Aqua-Lung vs ventilator

Aqua-Lung and ventilator both are nouns.

Word	Noun	Adjective	Verb	Adverb
Aqua-Lung	Yes	No	No	No
ventilator	Yes	No	No	No

As nouns, ventilator is a hypernym of Aqua-Lung; that is, ventilator is a word with a broader meaning than Aqua-Lung:

Aqua-Lung: a device (trade name Aqua-Lung) that lets divers breathe under water; scuba is an acronym for self-contained underwater breathing apparatus
ventilator: a device that facilitates breathing in cases of respiratory failure

Other hypernyms of Aqua-Lung include breathing apparatus, breathing device, breathing machine.

Aqua-Lung (noun)	ventilator (noun)
a device (trade name Aqua-Lung) that lets divers breathe under water; scuba is an acronym for self-contained underwater breathing apparatus	a device (such as a fan) that introduces fresh air or expels foul air
	a device that facilitates breathing in cases of respiratory failure