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Faisal Malmstrom, Critical Care Department SKMC

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1 Faisal Malmstrom, Critical Care Department SKMC
Oxygen Therapy Faisal Malmstrom, Critical Care Department SKMC

2 Carl Wilhelm Scheele Priestly and Lavoisier

3 ABC Air goes in and out, blood goes round and round.
Any variation on this is a bad thing. Airway obstruction needs to be addressed immediately

4 Respiratory failure Type 1 (hypoxemic)
Saturation < 90%. PaO2 <60 mm Hg Type 2 (hypercapnic) PCO2>50 mmHg, pH<7.35

5 Definitions Hypoxemia Hypoxia

6 Hypoxemia Low alveolar oxygen tension (ambient, hypoventilation)
Ventilation-perfusion mismatch Right to left shunt (venous admixture) intracardiac extracardiac Impaired oxygen diffusion (uncommon)

7 Alveolar gases

8 V/Q mismatch Ventilated but not perfused: increased dead space ventilation, VT=VD+VA VD= VD equipment + VD anatomic + VD physiologic Perfused but not ventilated: shunt >20% Shunt fraction, minimal improvement with increased FiO2

9 Hypoxia Hypoxemic Hypoxia Anaemic Hypoxia
Stagnant Hypoxia ( distributive or low CO) Histotoxic Hypoxia VDO2= CO x Hb x SAT/100 x 1.34ml/gHb+ (PaO2 x 0.003mlO2/100ml/mmHg)

10 Symptoms of Hypoxemia and Hypoxia
Dyspnea, tachypnea. Hyperventilation +/- Cyanosis ( Hb, perfusion) >15g/l Impaired mental performance----coma Seizures, permanent brain injury Tachycardia/Hypertension – Hypotension/Bradycardia( 30 mmHg) Lactic acidosis

11 Indications for Oxygen therapy
Cardiac and respiratory arrest Hypoxemia ( pO2 < 58.5 mmHg, Sat<90%) Hypotension ( Systolic BP < 100 mmHg) Low Cardiac Output and Metabolic Acidosis ( bicarbonate <18 mmol/l) Respiratory distress ( RR>24/minute) American College of Chest Physicians and NHLBI

12 Treatment I Empiric oxygen treatment Cardiac/ respiratory arrest
Hypotension Respiratory Distress Trauma GCS decrease from any cause Postoperative

13 Treatment II Verify hypoxemia Pulse oximetry ABG’s
Start Oxygen treatment. Treatment goal ( sat level) Administration mode, flow, when to stop

14 The oxyhaemoglobin dissociation curve showing the relation between partial pressure of oxygen and haemoglobin saturation Currie, G. P et al. BMJ 2006;333:34-36 Copyright ©2006 BMJ Publishing Group Ltd.

15 Charting Oxygen treatment
Dodd, M E et al. BMJ 2000;321: Copyright ©2000 BMJ Publishing Group Ltd.

16 Bad medicine To withhold Oxygen out of fear of hypercarbic ventilatory failure is poor practice Identify patients at risk (COPD) Use Venturi masks FiO2. ABG’s/ O2-sat to direct therapy Support ventilation (BiPAP, intubation)

17 Oxygen Hazards Fire ( airway fires)
Tissue toxicity, pulmonary and retina Decreased hypoxemic drive and increased VD in COPD. Seizures (hyperbaric) Mucosal damage due to lack of humidity

18 Oxygen administration
Low flow systems High Flow systems (HFOE)

19 Nasal Prongs

20 Bateman, N T et al. BMJ 1998;317: Copyright ©1998 BMJ Publishing Group Ltd.

21 Face Mask (“Hudson”)

22 Non-rebreather

23 Venturi Mask

24 Venturi valve

25 Bateman, N T et al. BMJ 1998;317: Copyright ©1998 BMJ Publishing Group Ltd.

26 Long term oxygen therapy prolongs survival in hypoxaemic patients with COPD when used for ≥15 hours/day. (Results from the nocturnal oxygen therapy trial (NOTT) and the MRC trial) Currie, G. P et al. BMJ 2006;333:34-36 Copyright ©2006 BMJ Publishing Group Ltd.

27 Take home message Acute empiric oxygen treatment is ok but hypoxemia should be verified with pulse oximetry and /or ABG’s when situation more stable. Oxygen is a drug and should be ordered as such: mode of administration, flow rate, FiO2 (venturi), treatment goal, monitoring, when to stop. Never withhold oxygen out of fear of possible hypercarbia Avoid overzealous treatment- Adequate saturation for the patient. COPD 88-90%

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