Non- conventional forms of

respiratory support

Dr Liesel Bosenberg

Specialist Physician & Fellow in Critical Care Medicine

Kalafong & Steve Biko Academic Hospitals

Points we will ponder:

ECMO

Liquid Ventilation

High frequency ventilation

One lung ventilation

Heliox

ECMO: Extra Corporeal Membrane

Oxygenation

In 1885 Franz and Gruber developed a device to oxygenate blood extracorporeal

In 1937 the first heart-lung machine was invented by Gibbon

In 1956 Clowes developed a membrane oxygenator “artificial lung”

ECMO introduced in 1972

Two main modalities:

Veno-Arterial ECMO: mainly for

Haemodynamic Support but can offer

respiratory support

Veno-Venous ECMO: only respiratory

support

ECMO: Indications:

VA ECMO:

Post- cardiotomy ( unable to liberate patient off bypass machine )

Post-heart transplant : primary graft failure

Severe CCF: decompensated cardiomiopathy, ACS with cardiogenic shock, sepsis,miocarditis,drug overdose

Bridge to transplant or VAD

Respiratory support

VV ECMO:

Hypoxemic respiratory failure with PF ratio < 100 mmHg despite optimal ventilatory settings and support ( ARDS due to whatever cause)

Hypercapnoeic respiratory failure with pH < 7.2 ( exacerbation of COPD)

Primary graft failure following lung transplantation

Relative contra-indications:

Conditions where anticoagulation is contra-indicated

Mechanical ventilation> 7 days ( ECMO considered an early intervention to make any difference)

If VAD/ transplant is contra-indicated

Pre-existing liver, renal failure, severe AI, aortic dissection

Advanced age, morbid obesity, neurodysfunction ( SBI), pre-existing poor functional status

Disseminated malignancy, Graft vs Host disease

Unwitnessed cardiac arrest/ arrest of unknown duration

ECMO: Technique:

Vascular access, tubing, oxygenator

Blood oxygenated , CO2 removed ,

reinfused into native system

Initiation: anticoagulate patient with IV

heparin then insert cannulae

Cannulation : position of catheter tips

in VV ECMO important

Titration:

Clearly defined respiratory and HD goals

Targets: ScvO2/ SvO2 75 %- 80%

VA ECMO: SaO2 100%

VV ECMO: SaO2 85-100%

Adequate tissue perfusion as determined by BP, Blood lactate and other determinants pertaining to DO2

Maintenance:

Maintain flow rates once foals are achieved

AC: continuous heparin infusion aPTT 210-230 s

Platelets > 100

Pplat < 30 cm H2O

FiO2 < 0,5

Aim for weaning off vasopressors in cases of VV ECMO

Early tracheostomy

Light sedation

Special considerations:

1. Blood Flow Rates:

Different for VA vs. VV ECMO

Higher in VV ECMO

FR in VA should be enough to still provide adequate preload to maintain LV output otherwise consider inotropes, IABP

2. Diuresis:

Ultrafiltration can be added only once stable on VV ECMO

3. LV monitoring:

VA ECMO in patients with underlying/ pre-existing LV dysfunction

Increased afterload due to retrograde flow

Insufficient unloading of LV

ECMO unloads RV – leads to decrease in preload

If uncontrolled- leads to progressive LV distension, left atrial Hypertension and intra-pulmonary haemorrhage

Consider inotropic support with dopamine, milrinone or even IABP

4. Mechanical issues:

ECMO flow can be very volume dependant

Will drop with hypovolemia, malpositioning of cannulae, pericardial effusion and pneumothorax

Management includes a fluid challenge, exclusion of tamponade, pneumothorax and abdominal distension/ compartement syndrome

Discontinuation:

Improved CXR

Improved SaO2

Improved pulmonary complience

In case of cardiac patients, increase in BP

requiring vasodilators, return of pulsatility of

the arterial pressure wave form

TOE is useful to establish the degree of

cardiac recovery

Complications:

Bleeding ( Cyclocapron / Novo 7)

HIT ( Rx with argatroban)

Thromboembolism

Cannulation –related :Limb ischaemia, vessel perforation, arterial dissection

Haemolysis

GIT perforation, ulceration due to changes in splanchnic perfusion

VA ECMO: pulmonary haemorrhage, pulmonary infarction, arterial thrombosis, coronary and cerebral hypoxia

Evidence: Cesar Trial Conventional ventilation versus ECMO for Severe Adult Respiratory failure

Peek GJ et al. Lancet 2009 Oct 17;374(9698):1351-63.

The first randomized trial data supporting the use of ECMO in the adult population were published in 2009 by Peak and colleagues.

The Conventional Ventilation or ECMO for Severe Adult Respiratory Failure (CESAR) trial, through a minimization strategy, enrolled 180 patients with severe ARDS (Murray score > 3 or pH < 7.20).

They were randomized to either care at a tertiary care center or transfer and management at a single ECMO center.

Of the 90 patients randomized for transfer to the ECMO center, 5 died prior to or during transfer, and 16 improved with conventional management. Sixty-eight patients received ECMO support, and overall survival or severe disability at 6 months was 63% for the ECMO group vs 47% for the conventional management group.

Appropriate criticisms of this study have focused on the lack of standardized management in the controls. Also, statistical significance was lost if patients from the ECMO center cohort who did not receive ECMO were removed. Many have reflected on CESAR as a trial of transfer of patients with severe ARDS to a comprehensive center with ECMO support rather than a trial of the ECMO technology itself.

Extra- Corporeal CO2 removal

( ECCO2R):

VV removal of CO2 at lower flow rates than ECMO; high diffusion gradient

Percutaneous catheterisation – simplifies vascular access

Heparinised membrane lung – no systemic anticoagulation needed

Usually combined with LFPPV ( 2-3 breaths a minute)

AV shunt, driven by BP of patient, no pump necessary

Novalung: iLA membrane

ventilator : PECLA ( pumpless extracorporeal

lung assist ; TAU Medical

Liquid ventilation:

Technique of mechanical ventilation where the lung are insufflated with PFC liquid – acts as an inert carrier of O2 and CO2

Advantages:

Decreases surface tension by maintaining fluid interface in alveoli

Decreases risk of barotrauma- hydraulic pressure opens alveoli

High efficiency heat exchanger

PFC’s:

Ideal fluid: non-toxic and chemically stable

Lower surface tension

Minimal systemic absoprtion

Able to dissolve large amounts of O2 and CO2

Thus: PFC fits all the above criteria

Also: does not wash out surfactant

Stored indefinately at room temperature

Dissolves 15x more oxygen than plasma

High viscosity

Liquid Ventilation:

Total LV: entire lung filled with liquid, tidal volume pumped into and out of lung

Partial LV: lungs slowly filled with volume of PFC close to FRC during gas ventilation

Physiological outcomes:

Alveolar recruitment

Better V/Q matching

Lavage ( removal of exudative material from lung )

Temperature regulation

Anti-inflammatory effects

LV:

Adult applications:

ARDS

Pneumonia( lavage, antibiotics e.g. gentamycin can be suspended in PFC vehicle)

Drug delivery

Cancer treatment ( augment the effects of radio- and chemotherapy)

Donor lung preservation

Adverse effects:

PFC fluid is 2x more dense than saline

( interfere with accurate weighing of

patient)

Radio-opaque : limited utility of CXR

Interfere with normal breath sounds

Requires deep sedation and paralysis

High Frequency ventilation: HFJV, HFOV, HFPV

HFOV:

Rescue treatment for severe oxygenation failure

Eligibility: patients with ARDS/ ALI , > 35 kg, currently failing on CV with a lung protective strategy

FiO2 > 60%, PEEP > 10 with a P/F ratio< 200

Plateau pressure > 39 cm H2O

Presence of bilateral infiltrates on CXR consistent with ARDS

Oxygenation index >24

OI: FiO2 x Pmean x 100 / PaO2

Decreases VILI and barotrauma

Provides a tidal volume below that of the anatomical dead space at Hz of > 60 breaths /min

( RR:3-15 Hz ; 900 breaths/min)

Potential benefits include:

Less HD compromise

Improved V/q matching

Indications in adult patients:

ALI/ ARDS

Severe UAO with Stridor

Bronchopleural fistula ( HFJV)

Contraindications:

COPD

Complications:

Inspissation and desiccation of

mucous

Airway damage at very high speed

Air trapping with generation of auto

PEEP

Dynamic hyperinflation

Evidence:

MOAT 2 trial ( multicentre oscillatory

ventilation for ARDS trial):

Derdak S, Mehta et al. High Frequency oscillatory ventilation for

ARDS in Adults: A randomized control trial. Am J Respiratory Critical

Care Medicine 2002; 166:801-808

Safety and efficacy of HFOV

148 ARDS

patients, randomized to HFOV/ CV

HFOV group: increased mean airway pressure, significant

improvement of PF ration within the first 16 hours , limited to no

benefit past 24 hours

30 day mortality rate 37 % in HFOV group vs. 57 % in the CV group

MOAT 2 :

Unfortunately study was not powered adequately to show a clinical significant decrease in mortality

Other evidence:

Mehta et al performed a retrospective review of 156 cases in which HFOV was performed as rescue treatment

Patients received on average 5.6-7.6 days of CV prior to HFOV

PF ratio and OI improved for > 72 hrs

One lung ventilation:

OLV in critical care:

Only 3 main indications for OLV

To improve surgical access

Lung protection

Unilateral lung disease in critically ill

patient: single lung transplant

Heliox:

Helium is a low density , inert gas with very solubility in blood

When nitrogen is substituted with helium in the gas mixture, the airway resistance in the absence of anatomical change

Used in patients with increased Paw; it improves ventilation and decreases work of breathing

Clinical studies several limitations:

< 30 patients enrolled

Inclusion and exclusion criteria not standardized making comparison difficult

Heliox interferes with the performance of diagnostic equipment

Indications for use:

Children:

UAO due to compression, post extubation stridor and croup

LAO : ARDS, Status asthmaticus, bronchiolitis

Bronchopulmonary dyplasia

Adults:

UAO: thyroid mass, radiation injury,angioedema, cancer

LAO: severe asthma and COPD

Asthma:

Used in cases of severe respiratory failure with associated respiratory acidosis

2 small uncontrolled series of patients

60-80% He

Improvement of respiratory indices with decrease of CO2 by 35 mmHg

COPD:

Acute exacerbation of COPD

In combination with NPPV

Decrease in PaO2 , dyspnoea, work of

breathing, improvement of respiratory

pattern

Current recommended

indications:

Mechanical UAO

Postoperative stridor

Severe COPD and NPPV

Severe asthma with respiratory failure

refractory to standard therapy

Bibliography:

The End