Wang-Zwische Double Lumen Cannula—Toward a
Percutaneous and Ambulatory Paracorporeal Artificial Lung
DONGFANG WANG,* XIAOQIN ZHOU,* XIAOJUN LIU,† BILL SIDOR,‡ JAMES LYNCH,† AND JOSEPH B. ZWISCHENBERGER*
We are developing a high performance double lumen cannula
(DLC) for a minimally invasive, ambulatory and percutaneous
paracorporeal artificial lung (PAL). The Wang-Zwische (W-Z)
DLC was designed for percutaneous insertion into the Inter-
nal Jugular (IJ) vein with a drainage lumen open to both the
superior vena cava (SVC) and the inferior vena cava (IVC)
maximizing venous drainage. A separate collapsible but non-
distensible membrane infusion lumen open to the right atrium
(RA) achieves minimal recirculation allowing for total gas
exchange. The W-Z DLC prototypes are made by a propri-
etary dip molding process with the “molded in” flat wire
spiral stainless steel spring resulting in a flexible yet kink
resistant thin wall (0.1 mm) outer cannula with one piece
construction. With the ultra thin membrane infusion lumen
collapsed, an introducer shaft fits tightly within the drainage
lumen to facilitate insertion with placement at the SVC-RA-IVC
junction. The W-Z DLC prototypes were tested while con-
nected to a compact pump-gas exchanger circuit in three
sheep (2 acute and one 15 day performance study). Insertion
was simple, using standard percutaneous insertion tech-
niques. Recirculation was as low as 2%. The 15 day perfor-
mance study demonstrated our prototype 26 Fr W-Z DLC can
achieve 2 L/min blood flow with minimal recirculation. The
W-Z DLC design minimizes recirculation rate, maximizes
flow lumen cross-sectional area, and maximizes achievable
blood flow to enhance gas exchange performance allowing
for one site percutaneous venovenous support. ASAIO Jour-
nal 2008; 54:606–611.
Our focus is to develop more efficient and less traumatic
extracorporeal gas exchange techniques as support. This tech-
nology could improve treatment for Acute Respiratory Distress
Syndrome (ARDS), which affects approximately 200,000
Americans per year with a 38.5% mortality,1and end stage
chronic lung diseases, which claims the lives of 123,884 pa-
tients per year.2
Extracorporeal membrane oxygenation
(ECMO), in both venoarterial (VA) and venovenous (VV) con-
figurations, has been the only practical extracorporeal gas
exchange technique for total respiratory support for 30 years,
but is limited by bulky size, complicated equipment, labor
intensive management, and traumatic blood/surface interac-
tions.3VV ECMO with a single, double lumen cannula (DLC)
was developed over 20 years ago to require just one central
venous cannulation either by cutdown or percutaneous access
to achieve gas exchange.4Commercial DLCs made by Ken-
dall, Jostra, and Origen allowed DLC VV ECMO to become
widely practiced in neonates and small children. Extracorpo-
real gas exchange physiologically equivalent to VA ECMO has
been consistently reported.5–7With currently available DLCs,
suitable for use in large children, there is significant recircu-
lation and insufficient venous drainage which leads to insuffi-
cient gas exchange,8–10and no DLC exists for adult VV ECMO.
Current DLCs either require gravity drainage or a roller pump.
If coupled with a centrifugal pump at the higher required
flows, the negative pressure generated can cause the septum of
the DLC to shift, limiting drainage. Our immediate goal was to
develop a high performance DLC to accomplish total gas
exchange in an adult.
In the last 15 years, our group has been developing or testing
alternative extracorporeal gas exchange techniques to achieve
partial or total oxygen or CO2removal including intravascular
oxygenator (IVOX),11arteriovenous CO2removal (AVCO2R),12
the paracorporeal artificial lung (PAL),13–16and OxyRVAD [a
pump assisted oxygenator from right atrium (RA) to pulmonary
artery],17,18all of which are limited by either insufficient gas
exchange or complex surgical placement limiting clinical appli-
cability. Our ultimate goal is to develop a minimally invasive,
ambulatory and percutaneous PAL utilizing our new Wang-
Zwische (W-Z) DLC as the key component, coupled with a
compact rotary blood pump and durable gas exchanger.
Materials and Methods
Cannula design and fabrication: The W-Z DLC was designed
by D. Wang and J.B. Zwischenberger (patent pending, the
rights have been purchased by Avalon Laboratories Inc.), to be
introduced percutaneously into the right jugular vein travers-
ing the superior vena cava (SVC) and RA into the inferior vena
cava (IVC). Design goals included: 1) Minimal recirculation by
opening the drainage lumen to the SVC and IVC and position-
ing the infusion lumen in the RA directed toward the tricuspid
valve (Figure 1); 2) Maximal cross-sectional area of each DLC
lumen with minimal blood resistance utilizing an ultra thin
nondistensible plastic membrane infusion lumen (Figure 2)
From the *Department of Surgery, University of Kentucky College of
Medicine, Lexington, Kentucky; †Department of Surgery, The Univer-
sity of Texas Medical Branch, Galveston, Texas; and ‡Avalon Labora-
tories, Rancho Dominguez, California.
Submitted for consideration June 2008; accepted for publication in
revised form August 2008.
Presented in part at the 54th Annual ASAIO Conference, San Fran-
cisco, CA, June 19–21, 2008.
Reprint Requests: Joseph B. Zwischenberger, MD, Department of
Surgery, MN264 A.B. Chandler Medical Center, 800 Rose Street,
Lexington, Kentucky 40536-0298. Email: firstname.lastname@example.org.
ASAIO Journal 2008
and thin wire wound kink resistant cannula walls; 3) Percuta-
neous access utilizing an atraumatic introducer within the
drainage lumen (the thin membrane infusion lumen is col-
lapsed upon insertion allowing a tapered introducer within a
smooth outer cannula wall for easy insertion) (Figure 2). Pro-
totypes incorporating each of these design features were fab-
ricated by Avalon Laboratories Inc. After several iterations, the
design requirements were met.
The prototypes were sized at 30 Fr for short term recirculation
testing and 26 Fr for a 15 day performance test. The outer wall
was fabricated out of high silicone content polyurethane copol-
ymer (0.38 mm thick) with wire wound stainless steel reinforce-
ment. The infusion lumen is a silicone-polyurethane nondistensible
membrane sleeve (0.15 mm thick). The drainage/infusion lumen
cross-section ratio is 2:1.4. With the infusion lumen sleeve col-
lapsed, an introducer shaft with a soft blunt tip fits tightly within
the drainage lumen. For the 30 Fr prototypes, an asymmetric
balloon was added above the SVC drainage opening to prevent
venous wall suction/occlusion and recirculation (Figure 3).
The DLCs are made by a proprietary dip molding process
resulting in flexible yet kink resistant one piece construction
because of the “molded in” (0.1 mm) flat wire stainless steel
spring. Thin (0.1 mm) custom formed stainless steel reinforce-
ments are used at the cannula tip and around all inlet and
outlet holes to provide structural integrity and maintain con-
formation in these areas. The drainage lumen inlets are sized to
provide appropriate flow balance between the SVC and IVC
W-Z DLC prototypes were tested in three sheep (free range
ewes, 3–4 years old, 35–45 kg), in a VV circuit using a
commercially available DeBakey VAD (MicroMed Cardiovas-
cular Inc., Houston, TX) and affinity gas exchanger (Medtronic
Inc., Minneapolis, MN). All animals received care according to
the “Guide for the Care and Use of Laboratory Animals (1985)”
prepared by the U.S. Department of Health and Human Ser-
vices and published by NIH. The study was approved by the
Institutional Animal Care and Use Committee (IACUC) of the
University of Texas Medical Branch, Galveston with strict
adherence to the IACUC guidelines regarding humane use of
prototypes were tested for recirculation in one day acute studies,
then one 26 Fr DLC prototype was tested for 15 day performance
and gas exchange in an awake sheep. All sheep were intubated
with an endotracheal tube (10 mm OD) after initial sedation with
12.5 mg/kg intramuscular ketamine and inhalation with 4%
Halothane. General anesthesia was maintained with 1%–2.5%
isoflurane delivered by an anesthesia machine (Ohmeda 7,000,
Figure 1. W-Z DLC is inserted from right jugular vein into superior
vena cava (SVC), traversing right atrium (RA) to inferior vena cava
(IVC). It drains venous blood from both SVC and IVC and delivers
oxygenated blood in RA toward tricuspid valve to achieve minimal
to no recirculation and potential total gas exchange.
Figure 2. The infusion lumen is a collapsible ultra thin plastic
membrane sleeve which allows a tight fit of the introducer in the
drainage lumen to maximize the DLC cross sectional area.
Figure 3. The first prototype (30 Fr) and performance chart. An
asymmetric balloon was added below inferior vena cava (IVC) open-
ing for prevention of venous wall suction-collapse and recirculation.
W-Z DLC—TOWARD PERCUTANEOUS AND AMBULATORY PAL
BOC Health Care, Liberty Corner, NJ), titrated to a heart rate of
75–120 beats per minute during surgery. The sheep’s neck and
groin underwent a sterile prep and drape in the supine position.
Two 16-gauge catheters (Intracath, Becton-Dickinson, Sandy,
UT) were inserted into the right femoral artery and right femoral
vein through a small right groin cut-down for arterial blood
pressure monitoring, intravenous infusion and blood gas analysis.
Mean arterial pressure (MAP) was continuously monitored using
a HP 78534B monitor. The right jugular vein was identified and
exposed through a small right neck cut-down (2 cm). After sys-
temic heparinization with bolus intravenous heparin (120 IU/kg),
the W-Z DLC was inserted through a small incision on the jugular
vein into the SVC, traversing the RA, with the tip positioned in the
IVC. The pump-gas exchanger circuit, primed with a heparin/
Ringer’s solution (3 unit heparin/ml), was then connected to the
inserted W-Z DLC. The pump was turned on to initiate blood
the gas exchanger. The venous blood was drained from both the
IVC and SVC drainage holes out the W-Z DLC drainage lumen to
the pump-gas exchanger. Oxygenated blood was pumped back
through the W-Z DLC infusion membrane sleeve into the RA
toward the tricuspid valve, then into the pulmonary circulation.
The pump-gas exchanger circuit blood flow was continu-
ously monitored by a Transonic 9XL tubing flowsensor and
HT110 flowmeter (Transonic System Inc., Ithaca, NY). Femoral
venous blood, pre and post gas exchanger blood were sampled
simultaneously for blood gas analysis to calculate the recircu-
lation rate by the formula19:
where SpreO2: pre device O2saturation; SpostO2: post device
O2saturation; SvO2: venous O2saturation.
The survival animal was transferred to the investigational
ICU, recovered from anesthesia, extubated, and allowed to
stand with free access to food and water. A continuous heparin
venous infusion was titrated to ACT of 180–300 seconds.
MAP and heart rate were continuously monitored by a
cage-side HP 78534B monitor. The circuit blood flow was
continuously monitored by a Transonic 9XL tubing flowsensor
and HT110 flowmeter. Blood gases (arterial, venous, pre, and
postgas exchange device) were analyzed by Synthesis 15 (In-
strumentation Laboratory, Lexington, MA). The outlet sweep
gas was collected for measurement of exhaust CO2concen-
tration (percentage). Pre and postgas exchange device pres-
sures were measured and documented. Sweep gas flow (pure
oxygen) was regulated by an oxygen flowmeter (Datex-Omeda
Inc., Madison, WI). The following standard formulae were
used to calculate gas exchange:
CO2removal (ml/min) ? sweep gas flow ? CO2
concentration of the exhaust sweep gas
O2transfer ? 1.34 ? Hb ? 10 ? ?O2
sat ? Q ? 0.003 ?PaO2? Q ? 10
Upon study completion, a large bolus of heparin (300 IU/kg)
was given intravenously to prevent postmortem thrombosis
formation within the animal and the pump-gas exchanger
circuit before autopsy. The acute study animals were eutha-
nized with saturated potassium chloride while still under
general anesthesia. The survival animal was euthanized at
day 15 when the gas exchange device failed. Autopsy was
performed to assess cannula position, thrombosis formation
and lung embolization.
All three W-Z DLCs were inserted and advanced smoothly
into the desired position in the SVC-RA-IVC within 30 seconds.
Placement was confirmed directly by visualization at autopsy
in the chronic survival study animal. In the acute study, the
cannula placements were presumed because of the minimal
recirculation rate measured (3.3 ? 0.2% at 2.0 L/min blood
flow). In one animal, recirculation rate increased to 51.3% as
the DLC tip was pulled back from the IVC to the RA from 2.1%
when properly positioned (Figure 4). The maximal blood flow
in the 30 Fr prototypes was 2.3 L/min. Inlet pressure from the
cannula was 23 mm Hg and outlet pressure was 89 mm Hg. At
2 L/min blood flow, the recirculation rate was as low as 2.2%
with the catheter properly positioned.
In the survival animal, the sheep stood and ate/drank freely
during the 15 day study. The dark desaturated venous drainage
blood was in sharp contrast visually to the bright red blood in
the infusion channel (Figure 5). The gas exchanger foamed and
failed on day 15, and the experiment was terminated.
The heart rate and MAP remained stable during the 15 day
experiment. Arterial blood gas analysis showed a normal
PaO2. As expected, the PaCO2trended low (?25 mm Hg
during the first week) (Table 1).
Device Function and Recirculation
Blood flow throughout the 15 day experiment was 2 L/min
(Figure 6). The pre pump drainage pressure was 19 ? 4 mm
Hg, whereas the pump infusion pressure was 86 ? 4 mm Hg.
The pump ?P was 104 ? 7 mm Hg. With 2 L/min blood flow,
up to 140 mL/min (102 ? 32.5) O2transfer and 230 ml/min
(151.7 ? 41.1) CO2removal was achieved. On day 12, the gas
exchanger began to fail as evidenced by plasma leakage
(foaming in sweep gas outlet) which compromised perfor-
mance (Figure 7) for the remainder of the experiment.
There was more recirculation intermittently during the 15
day study (20 ? 10%) than was seen in the acute studies
Figure 4. W-Z DLC showed only 2% recirculation at a flow of 2
L/min. DLC tip dislodgement from inferior vena cava (IVC) to right
atrium (RA) made recirculation jump to 50%.
WANG ET AL.
(Figure 8), but the O2saturation difference between drainage
and infusion channels was still as high as 41 ? 13%. Hemo-
globin remained above 9 g/dl with no blood transfusion
throughout the 15 days of respiratory support. The plasma free
hemoglobin averaged 35 ? 20 mg/dl.
For both the acute and chronic animals, the sheep lungs
grossly appeared normal. No atelectasis, emboli or thrombi
were found in the lungs by gross and cross-sectional exami-
nation. In the two acute studies, catheter position was optimal.
The cannula tip (IVC opening of drainage lumen) was posi-
tioned in the IVC, with the SVC opening in the mid SVC in both
animals. For the chronic sheep, the infusion lumen opening
was located just inside the RA-SVC conjunction (Figure 9).
This location appeared more cephalad from the tricuspid valve
than expected, given the lack of recirculation. No thrombosis
was found on the inner or outer cannula body or the three
drainage/infusion ports (Figure 10).
A large patient population persists that requires complete
respiratory support either for recovery from ARDS or as a
bridge to lung transplantation. During the last three decades,
ECMO, utilizing a modified heart-lung machine with a bulky,
relatively high resistance silicone membrane gas exchanger
has been used in select circumstances for prolonged respira-
tory support (weeks). Recently, a PAL has been developed for
long term ambulatory respiratory support but currently major
surgery is necessary to anastomose the PAL to the heart and
main pulmonary artery.17,18,20–22A DLC was developed two
decades ago for infant/pediatric VV ECMO and proved the
concept of respiratory support with a less invasive, single
cannula venous access. Although commercially available
since 1989 for application in newborns and small children, no
alternative for adults exists. Recirculation, kinking and insuffi-
cient blood flow plague broader application.23,24Our W-Z
DLC is designed to almost eliminate recirculation and enhance
performance in a larger patient. When combined with a com-
pact pump-gas exchanger, this system may supply total respi-
ratory support via minimally invasive percutaneous single
venous cannulation to adults and large children.
Our current feasibility study demonstrates a very low recir-
culation rate at only 2 L/min blood flow with proper DLC
placement. The asymmetric balloon below the SVC drainage
opening also contributes to the minimal recirculation seen in
Figure 5. A: The experimental sheep stood/seated freely and
ate/drank normally with dark black blood out of drainage lumen in
clear contrast against the vivid red blood in the infusion lumen. B:
Plasma leakage and gas exchanger failure on day 15 with less
contrasted blood colors in the drainage/infusion tubing.
Table 1. The HR, MBP, Hb, and PaO2, PaCO2During 15 d Paracorporeal Artificial Lung Study
Day on Artificial Lung123456789 10 1112 1314 15
HR, heart rate; MBP, mean arterial blood pressure; Hb, hemoglobin.
Figure 6. Steady 2 L/min blood pumping flow over the 15 day
W-Z DLC—TOWARD PERCUTANEOUS AND AMBULATORY PAL
our acute studies. Throughout our 15 day study, the O2satu-
ration gain across the gas exchanger is significant (up to 50%)
at 2 L/min blood flow, but recirculation was relatively higher
(20%) than in the acute studies. Positioning may have contrib-
uted to suboptimal DLC function evidenced by a more ceph-
alad RA position (conjuction between SVC and RA) of the DLC
infusion lumen opening found at autopsy in this animal.
We demonstrated the feasibility of percutaneous insertion
and advancement of the W-Z DLC into the SVC-RA-IVC (25 Fr
cannula) without fluoroscopic guidance in six consecutive
cadaver sheep before the current study. Our 1 day in vivo
studies further demonstrated feasibility of safe insertion with-
out fluoroscopic guidance. However, our single chronic study
emphasized the need for proper placement. In future studies
and for clinical applications, we recommend fluoroscopic
guidance during insertion. Similarly, transthoracic echocardi-
ography may prove helpful allowing safe percutaneous inser-
tion, advancement and optimal positioning in SVC-RA-IVC to
avoid right heart injury, and minimize recirculation.
Benefiting from our unique cannula construction with an
extremely thin membrane sleeve infusion lumen and thin wall
stainless steel reinforced polyurethane outer wall, our 26 Fr
DLC can achieve 2.0 L/min blood flow with ?120 mm Hg ?P.
We have previously shown that for total CO2removal, only 1
L/min arterial blood flow is needed.25At 2 L/min venous blood
flow, with no recirculation, a gas exchange device can remove
the total CO2production and transfer over 200 ml/min O2with
normal hemoglobin (12 g/l). Therefore, 2 L/min blood flow can
meet the gas exchange requirements for most patients. If nec-
essary, a larger DLC (up to 30 Fr) could be used for more blood
flow (up to 5 L/min) and more gas exchange allowing total
respiratory support under conditions of stress, hypermetabo-
lism or large body surface area.
The W-Z DLC prototype is constructed with a high silicone
content polyurethane copolymer with proven biostability char-
acteristics.26Under mild systemic heparinization (ACT 180–
230 seconds), we found the DLC shaft and drainage openings
completely thrombosis free at autopsy after the 15 day in vivo
animal study. During our 15 day feasibility study, our W-Z
DLC system did not require blood transfusion (blood hemo-
globin was maintained above 9 g/dl).
In this first study of our W-Z DLC, only one long-term
sheep was used; more studies are needed to prove consis-
tent performance. We did not directly verify DLC position
until autopsy, which can be very easily accomplished by
fluoroscopy or echocardiography in a clinical setting. Our
Figure 7. Gas exchange through the circuit over the 15 day
Figure 8. Fluctuations in the recirculation rate (average 20%) and
good O2saturation difference across the gas exchanger.
Figure 9. An autopsy with the right atrium (RA) opened showed
that the cannula tip was located in inferior vena cava (IVC) and the
infusion lumen opening in conjunction of superior vena cava (SVC)
Figure 10. The cannula taken out after experiment, showed no
WANG ET AL.
measures of recirculation are clinically sufficient but a com-
putational fluid dynamics (CFD) analysis may better eluci-
date the in vivo flow characteristics of the catheter.
In conclusion, the W-Z DLC minimizes recirculation rate,
maximizes the cross-sectional flow area at a given DLC size, to
maximize flow and to enhance the PAL system’s gas exchange
performance. The one site percutaneous venous cannulation
may allow total gas exchange as an ambulatory PAL circuit.
Our design refinements will be further tested in long-term large
animal studies and in prospective randomized outcome stud-
ies in our sheep model of ARDS.
Supported in part by a National Institutes of Health STTR Grant No.
5 R42 HL067523 and Avalon Laboratories, Rancho Dominguez, Cal-
ifornia. The large animal experiments were conducted at UTMB,
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W-Z DLC—TOWARD PERCUTANEOUS AND AMBULATORY PAL