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How to Perform a Maximum Venous Outflow Study (MVO)
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Why perform an MVO study?
Because deep vein thrombosis cannot be reliably diagnosed solely on the basis of external signs and symptoms, objective screening tests are valuable for confirming or ruling out suspected venous objections in the lower extremities. Undiagnosed Deep Vein Thrombosis (DVT) can lead to a pulmonary embolism. The MVO test uses PV (pneumoplethysmography). It is performed by inducing temporary venous pooling by means of a constricting thigh cuff, then measuring the rate at which emptying occurs when the constricting cuff is suddenly vented. Maximum Venous Outflow can be used in addition to venous compression or venous reflux studies. Koven Technology Vascular Doppler models Smartdop® 45, and Smartdop® 30EX, can be used to perform an MVO study. |
| Examination Procedure |
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- Connect the PV module to the Doppler and make sure the Doppler is set on separate or venous mode.
- Place the patient in a supine position with the leg and hip rotated outward. Wrap cuffs of appropriate width comfortably snug around the patient's mid thigh and mid calf.
- Connect a 3-way stopcock to the inlet of the PV module. Connect extender tubing to one of the two remaining sides of the stopcock and attach the tubing to the cuff at the mid calf. Attach a sphyg to the other side of the stopcock.
- Turn the stopcock so that air is routed from the sphyg to the cuff. The green arms on the stopcock will be at the 12, 3, and 6 o'clock positions.
- Inflate the cuff to 40 mmHg. Wait 10 seconds to allow time for settling, then deflate the cuff to 15 mmHg.
- Disconnect the sphyg from the stopcock, attach it to the thigh cuff and begin the measurement.
- Inflate the thigh cuff to 60 mmHg or more. After 90 seconds, disconnect the sphyg from the cuff.
- When performing an MVO study using a Koven Smartdop Doppler system, the results will be automatically plotted on the LCD
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| Interpreting the Results |
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Normal results will show a return of venous flow to the original baseline within 3 seconds.
A return of venous flow to baseline taking longer than 3 seconds is considered abnormal.
Another method of interpretation is by applying the following formula:
| MVO / VC x 100% = |
> 70% = Normal
< 70% = Abnormal |
VC = Venous Capacitance, 90 sec. sphyg disconnection point
MVO = Maximum Venous Outflow, 3 sec. after VC point |
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| The instructions provided above are intended as general guidelines. For specific instructions on performing a MVO study using your specific Doppler, please refer to the operation manual provided. |
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Copyright © 2008 Koven Technology, Inc.
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