Researchers in Greece seem to have a thing for testing airway resistance. Two Greek studies published last year found that use of electronic cigarettes increased airway resistance in smokers without COPD or asthma. In contrast, a third study performed by Greek researchers and published in February 2013 found that e-cig use did not affect short term lung function in comparison to both mainstream and sidestream tobacco smoke.
However, a temporary increase in airway resistance does not equate to lung damage nor does it cause a reduction in blood-oxygen levels. Things like humidity, cold air and exercise can also cause elevated airway obstruction yet aren't known to actually damage lungs.
The fact remains, not one of the three studies actually found e-cigs cause damage to the lungs. And from the most recent of the three, we know that tobacco cigarettes cause more airway resistance than e-cigs.
Dr. Michael Sigel has previously stated that the mild increase in airway resistance produced by e-cig use may be attributed to propylene glycol having a respiratory irritant effect. He went on to say “But this does not necessarily mean that long-term exposure would lead to any adverse effect on lung function. More research is necessary to clarify that point.”
An important thing to note is each of those studies only tested lung function immediately following e-cig use. While not scientific, surveys have found that, in general, vapers report improved lung capacity, smoker's cough and ability to exercise and perform strenuous activities. This is a sign that long term e-cigarette use could actually improve lung function in former smokers.
No Evidence E-Cigs Cause Lung Damage
Either way you look at it, more long term research is needed, as each of the studies suggest. But for now, there is still no evidence that electronic cigarette use causes any acute respiratory impact. And even if it did, vaping is highly unlikely to be worse than tobacco cigarette smoking, which is known to cause chronic obstructive lung disease.