Table 2 Different techniques for P.01 assessment

`Formal' occlusion

Precise;

Complicated;

technique

good;

requires specific

repeatable

equipment and

interruption of the

natural breathing

rhythm

`Quasi occlusion'

Simple;

Requires a pressure

technique (demand

no specific

trigger with an

valve)

equipment;

opening time in the

no interruption

demand valve

of the natural

> 100 ms;

breathing rhythm

can be influenced by

external factors

(endotracheal tube

obstruction)