Dr Vishram Buche Central India’s CHILD hospital & Research Institute, NAGPUR

1.Clinical physiology of OXYGEN transport 2.Oxygenation status…... Parameters to d/d Hypoxia Severity of hypoxia 3.Improving Oxygenation (DO 2 )……… Interventions to improve Hypoxia Body compensates Therapeutics..O 2 therapy, Drugs

O2O2 CO 2 O2 CO 2 PO 2 = 100 PO 2 = 150 CO 2 O2O2 Pulmonary circulation Systemic circulation O2O2 O2O2 CO 2 O 2 CO 2 O 2

Functions……!!! …….. O 2 ……...CO 2 ……...?? GLOBInGLOBIn HAEmHAEm α2β2α2β2 α β β α Simple structure..??

1.Hb is a stereotactic molecule, when it combines with O2, it goes in to conformational changes. 2.It behaves different at different situations, 3.It has more affinity towards o2 in pulmonary Capillaries so binds more o2, 4.Less affinity towards o2 at systemic tissue capillaries so deliveries more o2 5.At higher Partial pressure it loves to bind more o2, at lower partial pressure it loves to deliver more o2. Moods of haemoglobin………

SaO 2 % CaO 2 (ml/100ml) O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2

PaO 2 = 100 SaO 2 = 100% SO 2 = 75% O 2 = 95 CO 2 = 46 O2O2 CO 2 P A O 2 = 100 Atm = 760 FiO 2 = 21% PO 2 = 160 CO 2 = 40 O 2 = 100 CO 2 = 40 Pulmonary circulation Systemic circulation SO 2 = 75% PaO 2 = 95 SaO 2 = 97% PCO 2 = 40 O 2 = 40 After venous admixture O 2 = 40 CO 2 = 46 O 2 = 40 CO 2 = 46 External respiration Internal respiration

PaO 2 = 100 SaO 2 = 100% Content= 20.4 ml/dl SO 2 = 75% CaO 2 = 15 O 2 = 95 CO 2 = 46 O2O2 CO 2 = 40 P A O 2 = 100 Atm = 760 FiO 2 = 21% PO 2 = 160 CO 2 = 40 O 2 = 100 CO 2 = 40 Pulmonary circulation Systemic circulation SO 2 = 75% CaO 2 = 15 O2O2 PaO 2 = 95 SaO 2 = 97% Content= 20 ml/dl PCO 2 = 40 O 2 = 40 External respiration Internal respiration After venous admixture 2% 98% O 2 = 40 CO 2 = 46 O 2 = 40 CO 2 = 46

PO 2 SO 2

CaO 2 = Oxygen content 20 ml/100ml 2% Dissolved O 2 ( PaO 2  ml )  CaO 2 (20) = HbO 2 (19.7) + Dissol.O 2 (0.3) 98% O 2 is bound to Hb ( Hb  1.34  SaO 2 )

PaO 2 = 100 SaO 2 = 100% Content= 20.4 ml/dl SO 2 = 75% CaO 2 = 15 O 2 = 95 CO 2 = 46 O2O2 CO 2 = 40 P A O 2 = 100 Atm = 760 FiO 2 = 21% PO 2 = 160 CO 2 = 40 O 2 = 100 CO 2 = 40 Pulmonary circulation Systemic circulation SO 2 = 75% CaO 2 = 15 O2O2 PaO 2 = 95 SaO 2 = 97% Content= 20 ml/dl PCO 2 = 40 O 2 = 40 External respiration Internal respiration After venous admixture 2% 98% O 2 = 40 CO 2 = 46 O 2 = 40 CO 2 = 46

CaO2 DO2 PAO2 PaO2 SaO2 FiO2 OXYGEN 2 OXYGEN 2

100% 85% 50% 75% CaO 2 tissue lung PaO 2 SaO2 0

100% 50% 75% Content tissue lung PaO 2 SaO 2 0

100% 50% 75% CaO 2 tissue lung PaO 2 SaO tissue 10 18

↑ CO2 ↑ H+ ↑ Temp ↑ 2,3 DPG 85 ↓CO2 ↓ H+ ↓ Temp ↓ 2,3 DPG

Oxygen Cascade……. Dry Atmosph: PO Dry Atmosph: PO Humidified Tracheal gas: 150 Alveolar gas P A O 2 : 100 Arterial blood: PaO 2 : 95 Capillary blood: 95 Mitochondria: 1-2 Venous blood: PO 2 40, sat 97% …… FiO 2 =21% Tissue P (A-a) gradient

Alveolar-arterial O 2 Difference…….. FiO 2 = 21 % : (760-45) x.21= 150 mmHg O 2 CO 2 PAO 2 = 150 – 1.2 (PCO 2 ) = 150 – 1.2  40 = 150 – 50 = 100 mm Hg P a O 2 = 90 mmHg ………..PAO 2 – P a O 2 = ? PAO 2 – P a O 2 = 10 mmHg

Alveolar-arterial Difference… O 2 CO 2 Alveolar – arterial G = 55 ……………….Wide A-a Oxygenation Failure PCO 2 = 40 P A O 2 = 150 – 1.2 (40) = = 100 PaO 2 = 45 Ventilation Failure PCO 2 = 80 PAO 2 = (80) = = 50 PaO 2 = 45 Alveolar arterial G. 50 – 45 = 5 …………….Normal A-a

Measure Severe anemia V-Q mismatch High Altitude CO- poisoning PaO 2 SaO 2 CaO 2 N  N    N  

PaO 2 A-a gradient N  PCO2 Alveolar Hypoventilation  A-a gradient 100% O2 V-Q mismatch Diffusion Shunt Approach To Hypoxemia  Corrected PaO 2 Uncorrected PaO 2 Look for FiO2 PCO 2 N ↓FiO 2

CaO2 A…. Hb = 12 …..SaO 2 = 100% B…. Hb = 15 …..SaO 2 = 80% C…. Hb = 20……SaO 2 = 80%.. cyanotic D…. Hb = 7……..SaO 2 = 100%..acynotic WHO IS MORE CRITICAL ? normal

Master A …PICU.., breathing room air, monitored by pulse ox,blood drawn for ABG. ABG…..PaO2 = 77 Three SaO2 values…. 98% Pulse ox 95% Calculated from PaO2 85% Co-oximeter Why do these value disagree? Which is most reliable?

20 months…Persistant crying and irritable…2days No H/o respiratory infection, Refusal of feeds…day of admn O/E cynotic,vitals…normal, RS/CVS…WNL, O 2 inhaln ABG = pH-7.42, PaO , PCO 2 =33, SaO 2 =99% Pulse Ox=SpO2= 75%. Unexplained cyanosis, ↓SpO2, ↑↑ PaO2, RS/CVS….Ok MethHb 27%, Responded to Methylene blue METHMOGLOBINEMIA

PaO 2 SaO 2 O 2 bound Hb Dissolved O2 O. D. C. P A O 2 A.C.I. CaO 2 Content of oxygen Delivery Of Oxygen To Tissues DaO 2 O2O2 Cardiac output O2O2 FiO2

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