Respiratory A&P FCC 2024 PDF

Foundations of Critical Care Respiratory Physiology Objectives Understand systemic vs pulmonary circulation Review the relationship between alveoli and lung capillaries Understand the variables of O2 delivery Understand the Oxyhaemoglobin Dissociation Curve Discuss V/Q misma...

Foundations of Critical Care Respiratory Physiology Objectives Understand systemic vs pulmonary circulation Review the relationship between alveoli and lung capillaries Understand the variables of O2 delivery Understand the Oxyhaemoglobin Dissociation Curve Discuss V/Q mismatch - shunt and dead space University of Adelaide 2 Systemic vs Pulmonary Circulation White board University of Adelaide 4 Lung Capillaries University of Adelaide 5 University of Adelaide 6 University of Adelaide 8 University of Adelaide 9 Composition of atmospheric air Can you guess the composition of the air we breathe? University of Adelaide 10 Quick Review What is Cardiac Output? Pre Load Stroke Volume Contractility After Load Ejection Fraction?? University of Adelaide 11 Still unpacking… Difference between SaO2 and PaO2? Normal Hb? When do we top it up? How should we treat low SpO2? FiO2 – fraction of inspired Oxygen. Room Air = 21% FiO2 – 0.21% 10- 15L NRB = 60-80% FiO2 (depends on leak) University of Adelaide 12  Oxygen delivery variables DO2 CO x (SaO2 x Hb x 1.34) + 0.003(PaO2) x 10 University of Adelaide 13 Variables CO SaO2 Hb PaO2 Is giving more Oxygen the answer? University of Adelaide 14 Steps of Oxygen Delivery O2 Available to breathe Airway - Into the alveoli Transmembrane diffusion – A-a gradient Vascular – Red cells available for binding Cardiac Output – Blood moving to take O2 to the tissues Hb releasing O2 adequately – Tissue uptake Use of O2 by tissue University of Adelaide 15  Hypoxia vs Hypoxaemia from Greek hupo ‘under’ 1940s Hypo + Oxy = Hypoxia Haima (Greek) turned into hemia (Latin) = ‘blood’ What is Hypoxaemia? What is Hypoxia? University of Adelaide 16 Why is Hypoxia so bad? What happens in the tissues when there is no O2? What do they use? Do the cells die? University of Adelaide 17 Cellular Respiration Aerobic Metabolism Anaerobic Metabolism University of Adelaide 18 Aerobic Metabolism Glucose + Pyruvic acid + O2 = 38 ATP + CO2 + H2O University of Adelaide 19 Anaerobic Metabolism Glucose + Pyruvic Acid = 2 lactic acid + 2 ATP University of Adelaide 20 University of Adelaide 21 The Lactate Dilemma - Lactate is produced in the presence of anaerobic metabolism; - The problem with that is that for a cell to go into anaerobic metabolism it takes a very low Delivery of Oxygen; - Lactate is also produced in the presence of Oxygen, for fuel (glycolysis – pyruvic acid – lactate); - It is a marker of physiological stress; released when there is an adrenergic response, with or without tissue hypoxia; - What we know: a high lactate is associated with increased mortality. Why? It is not the lactate’s fault. It is just a marker of stress. University of Adelaide 22 More… - The decrease of lactate shows that the stress is going down. The patient is improving; - A high lactate shows a problem – always; University of Adelaide 23  West Zones PA Alveolar pressure Pa Arterial pressure PV Venous pressure University of Adelaide 24  Zones of Pulmonary Blood Flow Three functional zones of pulmonary blood flow can be defined based on the relevant pressure gradient actuating flow of blood. In Zone 1 where no blood flows the alveolar pressure (PA) is greater than both the arterial (Pa) and venous pressures (Pv). In Zone 2 where moderate blood flow occurs the relevant pressure gradient is between the arterial pressure and the alveolar pressure. In Zone 3 where the greatest blood flow occurs the relevant pressure gradient is between the arterial and venous pressures. University of Adelaide 25 University of Adelaide 26 VQ mismatch - Shunt and dead space https://ars.els-cdn.com/content/image/1-s2.0- S2049080122005805-gr5_lrg.jpg https://ars.els-cdn.com/content/image/1-s2.0-S2049080122005805- gr5_lrg.jpg University of Adelaide 27  Oxyhaemoglobin Dissociation Curve The same way it binds, now it needs to unbind; Oxygen has an affinity for Hb, it doesn’t want to unbind… In comes 2,3 DPG (Diphosphoglycerate) – by-product of glycolysis in the red cell. Helps regulate the affinity between Hb and O2 – repellent; The tissues have a very low concentration of O2, because it uses so much. The difference in concentration from SaO2 to the intracellular will weaken the affinity, promoting unloading. University of Adelaide 28 University of Adelaide 29 University of Adelaide 30 It is not pathological to shift to the right or to the left Muscles/placenta: Increased temperature (more blood flow) Higher level of CO2 (more acidic environment) High requirement of O2 (Exercise) Less affinity- needs to unload More 2,3 DPG Shift to the Right Lungs: Lower temperature High level of O2 More affinity - holds onto it Less 2,3 DPG Shift to the left University of Adelaide 31  It becomes pathological when it shifts out of balance… University of Adelaide 32  Questions? Thank you University of Adelaide 33