1. Dr Surinder Singh IGMC Shimla
Oxygen Therapy
Dr Surinder Singh
IGMC Shimla

2. Basic Concepts: Oxygen Cascade:
Inspired = 150 mmHg at Sea Level SML120
↓ Alveolar PO2= 103
↓ Arterial=100
↓ Capillary= 51
↓ Mitochondrial= 1-10
(FiO2 expressed as or %)

3. Oxygen Availability: Normal
Oxygen Flux or O2 availability/min:
= (Hb content+ Plasma content) x Q
= (1.39x Hb x SaO x PaO2 ) x Q ml
= (1.39 X 14.5 X X 100) X
= = 1000ml
Coefficient of Oxygen utilisation: O2 consumed/ O2 available
= 250 =25% Safety margin= 75%
1000

4. Oxygen Availability: Disease state
Low CO eg. 50%+ Normal Hb = 500 ml Safety=50%
Low CO eg 50%+ Low Hb 7gm= 250 ml Safety=??
Hemorrhagic Shock= ↓CO+↓Hb=↓↓↓↓ O2
MS+Anemia= ↓CO+↓Hb=↓↓↓↓ O2
Critical Flux= 500ml
Last 250ml can’t be extracted
The narrow safety margin is further reduced if oxygen demand increases in such patients

5. Perioperative State:
↑ Oxygen demand due to shivering, fever, sepsis, hypercatabolic state. Patients may be unable to increase cardiac output or VE or both A vicious cycle of hypoxemia may start .

6. Factors ↓ O2 Availability:
Low arterial O2 content:
↓ FiO2, ↓PaO2
↓ Diffusion eg ARDS, CPE
↓ pH or acidosis
Low Hemoglobin:
↓ Hb
↑ COHb
MetHb
Low cardiac output states

7. Factors ↑ O2 Requirement:
Pregnancy: ↑ 7-8 ml/kg/min Normal=4-5 ml/kg/min
Sepsis , Hypercatabolic state
Shivering= ↑ 500% of the Normal requirements
Fever: 7% increase /oC rise of body temperature
↑ Work of breathing
↑ Myocardial work: Tachycardia

8. How to ↓O2 Consumption: Minimize exertion
Digitalize, treat cardiac failure
Prevent & Treat fever
Under extreme circumstances:
Paralysis and IPPV
Induce hypothermia
ECMO
CPB

9. How to ↑ O2 availability:
Raise Arterial PaO2 & SaO2
Oxygen Therapy
Treat Bronchospasm/ respiratory lesions
Ventilation, PEEP, CPAP
Raise Hemoglobin:
Hb: BT, Pack cell transfusion
Raise Cardiac Output:
Correct Acidosis
Correct Hypovolemia
Inotropic Support
Treat Cardiac Lesions/ Shunts

10. Efficacy of oxygen therapy
∆ O2 /100 ml Art. Blood/percent ↑ FiO2
Diffusion Hypoxia & High Altitude 3 ml
Respiratory depression 3 ml
ARDS/CPE
Anemia ml
Shock, Valve defects ml
MetHb ml
Cytotoxic Hypoxia ml

11. BTS Indications: High concentration
Additional Comments
Target Sp O %
Grade of Recommendation
Cardiac arrest or resuscitation
Bag- valve- mask D
Shock, sepsis, major trauma, near drowning,
Target maximal SpO2
Add other treatments
Major Head Injury
Early intubation and ventilation if needed
Carbon monoxide poisoning
Bag valve with high flow to avoid rebreathing
SpO2 will be high
PaO2 will be normal
Patient will be hypoxic C

12. BTS Indications: Medium concentration
Additional comments
Evidence grade
Asthma
Supplement oxygen C
Pneumonia
Lung cancer
Postop breathlessness
Treat underlying cause, CPAP, BiPAP
Acute Heart failure
Consider CPAP, NIV Intubation and ventilation+PEEP D
Pulmonary embolism
Most do not require Severe ones not benifitted
Pleural effusions
Drainage of effusion
Pneumothaorax
Drainage/ aspiration of pneumothorax
ILD (Ac deterioration)
Bag valve mask if SpO2 < 85%
Severe anemia
Transfuse and correct anemia
B& D
Sickle cell crisis
Useful in hypoxemia; treat aggravating factors B
Nasal cannulae 2- 6 LPM or simple mask 5-10 LPM Target 94-98% SpO2
Reservoir mask if no improvement. If high risk hypercapnea; target 88-92% SpO2

13. BTS Indications: Low Concentrations
COPD and other conditions requiring low dose oxygen therapy (2 – 6 LPM)
COPD
24- 28% oxygen, % SpO2 ABG to assess PaCO2 D
If normocapnea target SpO2 of 94-98%
If below 88% despite 28% FiO2 switch over from ventimask to nasal cannula 2-6 LPM
Repeat ABG after min or on deterioration for PaCO2
LTOT > 17 hour/day improved quality of life and survival A
Oxygen Alert card for Hypercapnic respiratory failure patients should guide oxygen therapy
Chronic NM disorders eg MND, LAS
Chronic and subacute conditions require nocturnal CPAP, NIV and eventually end of life care C
Acute neuromuscular disorders
Rapidly progressing LGBS and Myasthenia gravis often require tracheal intubation and ventilatory support
Neurotoxins also fall in this category
A& B*

14. Specific conditions
Specific conditions
MI, ACS
Not hypoxic, benefits/harms of oxygen therapy unknown D
Stroke
Harmful in nonhypoxemic mild to moderate stroke patients B
Pregnancy& Obstetric patients
Major trauma, sepsis, shock states give oxygen to target
94-98% SpO2
Harmful to fetus in nonhypoxemic mothers causes, Fetal acidosis Use left lateral tilt in POG > 20wks
A – D
Hyperventilation& dysfunctional breathing
Oxygen not justified
Rebreathing may cause hypoxia thus not recommended C
Drug poisoning, overdose
Hypoventilation if present, treat with antidotes e.g. naloxone
Avoid hyper-oxygenation as hypercapnea may be present
Perform ABG
Paraquet/ bleomycin
Avoid oxygen

15. General considerations
PIFR:
Low: Respiratory depression
V High: Tachypnea, ARDS
Expiratory pause
Longer: Resp depression
Shorter: Tachypnea ARDS

16. General considerations
Use mask in distress :Mouth breathing
Humidification not useful < 10LPM
Use upright posture to the extent permissible
Appropriate FiO2 to achieve Target SPO2
Confirm oxygen delivery to the patient
Prescribe& document oxygen therapy
Monitor SpO2 ABG, Vitals, Narcosis
Diagnose and treat the underlying cause
MOST INDICATIONS FALL IN EVIDENCE LEVEL-D OR C

17. Devices for oxygen :History
BLB Mask 1938
Boothby
Lovelace
Bulbulian
Nasal mask with reservoir

18. Devices Nasal Catheters: : No/ low capacity Variable performance
2-4 LPM (BTS 2-6)
Upto 35% FiO2
Advantages:
Economical, Gas economy
No VD/ rebreathing
Eating, drinking, speaking possible
Useful for low FiO2
Can be used in Tracheal/ Tracheostomy tube
Disadvantages:
Irritation, No humidification
Encrestations, Ulceration

19. Nasal Prongs/ oxyarm: No/ Low capacity Variable performance
Better tolerance
Performance same as nasal catheters
Reservoir 20-30ml
ETCO2 sampling
Oxyarm:
Cloud of 28-35% FiO2 in front of nose& mouth

20. Simple Mask: Low capacity Variable performance
Simple Face Mask:
No limit of O2 flow
Usually 4-6 LPM
FiO2 ≈ oxygen flow
Usually 2- 4%/ LPM-1
Advantages:
Simple, No Flow limit/ FiO2 limit
Disadvantages:
? FiO2,
Cross Infection
No Humidification

21. Ventury masks: Fixed performance High flow
Medium Conc. Mask:
Comes with one adapter set at 35%
Required 5 LPM
Set of adapters
Multi Vent:
One or two adjustable adapters
Anaesthesia Breathing Circuits: Low flow
Fixed performance

22. Devices: High capacity Reservoir mask
60 – 95% FiO2
FiO2 dependant on FGF
Inversely related to VË
Rebreathing directly related to VË and inversely related to FGF
Valve between the reservoir & mask prevents rebreathing
Requires continued flow and observation

23. Hood, tent and Incubator
Large capacity for oxygen and CO2
Unpspecified FiO2

24. Ambulatory devices . .

25. Oxygen Toxicity: Described by Sir joseph Priestley
Generation of Superoxide radicals O -
Absorption atelectasis
↓ Surfactant production
Drying of mucosal epithelium and secretions
ROPM, Fibrocystic dysplasia, ARDS
↑ PCO 2 in COPD patients: Narcosis
FiO 2 100%= 4 hrs FiO %= 8 hrs
FiO %= 12 hrs FiO %= 24 hrs
FiO 2 ≤ 50%= Indefinite

26. Choose wisely - live well
THANKS FOR YOUR PATIENT LISTENING