Invasive mechanical ventilation (IMV) is a life support treatment for patients with acute respiratory failure. The IMV can generate adverse effects that may cause alterations in other organs besides the lung, creating an important problem during ICU stay, hospital stay and years after discharge. These consequences on morbidity and mortality have significant economic and social weight. In the United States the IMV represents 2.7 episodes per 1000 habitants, with an estimated cost of $27,000 million, representing 12% of all hospital expenses. The overall mortality in patients with IMV is 30-35%, increasing with age. Therefore, patients receiving IMV are a high-risk population and with higher costs.

A poor interaction between patient and ventilator during IMV can develop asynchronies. The asynchronies may present in 25% of patients. The majority of studies in ICU patients are limited to a evaluation of short periods of time. Asynchronies identification needs the application of respiratory physiology knowledge and the interpretation of respiratory signals from the ventilator waves. This allows identifying in an easy way different situations of "fight", but it also difficult the identification of situation where asynchronies are less obvious, doing that them remain underdiagnosed. Moreover, asynchronies can be only evaluated during a brief period of time, and it's difficult to know their incidence during all the IMV period and to make adjustments to improve them.

In our centre, it has been developed a continuous monitoring system during IMV which integrates, in real-time, all the information derived from digital monitors and ventilators. It allows a continuous and automatic detection of different events (through an intelligent alarm system) and quantification of asynchronies. It was demonstrated that asynchronies are frequent, that it can be present from the beginning of IMV, that it increase in severe patients under deep sedation and it can increase ICU and hospital mortality.

The investigators can study different factors that can influence over asynchronies development or can improve them.

The aim of this study is to analyze the real incidence of asynchronies of patients undergoing mechanical ventilation and to analyze what factors may have an association with their appearance.

This factors includes factors related with the pulmonary mechanics of each patient and other factors such as the treatment administered, especially drugs with sedative and analgesic effect will be taken into account.

This can help to implement strategies for the improvement of asynchronies.

Inclusion Criteria:

• Mechanical ventilation more than 48 hours.
• Included during the first 24 hours of mechanical ventilation.

Exclusion Criteria:

• Less than 18 years old
• Pregnant patients
• Do-not-resuscitate orders
• Admitted for organ donation
• Chest tubes with suspected bronchopleural fistula.

Patients admitted to the ICU under mechanical ventilation and monitorized with the Better Care System.