This document provides an overview of oxygen therapy. It discusses oxygen transport and delivery in the body, including how oxygen levels decrease from the atmosphere to tissues. It outlines indications for oxygen therapy when hypoxemia is present. Various oxygen delivery devices are described, including nasal cannulas, masks, and catheters. Low-flow systems provide variable oxygen concentrations while high-flow systems and reservoir masks provide more consistent fixed concentrations. Complications of oxygen therapy are also mentioned.

1. OXYGEN THERAPY
 Dr Bhavya Naithani,
MD,PDCC
 Assistant Professor critical
care
 King George’s Medical
University

2. OVERVIEW
 Introduction
 Oxygen transport
 Indications
 Oxygen delivery systems
 Hyperbaric oxygen therapy
 Complications of oxygen therapy

3. Stephen Hale – prepared oxygen along with other gases
Priestly –discovered it
Lavoisier- oxygen was absorbed by the lungs and
eliminated as carbon di oxide and water
Colourless, odourless tasteless gas
Boiling point at 1 atmosphere =-183 degree centigrade
Below this temperature it exists as a pale blue liquid
Critical temperature -118 degree centigrade
Cannot be ignited, aids combustion
Industrially prepared by liquefaction of air-fractional
distillation of liquefied air

4. OXYGEN THERAPY ….. WHAT?
Administration of O2 in concentration more
than in ambient air
↑Partial Pr of O2 in insp. Gas(Pi o2)
↑Partial Pr of O2 in alveoli (PAo2)
↑Partial Pr of O2 in arterial blood (Pao2)

5. “lack of O2 not only stops the machinery, but
also totally wrecks it “
J.S.Haldane

6. OXYGEN
 Oxygen is 21% of atmosphere
 760 mmHg x .21 = 160 mmHg PO2
 This mixes with “old” air already in alveolus to arrive at
PO2 of 105 mmHg
 Oxygen is either bound to haemoglobin (98%)
 Oxygen dissolved in plasma (3%)

7. CARBON DI OXIDE
 Carbon dioxide is .04% of atmosphere
 760 mmHg x .0004 = .3 mm Hg PCO2
 This mixes with high CO2 levels from residual volume
in the alveoli to arrive at PCO2 of 40 mmHg
 CO2 transport
 7% in plasma
 23% in carbamino compounds (bound to globin part
of Hb)
 70% as Bicarbonate

9. Arterial Blood Venous Blood
 O2 sat Hb 98% 40%
 PO2 95 45
 Hb bound to O2 19.7 14.7 ml/100ml
 Total O2 content 20 14.8 ml/100ml
 Dissolved O2 .003 .0012
 Blood volume 1.25 l 3.75 l
 Vol of O2 250ml 555ml

10. Oxygen content
Amount of O2 carried by 100 ml of blood
Co2 =Dissolved O2 + O2 Bound to hemoglobin
Co2 = Po2 × 0.0031 + So2 × Hb × 1.34
(Normal Cao2 = 20 ml/100ml blood
Normal Cvo2 = 15 ml/100ml blood)
C(a-v)o2 = 5 ml/100ml blood
Co2 = arterial oxygen content (vol%)
Hb = hemoglobin (g%)
1.34 = oxygen-carrying capacity of hemoglobin
Po2 = arterial partial pressure of oxygen (mmHg)
0.0031 = solubility coefficient of oxygen in plasma

11. O2Hb dissociation curve
0 20 40 60 80 100 120 140 160
0
20
40
60
80
100
%
Hb
Sat
with
O
2
PO2 mmHg

13. Oxygen Uptake (VO2)
 The Vo2 describes the volume of oxygen (in mL)
that leaves the capillary blood and moves into the
tissues each minute.
 VO2 = CO x C(a-v)o2 x 10
 normal VO2 = 200–300 mL/min or 110–160
mL/min/m2
 DO2 =vol that reaches systemic capillaries each
minute=CO x CaO2 x 10=900-1100 ml/min
 Direct VO2= M.Vx( FiO2-FeO2)

14. Oxygen-Extraction Ratio (O2ER)
 The fraction of the oxygen delivered to the
capillaries and then to tissues.
 An index of the efficiency of oxygen transport.
 O2ER = VO2 / DO2
= CO x C(a-v)o2 x 10
CO x Cao2 x 10
= SaO2 - SvO2 / SaO2
 Normal - 0.25 (range = 0.2–0.3)

15. VO2 versus DO2 DYSOXIA

16. What is Pasteur point ?
The critical level of PO2 below which aerobic
metabolism fails.
(1 – 2 mmHg PO2 in mitochondria)
Normal level (7-37mmhg)

17. REMEMBER……
 PaO2 implies adequacy of gas exchange not arterial
saturation
 Total vol of O2 805 ml, O2 consumption 250ml/min,
can only sustain aerobic metabolism for 3-4 min!!!!
 Amt of O2 in blood is only 20-25% of the amount
needed for the complete oidative metabolism of
blood…Why so little?
 Hb 15g/dl and C.O 5 L ,Total mass of circulating Hb
750gm….weight of heart 300gm

18. Is all this Hb necessary?
 When extraction of O2 from systemic capillaries is
maximal only 40-50% of Hb in venous blood remains
fully saturated with oxygen.
 This means half the circulating Hb is not being used to
support aerobic metabolism
 WHAT IS IT DOING ???

19. CARBON DI OXIDE
 Carbon dioxide is .04% of atmosphere Total Body CO2
130L total body water 45 L
 760 mmHg x .0004 = .3 mm Hg PCO2
 This mixes with high CO2 levels from residual volume
in the alveoli to arrive at PCO2 of 40 mmHg
 CO2 transport
 7% in plasma-.8 meq in plasma, 0.4 in RBC)
 23% in carbamino compounds (bound to globin part
of Hb) 1.2 meq only in RBC
 70% as Bicarbonate-16.2 plasma 4.6 RBC

20. Total Vol of CO2 in solution is
more than the solution

21. HALDANE EFFECT
The increase in
CO 2 content
that results from
oxyhaemoglobin
desaturation
60% increased
CO2 in venous
blood is d/t
PCO2 ,40% d/t
oxyhb
desaturation

22. C0 2 and 02 transport

23. CO 2 transport

24. Haemoglobin

25. What is the Oxygen Cascade?
The process of declining oxygen tension from atmosphere to
mitochondria
Atmosphere air (dry) (159 mm Hg) 760 x21%
↓ humidification
Lower resp tract (moist) (150 mm Hg) (760-47) x 21%
↓ O2 consumption and alveolar ventilation
Alveoli PAO2 (104 mm Hg)
↓ venous admixture
Arterial blood PaO2 (100 mm Hg)
↓ tissue extraction
Venous blood PV O2 (40 mm Hg)
↓
Mitochondria PO2 (7 – 37 mmHg)

26. O2 Cascade
Venous admixture
PA O2 = 104 mm Hg
Alveolar
air
Arteria
l blood Pa O2 = 100 mm Hg
A – a = 4 – 25 mmHg
PI O2
PV O2

27. Venous admixture
(physiological shunt)
O2 Cascade
Low VA/Q Normal True shunt
(normal anatomical
shunt)
Pulmonary
(Bronchial veins)
Extra Pulm.
(Thebesian
veins)
Normal = upto 5 % of cardiac

28. O2 Cascade
Utilization by
tissue
Arteria
l blood
Pa O2 = 100 mm Hg
(Sat. > 95 %)
Mixed
Venous
blood
PV O2 = 40mm Hg
Sat. 75%
Cell
Mitochondria
PO2 (7 – 37
mmHg)

29. O2 Cascade
Utilization by
tissue
Arteria
l blood
Pa O2 = 97mm Hg
(Sat. > 95 %)
Mixed
Venous
blood
PV O2 = 40mm Hg
Sat. 75%
Cell
Mitochondria
PO2 ( 7 – 37
mmHg)
Perfusion
O2 content (Hb Conc.)

30. Oxygen Flux
Amount of of O2 leaving left ventricle per minute.
= CO × art oxygen sat x Hb conc x 1.34
100 100
= 5000 x 97 x 15.4 x 1.34
100 100
= 1000 ml/min
CO = cardiac output in ml per minute.
Do2 = oxygen flux

31. Goal of oxygen therapy
To maintain adequate tissue oxygenation while
minimizing cardiopulmonary work

32. O2 Therapy : CLINICAL OBJECTIVES
1. Correct documented or suspected hypoxemia
2. Decrease the symptoms associated with chronic
hypoxemia
3. Decrease the workload hypoxemia imposes on the
cardiopulmonary system

33. O2 Therapy : Indications
 Documented hypoxemia as evidenced by
 PaO2 < 60 mmHg or SaO2 < 90% on room air
 PaO2 or SaO2 below desirable range for a specific clinical
situation
 Acute care situations in which hypoxemia is suspected
 Severe trauma
 Acute myocardial infarction
 Short term therapy (Post anaesthesia recovery)
Respir Care 2002;47:707-720

34. ASSESSMENT
 The need for oxygen therapy should be
assessed by
1. monitoring of ABG - PaO2,
SpO2
2. clinical assessment findings.

35. PaO2 as an indicator for Oxygen therapy
 PaO2 : 80 – 100 mm Hg : Normal
60 – 80 mm Hg : cold, clammy
extremities
< 60 mm Hg : cyanosis
< 40 mm Hg : mental deficiency
memory loss
< 30 mm Hg : bradycardia
cardiac arrest
PaO2 < 60 mm Hg is a strong indicator for
oxygen therapy

36. HYPOXIA
 Hypoxic Hypoxia= Decrease in PaO2
 Anemic hypoxia= Decrease in O2 content
 Anemia,carbon monooxide poisoning,methhb, sulfhb
 Stagnant hypoxia=reduced tissue perfusion general ,local
 Histotoxic hypoxia =poisoning of intracellular enzymes
cyanide poisoning septicaemia

37. Clinical assessment of hypoxia
mild to moderate severe
CNS : restlessness somnolence, confusion
disorientation impaired judgement
lassitude loss of coordination
headache obtunded mental status
Cardiac : tachycardia bradycardia, arrhythmia
mild hypertension hypotension
peripheral vasoconst.
Respiratory: dyspnea increasing dyspnoea,
tachypnea tachypnoea, possible
shallow & bradypnoea
laboured breathing
Skin : paleness, cold, clammy cyanosis

38. MONITORING
 Physical examination for C/F of hypoxemia
 Pulse oximetry
 ABG analysis
 pH
 pO2
 pCO2
 Mixed venous blood oxygenation

40. CLASSIFICATION
DESIGNS
 Low- flow system
 Reservoir systems
 High flow system
 Enclosures
PERFORMANCES (Based on predictability and
consistency of FiO2 provided)
 Fixed
 Variable

41. Low flow system
 The gas flow is insufficient to meet patient’s peak
inspiratory and minute ventilatory requirement
 O2 provided is always diluted with air
 FiO2 varies with the patient’s ventilatory pattern
Deliver low and variable FiO2 → Variable
performance device

42. High flow system
• The gas flow is sufficient to meet patient’s
peak inspiratory and minute ventilatory
requirement.
• FiO2 is independent of the the patient’s
ventilatory pattern
• Deliver low- moderate and fixed FiO2 →
Fixed performance device

43. Reservoir System
 Reservoir system stores a reserve volume of O2, that
equals or exceeds the patient’s tidal volume
 Delivers mod- high FiO2
 Variable performance device
 To provide a fixed FiO2, the reservoir volume must
exceed the patient’s tidal volume

44. O2 Delivery devices
o Low flow (Variable performance devices )
 Nasal cannula
 Nasal catheter
 Transtracheal catheter
o Reservoir system (Variable performance device)
 Reservoir cannula
 Simple face mask
 Partial rebreathing mask
 Non rebreathing mask
 Tracheostomy mask
o High flow (Fixed performance devices)
 Ventimask (HAFOE)
 Aerosol mask and T-piece with nebulisers

46. Nasal Cannula A plastic disposable device
consisting of two tips or
prongs 1 cm long,
connected to oxygen
tubing
Inserted into the vestibule
of the nose
FiO2 – 24-40%
Flow – ¼ - 8L/min (adult)
< 2 L/min(child)

47. Nasal Cannula
Merits Demerits
 Easy to fix
 Keeps hands free
 Not much interference
with further airway care
 Low cost
 Compliant
 Unstable
 Easily dislodged
 High flow uncomfortable
 Nasal trauma
 Mucosal irritation
 FiO2 can be inaccurate and
inconsistent

48. Nasal catheter

49. Nasal catheter
Merits Demerits
 Good stability
 Disposable
 Low cost
 Difficult to insert
 High flow increases back
pressure
 Needs regular changing
 May provoke gagging, air
swallowing, aspiration
 Nasal polyps, deviated
septum may block insertion

51. RESERVOIR MASKS
Commonly used reservoir system
Three types
1. Simple face mask
2. Partial rebreathing masks
3. Non rebreathing masks

52. Simple face mask
 Reservoir - 100-200 ml
Variable performance device
FiO2 varies with
 O2 input flow,
 mask volume,
 extent of air leakage
 patient’s breathing pattern
FiO2: 40 – 60%
Input flow range is 5-8 L/min
Minimum flow – 5L/min to
prevent CO2 rebreathing

53. Face mask
Merits
 Moderate but variable FiO2.
 Good for patients with blocked
nasal passages and mouth
breathers
 Easy to apply
Demerits
 Uncomfortable
 Interfere with further airway care
 Proper fitting is required
 Risk of aspiration in unconscious
pt
 Rebreathing (if input flow is less
than 5 L/min)
O2
Flowrate
(L/min)
Fi O2
5-6 0.4
6-7 0.5
7-8 0.6

54. Reservoir masks
Partial rebreathing mask Nonrebreathing mask

55. Partial rebreathing mask
 No valves
 Mechanics –
Exp: O2 + first 1/3 of
exhaled gas (anatomic dead
space) enters the bag and
last 2/3 of exhalation
escapes out through ports
Insp: the first exhaled gas
and O2 are inhaled
 FiO2 - 60-80%
 FGF > 8L/min
 The bag should remain
inflated to ensure the
highest FiO2 and to
prevent CO2 rebreathing
Exhalation
ports
O2
Reservoir
+

56. Non-rebreathing mask
 Has 3 unidirectional valves
 Expiratory valves prevents air
entrainment
 Inspiratory valve prevents
exhaled gas flow into
reservoir bag
 FiO2 - 0.80 – 0.90
 FGF – 10 – 15L/min
 To deliver ~100% O2, bag
should remain inflated
 Factors affecting FiO2
 air leakage and
 pt’s breathing pattern
O2
Reservoir
One-way valves

57. Tracheostomy Mask
 Used primarily to deliver
humidity to patients with
artificial airways.
 Variable performance
device

58. Air entrainment devices
Blending systems

59. Air entrainment devices
Based on Bernoulli principle –
A rapid velocity of gas exiting from a restricted
orifice will create subatmospheric lateral
pressures, resulting in atmospheric air being
entrained into the mainstream.

60. Principle of Air entrainment
devices
Principle of constant-pressure jet mixing – a
rapid velocity of gas through a restricted orifice creates
“viscous shearing forces” that entrain air into the
mainstream.
(Egan’s fundamentals of respiratory care;
Shapiro’s Clinical application of blood gases)

61. Mechanism of Air entrainment
devices
oxygen
room air
exhaled gas

62. Characteristics of Air entrainment
devices
 Amount of air entrained varies directly with
 size of the port and the velocity of O2 at jet
 They dilute O2 source with air - FiO2 < 100%
 The more air they entrain, the higher is the total
output flow but the lower is the delivered FiO2

63. 2 most common air-entrainment systems are
1. Air-Entrainment mask (venti-mask)
2. Air-Entrainment nebulizer

64. Venturi / Venti / HAFOE Mask
Mask consists of a jet orifice
around which is an air
entrainment port.
FiO2 regulated by size of jet
orifice and air entrainment
port
FiO2 – Low to moderate (0.24
– 0.60)
HIGH FLOW FIXED
PERFORMANCE DEVICE

65. Varieties of Venti Masks
A fixed Fio2 model A variable Fio2 model

66. Air entrainment nebulizer
 Have a fixed orifice, thus, air-to-O2 ratio can be altered
by varying entrainment port size.
 Fixed performance device
 Deliver FiO2 from 28-100%
 Max. gas flows – 14-16L/min
 Device of choice for delivering O2 to patients with
artificial tracheal airways.
 Provides humidity and temperature control

67. Air entrainment nebulizer
Aerosol
mask
Face tent
Tracheostomy
collar
T tube

68. Blending systems With a blending system,
separate pressurized air
and oxygen sources are
input.
 The gases are mixed either
manually or with a blender
 FiO2 – 24 – 100%
 Provide flow > 60L/min
 Allows precise control over
both FiO2 and total flow
output - True fixed
performance devices
OXYGEN BLENDER

69. Blending systems With a blending system,
separate pressurized air
and oxygen sources are
input.
 The gases are mixed either
manually or with a blender
 FiO2 – 24 – 100%
 Provide flow > 60L/min
 Allows precise control over
both FiO2 and total flow
output - True fixed
performance devices
OXYGEN BLENDER

70.  Oxygen tent
 Hood
 Incubator

71. OXYGEN TENT Consists of a canopy
placed over the head and
shoulders or over the
entire body of a patient
 FiO2 – 40-50% @12-15L/minO2
 Variable performance device
 Provides concurrent aerosol
therapy
 Disadvantage
 Expensive
 Cumbersome
 Difficult to clean
 Constant leakage
 Limits patient mobility

72. OXYGEN HOOD
 An oxygen hood covers only the
head of the infant
 O2 is delivered to hood through
either a heated entrainment
nebulizer or a blending system
 Fixed performance device
 Fio2 – 21-100%
 Minimum Flow > 7/min to prevent
CO2 accumulation

73. INCUBATOR  Incubators are polymethyl
methacrylate enclosures that
combine servo-controlled
convection heating with
supplemental O2
 Provides temperature control
 FiO2 – 40-50% @ flow of 8-15
L/min
 Variable performance device

75. DEFINITION
A mode of medical treatment wherein
the patient breathes 100% oxygen at a
pressure greater than one Atmosphere
Absolute (1 ATA)
1 ATA is equal to 760 mm Hg at sea level

76. Basis of Hyperbaric O2 Therapy
Dissolved O2 in plasm0.003ml / 100ml of blood / mm
PO2
(Henry’s Law -The concentration of any gas in
solution is
proportional to its partial pressure.)
Breathing Air (PaO2 100mm Hg)
0.3ml / 100ml of blood
Breathing 100% O2 (PaO2 600mm Hg)
1.8ml / 100ml of blood
Breathing 100% O2 at 3 AT.A (PaO2 2000 mm Hg)

77. Physiological effects of HBO
 Bubble reduction ( boyle’s law)
 Hyperoxia of blood
 Enhanced host immune function
 Neovascularization
 Vasoconstriction

78.  Decompression sickness
 Air embolism
 Carbon monoxide poisoning
 Severe crush injuries
 Thermal burns
 Acute arterial insufficiency
 Clostridial gangrene
 Necrotizing soft-tissue
infection
 Ischemic skin graft or flap
 Radiation necrosis
 Diabetic wounds of lower
limbs
 Refratory osteomyelitis
 Actinomycosis (chronic
systemic abscesses)
Uses

79. METHODS OF ADMINISTRATION of
HBOT

80. Hyperbaric oxygen therapy
 Barotrauma
 Ear/ sinus trauma
 Tympanic membrane rupture
 Pneumothorax
 Oxygen toxicity
 Fire hazards
 Clautrophobia
 Sudden decompression

82. Complications of Oxygen therapy
1. Oxygen toxicity
2. Depression of ventilation
3. Retinopathy of Prematurity
4. Absorption atelectasis
5. Fire hazard

83. 1. O2 Toxicity
 Primarily affects lung and CNS.
 2 factors: PaO2 & exposure time
 CNS O2 toxicity (Paul Bert effect)
 occurs on breathing O2 at pressure > 1 atm
 tremors, twitching, convulsions

84. Pulmonary Oxygen toxicity
C/F
 acute tracheobronchitis
 Cough and substernal pain
 ARDS like state

85. Pulmonary O2 Toxicity (Lorrain-
Smith effect)
Mechanism: High pO2 for a prolonged period of time
↓
intracellular generation of free radicals e.g.:
superoxide,H2O2 , singlet oxygen
↓
react with cellular DNA, sulphydryl proteins &lipids
↓
cytotoxicity
↓
damages capillary endothelium,
↓

86. Interstitial edema
Thickened alveolar capillary membrane.
↓
Pulmonary fibrosis and hypertension

87. Indications for 70% - 100% oxygen
therapy
1. Resuscitation
2. Periods of acute cardiopulmonary instability
3. Patient transport

88. 2. Depression of Ventilation
 Seen in COPD patients with chronic hypercapnia
 Mechanism
↑PaO2
suppresses peripheral V/Q mismatch
chemoreceptors
depresses ventilatory drive ↑ dead space/tidal volume
ratio
↑PaCO2

89. 3. Retinopathy of prematurity
(ROP)
 Premature or low-birth-weight infants who receive
supplemental O2
 Mechanism
↑PaO2
↓
retinal vasoconstriction
↓
necrosis of blood vessels
↓
new vessels formation
↓
Hemorrhage → retinal detachment and blindness
To minimize the risk of ROP - PaO2 below 80 mmHg

90. 5. Fire hazard
 High FiO2 increases the risk of fire
 Preventive measures
 Lowest effective FiO2 should be used
 Use of scavenging systems
 Avoid use of outdated equipment such as aluminium
gas regulators
 Fire prevention protocols should be followed for
hyperbaric O2 therapy

91. Implications of Oxygen challenge
concept
To identify refractory hpoxemia (as it does not respond
to increased FiO2)
Refractory hpoxemia depends on increased cardiac
output to maintain acceptable FiO2
Potentially deleterious effect of increased FiO2 can be
avoided

92. SUMMARY
Therapeutic effectiveness of oxygen therapy is
limited to 25% - 50%
• Low V/Q hypoxemia is reversed with less than 50%
• Denitrogenation absorption atelectasis occurs with
FiO2 more than 50%
• Pulmonary oxygen toxicity is a potential risk factor
with FiO2 more than 50%
Bronchodilators, bronchial hygiene therapy and
diuretic therapy decreases the need for high FiO2

93. Oxygen is a drug.
When appropriately used, it is extremely beneficial
When misused or abused, it is potentially harmful

94. Problems
 You are setting up an air-entrainment mask at an FIO2 of
0.40 and the oxygen flowmeter is set at 12 l/min. The
patient’s tidal volume is 600 mL and the inspiratory
time is 1.5 seconds. Is the flow from this system meeting
the patient’s inspiratory needs?
 Air: Oxygen Ratio: 100-FiO2/FiO2-21
 Air flow= air oxygen ratio x oxygen flow
 Total Liter Flow: Oxygen Flow + Air Flow = 12 L/min +
36 L/min = 48 L/min


95.  Peak Inspiratory Flowrate: ( Minute
ventilation/inspiratory time ) x 60 = .6/1.5 x 60= 24
L/min
 Is the FDO2 > FIO2? YES NO
 What FIO2 would the patient actually receive?
 0.40
 Less than 0.40
 Greater than 0.40

96.  You are setting up an air-entrainment nebulizer with a
tracheostomy mask at an FIO2 of 0.35 and the oxygen
flowmeter is set at 15 L/min. The patient’s minute
ventilation is 8 L/min and the I:E ratio is 1:3. Is the flow
from this system meeting the patient’s inspiratory
needs?
 Air: Oxygen Ratio:
 Total Liter Flow: Oxygen Flow + Air Flow = 15 L/min +
75 L/min = 90 L/min

97.  Peak Inspiratory Flowrate: Minute ventilation x(
inspiratory timr = expiratory time)
 Is the FDO2 > FIO2? YES NO
 What FIO2 is the patient actually receiving?
 0.35
 Less than 0.35
 Greater than 0.35