Topic 2 Objectives

Intications for supplemental O2

Documented hypoxemia, acute hypoxic states, specific toxic exposures, Peri-operative/post-op hypoxemia, acute anemia with tissue hypoxia

PaO₂ < 60 mmHg or SpO₂ < 90%

Indicates the need for oxygen therapy.

Acute hypoxic states requiring oxygen therapy

Respiratory failure, shock, severe trauma, cardiac arrest, myocardial ischemia, severe pneumonia/ARDS.

Toxic exposures requiring 100% O₂

Carbon monoxide poisoning, severe cyanide poisoning (temporizing).

Peri-operative or hematologic indications for O₂

Post-op hypoxemia, acute anemia with tissue hypoxia, situations to reduce cardiopulmonary workload.

Hazards of oxygen therarpy

oxygen toxicity/hyperoxia, absorption atelectasis, ventilation of depression, Retinopathy of prematurity (ROP), Fire hazard

Oxygen toxicity

Lung/CNS injury from prolonged high FiO₂ → free-radical mediated alveolar-capillary damage.

High FiO₂ in COPD patients

It may blunt hypoxic drive in chronic CO₂ retainers, worsening hypercapnia.

Retinopathy of prematurity (ROP)

Retinal vascular damage in premature infants caused by excessive O₂.

Absorption atelectasis

High FiO₂ washes out alveolar N₂ → alveolar collapse → shunt.

Non-physiological hazards of oxygen therapy

Fire hazard, nasal mucosal dryness/bleeding, pressure sores from devices.

Oxygen delivery system categories

Low-Flow (variable) - Nasal cannula, nasal catheter, Reservoir systems - simple mask, partial rebreather, non-rebreather,High flow (fixed) - Venturi (air-entrainment), High flow nasal cannula, blended heated high flow (AIRVO)

Fixed vs variable performance devices

Fixed devices deliver a set FiO₂ independent of patient demand; variable devices' FiO₂ changes with inspiratory flow.

FiO₂ range for nasal cannula at 1-6 L/min

Approximately 22-44%.

FiO2 range for Transtreacheal 0.25-4 lp,

24-44%

FiO2 range for HME at 1-6 lpm

24-44%

FiO₂ range for a simple face mask at 5-10 L/min

Approximately 35-50%.

FiO2 range for partial rebreather at 10 lpm

40-80%

FiO2 range for Air Entrainment Mask 3-15 lpm

24-50%

FiO₂ range for a non-rebreather at 10 L/min

Approximately 60-80%

High-flow nasal cannula (HFNC)

1-15 lpm, up to 80+%

FiO2 range for Air Entrainment Nebulizer at 14 lpm - flush

36-95%,

FiO2 range for Face Tent at 14 lpm - flush

36-95%’

FiO2 range for Aerosol mask/Trach mask/T-piece (briggs adapter) at 14 lpm - flush

36-95%/

FiO2 range for Oxygen Hood at 7-flush lpm

36-95%.

FiO2 range for heated air entranment system using oxyflow adapter at 4-15 lpm

28-90%

FiO2 range for blended heated high flow system (AIRVO) at 30-60 lpm

21-100%

FiO2 range for Oxymask at 1-15 lpm

24-90%

Venturi masks air entrainment principle

High-velocity O₂ jet creates low pressure, drawing room air through side ports.

Formula for air:O₂ ratio

(100 − FiO₂) / (FiO₂ − 21).

Formula for total flow

O₂ flow × (1 + air:O₂ ratio).

Rule of 4 in oxygen therapy

For nasal cannula, each 1 L/min ≈ +4% FiO₂ above room air (21%).

FiO₂ definition

Fraction of inspired oxygen (% of O₂ in inspired gas).

Hypoxemia definition

Low PaO₂ (< 60 mmHg).

Shunt definition

Perfused but non-ventilated alveoli; not fully corrected by O₂.

V/Q

Inequality of ventilation to perfusion in the lungs.

NRB bag collapse response

Increase flow to 10-15 L/min and check mask/valves.

Low SpO₂ but well-looking patient response

Check probe, perfusion, motion artifact; confirm with ABG.

Target SpO₂ for most adults

92-96%.

Target SpO₂ for COPD patients at risk of hypercapnia

88-92%.

Next step if PaO₂ < 60 mmHg despite O₂

Escalate to high-flow device, NRB, HFNC, NIV, or intubation.

Mild hypoxemia definition

PaO₂ 60-80 mmHg.

Moderate hypoxemia definition

PaO₂ 40-60 mmHg.

Severe hypoxemia definition

PaO₂ < 40 mmHg.

Post-op patient SpO₂ 91% on RA response

Nasal cannula 2 L/min (≈28-29% FiO₂).

Trauma patient SpO₂ 82% response

NRB 10-15 L/min or HFNC/intubation if needed.

COPD patient SpO₂ 86% in ED response

Controlled O₂, 1-2 L/min NC, titrate to 88-92%, monitor ABG.

Suspected CO poisoning response

100% O₂ via NRB or intubation/hyperbaric therapy.

Preterm neonate on O₂ critical aspect

Lowest FiO₂ to maintain safe SpO₂, avoid ROP.