Multilevel Physiologic Arterial Exam

When performing this exam on a patient with leg artery disease, three pressure cuffs are be placed on each leg – thigh, calf, and ankle level. One cuff is placed on each arm at the bicep level. We even have little infrared light sensors (PPGs) and tiny pressure cuffs for the toes when needed!

FloLab exams take about 1 hour to complete and is performed with the patient laying down flat – this is because arm and leg pressures are compared with the limbs resting at the same level as the heart.

The Flolab test has three parts:

1. Segmental Pressures
2. Pulse Volume Recordings (PVRs)
3. Dopplers

SEGMENTAL PRESSURES: these are blood pressure readings taken from all pressure cuffs; the leg pressures are then compared to the arm pressures.

When the pressure reading at the ankle is used for comparison it is specifically referred to as the Ankle-Brachial Index (ABI). When a toe pressure is taken, the result is called a Toe-Brachial Index (TBI). The TBI is particularly useful when the patient has feet and toe wounds.

A person with little or no arterial disease, will have very similar blood pressure readings in their arms and throughout their legs – thigh, calf and ankle. For example, If their arm pressures are 120mmhg, their leg pressures, down to their ankles will be very similar, maybe 100mmhg. Their ABI is calculated by dividing 100/110 which equals 0.92

For someone with PAD, and depending on where the level of arterial disease is, at least some of the leg and ankle blood pressures will be lower than the arm blood pressures. For example, someone with intermittent claudication may have arm pressures of 150mmhg, thigh pressures of 150mmhg, and calf and ankle pressures of 75mmhg. Obviously, there is a drop off in pressure between the thigh and calf. Their ABI is calculated by dividing the ankle pressure of 75 by the arm pressure of 150, which equals 0.50. And because the pressure decreases somewhere between the thigh cuff and calf cuff, we can deduce that the patient has moderate femoropopliteal disease consistent with their claudication symptoms.

To sum it up: Segmental Pressures, ABIs, and TBIs are a way to essentially quantify the severity of PAD at different levels in the leg. Typically, the lower the segmental pressure number, the more severe the arterial disease.

Interpreting the Ankle–Brachial Index:
0.90–1.30 Normal
0.70–0.89 Mild
0.40–0.69 Moderate
<0.40 Severe >1.30 Noncompressible vessels (too calcified to compress with the pressure cuffs)

PULSE VOLUME RECORDINGS (PVRs): For this part of the exam, the tech will gently inflate the various leg cuffs. First the thigh cuffs, then the calf, and finally the ankle cuffs. With the cuffs maintaining a gentle pressure, the flolab machine can created a waveform tracing based on the overall volume of blood in the leg as as blood is pumped through the arteries (and moved through veins). Based on how the waveforms look we can assess the overall volume of blood moving through the leg.

How is the PVR waveform useful? Well, for example, even if a main leg artery is blocked with plaque, the patient may have successfully used a supervised walking program to build collaterals around the blockage. If so, their PVR waveforms will look better than expected despite the blockage. This is because a good volume of blood is moving through the collateral and around the blockage.

DOPPLERS: A continuous wave doppler stick is used to document arterial waveforms at various locations throughout the feet and legs: the top of the leg (femoral artery), behind the knee (popliteal artery) and two arteries on the foot – one on top (the DPA) and one on the inner ankle (the PTA).

The doppler waveforms in a person with little or no leg artery disease will look like the traditional (triphasic) up and down heartbeat pattern everyone is familiar with. For a person with arterial disease, this waveforms will degrade – becoming shorter and rounder (bi or monophasic). The doppler waveforms give us another bit of information to assess the severity of the PAD. In some patients whose arteries are so heavily calcified that the ABI is not reliable, the doppler waveforms is an especially valuable way of assessing the leg arteries.

For patients with feet and toe wounds, we may additionally use a little device called a photoplethysmogram (PPG), which uses a tiny infrared sensor to detect blood volume changes in the small vessels of the toes. This method produces waveforms much like the doppler.