Differential Diagnosis for the Patient's Findings

• Single most likely diagnosis
  • High altitude-induced central apneas: The patient's symptoms started after arriving in Denver, Colorado, which is at a higher altitude than Houston, Texas. The pattern of breathing described, with cessations in breathing followed by gradual increases and then decreases in breathing effort, is consistent with central apneas. High altitude can induce central apneas due to the lower oxygen levels, which can affect the body's respiratory control mechanisms.
• Other Likely diagnoses
  • High altitude-related hypoxemia related to periodic breathing in the setting of occult heart disease: Although the patient has been responsive to CPAP for obstructive sleep apnea, the change in altitude could exacerbate underlying conditions, including potential occult heart disease, leading to periodic breathing patterns.
  • Higher CPAP pressure is required at higher altitudes: The effectiveness of CPAP can be influenced by altitude due to changes in air pressure. It's possible that the patient's current CPAP setting may not be adequate at the higher altitude, potentially leading to inadequate control of sleep apnea.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Pulmonary embolism: Although less likely, given the context of recent travel to a higher altitude, pulmonary embolism could present with sudden onset of respiratory distress or changes in breathing patterns. It's crucial to consider this diagnosis due to its high mortality rate if left untreated.
  • Acute coronary syndrome: The stress of traveling and the change in altitude could potentially precipitate an acute coronary event, especially if the patient has underlying heart disease. This condition would require immediate medical attention.
• Rare diagnoses
  • Cheyne-Stokes respiration: This is a rare condition characterized by a cyclic pattern of breathing, with periods of deep and rapid breathing followed by periods of apnea. It is often associated with severe heart failure or neurological diseases. Given the patient's recent change in altitude and the description of her breathing pattern, this could be considered, although it is less likely.
  • Sleep stage-dependent central apneas: These are central apneas that occur during specific stages of sleep and can be influenced by various factors, including altitude. However, this diagnosis would be less likely without further information on the patient's sleep stages during these episodes.