Endotracheal suctioning: an example of the problems of relevance and rigour in clinical research.

Endotracheal suctioning is a routine but potentially dangerous procedure. The literature documenting approaches to minimizing the cardiopulmonary complications of endotracheal suctioning is reviewed. Hyperoxygenation, hyperventilation, hyperinflation and the use of adaptors are all evaluated. The effects of endotracheal suctioning on haemodynamics and oxygen transport are also examined. The traditional dualist approach to the respiratory and cardiovascular systems is contrasted with the recent emphasis on oxygen transport by the cardiopulmonary system. The trade-off between the rigour of laboratory studies (which can be well controlled but are difficult to generalize) and the relevance of clinical research (which is more easily generalized but which often lacks internal validity) is discussed. Although research studies have become both more methodologically and conceptually sophisticated, definitive recommendations for a safe and effective suctioning procedure still remain elusive.