Panic Disorder or Anxiety-related Hyperventilation: This condition is characterized by episodes of intense fear or discomfort, often accompanied by symptoms such as chest tightness, shortness of breath (SOB), and palpitations. The hyperaerated lungs and visibility of 8 ribs on the chest X-ray suggest hyperventilation, which is a common feature of panic attacks.

Asthma: Although the patient is described as previously healthy, asthma can sometimes present in adulthood. The symptoms of intermittent chest tightness and SOB, along with hyperaerated lungs on the chest X-ray, could be consistent with asthma, especially if the patient has any allergic history or triggers.
Chronic Obstructive Pulmonary Disease (COPD): Less likely in a previously healthy 36-year-old without a significant smoking history, but possible, especially if the patient has been exposed to other lung irritants. However, the absence of a smoking history and the patient's age make this less likely.

Pulmonary Embolism (PE): Although less common in a previously healthy individual without clear risk factors, PE can present with sudden onset of chest pain and SOB. It's crucial to consider this diagnosis due to its high mortality rate if untreated.
Cardiac Conditions (e.g., Myocardial Infarction, Pericarditis): While the patient's age and previous health status make cardiac conditions less likely, they cannot be ruled out without further evaluation, especially given the symptoms of chest tightness and SOB.

Pneumothorax: The hyperaerated lungs could suggest a pneumothorax, but this would typically present with more acute symptoms and might be visible on the chest X-ray as a lack of lung markings in the affected area.
Cystic Fibrosis: Although rare in adults without a previous diagnosis, cystic fibrosis can lead to hyperinflation of the lungs. However, it would typically be associated with other symptoms such as recurrent infections and malabsorption.
Lymphangioleiomyomatosis (LAM): A rare lung disease that primarily affects women, characterized by cystic lung lesions leading to hyperinflation. Given the patient's gender and age, this is less likely but remains a consideration in the differential diagnosis of hyperaerated lungs.