The PD is being measured along the floor of the nose. This is a method commonly employed in Europe and is an adaptation of the technique established at the Brompton National Heart and Lung Institute, London. Anti-clockwise from the subject, one can see;

1. Exploring catheter in the nose (modified Foley catheter).

2. Bladder syringe filled with conductive cream into which is placed Ag/AgCl electrode.

3. Television (this is a boring test).

4. High resistance voltmeter.

5. Dialysis pump for perfusion of different solutions through the exploring catheter.

6. Psion minicomputer for data acquisition (interface between voltmeter and Psion can be seen behind).

7. Bottles with sterile perfusion liquids.

8. Reference electrode on surface of left forearm. 9. Washing up bowl.