A police officer has been sacked after he was filmed forcing his knee against a female suspect's neck until she collapsed unconscious.

James Medina was accused of using inappropriate force in a holding cell against the woman who had been arrested on charges of assaulting an officer.

Footage shows Medina struggling with Seryina Trujillo for around a minute before he forces his knee on her throat, causing her to go limp and fall to the floor.

Police administrators said Medina didn't seek medical attention for Trujillo, didn't seek the help of other officers to subdue her and didn't report the use of force.

Manhandled: Denver police officer James Medina has been fired after being accused of using inappropriate force while restraining female suspect Seryina Trujillo in a holding cell which was caught on CCTV (above)

Pinned down: During the scuffle, Medina puts his knee against Trujillo's neck until she goes limp

Another officer told a supervisor about the incident four days after it happened, KCNC-TV in Denver reported.

Medina, a 16-year veteran, has appealed the firing, said his attorney, Donald Sisson.

Sisson said Medina's actions were reasonable and that Trujillo had been scratching and biting the officer.

Sisson said Medina didn't file a use of force report because he didn't think Trujillo was injured.

The incident occurred July 10.

Trujillo had been arrested for allegedly kicking Medina in the face and spitting on another officer while police were taking her boyfriend into custody.

Out cold: Trujillo collapses on the floor. Police administrators said Medina didn't seek medical attention for her, didn't seek the help of other officers to subdue her and didn't report the use of force

Trujillo gets to her feet after she appeared to be unconscious for several seconds. Medina had earlier asked her to surrender her shoes and belt inside the holding cell, but she had resisted, prompting the fracas

Trujillo sits back down as Medina gathers her belongings. Medina said he will appeal the decision to fire him

Medina asked Trujillo to surrender her shoes and belt inside the holding cell, but she resisted.

In an ensuing struggle, Medina can be heard repeatedly telling her not to bite him.

According to the department, Medina placed his right knee against Trujillo's neck. When he got off, she went limp and appeared to lose consciousness for several seconds.

'Clearly his actions taken as a whole are not in line with the values of the police department,' said Cmdr Matt Murray.

'We have repeatedly talked about the fact there is a culture of change within the Denver Police Department demanded by the community and this is a part of it.'

Sgt Glenn Mahr, a member of the department's tactics review board, suggested after reviewing the tape that Medina used appropriate force because Trujillo displayed 'active aggression' toward him.

But Mahr faulted Medina for not seeking assistance from other officers.