Darth Vader may have been able to do this due to the way that his mask was cut and the influence of the light side of the Force. One reason Darth Vader could speak with Anakin's voice was that he could talk without the mask.
The mask has a built-in microphone that allows him to speak, and the chest plate has a speaker that amplifies his voice. The breathing sound that Darth Vader makes is actually the sound of the ventilator in his mask.
Vader's mask was one of the most important pieces of Vader's armor, and was vital to his survival. Without it, he would die unless in the pressurized, controlled atmosphere of one of his specially-made meditation chambers. Inside the mask were many needles that poked into his flesh to interface with him.
It's clear his suit's artificial breathing apparatus was disabled, meaning he's slowly asphyxiating because his lungs were fried back on Mustafar. Originally Answered: could darth vader have survived if he didnt take his mask off? No.
The helmet created Vader's menacing growl due to his natural voice being very weak from vocal-cord damage. It contained neural needles that painfully connected with the top of Vader's skull and spine to form one interconnected unit.
Admiral Piett’s Thoughts After Seeing Darth Vader Without his Helmet on in Episode 5! (Canon)
Why does KYLO Ren have Darth Vader's mask?
The helmet was designed to look sinister; as a Knight of Ren, Ren was part of an enclave of dark side warriors who wore masks to induce fear in their prey. Ren's helmet was a symbolic reminder of his lineage as Darth Vader's grandson, serving no practical use in his life.
When rage and anger seethe inside a dark side user, their eyes may burn yellow with a fiery-red rim." What that means is a Sith's emotions will be shown through their eyes. A Sith's power level can also be determined when their "Sith eyes" are visible.
The circuitry within the suit was damaged beyond repair and there were no medical facilities nearby that could come close to being what was required to save him. Even if Luke hadn't taken his helmet off, he likely would've passed away shortly after.
If he had survived, its doubtless that the New Republic would have had thoughts to put him on trial for his actions as Darth Vader, but ultimately it would be simpler just to claim Vader was dead and quietly exile Anakin Skywalker somewhere remote, as failed Jedi have been known to do.
Inside his suit and mask, Vader has a series of needles in his skin. Unfortunately, these needles, which transmit neurological data throughout his body and allow him to control his limbs, also cause him constant pain.
Darth Vader weighed 120kg (264 lbs), and most of that weight is because of the armor's steel and obsidian components. This means Darth Vader is unable to move at all at speed, and he needs the assistance of cybernetics.
In "Return of the Jedi", Darth Vader is seen shedding tears during the final confrontation between him, Luke Skywalker, and Emperor Palpatine. This moment occurs when Vader witnesses his son, Luke, being tortured by the Emperor's Force lightning, and he is torn between his loyalty to the Emperor and…
Darth Vader also experimented with Force healing fueled by the dark side, in which meditation on anger and frustration at his life and circumstances allowed his lungs to function without the aid of his hyperbaric chamber or his life support suit.
But while it was out of character for a traditional Sith Lord, Vader's past as Anakin Skywalker showed that his compassion towards the soldiers he led was a major part of his character.
As an addendum to what Infantry said: Sidious didn't ask to the med droids to put anesthesia in Anakin on purpose. He wanted him awake in order to feel the pain during the whole procedure, since pain is part of the Sith philosophy of life. Vader being born out of pain was not only metaphorical, but also literal.
The suit is made of a combination of different materials including obsidian, durasteel, plasteel, and plastoid. Other than serving as a means to provide Vader with some armor while in combat, the suit's primary function is to serve as a permanent life support system Vader.
However, joining the Sith means declaring loyalty to the dark side, which Anakin did before his eyes turned yellow. This may explain why Kylo Ren, torn between the light and dark, didn't have yellow eyes in the Star Wars sequel trilogy, as killing his father split his spirit even more.
Dooku was a weak Sith in that he wasn't fully immersed in the Dark. Kind of like Ventress. That is why neither had permanent eye change. Maul, Sidious, and Anakin all went full Dark.
Summary. Obi-Wan spared Anakin despite knowing killing him would "burn his heart to ash" and feeling regret for what Anakin could have become. Obi-Wan's decision to spare Anakin was influenced by the dark feeling that accompanied Emperor Palpatine's arrival, preventing him from finishing him off.
