Oxygen toxicity

- Primarily affects lungs and central nervous system
- Determining factors include PO2 and exposure time
- Prolonged exposure to high FIO2 can cause infiltrates in lung parenchyma

Depression of ventilation

Occurs in COPD patients with chronic hypercapnia.

Retinopathy of prematurity

Excessive blood O2 levels cause retinal vasoconstriction and necrosis.

Absorption atelectasis

- Can occur with FIO2 and above 0.50
- Patients breathing small tidal volumes at greater risk

Fire hazard

- Fires in O2 enriched environments continue to occur
- Practitioners in surgery suites and in presence of hyperbaric O2 therapy need to be most careful

Three basic designs of O2 delivery systems

1. Low-flow systems.
2. Reservoir systems.
3. High-flow systems.

Nasal cannula

- Delivers FIO2 of 0.24 to 0.40
- Used with flow rates of 1/4 to 8 L/min
- FIO2 depends on how much room air patient inhales in addition to O2
- Device is usually well-tolerated

Nasal catheter

- Used at flows of 1/4 to 8 L/min
- Delivers FIO2 of 0.22 to 0.45
- Rarely used in modern health care facilities today
- Has been replaced by nasal cannula

Trans-tracheal catheter

- Surgically placed in trachea through neck by physician
- Uses 40-60% less O2 to achieve same PaO2 by nasal cannula
- Used with flow rates of 1/4 to 4 L/min
- Requires careful maintenance and cleaning
- Complications such as infection are possible

Reservoir cannula

- Designed to conserve oxygen
- Nasal and pendent reservoir
- Can reduce as much as 50-75%
- Humidification usually not necessary

Increases FIO2

- Higher 02 input
- Mouth-closed breathing
- Low inspiratory flow
- Low tidal volume
- Slow rate of breathing
- Small minute ventilation
- Long inspiratory time
- High I:E ratio

Decreases FIO2

- Lower O2 input
- Mouth-open breathing
- High inspiratory flow
- High tidal volume
- Fast rate of breathing
- Large minute ventilation
- Short inspiratory time
- Low I:E ratio

Reservoir masks

- Most commonly used reservoir systems
- Three types:
1. Simple mask.
2. Partial re-breathing mask
3. Non re-breathing mask.

High flow systems

- Supply given O2 concentration at flow equaling or exceeding patient's peak inspiratory flo
- Can ensure fixed FIO2
- Most suitable for patients requiring precise FIO2, with higher or variable minute ventilation
- Include air-entrainment or blending systms (Venturi masks or air-entrainment nebulizers)

Enclosures

- Oxygen hood (oxyhood) is generally the bet method for delivering controlled oxygen to infants
- Incubators (isolette) can be used in conjuction with oxyhood
- Regulating cooling and FIO2 can be difficult in an oxygen tent

High flow nasal cannula

Provide high FIO2, high relative humidity, and positive pressure

Demand and pulse

Dose systems conserve by providing flow during inspiration only

Bag-mask device

Provide 100% FIO2 often during emergencies

Methods of administration

- HBO is administered in either multiplace or monoplace chamber
- Multiplace chamber can hold 12 or more people
- Monoplace chamber can hold only 1 patient

Two most common acute conditions

1. Air embolism.
2. Carbon monoxide poisoning.

Nitric oxide therapy

- Improves blood flow to lung
- Reduces shunting
- Improves oxygenation
- Decreases pulmonary vascular resistance
- Low cost alternative drug therapies, including inhaled epoprostenol sodium, are gaining popularity

Helium-oxygen therapy

- Value of helium as therapeutic gas is based solely on its low density
- Can decrease work of breathing for patients with airway obstruction (i.e. asthma, croup, etc.)

Heliox therapy guidelines

- Helium must always be mixed with O2
- Heliox can be prepared at bedside or used from premixed cylinders
- In general, heliox should be delivered to patients via tight-fitting non re-breathing mask with high flow

Heliox therapy troubleshooting and hazards

- Poor vehicle for aerosol transport
- Reduces effectiveness of coughing
- Badly distorts patient's voice
- Hypoxemia can be problem

Carbogen therapy

Used for:
- Hiccups
- Carbon monoxide poisoning
- Preventing complete washout of CO2 during cardiopulmonary bypass
- Available in mixtures of 5%:95% or 7%:93%