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CASE REPORT
24 BRITISH JOURNAL OF INTENSIVE CARE | SUMMER 2006
➟
Successful use of portable extra-
corporeal carbon-dioxide removal in a
patient with uncontrollable hypercapnoea
M Beed BM, BS, FRCA,
J Jayamaha MB, ChB, FRCA,
R Sherman MB, ChB, MRCP,
FRCA,
R Mahajan MB, ChB, FRCA, DM,
University Department of
Anaesthesia and Intensive
Care, City Hospital,
Nottingham
occasional cannabis user there was no significant past
medical history. Prior to admission he had been treated
with amoxicillin to no effect.
Following admission the patient was rapidly transferred
to the high-dependency unit (HDU) due to his significant
hypoxia (81% saturated on air). Chest and general
examination were unremarkable, but his pyrexia and
raised neutrophil count led to a provisional diagnosis of
community-acquired pneumonia. Chest X-ray revealed
diffuse bilateral shadowing and initial blood gas analysis
revealed type 1 respiratory failure with a PaO2of 8.6 kPa,
on 40% oxygen, and a PaCO2 of 4.8 kPa with no acidosis.
Differential diagnoses included atypical pneumonia,
myocarditis, auto-immune disease, viral pneumonitis and
pulmonary embolism. The patient was thoroughly invest-
igated during his stay yet no diagnosis was ever confirmed
and the cause of his respiratory failure remains a mystery.
Treatment was based around a broad range of antimi-
crobial agents, steroids and supportive therapy for his res-
piratory function.
Within 24 hours of admission, our patient was requiring
respiratory support. Initially this took the form of non-
invasive continuous positive airways pressure (CPAP) and
non-invasive bi-phasic positive airways pressure (BIPAP)
as tolerated by the patient. Positive end-expiratory pres-
sure (PEEP) requirements rapidly increased to 10 cmH2O
and although adequate oxygenation was maintained on
low levels of inspired oxygen (greater than 10 kPa on 40%)
his respiratory rate continued to rise to above 50 min-1
even when supported by non-invasive BIPAP, and he
developed type 2 respiratory failure with acidosis. On day
We report the case of a 23-year-old man who was admitted
to intensive care for ventilation following a presumed
community-acquired pneumonia and whose respiratory
failure required the use of a novel piece of equipment (the
Novalung®) which allowed portable arterio-venous carbon-
dioxide removal (AVCO2R).
Extra-corporeal membrane oxygenation (ECMO) and
extra-corporeal carbon-dioxide removal (ECCO2R)
have been used in the treatment of patients with acute
and chronic respiratory failure, but there is no clear con-
sensus as to their place in the management of such patients.1
Such techniques are highly specialised and traditionally it
has been necessary to transfer patients, who are often
amongst the sickest and most unstable, to regional centres
in order to offer such treatments. We report the case of a
young patient, for whom ECMO was considered, but who
was subsequently managed, without being transferred, using
a novel form of portable pumpless arterio-venous carbon-
dioxide removal (AVCO2R). The equipment helped us to
adopt ventilation strategies recognised to be beneficial in
avoiding adult respiratory distress syndrome (ARDS) whilst
maximising oxygenation and minimising hypercapnoea and
acidosis.2,3 To our knowledge this is the first such use of the
equipment within the UK.
CASE REPORT
A 23-year-old student with no significant past medical
history was admitted to hospital following a four-day
history of increasing shortness of breath with associated
cough, fever and haemoptysis. Although a smoker and
Spontaneous ventilation
Non-invasive ventilation
High flow oscillatory
ventilation
Days on ICU
Tracheostomy inserted
CPAP via
tracheostomy
IPPV-BIPAP
ACCO2R
02135468791110 12 14 15 16 17 18 19 20 21 22 23 2413
Figure 1. Timeline of respiratory
interventions.
EXTRA-CORPOREAL CARBON-DIOXIDE REMOVAL
25SPRING 2006 | BRITISH JOURNAL OF INTENSIVE CARE
➟
3 of admission he was transferred to the intensive care unit
(ICU) for intubation and ventilation.
Ventilation was commenced using a lung-protective
regimen of low tidal volume, limited peak airway
pressure and permissive hypercapnoea. Despite this the
patient developed progressively worsening lung
compliance, an increasing oxygen requirement and
worsening respiratory acidosis.. Heavy sedation and
paralysis with muscle relaxant resulted in only temporary
improvements in oxygenation and carbon-dioxide clear-
ance. The institution of high flow oscillatory ventilation
(HFOV) resulted in a temporary improvement in
respiratory function until day 6 when the attempts at
oxygenation and CO2removal started to become
unresponsive to manipulation of HFOV settings.
Extensive surgical emphysema developed at this time and,
although a pneumothorax was never seen, prophylactic
chest drains were inserted. Haemofiltration was also
commenced at this point, and was continued for a further
12 days, to aid the control of acidosis resulting from
hypercapnoea.
By day 7, PaCO2level had risen to 26 kPa and was
unresponsive to any respiratory manoeuvres. The result-
ing acidosis had progressed to a point where inotropes
were needed to support blood pressure. Referral to
the regional ECMO centre was considered, but was
not possible at this time. Instead the Novalung (manu-
factured by Novalung GmbH, Hechingen, Germany),
an
extra-corporeal AVCO2R device that has the advantage
of being very portable, was flown over from Germany.
Arterio-venous lines were inserted and the AVCO2R
remained in continuous use for a further five days until
poor flows through the filter rendered it ineffective.
Shortly after commencing CO2removal, the pH had
stabilised and inotropic requirement rapidly diminished
with our patient returning to single-organ failure.
Unfortunately oxygenation once more became a problem
requiring further intervention which included a switch
back to conventional (BIPAP) ventilation and prone
positioning.
By day 12 lung compliance began to improve and the
oxygen requirement gradually decreased. Although further
episodes of poor oxygenation occurred thereafter they
were treated with recruitment manoeuvres and suctioning
of airway secretions. The AVCO2R ceased to work
effectively at this point and, given the overall improve-
ment in the patient, it was decided not to replace it. Over
the next two days a rebound effect of rising PaCO2and
falling pH was noted. This was treated with tracheal gas
insufflation (TGI), and never approached the earlier
severity which had initiated the use of AVCO2R.
By day 19 both chest drains were removed and a trach-
eostomy performed. Further weaning was generally
uneventful and the patient has since made a full recovery.
DISCUSSION
Although other, more traditional, attempts at decreasing
carbon dioxide levels were ongoing at the same time, there
appears to be a clear temporal link between PaCO2and
pH levels and usage of AVCO2R (Figures 1–3) which had
the immediate benefit of removing inotrope requirement.
It is likely that respiratory manoeuvres used to improve
oxygenation such as inverse ratios would have been
difficult or impossible without the added assistance of
extra-corporeal membrane carbon-dioxide removal.
Patients with ARDS have an associated mortality of
30–50% and managing them in order to promote survival
can be problematic.4Lung-protective ventilation strategies
are known to be of benefit in helping to protect patients
from developing ARDS2and, although approaches vary,
the overall aims appear to be those of avoiding baro-
traumas, volutrauma and atelectrauma.3Our approach
was one of optimising PEEP whilst using pressure-
controlled ventilation aiming for tidal volumes of 6 ml/kg.
When this failed to maintain adequate oxygenation and
CO2 in the face of increasing inspiratory pressures, we
switched to high frequency oscillatory ventilation, an
approach which has been advocated in the management of
ARDS but which, despite many theoretical advantages, has
not as yet been shown to reduce mortality.3,5 Permissive
hypercapnoea is often considered an integral part of lung
protective strategies and it has been suggested that
hypercapnoea may in itself prove to be protective against
the development of ventilator associated lung injury.3
Excessive hypercapnoea has been associated with both
HFOV and other lung protective strategies, and there is no
clear consensus on how any resulting acidosis should be
managed.3,6
AVCO2R
7.6
7.5
7.4
7.3
7.2
7.1
7
6.9
Days on ICU
02135468791110 12 14 15 16 17 18 19 20 21 22 23 2413
AVCO2R
PaCO2
Days on ICU
30
25
20
15
10
5
0
02135468791110 12 14 15 16 17 18 19 20 21 22 23 2413
Figure 2. PaCO2variation over
time.
Figure 3. pH variation over time.
26
Methods which have been used to improve carbon
dioxide removal include HFOV via an uncuffed tube (a
technique which did not help in this case) and TGI,6,7
which was employed here to combat the rebound in
hypercapnoea which occurred once the AVCO2R mem-
brane ceased to function. Bicarbonate infusions have also
been used, but it is unclear how these affect any
intracellular acidosis.2,3
The use of ECMO has been studied in many conditions,
including ARDS,8where no improvement in mortality has
been demonstrated. Despite publication of a number of
studies and case reports it remains an ‘unconventional’
treatment for non-neonatal critically ill patients.9ECMO
can be considered in different ways, from full to partial
respiratory support delivered via central or peripheral
blood vessels. Partial support delivered peripherally in the
form of AVCO2R has been considered as a ‘bridge-to-
recovery’ strategy for ARDS, attractive because it is less
invasive and simpler than other forms of ECMO.10
Combinations of ventilation with ECCO2R have been
tried with mixed results,11,12 however the mode of
ECCO2R used in this case report differs in two significant
ways. Firstly the extreme portability of this unit meant that
it could easily be transported to the patient, avoiding
much of the complexity and mortality associated with the
transfer of such a critically ill patient. Secondly the ease of
use meant that staff could be quickly trained to manage
the apparatus: in fact it was significantly less complex than
the management of the haemofiltration unit that was
‘slaved’ onto the venous limb (Figure 4). A promising new
therapy would appear to be within reach of smaller
hospitals and intensive care units, and any potential
benefits warrant further investigation.
REFERENCES
1. Sim KM, Evans TW. Supporting the injured lung.
Br Med J
1993; 330077:: 1293–1294.
2. Ventilation with lower tidal volumes as compared with traditional tidal volumes
for acute lung injury and the acute respiratory distress syndrome. The Acute
Respiratory Distress Syndrome Network.
N Engl J Med
2000; 334422::1301–1308.
3. Moloney ED, Griffiths MJ. Protective ventilation of patients with acute respira-
tory distress syndrome.
Br J Anaesth
2004; 9922::261–270.
4. Burck R. Challenges of treating on the basis of knowledge: The ARDS Network
trials and the ensuing controversy.
Crit Care Med
2004; 3322::904–905.
5. Derdak S, Mehta S, Stewart TE
et al
. High-frequency oscillatory ventilation for
acute respiratory distress syndrome in adults: a randomized, controlled trial.
Am J Respir Crit Care Med
2002; 116666::801–808.
6. Dolan S, Derdak S, Solomon D,
et al
. Tracheal gas insufflation combined with
high–frequency oscillatory ventilation.
Crit Care Med
1996; 2244::458–465.
7. Hess DR, MacIntyre NR. Tracheal gas insufflation: overcoming obstacles to
clinical implementation.
Respir Care
2001; 4466::198–199.
8. Zapol WM, Snider MT, Hill JD,
et al
. Extracorporeal membrane oxygenation in
severe acute respiratory failure. A randomized prospective study.
JAMA
1979;
224422::2193–2196.
9. Weber TR. Extending the uses of ECMO.
Chest
2004; 112266::9–10.
10. Lick SD, Zwischenberger JB. Artificial lung: bench toward bedside.
Asaio J
2004; 5500::2–5.
11. Gattinoni L, Pesenti A, Mascheroni D
et al
. Low-frequency positive-pressure
ventilation with extracorporeal CO2 removal in severe acute respiratory failure.
JAMA
1986; 225566::881–886.
12. Morris AH, Wallace CJ, Menlove RL et al. Randomized clinical trial of pressure-con-
trolled inverse ratio ventilation and extracorporeal CO2 removal for adult respirato-
ry distress syndrome.
Am J Respir Crit Care Med
1994; 114499::295–305. ■
EXTRA-CORPOREAL CARBON-DIOXIDE REMOVAL
BRITISH JOURNAL OF INTENSIVE CARE | SPRING 2006
CORRESPONDENCE TO:
Martin Beed, BM, BS, FRCA
University Department of Anaesthesia and
Intensive Care
City Hospital
Nottingham
NG5 1PB
E-mail: martin.beed@nottingham.ac.uk
Figure 4: the Novalung®in situ.
1. Gas exchange membrane.
2. Fresh gas flow. 3. Lines to
haemofiltration. 4. Arterial &
venous access lines and flow
sensor.
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