Dementia with aspiration pneumonia: The patient's presentation of being in bed all the time, alert only approximately 25% of the time, coughing, moaning, groaning, growling, gurgling loudly with audible bubbles and liquid, suggests a high likelihood of aspiration pneumonia, which is often seen in patients with advanced dementia who have difficulty swallowing (dysphagia) and are at risk for aspirating food, liquids, or saliva into the lungs.

Stroke or cerebral vasculature disease: The patient's clenched left hand and occasional quivering of legs and feet could indicate a stroke or cerebral vasculature disease affecting motor control. The patient's quickness to anger and altered mental status could also be consistent with a stroke or vascular dementia.
Parkinson's disease with dementia: The quivering of legs and feet, along with the patient being alert only a portion of the time and having difficulty with eating (pureed food in small amounts), could suggest Parkinson's disease with associated dementia.
Chronic obstructive pulmonary disease (COPD) or other chronic respiratory condition: The patient's symptoms of coughing, moaning, and gurgling loudly could be indicative of a chronic respiratory condition such as COPD, especially if there's a history of smoking or exposure to lung irritants.

Pulmonary embolism: Although less likely given the chronic nature of the symptoms, a pulmonary embolism could present with sudden onset of respiratory distress and must be considered, especially if there are risk factors such as immobility.
Sepsis: Infection leading to sepsis could present with altered mental status, respiratory symptoms, and could be life-threatening if not promptly addressed.
Hydrocephalus: Normal pressure hydrocephalus (NPH) could present with dementia, gait disturbances, and urinary incontinence, and while less likely, it's a condition that could potentially be treated with shunting.

Creutzfeldt-Jakob disease: A rare, degenerative, fatal brain disorder that could explain the rapid progression of dementia and altered mental status, though it would be unusual for it to present with such prominent respiratory symptoms.
Amyotrophic lateral sclerosis (ALS): While primarily a motor neuron disease, ALS could lead to significant respiratory symptoms due to muscle weakness, including difficulty swallowing and breathing, though the absence of more typical ALS symptoms (e.g., fasciculations, significant muscle atrophy) makes this less likely.
Mitochondrial disorders: Rare genetic disorders affecting the mitochondria could lead to a wide range of symptoms including neurological decline, muscle weakness, and respiratory issues, though they would typically have an earlier onset and a more complex presentation.