Oxygen Therapy Faisal Malmstrom, Critical Care Department SKMC.

Oxygen TherapyOxygen Therapy

Faisal Malmstrom,Faisal Malmstrom,

Critical Care DepartmentCritical Care Department

SKMCSKMC

Carl Wilhelm ScheeleCarl Wilhelm ScheelePriestly and Lavoisier Priestly and Lavoisier

ABCABC

Air goes in and out, blood goes round Air goes in and out, blood goes round and round. and round.

Any variation on this is a bad thing.Any variation on this is a bad thing.

Airway obstruction needs to be Airway obstruction needs to be addressed immediately addressed immediately

Respiratory failureRespiratory failure

Type 1 (hypoxemic) Type 1 (hypoxemic)

Saturation Saturation < 90%. PaO< 90%. PaO2 2 <60 mm Hg<60 mm Hg

Type 2 (hypercapnic)Type 2 (hypercapnic)

PCOPCO22>50 mmHg, pH<7.35>50 mmHg, pH<7.35

Definitions Definitions

HypoxemiaHypoxemia

HypoxiaHypoxia

HypoxemiaHypoxemia

Low alveolar oxygen tensionLow alveolar oxygen tension

(ambient, hypoventilation)(ambient, hypoventilation) Ventilation-perfusion mismatchVentilation-perfusion mismatch Right to left shunt (venous admixture)Right to left shunt (venous admixture)

intracardiacintracardiac

extracardiacextracardiac Impaired oxygen diffusion (uncommon)Impaired oxygen diffusion (uncommon)

Alveolar gasesAlveolar gases

V/Q mismatchV/Q mismatch

Ventilated but not perfused: increased Ventilated but not perfused: increased dead space ventilation, VT=dead space ventilation, VT=VDVD+VA+VA

VD= VD= VD VD equipment equipment + VD+ VD anatomic anatomic + VD + VD physiologicphysiologic

Perfused but not ventilated: shuntPerfused but not ventilated: shunt

>20% Shunt fraction, minimal >20% Shunt fraction, minimal improvement with increased FiO2improvement with increased FiO2

Hypoxia Hypoxia

Hypoxemic HypoxiaHypoxemic Hypoxia Anaemic HypoxiaAnaemic Hypoxia Stagnant Hypoxia ( distributive or low Stagnant Hypoxia ( distributive or low

CO)CO) Histotoxic Hypoxia Histotoxic Hypoxia

VDO2VDO2= CO x Hb x SAT/100 x 1.34ml/gHb+ = CO x Hb x SAT/100 x 1.34ml/gHb+ (PaO2 x 0.003mlO2/100ml/mmHg)(PaO2 x 0.003mlO2/100ml/mmHg)

Symptoms of Hypoxemia Symptoms of Hypoxemia and Hypoxiaand Hypoxia

Dyspnea, tachypnea. HyperventilationDyspnea, tachypnea. Hyperventilation +/- Cyanosis ( Hb, perfusion) >15g/l+/- Cyanosis ( Hb, perfusion) >15g/l Impaired mental performance----comaImpaired mental performance----coma Seizures, permanent brain injurySeizures, permanent brain injury Tachycardia/Hypertension – Tachycardia/Hypertension –

Hypotension/Bradycardia( 30 mmHg)Hypotension/Bradycardia( 30 mmHg) Lactic acidosisLactic acidosis

Indications for Oxygen Indications for Oxygen therapytherapy

Cardiac and respiratory arrestCardiac and respiratory arrest Hypoxemia ( pO2 < 58.5 mmHg, Hypoxemia ( pO2 < 58.5 mmHg,

Sat<90%)Sat<90%) Hypotension ( Systolic BP < 100 mmHg)Hypotension ( Systolic BP < 100 mmHg) Low Cardiac Output and Metabolic Low Cardiac Output and Metabolic

Acidosis ( bicarbonate <18 mmol/l)Acidosis ( bicarbonate <18 mmol/l) Respiratory distress ( RR>24/minute)Respiratory distress ( RR>24/minute)American College of Chest Physicians and NHLBI American College of Chest Physicians and NHLBI

Treatment ITreatment I

EmpiricEmpiric oxygen treatment oxygen treatment

Cardiac/ respiratory arrestCardiac/ respiratory arrest

HypotensionHypotension

Respiratory Distress Respiratory Distress

TraumaTrauma

GCS decrease from any causeGCS decrease from any cause

Postoperative Postoperative

Treatment IITreatment II

Verify hypoxemiaVerify hypoxemia

Pulse oximetry Pulse oximetry

ABG’sABG’s Start Oxygen treatment.Start Oxygen treatment. Treatment goal ( sat level)Treatment goal ( sat level) Administration mode, flow, when to stop Administration mode, flow, when to stop

Copyright ©2006 BMJ Publishing Group Ltd.

Currie, G. P et al. BMJ 2006;333:34-36

The oxyhaemoglobin dissociation curve showing the relation between partial pressure of oxygen and haemoglobin saturation


Dodd, M E et al. BMJ 2000;321:864-865

Charting Oxygen treatment

Bad medicineBad medicine

To withhold Oxygen out of fear of hypercarbic To withhold Oxygen out of fear of hypercarbic ventilatory failure is poor practiceventilatory failure is poor practice

Identify patients at risk (COPD)Identify patients at risk (COPD)

Use Venturi masks 0.24 -0.28 ---- FiO2.Use Venturi masks 0.24 -0.28 ---- FiO2.

ABG’s/ O2-sat to direct therapyABG’s/ O2-sat to direct therapy

Support ventilation (BiPAP, intubationSupport ventilation (BiPAP, intubation))

Oxygen HazardsOxygen Hazards

Fire ( airway fires) Fire ( airway fires) Tissue toxicity, pulmonary and retinaTissue toxicity, pulmonary and retina Decreased hypoxemic drive and Decreased hypoxemic drive and

increased VDincreased VD in COPD. in COPD. Seizures (hyperbaric)Seizures (hyperbaric) Mucosal damage due to lack of humidityMucosal damage due to lack of humidity

Oxygen administrationOxygen administration

Low flow systemsLow flow systems

High Flow systems (HFOE)High Flow systems (HFOE)

Nasal ProngsNasal Prongs


Bateman, N T et al. BMJ 1998;317:798-801

Face Mask (“Hudson”)Face Mask (“Hudson”)

Non-rebreather Non-rebreather

Venturi MaskVenturi Mask

Venturi valveVenturi valve


Bateman, N T et al. BMJ 1998;317:798-801


Currie, G. P et al. BMJ 2006;333:34-36

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)

Take home messageTake home message

Acute empiric oxygen treatment is ok but hypoxemia Acute empiric oxygen treatment is ok but hypoxemia should be verified with pulse oximetry and /or ABG’s should be verified with pulse oximetry and /or ABG’s when situation more stable.when situation more stable.

Oxygen is a drug and should be ordered as such: Oxygen is a drug and should be ordered as such: mode of administration, flow rate, FiO2 (venturi), mode of administration, flow rate, FiO2 (venturi), treatment goal, monitoring, when to stop.treatment goal, monitoring, when to stop.

Never withhold oxygen out of fear of possible Never withhold oxygen out of fear of possible hypercarbiahypercarbia

Avoid overzealous treatment- Adequate saturation for Avoid overzealous treatment- Adequate saturation for the patient. COPD 88-90%the patient. COPD 88-90%

Oxygen Therapy Faisal Malmstrom, Critical Care Department SKMC.

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