Doctors treating former President George H W Bush for pneumonia are considering whether to take out a breathing tube inserted to clear his airway.

His wife, Barbara, diagnosed with bronchitis, was feeling "1,000 per cent better" on Thursday after antibiotics and rest.

The 92-year-old former president and the 91-year-old former first lady both had been admitted to Houston Methodist Hospital.

He was admitted on Saturday with difficulty breathing.

She was hospitalised Wednesday after feeling fatigued and coughing for weeks.

Family spokesman Jim McGrath said the 41st president remained in stable condition. Bush has been in the intensive care since Wednesday, relying on a ventilator to breathe.

Removing the tube a procedure known as extubation would allow Bush to breathe on his own.