A statistical approach to measuring the competence of anaesthetic trainees at practical procedures

Cusum analysis is a statistical technique to distinguish deviations from an acceptable failure rate. The progress of anaesthetic trainees learning four practical procedures (obstetric extradural anaesthesia, spinal anaesthesia, central venous cannulation and arterial cannulation) was monitored from their first attempt using cusum analysis. Suitable acceptable and unacceptable failure rates for each procedure were chosen by consultant anaesthetists. For obstetric extradural anaesthesia, four trainees eventually achieved acceptable failure rates (5%) and the number of attempts required to demonstrate this statistically ranged from 29 to 185; three trainees had an unacceptable failure rate (10%) and five trainees had inconclusive records. For spinal anaesthesia, two trainees achieved an acceptable failure rate (10%) and the number of attempts required to demonstrate this statistically ranged from 39 to 67; two trainees had an unacceptable failure rate (20%) and four trainees had inconclusive records. One trainee demonstrated statistically an acceptable failure rate in arterial cannulation (20%) after 14 attempts and four trainees had inconclusive records. Two records of central venous cannulation were inconclusive. Some records showed variable failure rates which were sometimes associated with lack of practice or a change in technique. Cusum analysis can be used to monitor training in practical procedures and as a continuous audit of quality of clinical practice.