oxygen therapy.pptx

Lecture on Oxygen therapy for
c2 medical student
Dr. Getaye Simachew ACCPM
resident
9/8/2022

Outline
Introduction
Hypoxia and detection of hypoxia
 Oxygen Sources and delivery system
Specific considerations in Pts with Obstructive
lung diseases
9/8/2022

objective
At the end of this lecture
You will explain normal and abnormal value of o2
in human body and the time we intiate treatment
You will know transport mechanism of o2
will understand different type and causes hypoxia
 will know common o2 sources and delivery
system
know the difference for o2 therapy in copd patient
9/8/2022

Brain storming question
when to use o2& and for what disease conditions?
 target for therapy?
How is o2 transported in the body+
the difference between hypoxia and hypoxemia?
List commen o2 delivery system and their
advantages ,disadvantages?
9/8/2022

Introduction
Oxygen is a gas found in air we breath, is
necessary for human life.
some people with breathing disorder can’t get
enough oxygen naturally and develop hypoxia
They may need oxygen supplementation or
therapy to improve energy level, sleep or in
general for better quality of life.
9/8/2022

Oxygen transport
oxygen pass different transport cascades until it
get into the target site(tissue)
ventilation, gas exchange and transport in the blood
Once O2 reaches the the blood, it is carried in
blood in two forms: dissolved in the blood and
bound to Hbn
and the overall delivery of O 2 ( ̇DO2) is the
product of the blood O2 content (CaO2) and
blood flow (cardiac output, ̇Q)
9/8/2022

cont,
The neurocardiopulmonary axis is designed to
optimise global oxygen delivery and carbon
dioxide clearance
the local tissue vascular beds are responsible for
the distribution of blood flow.

cont,
DO2 is expressed by the equation:
where CaO2 (O2 content) is the milliliters of O2 per 100 mL
of blood, SaO2 is the fraction of hemoglobin (Hb) that is
saturated with O2, O2-combining capacity of Hb is 1.34 mL
of O2 per gram of Hb, Hb is grams of Hb per 100 mL of
blood, Pao2 is the O2 tension (i.e., dissolved O2), and
solubility of O2 in plasma is 0.003 mL of O2 per 100 mL
plasma for each mm Hg Pao2,

cont,
9/8/2022
Bohr effect?
Haldane effect?
P50: the partial pressur of oxygen when
hemoglobin is 50% saturated with
oxygen
P50

Bohr effect:
occur at the tissue level
Rt ward shift of
oxyhemoglobin
dissosciation curve
Decrease in O2 binding
affinity of hemoglobin
due to ^ in CO2 level or
decrease in pH
Aids offloading of O2
from the Hbn at the
tissue
Haldane effect:
(reverse of Bohr effect)
Occurs at the pulmonary
circulation
Decrease in CO2 binding
affinity of hemoglobin
due to ^ in O2 level
 Aids release of CO2 from the
carboxyhemoglobin in the
lung
9/8/2022

Hypoxia:
Hypoxia occurs when oxygen supplies are
insufficient to meet oxygen demands in a
particular compartment
Tissue hypoxia may be subdivided into four
main Types: hypoxaemic, anaemic, stagnant
or histotoxic.
Oxygen therapy may only correct hypoxia
due to hypoxaemia,
9/8/2022

cont
NORMAL
pao2 is rage 80-100 at room air
Mild hypoxemia when pao2 is bn 60-80mmhg
Crtical hypoxemia pao2 less than 40
pH=7.35-7.45
PaCo2=35-45
HCO3=21-27
SaO2>95%
9/8/2022

Hypoxaemic hypoxia( hypoxic hypoxia):
 is present when the oxygen content in the blood
is low due to reduced partial pressure of oxygen.
This occurs naturally at altitude or occurs
secondary to right-to-left shunts, V/Q mismatch,
alveolar hypoventilation or diffusion impairment.

Anaemic hypoxia:
Anaemic hypoxia results from a reduced level of
haemoglobin available for oxygen transport.
Circulatory (Stagnant hypoxia):
s a low level of oxygen in the tissues due to
inadequate blood flow (either globally or regionally).
Histotoxic hypoxia:
Due to inability of the tissues to use oxygen due to
interruption of normal cellular metabolism. The best
known example of this occurs during cyanide
poisoning which impairs cytochrome function.

Respiratory system control
central
The basic breathing rhythm originates in the
medulla.
Two medullary groups of neurons are generally
recognized:
dorsal respiratory group, which is primarily active during
inspiration,
ventral respiratory group, which is active during
inspiration and expiration.
9/8/2022

cont,
The most important of these sensors are
chemoreceptors that respond to changes in
hydrogen ion concentration
 Central chemoreceptors are thought to lie on the
anterolateral surface of the medulla and respond
primarily to changes in cerebrospinal fluid [H+].
9/8/2022

Cont,
peripheral
 Peripheral chemoreceptors include the carotid
bodies (at the bifurcation of the common carotid
arteries)
and the aortic bodies (surrounding the aortic
arch). The carotid bodies are the principal
peripheral chemoreceptors in humans and are
sensitive more to changes in Pao2 usually
<60mmhg through cranial nerve 8
9/8/2022

Oxygen therapy
 Oxygen therapy, also known as supplemental
oxygen, is the use of oxygen as medical treatment
 Acute indications for therapy includes
hypoxemia (low blood oxygen levels), carbon
monoxide toxicity and cluster headache
 It may also be prophylactically given to maintain
blood oxygen levels during the induction
of anesthesia.
 Oxygen therapy is often useful in chronic hypoxemia
caused by conditions such as sever COPD or cystic
fibrosis.
9/8/2022

cont,
 oxygen is required for normal cellular
metabolism and energy production.
 However, excessively high concentrations can
result in oxygen toxicity leading to lung damage
and respiratory failure
 Higher oxygen concentrations can also increase
the risk of airway fires, particularly while
smoking.
 Oxygen therapy can also dry out the nasal
mucosa without humidification.
9/8/2022

cont,
 In most conditions an oxygen saturation of 94–98%
is adequate, while in those at risk of CO2 retentions
,like COPD pts, saturations of 88–92% are preferred
 Patients with hypoxemic-hypercarbic respiratory
failure use target saturation of 90-93%
 In cases of carbon monoxide toxicity or cardiac
arrest, saturations should be as high as possible.
 Atmospheric air is typically 21% oxygen by volume,
so oxygen therapy can increase O2 content of air up
to 100
9/8/2022

cont
Oxygen is widely used by hospitals, EMS,
and first-aid providers in a variety of conditions
and settings.
Only few indications frequently require high-
flow oxygen:
resuscitation,
major trauma,
anaphylaxsis
major bleeding &shock,
active convulsions and hypothermia.
9/8/2022

Acute condition
In acute hypoxemia, oxygen therapy
should be titrated to a target level based
on pulse oximetry (94–98% in most
patients, or 88–92% in people with
COPD).
This can be performed by increasing
oxygen delivery, fraction of inspired
oxygen.
9/8/2022

cont
 Most study recommended that oxygen therapy
be stopped for saturations greater than 98% and
not started for saturations above 90% .
 This may be due to an association between
excessive oxygenation in the acutely ill Pts and
increased mortality.
 Exceptions to these recommendations
include carbon monoxide poisoning, cluster
headaches, sickle cell crisis, and pneumothorax
9/8/2022

Chronic condition
Common conditions which may require a
baseline of supplementary oxygen
include chronic obstructive pulmonary
disease(COPD)
may also require additional oxygen during acute
exacerbations.
Oxygen may also be prescribed for end-stage
cardiac failure, respiratory failure, advanced
cancer, or neurodegenerative disease in spite
of relatively normal blood oxygen levels.
9/8/2022

Cont,
 Physiologically, it may be indicated in people with arterial
 oxygen partial pressure PaO2 ≤ 55mmHg (7.3kPa) or
arterial oxygen saturation SaO2 ≤ 88%.
 Careful titration of oxygen therapy should be
considered in patients with chronic conditions
predisposing them to carbon dioxide retention (e.g.,
COPD, emphysema).
 In these instances, oxygen therapy may decrease
respiratory drive, leading to accumulation of carbon
dioxide (hypercapnia), acidemia, and increased
mortality secondary to respiratory failure
9/8/2022

Cont,
 Improved outcomes have been observed with
titrated oxygen treatment
 The risks associated with loss of respiratory
drive are far outweighed by the risks of
withholding emergency oxygen,
 so emergency administration of oxygen is never
contraindicated.
9/8/2022

Cont,
Contradication:
there is no absolute contraindication for
oxygen
Oxygen therapy should be limited or be used
cautiously for people with pulmonary,
fibrosis, bleomycin-associated lung damage
or COPD.
also may enhance amiodarone associated
lung injury
9/8/2022

Cont,
 an excess amount of oxygen available to
organs is known as hyperoxia
risks of hyperoxaemia
Worsened V/Q mismatch.
Absorption atelectasis.
Coronary and cerebral vasoconstriction.
Reduced cardiac output.

Cont,
Damage from oxygen free radicals.
Increased systemic vascular resistance.
Worsening of hypercapnic respiratory failure,
retinopathy of prematurity(ROP)
In rare instances, people receiving hyperbaric
oxygen therapy have had seizures,
Pulmonary oxygen toxcicty
as an inflammatory lung injury that occurs in patients who
have inhaled O2 with an FIO2 > 60% for longer than 24
hours.
9/8/2022

O2 sources
Oxygen can be separated by a number of
methods(chemical reaction or fractional
distilation) to enable immediate or future use.
so oxygen we use can be from of the following:
inplanted pipeline source
Compressed gas storage from a cylinder
Via an electrically powered oxygen concentrator
• widely used for home oxygen therapy as portable
personal oxygen.
• One particular advantage includes continuous supply
without need for bulky oxygen cylinders
9/8/2022

Cont,
 the oxygen delivery system
consists:
Oxygen supply
Oxygen flow control
Connecting tubing
Reservoir
Patient
attachment(interface)
Expired gas facility
Humidification device
and O2 monitors
9/8/2022

Oxygen delivery system
Various devices are used for oxygen
administration.
 oxygen will first pass through a pressure
regulator, used to control the high pressur
of oxygen delivered from a cylinder (or
other source)
9/8/2022

cont
Oxygen delivery systems are classified as low-
flow systems, reservoir systems, and high-flow
systems .
Low-flow systems use standard nasal prongs, nasal
catheter, oxygen tent, face masks
 high-flow systems use air-entrainment masks or
heated, humidified O2 delivered through nasal
prongs.
9/8/2022

cont
Low-flow oxygen
Many people only require slight increases in
inhaled oxygen, rather than pure or near-pure
oxygen.
These requirements can be met through a
number of devices dependent on situation,
flow requirements, and personal preference.
9/8/2022

 Nasal cannulae
 Nasal cannulae can be used to deliver low-concentration and
medium-concentration oxygen concentrations
 However, there is wide variation in patients' breathing patterns
so the same flow rate of nasal oxygen may have widely different
effects on the blood oxygen and carbon dioxide levels of
different patients.
 Nasal cannulae at 1–4 L/min can have effects on oxygen
saturation approximately equivalent to those seen with 24–40%
oxygen
 The actual concentration of oxygen delivered (FiO2) cannot be
predicted
 The oxygen concentration continues to rise up to flows above
6 L/min..

Cont,
The upper range of oxygen delivery from nasal
cannulae is a little lower than the output of a
simple face mask, but the lower range goes a lot
lower than a simple face mask which should not
be used below a flow rate of 5 L/min (about 40%
oxygen)
 Another advantage of cannulae over simple face
masks is that they are less likely to be removed
accidentally and they allow the patient to speak
and eat.

Cont,
 Advantages of nasal cannulae compared with simple face masks for
medium-concentration oxygen therapy
 Comfort Adjustable flow gives wide oxygen concentration
range,suitable for variable oxygen therapy and concentration titration.
 Patient preference, No claustrophobic sensation.
 Not taken off to eat or speak and less likely to fall off.
 Less affected by movement of face.
 Less inspiratory resistance than simple face masks.
 No risk of rebreathing of carbon dioxide, Cheaper.
 easy to use, with no risk of CO2 retention
 Disadvantages of nasal cannulae
 May cause nasal irritation or soreness.
 May not work if nose is severely congested or blocked.
 Actual concentration of oxygen (FiO2) cannot be predict

Simple face mask
delivers oxygen concentrations between 40% and 60%
The oxygen supplied to the patient will be of variable
concentration depending on the flow of oxygen and
the patient's breathing pattern.
can be changed by increasing or decreasing the
oxygen flows between 5 and 10 L/min.
Flows of <5 L/min can cause increased resistance to
breathing, and there is a possibility of a build-up of
carbon dioxide within the mask and rebreathing may
occur

This mask is suitable for patients with respiratory
failure without hypercapnia
The mask may deliver a high concentration of
oxygen (>50%)
patients who require medium-concentration
oxygen therapy tend to prefer nasal cannulae to
simple face masks and the cannulae are more
likely to be left in position by the patient and less
likely to fall off

 Venturi Mask
 a low flow O2 delivery
method
 Deliver controlled &
accurate percentage of
O2(FIO2)
 One of good option for
patients having
hypercapnic respiratory
failure
 Can deliver FIO2 of 24-50%
using color coded venturi
devices
9/8/2022

High flow oxygen delivery
High-concentration reservoir mask (non-
rebreathing mask)
delivers oxygen at concentrations between 60%
and 90% when used at a flow rate of 15 L/min
The delivered oxygen concentration is variable and
will depend on the mask fit and the patient's
breathing pattern.
These masks are most suitable for trauma and
emergency use in patients in whom carbon
dioxide retention is unlikely

 High-flow nasal cannulae
There is increasing use of HFNC as an alternative
delivery device for adults requiring medium-
concentration and high-concentration oxygen therapy
The therapeutic effects are thought to be multifactorial
and include delivery of increased FiO2(upto 100%), a
CPAP effect and greater comfort for the patient when
compared with face masks.
To deliver HFNC, three elements are required: a patient
interface, a gas delivery device and a humidifier.
A flow of at least 60 L/min can be accommodated via
standard dimension prongs on adult nasal cannula.

High-flow nasal oxygen should be considered as
an alternative to reservoir mask treatment in
patients with acute respiratory failure without
hypercapnia.
allows the person to continue to talk, eat, and
drink while still receiving therapy.

cont
Positive pressure delivery
Patients who are unable to breathe on their
own will require positive pressure to move
oxygen into their lungs for gaseous exchange
to take place.
This can be achieved by:
 non invasively: delivery of positive pressure by
non invasive interface like nasal/facemask or nasal
prong. E.g CPAP/BPAP
Invasively: commonly via MV with endotracheal
intubation or tracheostomy tube
9/8/2022

NIV Can be used as a ventilatory support for Pts with
acute or chronic respiratory failure in ED, ICU or high
dependency unit
CPAP is the application of constant and continous
positive airway pressure during both the inspiratory
and expiratory phase
Commonly used in pts Cardiogenic pulmonary edema
BPAP is use of higher positive airway pressure during
inspiration and lower pressure during expiration
Best used for hypercapnic respiratory failure, COPD,
obesity hypoventilation disorder, drug overdose
9/8/2022

 Anesthesia Mask
 Parts?
9/8/2022

COPD
Oxygen therapy is used to prevent hypoxemia
(i.e., an arterial PO2 < 60 mm Hg or an arterial O2
saturation < 90%) .
The curent recommended target o2 tension in
exacerbated copd is about 60 – 65 0r spo2 88-92
9/8/2022

Reference
Miller text book of aneasthsia 9th edition
Morgan 18th editon
OH’S intensive care manual 8th ed
Marinos icu book
Up-to-date 21
9/8/2022

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