Introduction Undiagnosed obstructive sleep apnoea (OSA) presents a significant risk to patients undergoing general anaesthesia. The STOP-BANG questionnaire is a useful screening tool for predicting a high probability of OSA. This study examines the results of the pre-operative screening at Salford Royal NHS Foundation Trust.

Methods The sleep study results from 857 patients (658 male) aged 20–87 years (57.1±0.4 years) who underwent a pre-operative assessment and scored ≥3 on the STOP-BANG questionnaire were retrospectively analysed. Patients were categorised as have no, mild, moderate or severe OSA according to their Apnoea Hypopnoea Index (AHI) (n=675) or Oxygen Desaturation Index (ODI) (n=182). using AASM criteria b (4% desaturation).

The effects of gender, age, body mass index (BMI), neck circumference (NC) and Epworth Sleepiness Score (ESS) were independently assessed and differences between groups were compared using One Way ANOVA. Results are reported as mean ± standard error.

Results The number of patients having no, mild, moderate or severe OSA were 215 (25%), 250 (29%), 214 (25%) and 178 (21%), respectively.

The proportion of males increased as severity increased. The percentage of males who had no, mild, moderate or severe OSA was 64.6%, 72.0%, 86.0 and 87.0%, respectively.

Mean age was significantly lower (P<0.001) in the no OSA compared to all 3 OSA categories. Those with moderate OSA were also significantly older (P<0.05) than those with mild OSA.

Those with severe OSA had a significantly higher average BMI compared to all other categories (P<0.05).

Average neck circumference significantly increased with severity of OSA.

There was no significant difference in average ESS between groups.

Conclusion Seventy-five percent of pre-operative patients with a STOP-BANG score ≥3 had some degree of OSA. The severity of OSA was dependent on gender, age, BMI and neck circumference. ESS was not helpful in predicting presence or severity of OSA.