Breathe in, hold, breathe out

Breathe in, hold, breathe out…

A simple, subconscious action that our very lives depend on entirely, at times taken for granted in its subtlety. Air, the breath of life, comprised of 21%-part Oxygen, 78%-part Nitrogen, and tiny amounts of other gases like Argon, Methane, and Carbon Dioxide.

The very anatomical and physiological nature of breathing is vital to the human body’s ability to maintain control and function over a multitude of biological processes. From energy production to even waste management. Yes, where does all the fat go when you work so tirelessly to lose weight??

You literally exhale it out in the form of Carbon Dioxide.

We have been blessed with a fantastic ability to harness Oxygen from our environment in exchange for Carbon Dioxide, released to fuel our living plant life.

This mystical function is only made possible through one, the important anatomical structure within our bodies, your LUNGS.

Our lung tissue functions as a great gaseous exchange surface on a microscopic level, an environment constantly working hard to exchange Oxygen for Carbon Dioxide. The sheer size of this vital organ is truly remarkable. If we had to layout each lung cell, air sac, or alveolus (medical term) side by side, like morphological paving of anatomy, the surface it would cover would be that of a tennis court!

This enables humans to absorb and diffuse Oxygen into our bloodstream with enormous capacity.

Therefore, anything that impacts our lung’s ability to do so, endeavors to cause us to harm in the form of the disease and chronic conditions.

Our gaseous exchange surface membrane can be affected in various ways:

  • Compromised structural integrity due to inhaled pathogens.
  • Impaired surface membrane integrity leading to a swollen, thickened, poorly functioning exchange interface.

Ultimately leading to an inability to extract Oxygen from our environment, in exchange for Carbon Dioxide release. Literally one would suffocate.

Intuitively, one can assume, anything that fills the lung’s alveoli with a substrate, or fluid medium, will cause undue problems.

This substrate can take the form of:

  • Inflammatory or Infective fluid: secondary to chest trauma, or infection i.e. Pneumonia.
  • Blood: from trauma.
  • Oedema or fluid-filled swelling of the alveoli: due significant, rapid pressure increases within your lung’s tissue and blood supply i.e. Heart failure, Life-threatening allergic responses.

Implications of SARS- COV 2

Considering the pandemic that is COVID 19, the virus causes disruption to both the structural integrity and gaseous exchangeability of the lungs. Over time, a patient’s lungs become ‘stiff’.

Picture a balloon inflating, elasticity enables this to occur, with rebound deflation. Without this elastic component, the balloon would never inflate. The same applies to our lungs.

This added to an inflammatory fluid-filled alveolar complex, one can appreciate the difficulty that would arise in one’s ability to actively take a breath, hence leading to physical exhaustion and structural collapse of the alveolar air sacks.

Remember, it is always easier to inflate a balloon when it is partially blown up, compared to the effort needed to inflate it, when it is completely collapsed.

Medical technology has however, found innovative ways to mitigate such pathological processes to a point.

To understand these treatment modalities, questions need to be asked.

  • How can we improve a patient’s Oxygen capacity?
  • How can we release the body’s build-up of Carbon Dioxide?

The answer is of a practical nature, let us think about it…

Fundamentally, we need to:

  • Increase the amount of Oxygen available.
  • Improve the integrity and functionality of the Alveolar Gaseous Exchange Surface.
  • Prevent the collapse of the alveoli.
  • Decrease the workload on the patient’s breathing muscles.
  • Provide enough time for the patient to exhale excess Carbon Dioxide.
  • Treat the cause.

Various novel devices have emerged over the years to tackle these principles in unison with clinical judgement.


  • Face Mask Oxygen administration, delivering higher concentrations of available Oxygen.
  • High flow Nasal Oxygen delivery systems.

Fortunately, there also exists applications that combine that of the above, with certain pressure manipulation capabilities, to achieve a far greater therapeutic result i.e.

Non-Invasive Ventilation modalities, not requiring the invasive insertion of a breathing tube connecting to a mechanical breathing machine. Maintaining the patient’s own efforts to breathe.

A few principle terminologies and systems need explanation.


Positive End Expiratory Pressure


Continuous Positive Airway Pressure


Bi-level Positive Airway Pressure


Inspiratory Positive Airway Pressure


Expiratory Positive Airway Pressure

  • PEEP: Pressure that is left behind, or administered at the end, of an exhaled breath. Try breathing out through pursed lips, can you feel the pressure building up in your mouth? This ‘feeling’ is transferred down into your lungs. That is PEEP!

It is beneficial in the prevention of alveolar collapse i.e. it keeps the crucial structural component of gaseous exchange from collapsing closed, thereby maintaining the integrity of your gaseous exchange surface.

Result? More surface exposure, allowing Oxygen to diffuse into your blood, Carbon Dioxide from blood to lungs and ultimately to the environment.

  • CPAP delivery systems provide a single pressure to facilitate better breathing efforts to overcome difficulty during times of respiratory compromise. This, literally helps one to take in larger volumes of air, thus assisting respiratory muscle fatigue. With the added benefit of providing PEEP to prevent alveolar collapse.
  • BiPAP delivery systems, here, provide 2 separate pressures to improve respiratory functionality. Firstly, pressure administered during inspiration (IPAP) and secondly, pressure administered during exhalation (EPAP), essentially PEEP.

What have we achieved thus far from understanding the above processes:

  • We can increase Oxygen availability through augmented oxygen delivery systems.
  • We can create a supportive environment to assist breathing and reduce the effort or work of breathing.
  • We can provide structural integrity to our lung’s alveoli, preserving our vital gaseous exchange surface, thus managing Oxygen absorption and Carbon Dioxide release.

The goal is to foster better respiratory support practices to patients, in times of respiratory duress and compromised function.







An insightful post by Jonathan Toy.