Ultrasound evaluation of the respiratory changes of the inferior vena cava and axillary vein diameter at rest and during positive pressure ventilation in healthy volunteers
Date
2018
Authors
Molokoane, Keamogetswe
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Abstract
Introduction: Ultrasound assessment of the inferior vena cava (IVC), a large
compliant capacitance vein, has gained favour in aiding fluid management of
critically ill patients. The respiro-phasic changes in IVC diameter have given
clinicians a tool for assessing patient volume status. There are however, limitations
as to when and under what circumstances this tool can be reliably used. The aim of
this study was to assess IVC and axillary vein (Axv) diameter size and respiratory
variation in spontaneously breathing participants at rest and with the application of
increasing positive end-expiratory pressure (PEEP) via non-invasive ventilation
(NIV). The Axv was studied as an alternative vein to the IVC because it is accessible
for ultrasound visualisation and independent of intra-abdominal pressure.
Methods: The IVC and Axv diameters of 28 healthy adult volunteers were measured
using ultrasound, at rest and during positive pressure ventilation via NIV. The
collapsibility index (CI) and distensibility index (DI) of these vessels were calculated
and compared. The correlation between increasing PEEP levels and DI was
evaluated.
Results: Positive pressure ventilation delivered via NIV produced equivalent respirophasic
diameter changes in the IVC and Axv. Both vessel diameter variations at
baseline (collapsibility index) and with increasing levels of PEEP (distensibility index)
were non-uniform and unpredictable in this study population. The respiro-phasic
diameter changes of the IVC and Axv showed no correlation with the level of PEEP.
Conclusion: These findings confirm the current clinical limitations of determining
volume responsiveness using the IVC in spontaneously breathing patients with and
without PEEP. The Axv cannot be used as an alternative vessel to the IVC as it also
displays similar unpredictability.