2. OXYGEN
Essential element in life
A balance between oxygen demand and delivery needed to
maintain homeostatis within the body
In cardio- respiratory system, oxygen is extracted from the
atmosphere and deliver it to the mitochondria of cells
Oxygen cascade: process of declining of oxygen tension from
atmosphere to mitochondria
At sea level Patm is 760mmHg and oxygen makes 21% of inspired
air, thus partial pressure of oxygen, PaO2 is 159mmHg (760x 0.21)
But it will further reduced, diluted down through out the body to the
cell.
3. Atmospheric air:
21% oxygen = PaO2 of 159 mmHg
Airway gas mixture:
Diluted by water vapour = PaO2 of 149 mmHg
Alveolar gas mixture:
Diluted by CO2 = PaO2 of 99 mmHg
Also, some oxygen is taken up by the capillaries,
which decreases the alveolar PaO2
Endcapillary blood
Essentially the same as alveolar gas, in health
Arterial blood
Diluted by venous admixture= PaO2 of 92 mmHg
The difference between alveolar and arterial gas is the A-a
gradient
Normal A-a gradient is 7mmHg in the young, and
14mmHg in the old
Tissue oxygen tension
Drops due to diffusion distance
Varies from tissue to tissue, but is usually around 10-30
mmHg
Mitochondrial oxygen tension
Drops due to diffusion distance
Usually between 1-10 mmHg
OXYGEN CASCADE
4. Pathophysiology
• Hypoxaemia means low arterial oxygen tension (PaO2) below the normal value (85-100mmHg)
• Hypoxia means low oxygen content in tissue level (less than 7mmHg)
• Hypoxia occurs when there is a imbalance of oxygen demand and supply in the body
- Increased demand : sepsis, trauma, burns, myocardial ischemia
- Decreased oxygen supply : high altitude, impaired gas exchange in lungs, impaired myocardial
function, Hb defect,
5. Oxygen therapy means the administration of
oxygen greater than the ambient air(21%) in
order to prevent hypoxia by increasing paO2
Oxygen should be prescribed according to
the clinical condition and with proper
monitoring
Excessive and inappropriate oxygen therapy
may lead to toxicity
6. Indication
Pulmonary
• Acute hypoxaemia : asthma, pneumothorax,
pneumonia
• Chronic hypoxaemia : chronic lung disease,
OSA, pulmonary fibrosis
Non pulmonary
• Heart : MI, APO
• Hematological : anemia, sickle cell crisis
• CNS : brain injury
• Shock
• Metabolic acidosis
• Post operative care
• Palliative care for symptoms relief
7. Rule of thumb
Type 1 respiratory failure
- pao2 < 60 mmHg, arterial oxygen
saturation < 90 with normal pco2
when breathing room air
- Use high concentration of oxygen
via no rebreathe mask with reservoir
bag
- Target spo2 94-98
Type 2 respiratory failure
- po2 < 60 mmHg and pco2 > 55mmHg
- Those with previous normal lungs may
need oxygen and ventilator intervention
- Those with likely or known underlying
lung disease (hypercapnic respiratory
failure) will need titrated and controlled
oxygen therapy using venture mask
starting with 28% (try to avoid
mechanical ventilation)
- Target spo2 for hypercapnic respiratory
failure is 88-92
8. Goals
• Relive hypoxaemia by using appropriate oxygen delivery devices
• Reduce work of breathing
• Reduce work of myocardium to meet the oxygen demand
9.
10. Definition
Cause
Hypoxic hypoxemia •Occurs where blood flows through
parts of the lung which are un-
ventilated
•Inability to transfer oxygen across
the pulmonary membrane (gas
diffusion limitation)
•Acute bronchoconstriction:
insufficient gas flow in and out of
the lung
•Insufficient inspired oxygen
therapy (including faulty oxygen
delivery equipment)
•Primary respiratory
disease: COPD, pulmonary
fibrosis, asthma, CF, pneumonia, sputum
retention, decreased gas transfer across
thickened (fibrotic/ oedematous)
membrane
•Primary cardiac disease: heart failure,
congestive cardiac failure, pulmonary
oedema (causing a diffusion limitation
across the respiratory membrane)
Ischaemic hypoxemia •Usually due to inadequate blood
flow through the lung
•Pulmonary embolus
•Destruction of the pulmonary
vasculature (COPD, pulmonary trauma)
Anaemic hypoxemia •Reduction in the oxygen carrying
capacity of the blood
•Shock (significant blood loss with a
reduced Hb)
•Primary haematological diseases, e.g.
sickle cell crisis, anaemia
Toxic hypoxemia •Difficulty in the utilisation of
oxygen
•It is common in patients admitted
with inhalation burns/ smoke
inhalation injuries
•E.g. carbon monoxide poisoning,
cyanide poisoning
11. Sign Clinical feature Observation
Central cyanosis Blue-ish palor, blue lips Hypothermic <36.5
degrees C
Peripheral shut down Cool to touch, clammy Hypothermic <36.5
degrees C
Tachypnoea Increased respiratory
rate
>20 breaths per min,
appears in distress with
breathing
Low O2 Low O2 saturations <90%
Accessory muscle use Tracheal tug, flared
nostrils, bracing
through upper limbs
Reduced mental state Confused, agitated
SIGN AND SYMPTOMS
• Compensatory mechanism :
tachypnoea, usage of accessory
muscle, nasal flaring
• Symphatetic : palpitation,
sweating, tachycardia,
hypertensive
• Hypoxia : restless, altered
conscious, confusion, cyanosis,
12. OXYGEN DELIVERY SYSTEMS
LOW FLOW DELIVERY SYSTEM
• NASAL CANULA
• SIMPLE FACE MASK
• PARTIAL REBREATHER MASK
HIGH FLOW DELIVERY SYSTEM
• VENTURI MASK
• AEROSOL MASK
• TRACHEOSTOMY COLLARS
• NON REBREATHER MASK WITH RESERVOIR BAG
13. A. low dependency
• Variable performance devices
- Nasal cannula
- Facemask
• Fixed performance devices
- Venturi mask
- High flow nasal cannula
B. Medium dependency
- NIV
C. High dependency
- Ventilator
14. NASAL PRONG
• It can carry up to 1 – 6litres of O2 per minute
with fio2 0.24 – 0.44 (approximate 4% per liter
flow)
• fio2 decreases as ventilation rate increases.
• It is the recommended device for oxygen
delivery in children less than 5years of age
• It is ideal for long term oxygen therapy.
• It does not increase dead space
• there is no rebreathing
• More comfortable and less claustrophobic
• Allows eating, communication
• Oxygen flow more than 3L cause discomfort
and drying of the nasal mucosa
15. FACE MASK
• It can carry up to 5 – 10Litres of O2 per
Minute with FIO2 0.35 – 0.55 (approximate
flowrate of 40%).
• Flowrates should be set at 5 L/min or more
to avoid rebreathing expired CO2 retained
in the mask
• It slightly increases dead space and there
is little rebreathing
• It is usually uncomfortable for patients,
• obstruct eating and drinking,
• muffles speech.
Use for patient with type 1 respiratory
failure, those emerging from
anaesthesia
17. • the flowrate is at about FiO2 0.24 – 0.50 with
variable litre/min
• Flow and corresponding FiO2 varies by
manufacturer
• It can be used to accurately deliver preset oxygen
concentration to the trachea up to 40% but the
inspiratory flowrates is usually inadequate for
adults in respiratory distress
• Chosen for patient who has higher risk to retain CO2
VENTURI MASKS
18.
19. HIGH FLOW MASK
• a simple mask with a reservoir bag.
• Oxygen flow should always be supplied to
maintain the reservoir bag on inspiration thus
avoiding reservoir bag deflation.
• On inspiration, the patient only breathes in
from the reservoir bag; on exhalation, gases
are prevented from flowing into the reservoir
bag and are directed out through the
exhalation ports.
• The flow meter should be set to deliver O2 at
10 to 15 L/min to ensure that the reservoir
bag remains partially inflated during
inspiration.
• the mask can deliver between 60% and
80% FiO2 (fraction of inspired oxygen)
20. High flow nasal cannula
• Heat and humidified high flow nasal
cannula
• Takes up gas and heat it to 37 with a
100% relative humidity
Vs standard
• Which are cold and dry – airway
inflammation and mucociliary function
impair
Function
• Eliminate most of the anatomic dead space and
reduce co2 rebreathing
• Create a reservior with high fio2 in the nasal cavity
• Improve gas exchange via cpap effect
• Reduce work of breathing
• Improve compliance with more comfort (compared to
niv)
• Better secretion clearance
Contraindication
• Maxillofacial trauma
• Nasal obstruction
• Suspected base of skull fracture
21.
22. NON INVASIVE VENTILATION
• A form of breathing support delivering air, usually with added
oxygen, via a facemask by positive pressure, used in respiratory
failure
• NIV works by creating a positive airway pressure - the pressure
outside the lungs being greater than the pressure inside of the
lungs.
• This causes air to be forced into the lungs (down the pressure
gradient), lessening the respiratory effort and reducing the work of
breathing.
• It also helps to keep the chest and lungs expanded by increasing
the functional residual capacity (the amount of air remaining in the
lungs after expiration) after a normal (tidal) expiration; thus the air
available in the alveoli available for gaseous exchange
• There are two types of NIV non-invasive positive-pressure (NIPPV)
and Negative-Pressure Ventilation (NPV).
• the use of NIV is associated with a marked reduction in the need
for endotracheal intubation, a decrease in complication rate, a
reduced duration of hospital stay and a substantial reduction in
hospital mortality
23. Which mode ?
1) Hypoxaemia = CPAP
2) Hypercapnia and
hypoxaemia = Bi level (BiPaP)
Initially was used for treatment of
hypoventilation with neuromuscular
disease
Now treatment of acute respiratory
failure – without needing tracheal
intubation
Effect of NIV
1) improves alveolar ventilation to
reverse respiratory acidosis and
hypercarbia
2) Reduces work of breathing
24.
25.
26.
27. Requirement for successful niv
• A co operative patient who can control their airway and secretions
with an adequate cough reflex
• The patient should be able to co ordinate breathing with the
ventilator and breathe unaided for several minutes
• Haemodynamically stable
• Blood ph >7.1 and Pa Co2 < 92mmHg
• The patient should ideally show improvement in gas exchange , heart
rate and respiratory rate within first two hours
28. CPAP
• CPAP aka PEEP is the most basic level of support and
provides constant fixed positive pressure throughout
inspiration and expiration, causing the airways to
remain open and reduce the work of breathing. This
results in a higher degree of inspired oxygen than other
oxygen masks.
• High flow systems used in a hospital environment are
designed to ensure that airflow rates delivered are
greater than those generated by the distressed patient
• Decrease hypoxia by reduces (left ventricular transmural
pressure)intrapulmonary shunt – increases cardiac
output – effective for treatment of pulmonary oedema
• As well as having an effect on respiratory function it can
also assist cardiac function where patients have a low
cardiac output with pre-existing low blood pressure
• set the CPAP pressure at 10cm H2O. This pressure can
be adjusted up or down depending on patient comfort.
29. BiPAP
• As the name suggests provides differing airway pressure depending on inspiration and expiration.
• The inspiratory positive airways pressure (iPAP) is higher than the expiratory positive airways pressure (ePAP)
Therefore, ventilation is provided mainly by iPAP, whereas ePAP recruits under ventilated or collapsed alveoli
for gas exchange and allows for the removal of the exhaled gas.
• For patients receiving BiPAP start with an IPAP of between 12-15cm H2O, and EPAP of between 4-7cm H2O.
• These pressure can be titrated up or down depending on the combination of clinical effect as well as patient
comfort.
• Failure to improve oxygenation should prompt an increase in fractional inspired oxygen and EPAP.
• Failure to improve the hypercarbia should lead to an increase in IPAP.
30.
31. CPAP
• When a patient remains hypoxic
despite medical intervention
• Atelectasis - Complete or partial
collapse of a lung or lobe
• Rib fractures - to splint the rib cage
open; to stabilise the fracture and
prevent damage to the lung
• Type I respiratory failure
• Congestive Heart Failure
• Cardiogenic pulmonary oedema
• Obstructive sleep apnoea
• Pneumonia as an interim measure
before invasive ventilation or as a
ceiling of treatment
• Nasal CPAP is more commonly used
with infants.
BIPAP
• Type II respiratory failure
• Acidotic exacerbation of chronic obstructive
pulmonary disease (COPD)
• Increased work of breath causing ventilatory
failure, for example, hypercapnia (increased
CO2 in arterial blood gas), fatigue or
neuromuscular disorder
• Weaning from tracheal intubation
• Negative-Pressure Vent
INDICATIONS
32. NEGATIVE PRESSURE VENTILATION
• Attempts to mimic the muscle of respiratory muscle to allow
breathing to normal physiological mechanism
• They work by lowering the pressure surrounding the thorax,
creating subatmospheric pressure which passively expands
the chest wall to inflate the lungs
• Removed negative pressure allow passive exhalation which
occurs with passive recoil of the chest wall
Biphasic cuirass ventilator
33. COMPLICATIONS OF NIV
• pressure ulcers/necrosis (nasal bridge)
• facial or ocular abrasions
• claustrophobia/anxiety
• agitation
• air swallowing with gastric/ abdominal distension, potentially leading to vomiting and aspiration
• hypotension if hypovolaemic
• aspiration
• oronasal mucosal dryness
• raised ICP
• increased intraocular pressure
• impaired communication
• impaired nutrition
34. CONTRAINDICATIONS
• Coma
• Undrained pneumothorax
• Frank haemoptysis
• Vomiting blood (haematemesis)
• Facial fractures
• Cardiovascular system instability
• Cardiac Arrest
• Respiratory Failure
• Raised ICP
• Recent upper GI surgery
• Active Tuberculosis
• Lung abscess
35. Criteria to terminate niv and switch to mechanical
ventilation
• Worsening ph and pco2
• Tachypnea
• Hemodynamic instability
• Spo2 < 90
• Decreased level of consciousness
• Inability to clear secretion
• Inability to tolerate niv
36. INVASIVE MECHANICAL
VENTILATION
• Assistor mode: Inspiration is triggered by the patient.
• pressure sensor responds to the slight negative
pressure that occurs each time a patient attempts to
inhale and triggers are equipment to begin inflating the
lungs. Thus, the ventilator helps the patient inspire
when he wants to breathe.
• A sensitivity adjustment is provided to select the
amount of patient effort required to trigger the
ventilator.
• The assistor mode is used for patients who are able to
control the breathing but are unable to inhale a
sufficient amount of air without assistance, or for whom
the breathing requires too much effort (i.e. asthmatics,
pulmonary pneumonia, etc.)
37. A machine that generates a controlled flow of
blended air and oxygen into a patient’s airway.
Ventilators
39. Goals
• Treat hypoxemia/hypercapnia
• Relieve respiratory distress/reverse fatigue
• Decrease Myocardial O2 demand
• Prevention or reversal of atelectasis
• Breath for the sedated/paralysed patient
• Stabilise the chest wall
40. • Two categories Volume or Pressure
• This refers to the mode of breath delivery rather than the
mode itself
Ventilation
• In volume category modes of ventilation the
machine generates flow to achieve a set volume
known as tidal volume
• Tidal volume definition – the volume of air that is
inspired or expired in a single breath during regular
breathing
Volume
• In pressure modes of
ventilation a pressure limit is
set, the machine generates
flow until the peak pressure
limit is achieved
Peak airway (inspiratory)
pressure – ‘is the highest level of
pressure applied to the lungs
during inhalation expressed in
cmh2o’
Pressure
41. Volume Modes
Advantages
• Guaranteed Minute Ventilation (Mv).
• Definition –‘the total volume of gas in
litres expelled from the lungs per
minute’
Disadvantages
• Increased monitoring of airway
pressures.
• Airway pressures will increase if
lung compliance decreases.
• Risk of barotrauma.
42. Pressure Modes
Advantages
• Greater control of airway
pressure.
• Less risk of barotrauma.
Disadvantages
• No guaranteed minute ventilation.
• Increased monitoring of VT
required.
• Rapid changes in the compliance
can cause hypoventilation/hypoxia.
44. A. IPPV - Intermittent Positive Pressure Ventilation
• Set: TV, rate, Fi02, PEEP,
• No capacity for the patient to trigger a breath
• Uncomfortable if patient not fully sedated &/ paralysed
• Suitable only for patients who have no ability to breathe spontaneously
45. • Provides a set TIDAL VOLUME at a set RATE (F)
• Patient can breathe in-between mandatory ventilation
• Spontaneous breaths are supported with pressure support
• Ventilator synchronises mandatory breaths and spontaneous breaths for increased patient
comfort
B. SIMV - Synchronized Intermittent
Mandatory Ventilation
46.
47. • Provides a set P-insp at a set RATE (F)
• Patient can breathe in-between mandatory ventilation
• Spontaneous breaths are supported with pressure support
• Pt can breathe at any point of respiratory cycle, not just between breaths
• Breathing takes between two levels Pinsp and PEEP
C. BiPAP - Bilevel Positive Airway Pressure
48. BiPAP
Advantages
• Increased patient comfort
• Can limit high airway pressures
• Reduce risk of barotrauma
Disadvantages
• No guaranteed Minute Ventilation
• Increased monitoring of Tidal
Volumes
• Patient may hypo-ventilate and
become hypoxic if lung compliance
changes suddenly
49. D. Spontaneous Modes of Ventilation
• Spontaneous modes are triggered and cycled by the patient
• The patient triggers the ventilator and receives a supported breath at a pre-set
pressure.
• This helps overcome the increased work of breathing or resistance of breathing
through an endotracheal tube.
50. PEEP
• Maintains pressure within the breathing circuit at a pre-set level at the end of expiration
• When used during spontaneous respiration it is called CPAP
• A degree of PEEP should be applied on all ventilation modes to minimise risk of atelectasis
51.
52. • A/B – Airway and Breathing
• Passed a spontaneous breathing trial (SBT) with minimal settings –
pressure support of 5 cm H2O, positive end-expiratory pressure
(PEEP) of 5 cm H2O, no more than 40% oxygen
• Assess appropriate gas exchange (ie, PaO2 > 60 mmHg)
• A chest x-ray (CXR) that’s either stable or improving. Remember that
CXRs sometimes take many weeks to show significant radiographic
changes.
• Peak expiratory flow of > 60 liters/minute with coughing
• Thin secretions requiring suctioning no more than every 2-3 hours
• C – Circulation
• Hemodynamic stability with minimal pressor support (MAP > 60
mmHg)
• No evidence of myocardial ischemia
• Controlled dysrhythmia/tachycardia
• D – Disability
• Follows commands: eye opening and tracking, sustained hand
squeeze, head raise
• Neuromuscular blockade has been fully reversed.
• Appropriate analgesic regimen.
• E – Everything Else
• Acid-base status is acceptable
• Electrolytes have been corrected
• Place an NG tube if you foresee that the patient will have difficulty
swallowing
EXTUBATION CRITERIA
53. COMPLICATION OF LONG TERM OXYGEN
THERAPY
Cytotoxic
damage
Absorption
Atelectasis
Retrolental
fibroplasia
Depression of
ventilation
54. • BUT!!! Oxygen therapy cannot be stopped
abruptly
• Need to decrease the oxygen concentration
periodically
• Always reassess back the saturation, vital signs and
clinical parameters; ABG after 30mins to 1hr of
weaning down.
• Weaning off from oxygen therapy can be
considered once underlying cause ( pathology,
clinical signs and clinical condition) has stabilised
and improved.
THANK YOU….
