteroids © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 7-5.  Compensation (Partial or Full) As a general rule, kidneys do not overcompensate for abnormal pH If patient’s blood pH becomes acidic for long period of time due to hypoventilation, kidneys will not retain enough HCO3– for pH to climb higher than 7.40 The kidneys help bring the pH back to within its normal limit. To reach it ! © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Metabolic Alkalosis with Respiratory Compensation Example: – pH is 7.50 (↑) – PCO2 is 60 (↑) – HCO3– is 46 mEq/L (↑) – metabolic alkalosis with partial respiratory compensation present – Partially compensated metabolic alkalosis © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 7-13.  Common Acid-Base Disturbance Classifications Respiratory acid-base disturbances – Acute ventilatory failure (respiratory acidosis) Uncompensated respiratory acidosis – Acute ventilatory failure with partial renal compensation Partially compensated respiratory failure – Chronic ventilatory failure with complete renal compensation © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 7-1.  Common Acid-Base Disturbance Classifications Respiratory acid-base disturbances – Acute alveolar hyperventilation (respiratory alkalosis) – Acute alveolar hyperventilation with partial renal compensation Partially compenstated respiratory alkalosis – Chronic alveolar hyperventilation with complete renal compensation Fully compensated respiratory alkalosis © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 7-1.  Common Acid-Base Disturbance Classifications Metabolic acid-base disturbances – Metabolic acidosis – Metabolic acidosis with partial respiratory compensation – Metabolic acidosis with complete respiratory compensation – Combined (metabolic and respiratory) acidosis © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 7-1.  Common Acid-Base Disturbance Classifications Metabolic acid-base disturbances – Metabolic alkalosis – Metabolic alkalosis with partial respiratory compensation – Metabolic alkalosis with complete respiratory compensation – Combined (metabolic and respiratory) alkalosis © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Table 7-1.  Mixed (combined) Yes, it can happen…. E.g. Combined acidosis Combined respiratory and metabolic acidosis pH: 7.30 PC02 = 50 mmHg HC03 = 18 mEq/L © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Combined Metabolic and Respiratory Acidosis Example: – pH is 7.10 ↓ – PCO2 is 70 torr ↑ – HCO3– is 21 mEq/L ↓ – combined metabolic and respiratory acidosis present © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Figure 7-11.  Combined Metabolic and Respiratory Alkalosis Yes, it can happen pH is 7.62 – Alkalotic (↑) PCO2 is 25 torr – ↓ - increases pH HCO3– is 28 mEq/L – ↑ - also increases pH both metabolic and respiratory alkalosis present © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Base Excess/Deficit Example: – If pH is 7.25 and HCO3– is 17 mEq/L at a time when PaCO2 is 40 mmHg, PCO2/HCO3–/pH nomogram will confirm presence of: Metabolic acidosis base deficit of +7 mEq/L – More properly called Base excess of -7 mEq/L See Figure 7-9 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Base Excess/Deficit Metabolic acidosis may be treated by careful intravenous infusion of sodium bicarbonate (NaHCO3) – In contrast, if pH is 7.50 and HCO3– is 31 mEq/L at a time when PaCO2 is 40 mmHg, PCO2/ HCO3–/pH nomogram will verify presence of: Metabolic alkalosis Base excess of +7 mEq/L – Base deficit of – 7 mEq/L See Figure 7-12 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Let’s practice pH = 7.52 PaC02 = 34 mmHg HC03 = 26 Pa02 = 86 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  pH = 7.35 PaC02 = 45 mmHg HC03 = 25.5 mEq/L Pa02 = 125 mmHg © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  pH = 7.47 PaC02 = 45.2 mmHg HC03 = 33.4 mEq/L Pa02 = 75 mmHg © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Clinical Application After ventilator changes are made, another arterial blood gas should be obtained in approximately 20 minutes pH, PaCO2 & Pa02 should be reevaluated – Followed by appropriate ventilator adjustments, if necessary © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.  Formula pH: 7.34 to 7.45 PaC02: 35 to 45 mmHg HC03- : 22 to 26 mEq/L Pa02: 80 to 100 mmHg Dissolved C02 in plasma (H2C03) H2C03 = (0.03 x PC02) pH = pK + log [HC03) / H2C03] –pK = 6.1 –Log ratio is 20 / 1 Range 18/1 to 22/1 © 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.