Concussion and Breathing - 60 Years of Research

Introduction: Concussion effect on the brain and breathing

In the United Kingdom 2% of the population (*1.4 million people) attend emergency departments each year with a head injury. It is the leading cause of death in people under the age of 40 (Lennon, 2023).. Traumatic brain injury (TBI) increases the risk of dementia by 1.5–3 times (Lennon, 2023). It’s been well known and documented that risks of concussions and brain injuries are higher in sports. In 2006 it was reported that annually there are nearly 4 million sports-related traumatic brain injuries (TBIs), the majority of which are concussions (Langlois, 2006).

There can be a lot of confusion or misunderstanding of what is a head injury and the different types or classification. Typically, people think that to suffer a concussion you have to be knocked out or unconscious, which is not the case. Concussion is a form of mild traumatic brain injury (mTBI), which results in a cascade of pathophysiological changes and alterations in brain function, including breathing rate, mechanics and end tidal carbon dioxide, which is an indication of carbon dioxide sensitivity in the brain (Churchill, 2017).

The dangers of repeat concussions before the brain has fully healed and recovered at worst can cause immediate death with ‘second impact syndrome (Singh, 2014). Accumulative build up from previous concussion is well documented and known within the medical world. It’s reports that it takes longer to recovery and less severe impacts to cause increased severity of symptoms, in subsequent impact to the head.

Determining when a brain has fully recovered is something that is less well known and understood. The research within the literature is showing that simply management of symptoms is not a good indicator of the absence of brain injury and its repeated affect cumulative effects.

We’ll see as we dive into the research that simply managing symptoms is putting sports people at risk in returning to their sports before the brain is fully healed, at worst being exposed to second impact syndrome in the acute phase or longer term being subjects to an accumulative build-up of concussion, which permanently effects cognitive function after just 3 concussion (Lennon, 2023).

In this article I aim to highlight the link between brain injuries and concussion with breathing and the relationship with breathing and Heart Rate Variability (HRV), which together can provide not only a way to restore blood flow and oxygen supply to the brain but also a more appropriate way to access brain recovery over symptom management.

Listen to Podcast Episode: Concussions & Breathing

60 Years of Concussion & Breathing Research

Since the 1960’s it’s been known in the literature that head injuries frequently disrupt and affect an individual’s breathing. A study from 1968 in the British Journal of Anaesthesia sited both an ‘increase in minute volume and a reduction in arterial carbon dioxide tension is commonly found in such patients’ (Froman, 1968). In other words, increasing the amount someone is breathing (hyperventilation) and reducing carbon dioxide levels within the body, which is detrimental to blood flow and oxygen supply to the brain. Something which is vitally important to brain health and recovery of the brain from an injury.

The classic symptoms of headaches, memory loss, cognitive function will all be impacted by reduced oxygen and blood supply to the brain, of which the reported breathing dysfunctions contribute too. Symptoms are potentially reflective of reduced oxygen delivery to grey matter (Toledo, 2012). Therefore the primary objective of restoring brain health post injury is to improve blood flow and oxygen supply to the brain, of which breathing is a key influencer.

The effect that head injuries have on an individual’s breathing and respiration seems to have been overlooked and the opportunity to use breathing exercises and techniques to help reduce symptoms like sleep, cognitive and emotional issues, headaches and depression and improve recovery of the brain as clear from both the literature and the practical applications of coaches like myself who’s both personally and with clients had life changing results from restoring breathing function in biomechanical, biochemical and psycho-phycological dimensions.

A big question is how long will these symptoms and issues affecting the brain last. I believe the answer is not until the individuals breathing had been assessed and re-trained.

How head injuries, concussions and TBIs affect the brain

The brain controls various different autonomic functions within the body and via the vagus nerve we have communication back from the body to the brain, so the body and brain are interconnected and ‘talking’ back to each other. When either a direct impact to the head or a shacking of the brain within the skull caused by an impact to the body various parts of the brain can be affected depending on where the impact is.

The exact mechanism in which a head injury causes changes to the brain, alters breathing and other brain related symptoms is not clearly defined or fully understood from the current literature but a number of parts are well understood that are all contributing factors.

It’s well known that the respiratory centres that control breathing are located in the brain stem (medulla and pons). The brain stem is located at the top of the spinal cord, with the brain sitting on top. Upon impact to either the head or the body which creates a shaking effect of the head causes both the brain to rebound within the inside of the skull as well as disrupting and injuring the brain stems as it pivots about the brain stem during these forceful movements. This has potential to cause bruising, swelling and inflammatory response to localised areas of the brain due to the impact on the inside of the skull as well as to the brain stem.

Depending on the force of the impact this can affect specific areas of the brain (where the impact occurs) but most commonly damage to the brain stem, simple because the movement of the brain pivots about this point regardless of where the impact as come from. Hence why studies like Froman’s from 1968 in the British Journal of Anaesthesia report that breathing alterations from affected respiratory centres are most common amongst head injury patients. It’s believed that bruising and inflammation can cause pressure changes within the brain and reduce blood flow to the brain (cerebral blood flow).

Altered breathing can negatively affect both cerebral blood flow (CBF) and oxygen delivery to the brain. Equally though, re-training breathing patterns and recalibrating the body’s relationship with carbon dioxide has been shown to improve both cerebral blood flow and oxygen supply to the brain.
The brain accounts for only 2% of our mass yet the neurons within the brain use 20% of the total oxygen used by the body (Cornet, 2013). Oxygen delivery to the brain and therefore the blood flow to the brain is hugely important in head injury recovery and restoring normal cognitive function to the brain.

Symptoms Vs Brain Scan & Heart Rate Variability (HRV) to Evaluate Brain Recovery

Concussions have been shown to negatively affect cerebral blood flow (CBF), reducing blood flow and oxygen supply to the brain. Brain scans using detailed fMRI imagery have shown reduced CBF even once reported symptoms after 1 month had reduced (Meier, 2015). Using symptoms as a way to assess recovery of the brain from a concussion has been shown in the literature to give a false indication of the brain’s recovery.

While the clinical symptoms and functional impairments typically resolve within several days, increasing evidence suggests persistent neurophysiological abnormalities beyond the point of clinical recovery after injury (Wang, 2016), which potential places an individual in a false sense of brain recovery. Their symptoms have resolved yet the brain is still showing signs of brain injury in fMRI scans.

Even after symptom resolution, neurons under a state of physiologic stress function abnormally and may remain susceptible to second injury (Maugans, 2012), which is a mechanism behind the worrying high level of accumulative build-up of multiple concussions we see in contact sports.
Moreover, cerebral autoregulation, the intrinsic ability of the brain to maintain a constant CBF in response to variations in systemic blood pressure, has been found to be lost or impaired following mTBI for up to 14 days (Len, 2011) and (Wang, 2015) reported post-concussion cerebral blood flow reduced still after 7 months without reported symptoms.

This is what’s so worrying. We know we can’t continually scan individuals brain due to increased exposure to radiation from the scan. Yet, simply managing symptoms may not be appropriate or reliable after 7 months or even more, after individuals report being ‘symptom free’. We need more reliable ways to accurately assess brain recovery and both breathing and Heart Rate Variability could provide the answer for evaluation as well as form the basis for the recovery process and protocols.

HRV and Breathing –  A tool to access brain recovery

Heart rate variability (HRV), an index of autonomic function that is more robustly studied in patients with concussion, is associated with symptom burden and concussion recovery (Bishop, 2018). Within a few days post-injury, patients with mild traumatic brain injury have demonstrated impaired ability to modulate cerebral blood flow in response to CO2 changes from respiratory challenge (Len, 2013).

It has been shown that challenges in modulating cerebral blood flow is greater with patients with increased post-concussive symptoms, and reductions in HRV can last for typically 3 to 4 months (AlBalawi, 2017). The ability for the brain to modulate cerebral blood flow highlights the potential reciprocal impact of altered CO2 sensitivity on recovery after brain injury.

Breathing affects CO2 sensitivity and CO2 sensitivity affects a person’s breathing which as we’ve seen in the literature above negatively affects the brains ability to manage ‘stress’ and resulting cerebral blood flow. HRV is closely linked to breathing, with as much as 70% of the variation in HRV accounted for by respiratory dynamics (Pöyhönen, 2003). By using HRV as a monitoring ‘tool’ we can access both an individual’s anatomic nervous system function as well as the impact on their breathing post-concussion.

Dangers of accumulative build up on cognitive decline

As recent study from 2023 reported long terms effects and cognitive decline after just 3 mTBIs (Lennon, 2023). A signal to the fact that brains which have not fully recovered beyond the typical symptom management are susceptible to an accumulative build up as the brain isn’t actually fully healed, despite no symptoms reported, and only 3 concussion later long term effects on cognitive function.

significant long-term cognitive deficits begin to be seen after only three lifetime mTBIs. This should be carefully considered when counselling individuals post-TBI about continuing high-risk activities.“ (Lennon, 2023).

Concussion & follow up articles

Breathing assessments and HRV monitoring could provide a more accurate of assessing a brain’s recovery post injury compared with symptom management when fMRI isn’t an option or multiple scans are not safe and / or appropriate for an individual’s health.

In the follow up article to this blog I will share how and which breathing assessments can provide a quantitative evaluation of the brains recovery alongside HRV data.

*Special thank you to Patrick McKeown from Oxygen Advantage for his help and research in this area.

I'd love to hear from you if you have experience concussion or brain injuries, if this has been helpful and / or if you work with clients or athletes that suffer head injuries. My email is info@probreathwork.com

If I can help in any way, please get in touch.



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