We carry out a prospective study in order to determine the prognostic factors in the development of injuries of upper airways, and their influence in the decision to perform a tracheotomy. The time to tracheotomy was previously stated, according to the type of patient (neurological or non-neurological). This study includes the clinical data and the upper airways endoscopic exploration of 654 patients with oro-tracheal intubation and mechanical ventilation for more than 48 hours in a 6 year period. Three endoscopic explorations were carried out in the first month (early exploration), with two additional explorations at six and twelve months (late exploration). Using a multivariable statistical study we have analysed the prognostic factors and the risk groups for the development of later injuries of the upper airway of these patients. The later endoscopic exploration of the upper airways has shown injuries in 30 of 280 cases (11%). In this study, the main factor that determines the development of injuries of the upper airway was the time of intubation. The risk groups to develop later lesions of the upper airways include: patients with pathological background, patients with medical admissions, non-neurological patients and patients with serious lesions in the earlier endoscopic exploration. We conclude that it is necessary to state the time to perform a tracheotomy in patients with oro-tracheal intubation. It must be based on the own experience, the patient's clinical condition and the disease that caused hospital admission.