M5 BOARD REVIEW. Q s. Q s. Q s. Q s. Q s. Equations. Be Brilliant Today. Respiratory ( ) Alveolar Gas Equation. Dead Space (Bohr Equation)

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1 Be Brilliant Today Respiratory Alveolar Gas Equation Dead Space (Bohr Equation) PA O2 FI O2 ( P ATM P H2 O ) Pa CO2 / RQ V D V T P a P ECO CO2 2 P a CO 2 PA O2 Alveolar partial pressure of oxygen P a CO 2 Arterial partial pressure of oxygen Pa CO2 FI O2 P ATM P H2 O Arterial partial pressure of CO2 Inspired O2 Atmospheric pressure Saturated vapor pressure P ECO 2 Partial pressure of CO2 from all expired gases Basic Pulmonary Physiology: Q14 RQ Respiratory Quotient Respiratory Physiology: Q14 Basic Pulmonary Physiology: Q7 Shunt Equation Q shunt (Cc O 2 - Ca O2 ) Q total (Cc O2 - C mvo ) 2 Ventilation/Perfusion Index (ratio) VQI ( 1 Arterial Hbsat) 1 Mixed Venous Hbsat ( ) Basic Pulmonary Physiology: Q17 Cc O2 Ca O2 C mvo 2 Post-capillary blood oxygen content (typically assumed to be the Saturation of haemoglobin utilizing the PAO2 haemoglobin concentration 1.34) Arterial Hbsat Hb 1.34 Mixed venous Hbsat Hb 1.34 Basic Pulmonary Physiology: Q17 Ohm s Law Pressure Gradient Air Flow Airway Resistance Basic Pulmonary Physiology: Q17 p1

2 Respiratory Airway Resistance for Laminar Flow (Poiseuille s Law) Laminar Flow Resistance 8 Length Viscosity of gas ( ) Radius 4 ( ) Respiratory Physiology: Q7 Basic Pulmonary Physiology: Q5 Law of LaPlace Pressure Note: 2 Wall Tension Radius Wall thickness is typically not considered for alveoli Basic Pulmonary Physiology: Q5 Reynold s Number R ( Velocity Density Diameter) Viscosity >2000 consistent with turbulent flow Respiratory Physiology: Q7 Respiratory Physiology: Q8 Basic Pulmonary Physiology: Q4 Time Constant TC Compliance Resistance Basic Pulmonary Physiology: Q5 Static Compliance Static compliance Volume Pressure Tidal volume delivered Plateau pressure PEEP ( ) Basic Pulmonary Physiology: Q33 Dynamic Compliance Dynamic compliance Volume Pressure Tidal volume delivered Peak pressure PEEP ( ) Basic Pulmonary Physiology: Q33 p2

3 Respiratory Transpulmonary Pressure Transpulmonary pressure Alveolar pressure Pleural pressure ICU: Advanced Cardiopulmonary: Q1 Transthoracic Pressure Transthoracic pressure Pleural pressure Atmospheric pressure ICU: Advanced Cardiopulmonary: Q1 Predicted PaO2 by Age Predicted PaO2 110-(age 0.4) Special Situations: Q12 Respiratory Physiology: Q6 Boyle s Law Pressure1 Volume1 Pressure2 Volume2 Basic Cardiac Physiology: Q12 p3

4 Respiratory Henry s Law Partial Pressure k C k Henry s Law Constant C Concentration of dissolved gas Ohm s Law Pressure Cardiac Output Resistance Cardiac Physiology: Q14 Henderson-Hasselbach ph pk + log[hco3-/ (0.03 PaCO2)] p4

5 Cardiac Myocardial Perfusion Pressure MPP Aortic diastolic pressure LVEDP Cardiac Physiology: Q23 LaPlace Law Tension (Pressure Radius)/(2 Wall Thickness) Note: Notice that as opposed to the equation in the Respiratory Section, the equation is solved for wall tension Basic Cardiac Physiology: Q12 Poiseuille s Law Flow Rate (π Pressure radius4)/(8 viscosity length) Note: Notice that as opposed to the equation in the Respiratory Section, the equation is solved for flow. Basic Cardiac Physiology: Q12 p5

6 Cardiac Fick Principle CO VO2/(CaO2 CmvO2) CO Cardiac Output VO2 Oxygen consumption CaO2 Arterial content of oxygen CmvO2 Mixed venous content of oxygen ICU Principles: Q1 Consumption of Oxygen (not including O2 dissolved in blood for simplicity) VO2 Hb (Sata - Satmv) X 1.34 CO Rearranged: Satmv Sata [VO2/ (Hb 1.34 CO)] CO Cardiac Output VO2 Oxygen consumption Sata Arterial saturation of haemoglobin Satmv Mixed venous saturation of haemoglobin Hb Haemoglobin ICU Principles: Q1 ICU Principles: Q2 ICU Principles: Q19 p6

7 Cardiac Arterial Content of Oxygen CaO2 [Hb Sata 1.34] PaO2 Oxygen Delivery DO2 CaO2 CO Sata Arterial saturation of haemoglobin Pa O2 Partial pressure of oxygen in arterial blood CaO2 Arterial content of oxygen CO Cardiac Output ICU Principles: Q1 ICU Principles: Q1 Elimination of CO2 VCO2 Hb X SatmvCO2 CO Oxygen Extraction Ratio ER VO2/DO2 SatmvCO2 CO2 saturation in mixed venous blood VO2 Oxygen consumption DO2 Delivery of oxygen ICU Principles: Q1 ICU Principles: Q1 ICU Principles: Q3 Respiratory Quotient RQ VCO2/VO2 Cardiac Output CO Stroke Volume Heart Rate VCO2 Elimination of CO2 VO2 Oxygen consumption ICU Principles: Q15 p7

8 Cardiac Stroke Volume SV End-diastolic volume End-systolic volume Cardiac Index CI CO/BSA Basic Cardiac Physiology: Q29 CO Cardiac Output BSA Body Surface Area Pulmonary Vascular Resistance PVR [(PAP-Wedge)/CO] 80 PAP Pulmonary Arterial Mean Mressure CO Cardiac Output ICU Principles: Q6 Systemic Vascular Resistance SVR [(MAP-CVP)/CO] 80 MAP Mean Arterial Pressure CVP Central Venous Pressure CO Cardiac output Stroke Work Basic Cardiac Physiology: Q13 SW Stroke volume mean arterial pressure Basic Cardiac Physiology: Q29 p8

9 Cardiac Starling Equation Q ka X [(Pc Pi) + σ(πi-πc)] Cerebral Perfusion Pressure CPP MAP ICP Q Net Fluid Filtration k Capillary Filtration Coefficient (of water) A Area of the Membrane σ Reflection Coefficient (of albumin) Pc Capillary Hydrostatic Pressure Pi Interstitial Hydrostatic Pressure πi Interstitial Colloid Osmotic Pressure πc Capillary Colloid Osmotic Pressure. Basic Cardiac Physiology: Q30 MAP Mean arterial pressure ICP Intracranial pressure Clinical Neurophysiology: Q2 Clinical Neurophysiology: Q3 Perfusion Pressure PP MAP Venous Presure Allowable Blood Loss ABL EBV X [(Hb Minimum allowable Hb)/Hb] EBV Estimated Blood Volume p9

10 Pharmacology It is important to understand the concepts of pharmacokinetics, but few equations need to be memorized. Memorizing complex clearance and half-life equations, accounting for peripheral compartments are very low yield just understand the concept. Volume of Distribution VD Dose / Concentration Basic Pharmacology: Anesthesia Adjuncts Q1 Basic Pharmacology: Anesthesia Adjuncts Q2 Basic Pharmacology: Induction Agents Q12 Half Life Half-life Volume of distribution / Rate of clearance Basic Pharmacology: Anesthesia Adjuncts Q1 Basic Pharmacology: Anesthesia Adjuncts Q2 Basic Pharmacology: Induction Agents Q12 Clearance Clearance dose/ area under time concentration curve Clearance (Urine concentration Urine flow) / Plasma concentration Basic Pharmacology: Anesthesia Adjuncts Q1 Basic Pharmacology: Anesthesia Adjuncts Q2 Basic Pharmacology: Induction Agents Q12 p10

11 Pharmacology Opioid Conversions Drug IV Oral Morphine 10 mg 30 mg Hydromorphone 1.5 mg 7.5 mg Fentanyl 100 mcg N/A Codeine N/A 200 mg Hydrocodone N/A 30 mg Oxycodone N/A mg p11

12 Equipment Endotracheal Size (for children) Size 4 + (Age/4) Endotracheal Depth Depth 12 + (Age/2), or 3 ETT size Pediatrics: Q4 Gas Tanks (E) Gas Volume Pressure Oxygen 625 L (US) 2200 psig Nitrous Oxide 1590 L 745 psig Equipment: Q1 Equipment: Q2 p12

13 Statistics Incidence & Prevalence Incidence Number of occurrences / Sum of person-time at risk Prevalence Number of cases/ Number of individuals sampled Measure of Effect Absolute measure of effect Rate Difference Rate of risk exposed Rate of risk not exposed Relative measure of effect Rate Ratio Rate of risk exposed /Rate of risk not exposed p13

14 Statistics Disease Screening Has Disease No Disease Positive Test True Positive (TP) False Positive (FP) Negative Test False Negative (FN) True Negative (TN) Sensitivity TP/ (TP + FN) Specificity TN/ (TN + FP) Positive Predictive Value TP/ (TP + FP) Negative Predictive Value TN/ (TN + FN) Statistics: Q17 Statistics: Q18 p14

15 Statistics Disease Screening Has Disease No Disease Exposed A B Not Exposed C D Odds Ratio AD/BC Relative Risk [A/(A+B)] / [C/(C+D)] Statistics: Q16 Number needed to Treat NNT 1 / ARR ARR Absolute Risk Reduction Control event rate Experimental event rate Statistics: Q19 p15