Mrs Brown, a 78 year-old female, was admitted to the Emergency Department at 6am after waking up with severe breathlessness. Her family informed you that the patient has a history of heart failure that had been diagnosed two years ago. On admission to the Emergency Department the clinical manifestations were:
Respiratory rate of 24 breaths/minute
SpO2 85%, on room air
Pulse rate of 120 beats/minute, in atrial fibrillation
Auscultation of lungs identifies bilateral basal crackles
A diagnosis of acute exacerbation of chronic heart failure was made.
Explain the pathogenesis causing the clinical manifestations with which Mrs Brown presented.