Ventilator-associated pneumonia rates were 9.64 per 1000 ventilator days (SE 0.98, 95% CI was 7.97-11.60) in the control group (48-h circuit changes) and 8.62 per 1000 ventilator days (SE 0.97, 95% CI 6.69 - 10.56) in the study group (1-week circuit changes). There were significantly greater odds of developing a ventilator-associated pneumonia in surgical patients (odds ratio 1.77, p= 0.02) and patients in critical care units (odds ratio 1.54, p= 0.005), but no significant risk of ventilator-associated pneumonia in patients with 1-week circuit changes (odds ratio 0.82, p= 0.22). The difference between the study and control groups (total patients and subgroups) was not statistically significant (p >0.05).