Analgesics/therapeutic use; Hypnotics and Sedatives/therapeutic use; Influenza A Virus, H1N1 Subtype; Influenza, Human/drug therapy; Pneumonia, Viral/drug therapy; Respiratory Insufficiency/drug therapy; Adult; Analgesics/administration & dosage; Cohort Studies; Critical Care/methods; Drug Therapy, Combination; Female; Humans; Hypnotics and Sedatives/administration & dosage; Influenza A Virus, H1N1 Subtype/isolation & purification; Influenza, Human/epidemiology; Influenza, Human/psychology; Influenza, Human/virology; Intensive Care Units; Length of Stay; Male; Middle Aged; Pandemics; Pneumonia, Bacterial/drug therapy; Pneumonia, Bacterial/psychology; Pneumonia, Viral/epidemiology; Pneumonia, Viral/psychology; Pneumonia, Viral/therapy; Pneumonia, Viral/virology; Respiration, Artificial; Respiratory Insufficiency/etiology; Respiratory Insufficiency/psychology; Respiratory Insufficiency/therapy; Treatment Outcome