Ventilator associated pneumonia (VAP) remains in the intensive care unit the infection associated with the highest morbidity and mortality.

Respiratory infection with resistant organism are increasing in prevalence. Because of lack of alternatives, amino glycoside, old antibiotics family, can be used for several infection.

Aerosolized Amikacin or Tobramycin are used in mechanically ventilated patients for respiratory infections. Gentamicin,which is effective against numerous multi drug resistant Gram-negative organism and Gram-positive like Staphylococcus aureus, could be a great option for nebulisation.

The investigators assume that nebulisation of gentamicin allows to obtain a higher lung concentration while assuring a systematic toxicity much lesser than a parenteral administration.

Inclusion Criteria:

• to be in critical care unit
• to be mechanically ventilated
• to have a ventilator-associated pneumonia requiring a treatment by gentamicin
• to be affiliated to a national insurance scheme
• to have given an informed consent (patient or close person)

Exclusion Criteria:

• to be obese (BMI > 40 kg/m²)
• to have been treated by gentamicin for 7 days
• to be allergic to aminoglycoside
• to have a severe respiratory failure (PaO2 / FiO2 < 150)
• to have a renal failure (Cl creat < 60 ml/min/1.73m²)
• to be under reinforced protection measure