Non-invasive ventilation: when and how

Transcription

1 Non-invasive ventilation: when and how Susanna Price MBBS BSc MRCP EDICM PhD FFICM FESC Consultant Cardiologist & Intensivist Royal Brompton Hospital London, UK

2 Declaration Educational contract: Medtronic Advisory board: Abbott (MitraClip)

3 Outline Revise heart-lung interactions Principles and terminology of non-invasive ventilation Summarise the evidence Practicalities and realities

4 Acute heart failure Common ,000 hospital admissions per annum in UK Deadly % in-hospital mortality Costly million hospital days per annum in USA

5 Acute heart failure

6 Normal cardiovascular function Blood pumped through arterial resistance into compliance Pressure at outflow is mean systemic (Psyst): determined by elastic properties of systemic circulation and volume of blood contained therein Much volume in venous system: pressure closer to central venous than arterial Venous return: driven by gradient Psyst to right heart Right heart pressures near zero: main increases in CO related to increases in Psyst

7 Simplified HL interactions 3 areas: Thorax: ITP Abdomen: diaphragm Periphery: atmospheric pressure Inspiration: ITP falls Diaphragm descends Peripheral venous pressure stable Venous return-main determinant of CO: gradient between extrathoracic veins and RAP, therefore increases Increase in ITP: Fall in pressure difference, reduction in venous return and CO (ie valsalva, IPPV) in normal patients

8 Heart-lung interaction: the Valsalva manouvre 1. BP increases: increased ITP forces blood from PVs to LV 2. BP falls: falling venous return due to raised then venoconstriction restores pressure (reflex due to fall in SV). CO and SV remain low, HR increases 3. Pressure release: PV, PA and aorta re-expand, initial fall in SV (reduced venous return to LV) 4. Return of cardiac output: Restoration of venous return increase in SV, CO, BP. HR falls to normal. Andre Cournand ( )

9 Normal HL interactions Complicated: Collapsible vessels Chambers with differing external pressures Right and left: very different circulations Abdominal pathology profoundly influences Collapsiblevessels Chamberswithdifferin gexternalpressure RV and LV on oppositesidesofpulm onarycirculation

10 Pulmonary oedema Increased venous & capillary pressure Fluid movement from vessels to interstitium Increased interstitial oedema Reduced FRC Hydrostatic: Increased Pcap (usually >18mmHg depends on chronicity and co-existing endothelial injury

11 Low CO state: change in MV and blood flow

12 Alía and Esteban Critical Care :72 doi: /cc660 Cardiac Contribution: respiratory distress Factors that increase the load Increased resistive loads Increased chest wall elastic loads Increased lung elastic loads Bronchospasm Pleural effusion Hyperinflation (intrinsic positive endexpiratory pressure) Airway oedema, secretions Pneumothorax Alveolar oedema Upper airway obstruction Flail chest Infection Obstructive sleep apnoea Obesity Atelectasis Secretions encrustation Ascites Interstitial inflammation / oedema Abdominal distension Factors that result in decreased neuromuscular competence Decreased drive Muscle weakness Impaired neuromuscular transmission Drug overdose Electrolyte derangement Critical illness polyneuropathy Altered cerebration Malnutrition Sleep deprivation Myopathy Aminoglycosides Hypothyroidism Hyperinflation Guillain-Barré syndrome Starvation/malnutrition Drugs, corticosteroids Myasthenia gravis Metabolic alkalosis Sepsis Phrenic nerve injury Myotonic dystrophy Spinal cord lesion

13 Initial assessment of patient with suspected AHF Authors/Task Force Members et al. Eur J Heart Fail 2012;14:

14 Positive pressure ventilation Increase alveolar pressure Increase intrathoracic pressure Increase in transpulmonary pressure Reduction in transmural pressure

15 What are the effects of CPAP Measured oesophageal pressures and amplitude of pressure swings (substitute for work of breathing) Additionally measured: Stroke volume + CO Brachial artery pressures Calculated: LV transmural pressure (peak inspiration and systolic) Inspiratory muscle force & energy Rate pressure product

16 Plots of group data of the respiratory rate (RR) and the product of Pesamp and RR. RR decreased at all levels of CPAP in the healthy subjects but not in the patients with CHF. There was a CPAP dose-related decrease in Pesamp RR that was more pronounced in... Naughton M T et al. Circulation 1995;91: Copyright American Heart Association

17 Plots of left ventricular transmural pressure gradient during peak inspiration (LVPtmpi) and cardiac systole (LVPtmsys). Naughton M T et al. Circulation 1995;91: Copyright American Heart Association

18 Effects of positive pressure ventilation Increases airway (including alveolar) pressures Increases recruitment Improves pulmonary compliance Maintenance/improvement of gas exchange Increase in FRC Reduction venous return & LV transmural pressures Reduced transdiaphragmatic pressure swings and activity Reduction in work of breathing No fall in CO (HF)

19 Authors/Task Force Members et al. Eur J Heart Fail 2012;14:

20 Definition Delivery of positive pressure into the lungs without an invasive endotracheal airway (ET tube or tracheostomy) Advantages Avoids stresses of intubation (increased RPP, increased catecholamines) Avoids complications during intubation Avoids complications of ventilation (esp VAP) Avoids stresses of extubation Avoids requirement for sedation Disadvantages High intensity of nursing input Aerophagia Hypotension Bronchoaspiration Pneumothrax Mask-related: ocular irritation, nasal congestion, skin lacerations

21 History of ventilation Iron lung: first clinical use Boston, 1928 (paediatrics), widely used in polio pandemics (1930s and 1940s) Invasive positive pressure ventilation: First clinical use Copenhagen,1952 Non-invasive positive pressure ventilation: Drager pulmotor: first non-invasive positive pressure, 1907 Anaesth UK, 2010

22 Current principles non-invasive ventilation Source of O2/air: ventilator Patient:ventilator interface: mask

23 Portable NIV ICU ventilators Prof Masip, Barcelona

24 Prof Masip, Barcelona

25 Prof Masip, Barcelona

26 cmh2o Modes of NIV: CPAP Continuous positive airway pressure Generated through a hermetic mask with a PEEP valve, holding quantity of air in lungs on expiration Recruits collapsed alveolar units Increases FRC and lung compliance Improving oxygenation and work of breathing CPAP 10 cm H20

27 cmh2o Modes of NIV: bilevel support Non-invasive pressure support Requires a ventilator programmed with two levels of pressure IPAP triggered by patients inspiratory effort using decelerated flow When inspiratory flow falls below 25% of maximum, assistance discontinued Increased TV, increased offloading of respiratory muscles ipap 22cmH20 PS 12 cmh20 epap 10 cm H20 Pressure support

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30 Summary of the evidence 20 RCTs published to date One accounts for 40% all CPAP patients, 70% all bilevel patients studied Between these, 5 separate systematic reviews, all showing significant reduction endotracheal intubation with both types of noninvasive ventilation Study groups Number of studies Bilevel vs usual treatment 3 CPAP+usual vs usual treatment 7 PAP+usual vs Bilevel+usual 6 All three 4

31 Multicenter, open, prospective, randomized, controlled trial Patients assigned to standard oxygen therapy, CPAP (5 to 15 cm of water), or NIPPV (inspiratory pressure, 8 to 20 cm of water; expiratory pressure, 4 to 10 cm of water) Primary end point; noninvasive ventilation vs standard oxygen therapy 7 day mortality Primary end point: NIPPV vs CPAP - death or intubation within 7 days

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33 Greater reduction in respiratory distress and metabolic abnormalities Fewer treatment failures due to respiratory distress No difference in therapeutic efficacy between two non-invasive methods

34 Why C3PO differs: cross-over Patients who met criteria allowed to cross over to other form of NIV rather than intubation Intubation rates same in two arms, however proportion crossing over differed: O2 to bilevel: 56/367 CPAP to bilevel5/346 Bilevel to CPAP: 12/346

35 Why C3PO differs: cross-over Patients with respiratory distress allowed to cross over to other form of NIV rather than intubation Cross-over higher in O2 group (p<0.001): O2: 8.4% CPAP 1.4% Bilevel: 3.4%

36 Intubation rate lower for non-invasive ventilation NIV: relative risk 0.36, 95% CI CPAP: relative risk 0.23, 95% CI Trend towards reduction in hospital mortality NIV: relative risk 0.84, 95% CI CPAP: relative risk 0.73, 95% CI

37 Need for intubation

38 Mortality

39 CPAP: Reduction in in-hospital mortality and need for intubation vs standard therapy No increase in new MI Particularly effective when MI/ischaemia was cause of pulmonary oedema Bilevel: Reduction in need for intubation vs standard therapy No reduction in mortality No increase in new MI Bilevel vs CPAP: no diference when directly compared

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41 Patient selection Indications Physical exam Mod-severe dyspnoea Tachoepnea Increased WOB Gas exchange Ventilatory failure (hypercapnia, acidosis) Hypoxaemia Contraindications Absolute Cardiac/respiratory arrest Facial abnorality Refratory hypoxia Shock Relative Agitation/unco-operative Unable to protect airway Excessive secretions MOF Mild hypotension

42 Relevant interfaces >70% Full face mask: Total face mask: Boussignac mask: Helmet: Claustrophobia, vomiting, difficulty speaking, aerophagia, discomfort, facial erythema, skin ulcers, nasal congestion, sinusitis, aspiration pneumonia, hypotension, pneumothorax Appropriate expertise

43 Success? Patient Team Severity Adaptation Cerebration Pt selection SUCCESS Other Rx Experience Team attitude Synchrony Vent tuning Plus, consider, is intubation preferred? Intervention requiring intubation planned Incorrect adjustment Inadequate interface Excessive leakage Device NIV likely to fail (high SAPS/APAHE, very low ph, low GCS) Masip ACC Textbook 2011

44 Acute respiratory failure Acute pulmonary oedema Need for ventilatory support No NIV criteria PaO2/FiO2 <145 APACHE II >34 ph <7.0 GCS <11 Intubation criteria YES NO Palliative NIV NIV: CPAP vs NIPSV PS 8-10 cmh20 PEEP 4-5 cmh20 60min NIV C/I Adequate synchrony WOB decreased Gas exchange improved NO YES ET intubation Mechanical ventilation Weaning Extubation YES NO NIV weaning FiO2<0.4 SpO2 >90% Improved ARF

45 Monitoring Patient Ventilator parameters Gas exchange Respiratory rate T (6-7ml/kg) Coninuous pulse oximetry Vital signs Minute ventilation ABG sampling Dyspnoea Air leakage volume Venous gas (for ph) Conscious level Pressure support/peep setting Mask comfort Synchrony/ineffective efforts Collaboration Trigger/slope/insp time/exp setting Auto-PEEP Alarms (max peak pressure, min MV) Masip ACC Textbook 2011

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48 The real world: current status in Europe Late 1980s: NIV used in critical care settings as alternative to ET intubation (Brochard L et al., N Engl J Med, 1995; Gray A et al., N Engl J Med, 2008) NIV in European ICUs: 12-25% rate of use >50% patients with respiratory failure on ICU (unintubated) >90% patients with COPD or acute pulmonary oedema (unintubated) Masip, ACC Textook, 2011

49 The real wold: current status in UK 185 NHS Trusts with CCUs, 153 responded to survey Non-invasive respiratory support in 73% Of these, 96% offered CPAP, 40% offered CPAP and BiPAP, and 4% offered BiPAP alone In Trusts with critical care facilities, 100% provided both CPAP and BiPAP on the ICU Only 29% CCUs had protocolised non-invasive ventilation Only 13% had mandtory DNAR/not for intubation decision-making documented in notes Only 18% regularly audited their practice JICS, 2010

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51 Key messages AHF: most evidence-base in the literature for use of non-invasive ventilation for acute respiratory failure Use kit/system most appropriate for patient and your hospital Re-assess constantly and plan ahead