The patient’s oxygen requirement declined rapidly after the first day. He was discharged to home on Day 5 with ambulatory Sp O 2 >95% while breathing ambient air. Because of the rapid improvement, he was not treated with a corticosteroid. A repeat computed tomographic scan of the chest obtained 2 weeks after discharge showed complete resolution of lung opacities ( Figure 3 ).

Flexible bronchoscopy yielded bloody lavage fluid suspicious for diffuse alveolar hemorrhage, with 61% neutrophils, 8% lymphocytes, and 2% eosinophils. Flow cytometry of the fluid showed a CD4/CD8 ratio of 0.46. Histopathology of alveolar tissue obtained via transbronchial biopsy showed organizing pneumonia ( Figure 2 ). Urine antigens for legionella and histoplasmosis were negative. An upper respiratory viral panel was negative and HIV serology and rheumatologic tests were all negative. Microbiologic culture was negative for all samples.

Antibiotic therapy was initiated after blood and sputum samples were sent for culture. Urine toxicity screening was positive for cannabinoids only. The patient was admitted to the intensive care unit on 50% oxygen via nasal cannula at a high flow rate to maintain Sp O 2 ≥92%.

In the ED, the patient’s Sp O 2 was 91% at rest while breathing supplemental oxygen at 6 liters per minute via nasal cannula. Physical examination was unremarkable except for tachypnea. A computed tomographic angiogram of the chest did not reveal pulmonary embolism, but instead showed extensive airspace opacification in a centrilobular nodular pattern roughly resembling a “tree in bloom” ( Figure 1 ).

One day before presentation and 6 hours after vaping cannabis oil, the man developed dyspnea. His wife noticed that his breathing was rapid and shallow. He remained dyspneic the next day and started to expectorate blood-tinged sputum, which progressed to small quantities of “pure blood.” This prompted a visit to a physician who advised him to go to an ED after he noted resting oxygen saturation (Sp O 2 ) of 82%.

A relatively healthy 54-year-old man was admitted to the hospital through the emergency department (ED) for acute onset of dyspnea and hemoptysis. He had never smoked cigarettes but had been vaping cannabis oil approximately once weekly for several years.

Discussion

We believe that vaping a product sold as cannabis oil was the cause of our patient’s respiratory failure, given the temporal relationship between inhalation and the onset of symptoms, his rapid improvement without further exposure, and the fact that no other plausible cause was identified. The findings of pulmonary alveolar hemorrhage, neutrophil-predominant lavage, a reverse CD4/CD8 ratio (3), and organizing pneumonia in lung tissue biopsy specimens further support acute inhalational lung injury as the cause of respiratory failure.

Detrimental respiratory effects have been associated with the inhalation of combustion products of marijuana, including smoking hand-rolled leaves (joints) or water pipes (bong). Acute use can cause pneumothorax (4) and bronchodilation, which was exploited to treat asthma in the 19th century (5). Habitual use increases the prevalence of respiratory symptoms such as chronic cough and dyspnea (6). Chronic bronchitis is likely caused by products of combustion, which include pyrolytics such as tar and irritants such as ammonia and nitrogen oxides (7). Whether inhalation of marijuana smoke can cause emphysema or lung cancer is controversial (6, 8, 9). Marijuana smoke inhalation, which may be associated with damage to the pulmonary epithelial barrier (10), has rarely been reported to cause severe lung injury (11–13).

Vaporizing systems were developed with the goal of reducing the adverse respiratory effects of inhaling tobacco and cannabis derivatives. Ideally, cannabis vaporizers should have high efficiency for delivering THC and should minimize the generation of deleterious byproducts. Currently available products are designed to achieve those goals by heating dried marijuana parts to a temperature above 180°C (to vaporize cannabinoids) and below 230°C (to avoid combustion) (14, 15). Cannabis oil vaping is a newer method of use; a prefilled cartridge of cannabinoid concentrated oil is loaded into a hand-held vaporizer, which has a battery-operated heating system. This method avoids vaporizing crude marijuana parts and is thought to be safer.

However, some oil products are extracted from marijuana using additives such as propylene glycol which, although classified as “generally recognized as safe” by the Food and Drug Administration when ingested orally, can potentially cause lung injury when inhaled at a high temperature (16). Heating can also transform propylene glycol into carbonyls such as formaldehyde, a carcinogen and respiratory irritant (17). Flavoring ingredients, including diacetyl, may also pose risks to respiratory health (18); although it is more recognized in e-cigarette use, it can be present in cannabis oil vaping.