As colder months set in, respiratory infections begin to climb: everything from the common cold and flu to COVID-19. It's a time when healthy lungs matter more than ever. Yet the very tissue that lets oxygen pass from air to blood is remarkably delicate, and habits such as vaping can weaken it just when protection is most needed.
Author
- Keith Rochfort
Assistant Professor, School of Biotechnology, Life Sciences Institute, Dublin City University
The lungs are often pictured as two simple balloons, but their work is far more intricate. They act as a finely tuned exchange system, moving oxygen from inhaled air into the bloodstream while releasing carbon dioxide produced by the body's cells.
At the centre of this process lies the blood-air barrier : a paper-thin layer where tiny air sacs called alveoli meet a dense network of hair-thin pulmonary capillaries. This barrier must remain both strong and flexible for efficient breathing, yet it is constantly exposed to stress from air pollution, microscopic particles and infectious microbes.
Vaping can add another layer of strain, and growing evidence shows that this extra pressure can damage the surface that makes every breath possible.
The cloud from an e-cigarette carries solvents such as propylene glycol, flavouring chemicals, nicotine (in most products) and even trace metals from the device itself . When this cocktail reaches the lungs it doesn't stay on the surface. It seeps deeper, irritating the endothelium - the thin layer of cells lining the blood vessels that mesh with the air sacs.
Healthy endothelium keeps blood flowing smoothly, discourages unnecessary clotting and acts as a selective gatekeeper for the bloodstream - controlling which substances, such as nutrients, hormones and immune cells, can pass in or out of the blood vessels while blocking harmful or unnecessary ones.
Studies show vaping can disrupt these defences, causing endothelial dysfunction even in young, otherwise healthy people . Controlled human exposure experiments reveal rises in endothelial microparticles - tiny cell fragments released when vessel linings are under stress.
My own research group has linked these changes to surges in inflammatory signals and stress markers in the blood after exposure to vaping aerosols. Together these findings indicate that the endothelium is struggling to maintain its protective role.
Laboratory work shows that vaping aerosols (even without nicotine) can loosen the tight seal of pulmonary endothelial cells . When the barrier leaks, fluid and inflammatory molecules seep into the alveoli. The result: blood-gas exchange is disrupted and respiratory infections become harder to fight.
COVID-19 is usually thought of as an infection of the airways, but the SARS-CoV-2 virus also injures blood vessels. Doctors now describe the condition as causing endotheliopathies - diseases of the blood-vessel lining. In severe cases, capillaries become inflamed, leaky and prone to clotting. That helps explain why some patients develop dangerously low oxygen levels even when their lungs are not full of fluid: the blood side of the barrier is failing.
The virus exploits a key protein called ACE2, normally a "thermostat" that helps regulate blood pressure and vessel health. SARS-CoV-2 uses ACE2 as its doorway into cells ; once the virus binds, the receptor's protective role is disrupted and vessels become inflamed and unstable.
Vaping and COVID-19: a dangerous combination
My team is using computer models to investigate how vaping may affect COVID-19 infections. Evidence already shows vaping can increase the number of ACE2 receptors in the airways and lung tissue. More ACE2 means more potential entry points for the virus - and more disruption exactly where the blood-air barrier needs to be strongest.
Both vaping and COVID-19 drive inflammation. Vaping irritates and inflames the blood-vessel lining while COVID-19 floods the lungs with pro-inflammatory molecules. Together they create a "perfect storm": capillaries become leaky, fluid seeps into the air sacs and oxygen struggles to cross the blood-air barrier. COVID-19 also raises the risk of blood clots in the lung's vessels, while vaping has been linked to the same, compounding the danger.
Vaping can also hinder recovery after a bout of COVID-19. Healing the fragile exchange surface requires every bit of support the lungs can get. Vaping adds extra stress to tissues the virus has already damaged, even if the vaper feels no immediate symptoms. The result can be prolonged breathlessness, persistent fatigue and a slower return to pre-illness activity levels.
The blood-air barrier is like a piece of delicate fabric: it holds together under normal wear but can tear when pushed too hard. Vaping weakens that weave before illness strikes, making an infection such as COVID-19 harder to overcome. The science is still evolving, but the message is clear: vaping undermines vascular health. Quitting, even temporarily, gives the lungs and blood vessels the cleaner environment they need to heal and to keep every breath effortless.
Keith Rochfort receives funding from Research Ireland.
