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
is required for
survival?
Aerobic metabolism
oxidative phosphorylation
Glucose → CO2 + H2O + 38 ATP
Anaerobic metabolism
Glucose → Lactic acid + 2 ATP
↓
H+ + lactate –
c
i
s
a
B
s
Anoxia
No oxygen availability in
tissues
Hypoxia
Lack of oxygen availability in
tissues
Hypoxemia
Lack of oxygen in the blood
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 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
Hb X 1.34 X SaO2
Dissolved O2
•
•
Solubility of oxygen in plasma
– solubility coefficient 0.003 mL/100 mL/mm Hg
Partial pressure of oxygen (PO2) in blood.
0.003 X PaO2 mmHg
Arterial O2 Content (CaO2)
Hb X 1.34 X SaO2
0.003 X PaO2 mmHg
eg
Normal person
Hb: 14g
SaO2: 98-100%
PaO2: 100 mmHg
Art. blood = 14g x 1.39 x 100% + 0.3 = 20 ml / 100ml of blood
Venous O2 Content (CvO2)
Hb X 1.34 X SvO2
0.003 X PvO2 mmHg
Normal Person
Hb: 14g
SvO2: 75 %
PvO2: 40 mmhg
Ven. blood 14g x 1.39 x 75% + 0.1 = 15ml /100ml of blood
Tissue extraction = 5ml/ 100 ml of blood
Dissolved O2 in
plasma
0.003ml / mm PO2 / 100ml of blood
Breathing Air (PaO2 100mm Hg)
0.3ml / 100ml of blood
O2 therapy
Orthobaric
Breathing 100% O2 (PaO2 600mm Hg)
1.8ml / 100ml of blood
Hyperbaric
Breathing 100% O2 at 3 Atm. Pressure
What are the Types of
Hypoxia?
Types of hypoxia
• Hypoxic hypoxia – PaO2↓
• Anaemic hypoxia – O2 content ↓, PaO2 normal
• Stagnant hypoxia
• Histotoxic hypoxia
Hypoxic 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 O2 therapy in
Hypoxia
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 (tachycardiabrady )
• 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
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 range
4. The level of humidification and /or
nebulization
5. Minimal resistance to breathing
6. Efficient & economical use of oxygen
Orthobaric Oxygen therapy
Oxygen therapy devices
Variable 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
FiO2 depends on
•O2 flow
•Patient factors
•Device factors
e.g.
• Nasal cannula
• Simple face mask
• Partial rebreathing mask
• Non - rebreathing mask
Nasal Catheter
O2 Flowrate (L/min)
Fi O2
1
2
3
4
5
6
0.24
0.28
0.32
0.36
0.40
0.44
Nasal Catheter
Merits
•
•
•
•
Easy to fix
Keeps hands free
Not much interference with further airway
care
Useful in both spont. breathing and
apnoeic
Demerits
•
•
Mucosal irritation (uncomfortable)
Gastric dilatation (especially with high flows)
Nasal cannula
• Simple plastic tubing + prongs
Simple Face Mask – ?
Simple face mask
Simple Face Mask
Simple face mask
NO
YES
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.
Simple face mask
O2 Flowrate (L/min)
Fi O2
5-6
6-7
7-8
0.40
0.50
0.60
• 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
(polymask)
Partial Rebreathing mask
(polymask)
O2 Flowrate (L/min)
Fi O2
6
7
8
0.60
0.70
0.80
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 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
Simple Face Mask
Simple face mask
NO
YES
VENTURI VALVE
Venturi valve
Color
FiO2
O2 Flow
Blue
White
24%
28%
2 L/min
4 L/min
Orange
31%
6 L/min
Yellow
35%
8 L/min
Red
Green
40%
60%
10 L/min
15 L/min
Venturi principle
Hyperbaric Oxygen therapy
Hyperbaric oxygen (HBO) exposure (breathing
oxygen at increased ambient pressure, typically 23 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
O2 Toxicity
If conc. of O2 which a patient is getting
is not known
then the situation is similar to
a drug being administered
without knowing the dose
which can do harm if given more
or provide insufficient effect if given less
Side Effects
• Rentrolental fibroplasia in neonates
• Resp system:
– Loss of surfactant
– Atelactasis
– Hypoventilation in COPD pt
• CNS:
– Convulsion (HBOT)
100% - not more than 12hrs
80% - not more than 24hrs
60% - not more than 36hrs