Ventilatory ratio : a simple bedside index to monitor ventilatory efficiency
Author(s)
Sinha, Pratik
Type
Thesis
Abstract
A lack of a simple index that monitors ventilatory efficiency at the bedside has meant
that oxygenation has been the predominant variable that is used to monitor adequacy
of ventilatory strategies and disease severity in mechanically ventilated patients. Due
to complexities in its measurement, deadspace ventilation, the traditional method to
track ventilatory failure, has failed to become integral in the management of
mechanically ventilated patients.
Ventilatory ratio (VR) is an easy to calculate index that uses variables measured at the
bedside: [Mathematical equation appears here. To view, please open pdf attachment] where [Symbols appears here. To view, please open pdf attachment] is taken to be 100 ml.kg-1.min-1 based on predicted body weight and [Symbols appears here. To view, please open pdf attachment]
is taken to be 5 kPa. Physiological analysis of VR dictates that it is
influenced by deadspace fraction and CO2 production.
Physiological analysis of VR was validated in a benchside lung model and a high
fidelity computational cardiopulmonary physiology model. The impact of CO2
production on VR was investigated in patients undergoing laparoscopic surgery who
received exogenous intraperitoneal CO2. This showed that delta values of the 2
variables were linear. The variability of CO2 production was examined in ICU
patients and results of the study showed that variability of CO2 production was small.
In an ICU population correlation of VR was stronger with deadspace in comparison to
CO2 production. Of these two variables, deadspace had the greater effect on VR.
The clinical uses of VR were examined in 4 databases of ICU patients. VR was
significantly higher in non-survivors compared to survivors. Higher values of VR
were associated with increased mortality and more ventilator days. A rising values of
VR over time was also associated with worse outcome.
VR is a simple bedside index that provides clinicians with useful information
regarding ventilatory efficiency and is associated with outcome.
that oxygenation has been the predominant variable that is used to monitor adequacy
of ventilatory strategies and disease severity in mechanically ventilated patients. Due
to complexities in its measurement, deadspace ventilation, the traditional method to
track ventilatory failure, has failed to become integral in the management of
mechanically ventilated patients.
Ventilatory ratio (VR) is an easy to calculate index that uses variables measured at the
bedside: [Mathematical equation appears here. To view, please open pdf attachment] where [Symbols appears here. To view, please open pdf attachment] is taken to be 100 ml.kg-1.min-1 based on predicted body weight and [Symbols appears here. To view, please open pdf attachment]
is taken to be 5 kPa. Physiological analysis of VR dictates that it is
influenced by deadspace fraction and CO2 production.
Physiological analysis of VR was validated in a benchside lung model and a high
fidelity computational cardiopulmonary physiology model. The impact of CO2
production on VR was investigated in patients undergoing laparoscopic surgery who
received exogenous intraperitoneal CO2. This showed that delta values of the 2
variables were linear. The variability of CO2 production was examined in ICU
patients and results of the study showed that variability of CO2 production was small.
In an ICU population correlation of VR was stronger with deadspace in comparison to
CO2 production. Of these two variables, deadspace had the greater effect on VR.
The clinical uses of VR were examined in 4 databases of ICU patients. VR was
significantly higher in non-survivors compared to survivors. Higher values of VR
were associated with increased mortality and more ventilator days. A rising values of
VR over time was also associated with worse outcome.
VR is a simple bedside index that provides clinicians with useful information
regarding ventilatory efficiency and is associated with outcome.
Date Issued
2012-08
Date Awarded
2013-10
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Takata, Masao
Soni, Neil
Sponsor
Westminster Hospital. Medical School
Publisher Department
Surgery and Cancer
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)