Respiration

Invasive respiration

What does invasive respiration mean?

For people with spinal cord injuries with a lesion at a level of C4 or higher, breathing is inadequate, or there is a complete absence of it. As a result, people affected are dependent upon invasive respiration – invasive because the respiration takes place through a tracheostomy tube which runs through the neck directly into the airway.

Artificial respiration is the partial or complete performance of natural breathing via an external aid (respirator). A distinction is made between controlled and assisted respiration. In the case of controlled respiration, the breathing work is performed completely by the respirator. Respiratory frequency, depth and tidal volume are controlled by the machine’s settings. Depending on which parameters are defined, you may be dealing with pressure or volume-controlled respiration.

Controlled respiration

Pressure-controlled respiration

This is the most frequent form of respiration that is applied. It is easier for the person to tolerate than volume-controlled respiration because excessive pressure is unable to form. The following two pressure levels are set:

• Upper pressure = inhalation pressure
• Lower pressure = pressure remaining in the lung after exhalation

The tidal volume results from the difference between the two pressure levels. However, this reduces as the airway resistance rises, e.g. based on the presence of a secretion.

Volume-controlled respiration

In this form of respiration, a certain tidal volume is applied to the lung within a certain period of time which can be set. In this form, very high peak pressures can arise because the respirator¹ only monitors the volume being applied. Previously, this form used to be applied frequently in the intensive care unit; however, this is rarely the case now.

Assisted respiration

The natural respiratory impulse of the person affected is taken into consideration in this form. When they start to breathe, the breathing process is supported. If they experience lengthy interruptions in breathing, they undergo intermediate respiration under controlled conditions.

Non-invasive respiration

What does non-invasive respiration mean?

Non-invasive respiration means mechanical breathing support without endotracheal access, i.e. without the insertion of a tracheostomy tube in the windpipe. Respiration takes the form of excess pressure via a face mask, oronasal mask or nasal mask.

The adjustment and setting of non-invasive respiration is done by experienced personnel and require continuous monitoring at the start.

The person has to get used to wearing a respiration mask, and they must receive training in this.

When is non-invasive respiration applied?

The best known example of this is non-invasive respiration for people suffering from sleep apnoea at night; this means that they have lengthy breathing pauses while they are sleeping which reduce their supply of oxygen.

Another group for whom non-invasive respiration is suitable is people with a weakened diaphragm. Possible reasons for this include:

• High-level spinal cord injury
• ALS (amyotrophic lateral sclerosis²)
• Critical illness polyneuropathy³

When is non-invasive respiration not suitable?

Non-invasive respiration is unsuitable if the person does not have any spontaneous breathing⁴ capability. Where people have consciousness disorders such as somnolence or coma, this technique is not applied due to the absence of protective reflexes (for instance, vomiting reflex). Application is also difficult in the case of people who experience agitation or who have a lack of understanding of the measure.

Other possible reasons for not applying non-invasive respiration (and which thus necessitate invasive respiration) include:

• High level of bronchial secretion in combination with inadequate coughing
• Obstruction of the airways by tumours or foreign bodies
• Problems putting on the mask, for instance due to anatomical reasons, facial injuries or burns

What possible complications may arise during non-invasive respiration?

Risk of aspiration⁵ and gastric flatulence

• Conjunctivitis⁶ caused by the escape of air in the case of leaks in the area of the nasal root
• Pressure sores because the face mask is too tight

What are the advantages and disadvantages of non-invasive respiration?

Non-invasive respiration improves the quality of life for people who suffer from sleep apnoea. Tiredness during the day due to interrupted sleep at night caused by the lack of oxygen is reduced significantly.

One disadvantage is that it may be a nuisance having to wear the mask, especially when you turn over in bed at night. In addition, you always have to take the breathing device with you if you need it during the day.

Generally speaking, the objective of any breathing support should be that it is non-invasive in order to reduce the risk of complications.

¹ Respiration device

² Degenerative nerve disease

³ Situation after multiple organ failure

⁴ Independent breathing stimulus

⁵ Ingress of material into the airways

⁶ Inflammation of the conjunctiva