We report a case of a contraindicated attachment of a speaking valve to a tracheal tube with an inflated cuff, which rapidly resulted in the patient’s death. The attached one-way valve allowed unrestrained inspiration through the tracheal tube but prevented physiological expiration. The increased pulmonary pressure resulted in alveolar rupture and replaced expiration with a steady release of air into the peribronchial sheaths and the mediastinum, resulting in what is commonly known as the Macklin effect. From the mediastinum, air inflated both pleural cavities, the peritoneum, and the subcutaneous tissue of the entire body. No gas was found in the blood vessels, the brain, the bones, or in the inner organs. The entire air volume was estimated by radiological segmentation to be more than 25 l. This implies continuous inspiration, while expiration turned into an aberrant pulmonary decompression by whole-body gas-enclosure. Death ultimately resulted from asphyxia following bilateral (tension) pneumothorax.