oxygen therapy

Oxygen Therapy

Dr.Indubala Maurya MD,DNB,MNAMS

Assistant Professor Dept of Aanesthesia & Critical

Care,MGMCRI

• Definition • Physiology

– O2 content – Hypoxia

• Orthobaric Oxygen Therapy – Indication – Device for oxygen therapy

• Hyperbaric oxygen therapy• Side effects of Oxygen Therapy

Why oxygen Why oxygen is required for is required for

survival?survival?

Aerobic metabolism Aerobic metabolism oxidative phosphorylationoxidative phosphorylation

Glucose → CO2 + H2O + 38 ATP Glucose → CO2 + H2O + 38 ATP

Anaerobic metabolismAnaerobic metabolismGlucose → Lactic acid + 2 ATPGlucose → Lactic acid + 2 ATP

↓↓

H+ + lactate –H+ + lactate –

Anoxia No oxygen availability in

tissues

Hypoxia Lack of oxygen availability in

tissues

Hypoxemia Lack of oxygen in the blood

Basics

What is O2 Therapy ?

Oxygen therapy is the administration of oxygen at concentrations greater than that in room air to treat or prevent hypoxia.

Types of Oxygen TherapyTypes of Oxygen Therapy• Giving Oxygen more

than 21% at ambient atm pressure

• Giving Oxygen more than 21% at high atm pressure ( >1 atm)

Orthobaric Hyperbaric

Three clinical goals of O2 therapy

1. Treat hypoxia

2. Decrease work of breathing

3. Decrease myocardial Work

• FIO2 ( Fraction of O2 in inspired gas)– 0.21 (21%)

• PaO2(Partial pressure of Oxygen in arterial blood– 98-100 mmHg ( 5 -6 times of FIO2)

• SaO2(saturation of Hb in arterial Blood) – 100%

• PvO2 (Partial pressure of Oxygen in Venous blood )– 40 mmHg

• SvO2 (saturation of Hb in Venous Blood) – 75%

Oxygen Transport

O2 Content in Blood

Hemoglobin-Bound O2• Oxygen-binding capacity of hemoglobin : 1.34 mL O2 /gm of Hb)• SO2 : O2 saturation of Hb

Dissolved O2• Solubility of oxygen in plasma

– solubility coefficient 0.003 mL/100 mL/mm Hg• Partial pressure of oxygen (PO2) in blood.

Hb X 1.34 X SaO2

0.003 X PaO2 mmHg

Arterial O2 Content (CaO2)

egNormal person Hb: 14gSaO2: 98-100%PaO2: 100 mmHgArt. blood Art. blood = 14g x 1.39 x 100% + 0.3 = 14g x 1.39 x 100% + 0.3 = 20 ml / 100ml of blood= 20 ml / 100ml of blood

0.003 X PaO2 mmHgHb X 1.34 X SaO2

Venous O2 Content (CvO2)

Normal PersonHb: 14gSvO2: 75 %PvO2: 40 mmhg

Ven. blood Ven. blood 14g x 1.39 x 75% + 0.1 = 14g x 1.39 x 75% + 0.1 = 15ml /100ml of blood15ml /100ml of blood

Tissue extraction = 5ml/ 100 ml of bloodTissue extraction = 5ml/ 100 ml of blood

Hb X 1.34 X SvO2 0.003 X PvO2 mmHg

Dissolved ODissolved O22 in in plasmaplasma

0.003ml / mm PO2 / 100ml of blood

Breathing Air (PaO2 100mm Hg)

0.3ml / 100ml of blood

O2 therapyOrthobaricBreathing 100% O2 (PaO2 600mm Hg)

1.8ml / 100ml of blood HyperbaricBreathing 100% O2 at 3 Atm. Pressure5.4ml / 100ml of blood

What are the Types of What are the Types of

HypoxiaHypoxia??

Types of hypoxiaTypes of hypoxia• Hypoxic hypoxia – PaO2↓

• Anaemic hypoxia – O2 content ↓, PaO2 normal

• Stagnant hypoxia

• Histotoxic hypoxia

Hypoxic hypoxiaHypoxic hypoxia• Causes

– O2 poor air, hypoxic gas mixture– High altitude – Hypoventilation– Shunts – Septal defects – Diffusion defects - pneumonia, lobar

collapse

Anaemic hypoxia• Oxygen carrying capacity of blood is

decreased. – Anemia :↓ haemoglobin– Altered haemoglobin

• CO poisoning • meth / sulph-haemoglobin

Normal Person (breathing 100% O2)

(14gm x 1.34ml ) + 1.8ml = 20.5ml (1.8 is 9% 20.5)Anaemic patient (breathing 100% O2)

(4gm x 1.34ml )+ 1.8ml = 7.2 ml (1.8 is 25% of 7.2)

Stagnant hypoxia• Inadequate tissue perfusion• Generalized:

- Hypovolemia- Mitral stenosis- Constrictive pericerditis- Myocardial ischaemia

• Localized hypo perfusion: - Arterial obstruction, thrombus,

oedema

Histotoxic hypoxia

• Cells can not utilize the oxygen .• Electron transfer system of cytochrome

oxidase is paralysed.• e.g.

– cyanide poisoning

Benefit of OBenefit of O22 therapy in therapy in HypoxiaHypoxia

Hypoxic hypoxia + + +Anaemic hypoxia +Stagnant hypoxia +Histotoxic hypoxia -

Clinical presentation of Hypoxia

Effects of hypoxia• Acute hypoxia :

- Restlessness- Disorientation, confusion- In-coordination, Impaired judgment

- Hyperventilation air hunger-Circulatory changes

(tachycardiabrady )

• Chronic hypoxia :- fatigue, drowsiness, ↓ work capacity- inattentiveness ,apathy, delayed reaction time

Assessment of need• Presence of clinical indicators • Measurement of inadequate oxygen saturations

– by invasive or noninvasive methods,• Arterial blood gas• Pulse oximetry

Errors in pulse oximetry• Artificial fingernails• Dark pigmentation • Electrical interference • Intravenous dyes • Movement• Nail Polish • Pulsatile venous system• Radiated light

How to assess oxygenation ?

• Arterial blood gases• PaO2 = 100 mmhg• Pulse oximetry• SpO2=98-100%

Oxygen therapy is must whenever Oxygen therapy is must whenever PaO2 < 60 mmHg or SpO2 < 90 %PaO2 < 60 mmHg or SpO2 < 90 %

FACTORS THAT DETERMINE WHICH SYSTEM TO USE

1. Patient comfort / acceptance 2. The level of FiO2 that is needed

3. The requirement that the FiO2 be controlled within a certain range4. The level of humidification and /or nebulization5. Minimal resistance to breathing6. Efficient & economical use of oxygen

Orthobaric Oxygen therapy

Oxygen therapy devicesVariable performance devices

• No capacity – nasal catheters, cannulae• Small capacity – masks• Large capacity – mask with bag

Fixed performance devices• HAFOE systems (High air flow oxygen enrichment

device » Venti Mask

• Anaesthesia circuits• Ventilators

Variable performance device

e.g.• Nasal cannula• Simple face mask• Partial rebreathing mask• Non - rebreathing mask

FiO2 depends on

•O2 flow

•Patient factors

•Device factors

Nasal CatheterNasal Catheter

O2 Flowrate (L/min)

123456

Fi O2

0.240.280.320.360.400.44

Nasal CatheterNasal CatheterMerits• Easy to fix• Keeps hands free• Not much interference with further airway

care• Useful in both spont. breathing and

apnoeicDemerits• Mucosal irritation (uncomfortable)• Gastric dilatation (especially with high flows)

Nasal cannula• Simple plastic tubing + prongs

Simple face maskSimple face mask

Simple Face Mask – ?


NO YES

Simple Face Mask

Simple face mask

Placing of mask over the patient’s face increases the size of the oxygen reservoir beyond the limits of the anatomic reservoir ;therefore a higher FiO2 can be delivered.

.


O2 Flowrate (L/min)

5-66-77-8

Fi O2

0.400.500.60

• Advantages: – Simple– lightweight, FiO2 upto 0.60

• Disadvantages: – need to remove when speak, eat, drink, vomiting,

expectoration of secretions– drying / irritation of eyes– uncomfortable when facial burns / trauma – Application problem when RT in situ

Partial Rebreathing mask Partial Rebreathing mask (polymask)(polymask)

Partial Rebreathing maskPartial Rebreathing mask(polymask)(polymask)

O2 Flowrate (L/min)

678

Fi O2

0.600.700.80

Advantages: • FiO2 delivered >0.60 is delivered in mod. to

severe hypoxia, • Exhaled oxygen from anatomic dead space is

conserved.

Disadvantages: • insufficient flow rate may lead to rebreathing of

CO2,• Claustrophobia• drying and irritation of eyes

Non Rebreathing maskNon Rebreathing mask

10 – 15 Ltr/min flow rate – 50-100 O2 conc.

Merits• Higher Oxygen Conc.

Demerits• Air dilution (if not fitting properly) • Rebreathing (if O2 flow is inadequate)

• Interfere with further airway care• Uncomfortable (sweating, spitting)

Fixed performance device: Ventimask


NO YES

Simple Face Mask

VENTURI VALVE

Color FiO2 O2 Flow

Blue 24% 2 L/minWhite 28% 4 L/min

Orange 31% 6 L/minYellow 35% 8 L/min

Red 40% 10 L/minGreen 60% 15 L/min

Venturi valve

Venturi principle

Hyperbaric Oxygen therapy

Hyperbaric oxygen (HBO) exposure (breathing oxygen at increased ambient pressure, typically 2-3 atmospheres absolute [ATA]) causes an increase in PaO2.

Indication For HBOT • Poisoning :• Carbon monoxide • Infections :

– Clostridial myonecrosis• Acute ischemia

– Crush injury• Chronic ischemia

– Radiation necrosis • Ischemic ulcers

– diabetic ulcers

If conc. of OIf conc. of O22 which a patient is getting which a patient is getting is not known is not known

then the situation is similar to then the situation is similar toa drug being administereda drug being administered without knowing the dose without knowing the dose

which can do harm if given morewhich can do harm if given more or provide insufficient effect if given less or provide insufficient effect if given less

O2 ToxicityO2 Toxicity

Side Effects • Rentrolental fibroplasia in neonates• Resp system:

– Loss of surfactant – Atelactasis – Hypoventilation in COPD pt

• CNS: – Convulsion (HBOT)

100% - not more than 12hrs100% - not more than 12hrs 80% - not more than 24hrs 80% - not more than 24hrs 60% - not more than 36hrs 60% - not more than 36hrs

oxygen therapy

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