Oxygen Administration Oxygen is a colourless, odourless, tasteless gas that is essential for the body to function properly and to survive. The air that we breathe contains approximately 21% oxygen, and the heart relies on oxygen to pump blood. If not enough oxygen is circulating in the blood, it’s difficult for the tissues of the heart to keep pumping. Supplemental oxygen is used to treat medical conditions in which the tissues of the body do not have enough oxygen.

Oxygen is a gas, but when administered as a supplement to normal atmospheric air, may also be considered a medication (or drug) in the way it is delivered.

The respiratory system The anatomical features of the respiratory system involve those structures of the body that conduct air from outside the body to the lungs, and those elements that control and facilitate the process.

The Central Nervous System (CNS) The brain and the spinal cord that make up the CNS and are the controlling mechanism. The CNS is located at the brain stem, just above the spinal cord.

The Upper Airway The upper airway consists of those spaces and structures that assist and guide the movement of air from the nose and mouth to the ‘wind pipe’.

Nasal cavityThe nasal cavity, also known as the nasopharynx, is the space behind the nose and extends over the roof of the mouth. It is into this cavity that air is initially drawn when a breath is taken and dry air is warmed and moistened prior to its journey to the lungs. OropharynxThe oropharynx is the cavity that extends from the nasal cavity to the hyoid bone above the opening to the ‘wind pipe’. This cavity contains the tonsils. LaryngopharynxThe Laryngopharynx is the space immediately above the complex structure located at the top of the airway proper – the larynx. The Laryngopharynx includes the glottis, the opening between the larynx and the vocal cords. LarynxThe larynx, also known as the ‘Adam’s apple’, is the cartilaginous structure located above the entry to the lower airway and close to the oesophagus, the entry to the stomach.

Lower Airway

TracheaThe trachea or ‘wind pipe’, is a thin-walled tube approximately the same diameter as a garden hose. The trachea extends to the bronchial tree where the airway branches to the lungs. Bronchi and bronchiolesThe trachea branches into the left and right main bronchi, which successively branch into smaller bronchi, much like the structure of the branches of a tree. These smaller bronchi are located within the lobes of the lungs. LungsThe two lungs develop at the end of the bronchi, and are contained within a cavity in the chest. The lungs are porous elastic organs that appear similar to a sponge. LobesEach lung is composed of compartments called lobes; the right lung with three lobes, the left, two. AlveoliIn the extremities of the lobes, groups of respiratory bronchioles terminate in clusters of structures called alveoli. The alveoli are small sacs composed of elastic tissue, covered by a thin membrane. It is through this membrane that gas exchange takes place.

Associated muscles Diaphragm. The diaphragm is a long, flat, smooth muscle attached to the lower six ribs, the sternum and the spine. When relaxed it is convex in shape, forming a ‘dome’ beneath the lungs. When the CNS stimulates the need for inhalation, the diaphragm flattens, enlarging the chest cavity and allowing expansion of the lungs.

Intercostal muscles. The intercostal muscles are the small smooth muscles between the ribs. When contracted, these muscles expand the chest cavity in an outward direction, providing an enlargement of the chest cavity.

Associated blood structures Red blood cells. Red blood cells, or erythrocytes, are the most numerous and specialised cells in the body.

Erythrocytes are flexible concave microscopic discs, adapted to produce haemoglobin.

Erythrocytes circulate through the lungs in the alveolar capillaries, collecting oxygen diffused through the membranes of the alveoli.

Haemoglobin is a hormone which attracts and binds oxygen, and to a lesser extent, carbon dioxide. It has a red pigment which gives blood its red colour. When oxygen combines with haemoglobin, it is known as oxyhaemoglobin, and the enriched blood is a bright red colour. As carbon dioxide does not combine with haemoglobin as effectively, the resultant colour of the blood is dark red.

Respiration The physiology (or function) of respiration involves all those anatomical features discussed previously. Respiration can be considered to start with the process of inhalation, or ‘breathing in’.

At the start of each breath, our CNS is stimulated to direct the muscular diaphragm below the lungs to contract. As it contracts, or ‘flattens’, the chest cavity is enlarged. Because at this point the lungs are deflated, the pressure in them is low. As the air outside our body is at atmospheric pressure (14.7 psi, or 100 kPa), it spontaneously moves into the lungs through the oropharynx to ‘even up the pressure’.

The air that has been inhaled moves through the upper and lower airways to the membranes of the lungs, into the alveoli.

At this point, the oxygen content of the air is selectively moved through the walls of the alveoli.

Respiration occurs regularly, depending on the body’s demands. An adult awake and at rest will generally have a respiratory rate of 14-18 breaths per minute. When the body is under stress, either physical or emotional, the rate rises accordingly, and could be as high as 30 per minute. When deeply asleep, with the body completely at rest, the body’s respiratory rate is somewhat slower, eg 10-12 per minute.

Oxygen therapy Oxygen therapy is a treatment that provides extra oxygen to the tissues of the body through the lungs, and is provided to a casualty as a supplement to normal respiration. Certain injuries and conditions lead to a loss of ability to maintain oxygen to the body at the required level.

Oxygen therapy provides a regulated flow of supplementary oxygen to ‘build up’ to the necessary level. Oxygen therapy is usually delivered by a face mask, but nasal prongs can also be used.

Face masks
These are adult or child sized plastic disposable items which fit over the casualty’s nose, mouth and chin. They are attached to the regulating device outlet by clear plastic tubing.

Oxygen delivered via a face mask mixes with air drawn in through holes in the body of the mask. Expired air is exhausted through the holes when the casualty exhales. The percentage of oxygen administered depends on the flow rate from the outlet.

The main disadvantages are that the casualty may feel claustrophobic, and that speech is distorted through the mask.

Nasal prongs
These are plastic prongs set within a length of clear plastic tubing, and are designed to fit into the casualty’s nostrils. The disadvantage is that a blocked nose, sinusitis, or a cold sometimes negates the benefits and delivers only low concentrations of oxygen.

100% oxygen 100% oxygen is administered to casualties in respiratory arrest or whose unsupported breathing is insufficient to maintain consciousness.

Demand valve devices
100% oxygen is delivered from the regulating device directly to a demand valve. A firmly fitting, sealed mask is attached to the demand valve.

When the casualty breathes, the demand valve is triggered, and a measured amount of 100% oxygen is delivered.

Manually triggered devices
On some mechanical devices, the demand valve can be triggered by an operator and oxygen can be administered to a non-breathing casualty.

Soft bag and mask devices
These devices consist of a soft bag and reservoir attached to a mask. 100% oxygen is delivered into the bag via the reservoir, and the bag is compressed to administer oxygen to the casualty through the mask.


The disadvantage of these devices is the care required to continually assess the casualty. It is easy to inflate the casualty’s stomach, or worsen chest and lung injuries or conditions. Due to the skill required to use these devices, they should be restricted to only those first aid providers qualified in their use.

Care in the use of oxygen Although oxygen is beneficial, care is essential in administering it. Provided you give oxygen in accordance with your level of training, and observe certain precautions, you should encounter no problems.



Oxygen for medical use Medical oxygen is stored under pressure (up to 13,400 kPa) in steel or aluminium cylinders.

Medical oxygen cylinders can be identified using the following features.

• Australian standard pin index valve for oxygen equipment
• Black cylinder with white collar
• The cylinders should be labelled ‘Medical Oxygen’

Common cylinder sizes are:

• ‘B’ – 200 litres when full
• ‘C’ – 400-490 litres when full
• ‘D’ – 1500 litres when full
• ‘G’ – 7600 litres when full

Oxygen cylinders from different companies often hold slightly different quantities of gas. The most common sizes for mechanical resuscitators are the ‘B’ and ‘C’, and fixed oxygen equipment normally use ‘D’ size cylinders or larger.

Preparing a cylinder for use A full cylinder should have a plastic stopper inserted in the valve outlet, or if a smaller cylinder, plastic tape wound around the outlet.

When preparing a cylinder for use:

• check the external condition and colour of the cylinder
• check the valve and outlet port, and wipe them clean
• remove the plastic stopper or tape, and check for moisture in the outlet port
• point the cylinder away from you and ‘crack’ the valve for one second
• ensure the valve is turned off tightly

Oxygen delivery The gas is delivered through a valve to a regulating device which reduces the pressure to a safe 390-400 kPa. The oxygen flow is then delivered through a ‘yoke’ device that fits onto the valve stem of the cylinder. The yoke has fittings that match the valve stem, and has a measuring device attached to control the flow of oxygen.

Flow rates of oxygen are varied by either a fixed flow outlet set between 3-8 litres per minute (lpm), or by an adjustable flow meter that delivers between 1-25 lpm. This is consistent with the requirements for supplementary oxygen therapy. Full flow rates of oxygen are supplied directly to a demand valve in the case of a mechanical resuscitator.

When delivering oxygen via a therapy mask the following table outlines expected operating duration from a full ‘C’ cylinder (440 Litres):

Flow Rate	Duration
15 lpm	30 Minutes
8 lpm	55 Minutes

Connecting oxygen equipment When the selected cylinder has been prepared, connect the equipment as follows:

• attach the appropriate yoke device, ensuring that the valve fittings correspond to those on the valve stem
• tighten the locking screw gently with a cylinder spanner (larger cylinders), or ‘finger tight’ (smaller cylinders)
• attach appropriate oxygen therapy or mechanical resuscitator devices

Cylinder storage Store oxygen cylinders carefully in accordance with relevant government regulations. Prior to storing cylinders, you should contact your company or organisation’s OH&S representative for direction and advice.

Some important points are:

• cylinders should be kept cool, dry and undercover
• all cylinders should be kept in a secure but accessible area near the oxygen equipment
• cylinders should be contained or secured to prevent movement and precautions should be taken to prevent them falling over
• the storage area should be out of direct sunlight and away from heat
• full and empty cylinders should be clearly marked and kept stored separately
• the storage area should have the regulation signage
• there should be no naked flames or smoking allowed within 25 metres of stored oxygen cylinders
• empty cylinders should be returned for filling without delay
• DO NOT store near grease or oil

Safety with oxygen

• always check that the cylinder is clean
• ensure that the cylinder is black with white shoulders
• always use the correct yoke with pressure gauges
• ensure that the bodock seal (‘O’ ring) and valve seat are clean and undamaged
• store cylinders upright and secure
• adhere to Government regulations regarding the storage of oxygen cylinders
• store full and empty cylinders separately. Mark empty cylinders clearly
• ensure that you are qualified prior to using oxygen equipment
• DO NOT drop or roll cylinders
• DO NOT completely empty a cylinder – leave pressure in the cylinder to prevent moisture entering
• DO NOT expose cylinders to extreme heat or flame (oxygen is flammable and potentially explosive)
• DO NOT smoke near oxygen equipment
• DO NOT use petroleum based oil or grease products near oxygen equipment

Checking oxygen equipment Oxygen equipment should be checked regularly for cleanliness and contents.

DAILY MAINTENANCE AND AFTER EACH USE.

• ensure that all supplies and spares, such as oxygen masks and seals are available and undamaged
• check the contents of the cylinder and replace as necessary

WEEKLY MAINTENANCE AND AFTER EACH USE

• inspect the exterior and connector sockets for cracks and signs of damage
• check the contents of the cylinder and replace as necessary

AFTER EACH USE

• ensure that all supplies and spares, such as oxygen masks, suction tubing and suckers and seals are available and undamaged
• check the contents of the cylinder and replace as necessary
• clean the unit
• replace the masks and airways as necessary

The minimum contents of a portable resuscitation unit should be:

• oxygen cylinder not less than half full
• regulator and flow meter (regulator may incorporate the flow meter)
• oxygen therapy mask
  • adult
  • child
• Oxygen therapy tubing
• resuscitation mask
  • adult
  • child
• oxygen cylinder key-wheel
• spare bodock seal

Additional supplies may include:

• suction unit (manual or oxygen powered)
• oropharyngeal airways sizes 1– 4

Oropharyngeal airway An oropharyngeal airway is a plastic or compound device, shaped in a curve and designed to fit into a casualty’s mouth over the tongue to establish and maintain an open airway.

The oropharyngeal airway should be used on an unconscious casualty without a ‘gag reflex’, and is essential when using a mechanical resuscitator.

Prior to inserting the airway, take care to ensure the airway is clear of any obstruction such as vomitus, water, etc. Ensure that the correct size airway is inserted, and should the casualty ‘gag’, or attempt to reject the airway, remove it immediately.

Method of Insertion

• select the correct size airway by measuring the airway from the point of the ear to the chin
• hold the casualty’s mouth open, and with the airway curve towards the nose, insert it to approximately half its length
  
  
• rotate the airway 180 degrees, and push gently so that it clears the tongue
• the lip of the airway should be external to the casualty’s lips
• ensure that the casualty’s head is extended, and that no soiling of the oropharynx has occurred
  
  

Administering oxygen BY FACE MASK

• reassure the casualty
• explain the need for oxygen therapy
• explain that the oxygen mask will assist with breathing
• turn on oxygen
• select mask (adult or child)
• connect oxygen tubing to mask
• connect oxygen tubing to flowmeter
• turn on flowmeter to appropriate rate (lpm)
• place mask comfortably over casualty’s face covering the mouth and nose
• adjust straps
• adjust metal strip over nose
• continue to reassure the casualty
• continue to observe the casualty

BY NASAL PRONGS

• reassure the casualty
• explain the need for oxygen therapy
• explain that the prongs will assist with breathing
• turn on oxygen
• select appropriate size nasal prongs
• connect oxygen tubing to flowmeter
• turn on flowmeter to appropriate rate (lpm)
• place tips into casualty’s nostrils
• place tubing over and then under casualty’s ears
• adjust for comfort
• secure tubing to casualty’s clothing
• continue to reassure the casualty
• continue to observe the casualty

BY BAG AND MASK

• turn on oxygen
• select appropriate size resuscitation mask
• connect oxygen tubing to resuscitation bag oxygen inlet
• connect oxygen tubing to flowmeter
• turn on flowmeter to appropriate rate (10 lpm)
• place mask over casualty’s face covering the mouth and nose
• hold the mask firmly in place, ensuring a good seal
• maintain head tilt and jaw lift
• squeeze the resuscitation bag until the casualty’s chest rises, then release (2 seconds)
• continue to observe the casualty for airway secretions and obstructions

Resuscitation using a bag and mask is a two person procedure, with one person holding the mask and the second person squeezing the bag.