Nicotine vapes, also known as e-cigarettes or electronic nicotine delivery systems (ENDS), are battery-operated devices that heat a liquid solution to create an aerosol for inhalation. The e-liquid typically contains nicotine, flavorings, and solvents such as propylene glycol (PG) or vegetable glycerin (VG). This heating process turns the liquid into a fine mist that is drawn into the lungs. The entire function of the device relies on the user inhaling this aerosol to deliver nicotine to the body.
Understanding Vaping Inhalation Techniques
Inhaling the aerosol is performed using one of two primary techniques, depending on the device and the user’s preference. The first method is Mouth-to-Lung (MTL) inhalation, which closely mimics the way a traditional cigarette is smoked. With MTL, the user draws the vapor into their mouth first, holds it briefly, and then inhales it into the lungs. This two-step process provides a tighter draw and a more pronounced “throat hit,” often leading users to choose e-liquids with higher nicotine concentrations.
The second common method is Direct-to-Lung (DTL) inhalation, which is a single, continuous breath straight into the lungs. This technique is similar to taking a deep breath, bypassing the mouth-holding step. DTL requires devices with more power and a wider airflow to handle the larger volume of aerosol. Users who employ the DTL style generally prefer e-liquids with lower nicotine concentrations, as the cloud production can deliver a large dose of nicotine quickly. A variation called Restricted Direct-to-Lung (RDL) exists, which uses a looser draw than MTL but is not as airy as a full DTL inhale, offering a middle ground for users.
How Nicotine Vapor Enters the Body
Inhalation of the aerosol is the mechanism for nicotine delivery, with absorption occurring rapidly through the lungs’ vast surface area. Once the aerosol reaches the lungs, the nicotine quickly crosses the alveolar membrane, which separates the air sacs from the bloodstream. This pulmonary absorption allows for a fast rise in blood nicotine levels, providing a near-immediate effect comparable in speed to smoking a traditional cigarette. This rapid delivery is a significant factor in the addictive potential of these products.
The specific chemical formulation of the nicotine can affect how quickly and smoothly it is absorbed. Nicotine in e-liquids comes in two forms: freebase nicotine or nicotine salts. Nicotine salts are created by combining freebase nicotine with an acid, such as benzoic acid, which lowers the pH of the liquid. This chemical alteration makes the aerosol much smoother to inhale, even at higher concentrations, and some studies suggest it is absorbed into the bloodstream faster than freebase nicotine. The speed of absorption via the lungs is a key function of vaping, distinguishing it from slower nicotine replacement methods like patches or gums.
Potential Health Effects on the Lungs
While nicotine is the addictive substance, the other compounds in the inhaled aerosol are responsible for many of the potential health effects on the lungs. The solvents propylene glycol (PG) and vegetable glycerin (VG) are regarded as safe for ingestion but can break down into toxic compounds when heated. When aerosolized and inhaled, these solvents can cause inflammation and irritation in the airways. Chronic exposure to the aerosol may contribute to long-term issues like reduced lung function and chronic respiratory diseases.
The flavorings added to e-liquids also introduce chemicals that may be harmful when inhaled, even if they are safe to eat. For example, flavor chemicals like diacetyl have been linked to bronchiolitis obliterans, a severe and irreversible lung disease. Furthermore, the aerosol is not harmless water vapor but a complex mixture of fine particulate matter, volatile organic compounds, and heavy metals like lead and nickel, which can deposit deep within the lungs. A severe, acute inflammatory lung condition known as E-cigarette or Vaping Product Use-Associated Lung Injury (EVALI) has been identified, characterized by symptoms like cough, shortness of breath, and chest pain. EVALI has been strongly associated with the inhalation of products containing Vitamin E acetate, a compound sometimes added to illicit THC-containing vape liquids.