Non- conventional forms of respiratory support

Transcription

1 Non- conventional forms of respiratory support Dr Liesel Bosenberg Specialist Physician & Fellow in Critical Care Medicine Kalafong & Steve Biko Academic Hospitals

2 Points we will ponder: ECMO Liquid Ventilation High frequency ventilation One lung ventilation Heliox

3 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

4 Two main modalities: Veno-Arterial ECMO: mainly for Haemodynamic Support but can offer respiratory support Veno-Venous ECMO: only respiratory support

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8 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

9 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

10 Relative contra-indications: Conditions where anticoagulation is contraindicated 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

11 ECMO: Technique: Vascular access, tubing, oxygenator Blood oxygenated, CO 2 removed, reinfused into native system Initiation: anticoagulate patient with IV heparin then insert cannulae Cannulation : position of catheter tips in VV ECMO important

12 Titration: Clearly defined respiratory and HD goals Targets: ScvO 2 / SvO 2 75 %- 80% VA ECMO: SaO 2 100% VV ECMO: SaO % Adequate tissue perfusion as determined by BP, Blood lactate and other determinants pertaining to DO 2

13 Maintenance: Maintain flow rates once foals are achieved AC: continuous heparin infusion aptt s Platelets > 100 P plat < 30 cm H 2 O FiO 2 < 0,5 Aim for weaning off vasopressors in cases of VV ECMO Early tracheostomy Light sedation

14 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

15 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

16 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

17 Discontinuation: Improved CXR Improved SaO 2 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

18 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

19 Evidence: Cesar Trial Conventional ventilation versus ECMO for Severe Adult Respiratory failure Peek GJ et al. Lancet 2009 Oct 17;374(9698): 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.

20 Extra- Corporeal CO 2 removal ( ECCO 2 R): VV removal of CO 2 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

21 Novalung: ila membrane ventilator : PECLA ( pumpless extracorporeal lung assist ; TAU Medical

22 Liquid ventilation: Technique of mechanical ventilation where the lung are insufflated with PFC liquid acts as an inert carrier of O 2 and CO 2 Advantages: Decreases surface tension by maintaining fluid interface in alveoli Decreases risk of barotrauma- hydraulic pressure opens alveoli High efficiency heat exchanger

23 PFC s: Ideal fluid: non-toxic and chemically stable Lower surface tension Minimal systemic absoprtion Able to dissolve large amounts of O 2 and CO 2 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

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25 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

26 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

27 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

28 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 FiO 2 > 60%, PEEP > 10 with a P/F ratio< 200 Plateau pressure > 39 cm H 2 O Presence of bilateral infiltrates on CXR consistent with ARDS Oxygenation index >24 OI: FiO 2 x P mean x 100 / PaO 2 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

29 Indications in adult patients: ALI/ ARDS Severe UAO with Stridor Bronchopleural fistula ( HFJV) Contraindications: COPD

30 Complications: Inspissation and desiccation of mucous Airway damage at very high speed Air trapping with generation of auto PEEP Dynamic hyperinflation

31 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: 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

32 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 days of CV prior to HFOV PF ratio and OI improved for > 72 hrs

33 One lung ventilation:

34 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

35 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 P aw; 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

36 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

37 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 CO 2 by 35 mmhg

38 COPD: Acute exacerbation of COPD In combination with NPPV Decrease in PaO 2, dyspnoea, work of breathing, improvement of respiratory pattern

39 Current recommended indications: Mechanical UAO Postoperative stridor Severe COPD and NPPV Severe asthma with respiratory failure refractory to standard therapy

40 Bibliography:

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