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RESPIRATORY CHANGE IN BRACHIAL BLOOD VELOCITY AS A NONINVASIVE, BEDSIDE CORRELATE TO PULSE PRESSURE VARIATION IN THE VENTILATED PATIENT

The University of Chicago Hospitals, Chicago, IL

PURPOSE: Rapid prediction of the effect of volume expansion (VE) is crucial in hemodynamically unstable patients on mechanical ventilation. While accurate, both radial artery pulse pressure variation (PP) and changes of aortic blood flow peak velocity (VPeakAo) have limitations that make them impractical as point-of-care tools. In this study, we sought to determine whether respiratory changes in the brachial artery blood flow velocity (VPeakBA) as measured by Internal Medicine residents using a hand-carried ultrasound (HCU) could provide an accurate corollary to PP in mechanically ventilated patients.

METHODS: Thirty mechanically ventilated patients with pre-existing radial artery catheters admitted to the intensive care unit (ICU) at the University of Chicago Hospital were enrolled in the study. All patients passively received volume control ventilation with a tidal volume of at least 8 cc/kg ideal body weight for the duration of the study. The brachial artery Doppler signal was recorded and analyzed over a 30-second interval by Internal Medicine residents using a SonoSite TITAN HCU device. A simultaneous recording of the contra lateral arm radial artery pulse wave and corresponding telemetry strip was analyzed by a critical care physician blinded to both the VPeakBA results and clinical status of the patient. When available, a CVP measurement was obtained. The correlation between VPeakBA, PP, and CVP was determined using the Pearson correlation coefficient.

RESULTS: An adequate Doppler signal was obtained in all 30 patients. The intra-observer variability for the technique was 1.2% (+/-1.2%). The brachial artery VPeak correlated well with the radial artery PP (r=0.84). The mean variance between PP and VPeakBA was 1.0% (+/-3.87%). A poor correlation existed between the CVP and both VPeakBA (r=-0.21) and PP (r=-0.16).

CONCLUSION: The HCU Doppler assessment of the brachial artery VPeak as performed by Internal Medicine residents is a rapid, non-invasive bedside correlate to PP.

CLINICAL IMPLICATIONS: The VPeakBA may prove useful as a point-of-care tool for the prediction of volume responsiveness in mechanically ventilated ICU and emergency room patients.

DISCLOSURE: J. Matthew Brennan, None.