PSV versus PCV

I am very pleased to read a well-designed randomised control trial proving significant benefits in the physiological parameters following pressure support ventilation (PSV) against the pressure controlled ventilation (PCV) in obese patients [1]. I have always believed the presence of physiological benefit of PSV, especially in the obese individuals and was often able to follow it in my clinical practice until recently. Unfortunately, the new hospital in my training rotation does not have anaesthetic machines that can provide PSV.

Though the new anaesthetic with PSV facility machines would eventually replace the old ones, it may be possible to justify the huge economic burden of purchasing the new anaesthetic machines with PSV facility if additional clinical data is available supporting the clinical benefits of PSV. Did the authors manage to collect and analyse related clinical data in these individuals such as postoperative oxygen requirements, duration of recovery/hospital stay and incidence of chest infection? These data would be very useful if available.

P. Gandre

Bart's & London School of Anaesthesia

London, UK

References

1. Zoremba M, Kalmus G, Dette F, et al. Effect of intra-operative pressure support vs pressure controlled ventilation on oxygenation and lung function in moderately obese adults. Anaesthesia 2010; 65: 124-9.

I am pleased at your interest in my work. However, the primary aim of the study was not to reveal outcome relevant data as overall power in our study was too small. Our primary interest was to show the feasibilty of pressure support ventilation(PSV) in the obese population and to show the possible benefits of its use in terms of lung function and oxygenation. Moreover, we showed that removal times of the LMA in this population were significantly shorter, than within the pressure control ventilation group. This is a benefit with regards to utilisation of staff. In summary, to reveal outcome relevant benefits of PSV (e.g. intra-operative weaning strategies) with regards to pneumonia rates etc., the overall power of the study needs to be increased (possibly more than 1000 patients).

M Zoremba

Department of Anaesthesia and Intensive Care Medicine

University of Marburg, Marburg, Germany

Email: zoremba@med.uni-marburg.de