{
  "abstract": "A 21-year-old man who suffered recurrent panic attacks presented with persistent dyspnoea after forceful hyperventilation. He was transferred to our hospital approximately 4 hours after symptom worsening. On admission, his respiratory rate was 24 breaths/min and oxygen saturation was 83% on room air. Arterial blood gas analysis performed while the patient was receiving oxygen via nasal cannula at 4 L/min, corresponding to an estimated fractional inspired oxygen (FiO2) of 0.36, showed pH 7.321, partial pressure of arterial carbon dioxide (PaCO2) 50.3 mm Hg, partial pressure of arterial oxygen (PaO2) 88.0 mm Hg, HCO3− 25.2 mmol/L, a PaO2/FiO2 ratio of 244 and an estimated P(A–a)O2 of 110.3 mm Hg. Because dyspnoea and oxygen requirement persisted, oxygen therapy was escalated to a reservoir mask at 10 L/min, after which SpO2 was maintained at approximately 98%. Hyperbaric oxygen therapy, high-flow nasal cannula, non-invasive ventilation and mechanical ventilation were not used. Contrast-enhanced CT (following the pulmonary angiography protocol) excluded pulmonary embolism. Thin-section CT indicated interstitial air tracking along the interlobar fissure extending to the mediastinal pleura (figure 1A, arrow) and perivascular air outlining the pulmonary vein (figure 1B, arrowheads) without pneumomediastinum or pneumothorax. The distribution of linear peribronchovascular and interstitial air without free pleural or mediastinal air collection was consistent with pulmonary interstitial emphysema. A follow-up CT performed the next day showed a decrease in the interstitial air (figure 1C, arrow and figure 1D arrowheads). Oxygen via a reservoir mask at 10 L/min was administered overnight, primarily to correct hypoxaemia and promote the resorption of extra-alveolar air by reducing alveolar nitrogen partial pressure and increasing the diffusion gradient for nitrogen. Oxygen therapy was de-escalated to a face mask at 6 L/min the following day and completely discontinued on hospital day 3. After psychiatric liaison intervention, the patient was discharged on day 4 without complications.",
  "authors": [
    {
      "affiliations": [
        "Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan"
      ],
      "name": "Ryota Inokuchi"
    },
    {
      "affiliations": [
        "Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan"
      ],
      "name": "Tomoki Wada"
    },
    {
      "affiliations": [
        "Department of Emergency and Critical Care Medicine, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan"
      ],
      "name": "Kent Doi"
    }
  ],
  "title": "Pulmonary interstitial emphysema after hyperventilation",
  "uid": "bf67b126-957c-5b55-ae2f-a7756181ce0a"
}