Imaging studies such as X-ray and CT imaging of the chest may reveal thoracic infiltrates that can be seen as opaque patches. One distinct feature of HAPE is that pulse oximetry saturation levels (SpO2) are often decreased from what would be expected for the altitude. People typically do not appear as ill as SpO2 and chest X-ray films would suggest. Giving extra oxygen rapidly improves symptoms and SpO2 values; in the setting of infiltrative changes on chest X-ray, this is nearly pathognomonic for HAPE. Severity
The severity of HAPE is graded. The grades of mild, moderate, or severe HAPE are assigned based upon symptoms, clinical signs, and chest x-ray results for individuals. The symptoms that are taken in to account while evaluation the severity of HAPE are difficulty breathing while exerting or while at rest, the presence of a cough and the quality of that cough, and the level of fatigue of the patient. On physical exam of a suspected HAPE patient the exam findings used to grade the severity are the heart rate, respiratory rate, signs of cyanosis, and severity of lung sounds. Both symptoms and signs on physical exam can be used to evaluate a patient in the field. Chest X-rays are also used to evaluate the severity of HAPE when they are available. Differential diagnosis
Differential diagnosis:
Pneumonia
Bronchitis
Mucous plugging
Pulmonary embolism
Acute coronary syndrome
Acute decompensated heart failure
Asthma
Reactive airway disease
Exercise-associated hyponatremia
Pneumothorax

Prevention
The primary recommendation for the prevention of HAPE is gradual ascent.
This is evidenced by the appearance of "diffuse," "fluffy," and "patchy" infiltrates described on imaging studies of climbers with known HAPE.Although higher pulmonary arterial pressures are associated with the development of HAPE, the presence of pulmonary hypertension may not in itself be sufficient to explain the development of edema; severe pulmonary hypertension can exist in the absence of clinical HAPE in subjects at high altitude. Diagnosis
The diagnosis of HAPE is entirely based on symptoms and many of the symptoms overlap with other diagnoses. Before HAPE was understood it was commonly confused with pneumonia which resulted in inappropriate treatment.HAPE generally develops in the first 2 to 4 days of hiking at altitudes >2,500 meters (8,200 ft), and symptoms seem to worsen most commonly on the second night. Initial symptoms are vague and include shortness of breath, decreased exercise ability, increased recovery time, fatigue, and weakness, especially with walking uphill. People then develop a dry, persistent cough, and often cyanosis of the lips. Another cardinal feature of HAPE is the rapid progression to dyspnea at rest. The development of pink, frothy, or frankly bloody sputum are late features of HAPE. In some cases, people will develop concomitant neurological features such as poor coordination, altered consciousness, or cerebral edema (High-altitude cerebral edema).On physical exam, increased breathing rates, increased heart rates, and a low-grade fever 38.5o (101.3o F) are common. Listening to the lungs may reveal crackles in one or both lungs, often starting in the right middle lobe.