OPEN LUNG APPROACH CONCEPT OF MECHANICAL VENTILATION

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1 OPEN LUNG APPROACH CONCEPT OF MECHANICAL VENTILATION L. Rudo Mathivha Intensive Care Unit Chris Hani Baragwanath Aacademic Hospital & the University of the Witwatersrand

2 OUTLINE Introduction Goals & Indications of Mechanical Ventilation Physiology/Pathophysiology of Mechanical Ventilation Recruitment strategies/open Lung concept Choosing an Appropriate Ventilatory Strategy Monitoring; Adverse Effects Non-Conventional Approaches

3 WARNING/CAUTION Do not attempt this if you have never seen a mechanical ventilator Some of the principles may be harmful in Neonates Learning and responsible practice will get you with the programme! Use strategy that suits your patient and you best!

patients Initially for totally apnoeic patients Ventilator

4 History INTRODUCTION Vivisection work; Polio Epidemics Conventional Ventilation Principal mode in critically ill patients Initially for totally apnoeic patients Ventilator design From Iron Lung to Total Sophistication No ideal ventilator

5 INTRODUCTION One of the key measures of patient outcome and the quality of care in ICU is ventilator-free days. Ventilatory protocols for acutely ill patients in the ICU have improved favourably over time. Strategies have changed from optimizing convenient physiology variables, such as O2 and CO2 levels, to protecting the lung from injury and cytokine modulation of the lung

6 PHYSIOLOGY OF MECHANICAL VENTILATION Positive pressure via ETT Large pressures applied Increase in Mean Intrathoracic Pressure Decreased venous return and CO : Compensated for by normal vascular reflexes Pronounced in hypovolaemic patients and at extremely high mean airway pressures

7 PATHOPHYSIOLOGY OF MECHANICAL VENTILATION The cycle of continuous expansion and collapse of alveoli in respiratory cycle structural changes by barotrauma and volutrauma, as well as surfactant function and cytokine releasealveolar collapse with improper mechanical ventilation( PEEP VT) activation of SIRS Disruption of Alveolar gas membrane Surfactant system dysfunction The lung is an important causative part of an inflammation-induced systemic disease state MOF,not only a pulmonary disease process.

8 ARDS Catastrophic pulmonary or non-pulmonary event resulting in ALI & respiratory failure Increased intrapulmonary shunt Hypoxaemia Decreased pulmonary compliance Diffuse pulmonary infiltrates Exclusion of left heart failure Need for mechanical ventilation

9 Goals of Mechanical Ventilation Optimise oxygen delivery and ventilation Oxygenation Carbon dioxide Removal Minimise toxicity Barotrauma Volutrauma Cardiorespiratory Interractions Optimise patient work of breathing

10 VOLUTRAUMA:Stretch Injury -alters capillary transmural pressures -causes breaks in capillary endothelium & epithelium -increases leak of proteinaceous material

11 BAROTRAUMA -air-leak into pleural or interstitial space -tearing at bronchoalveolar junction as lung is recruited & allowed to collapse -most occurs in dependent lung at transition zone

12 OPTIMISED LUNG VOLUME high lung volume ventilation overdistends resulting in volutrauma low lung volume ventilation tears adhesive surfaces

13 OPEN LUNG CONCEPT The strategy of lung recruitment or open lung concept (OLC) refers to the dynamic process of opening previously collapsed lung units by transpulmonary pressure. The OLC may play an important role in preventing ventilator-induced lung injury

14 LUNG RECRUITMENT Recruitment maneouvre controlled positive ventilatory pressure necessary to expand alveoli. In true alveolar collapse, the pressure needed for alveolar recruitment may reach above 70 cmh2o Alveolar bed may be opened best using the decelerating wave pattern of Methods vary: Sustained inflation with 30cmH2O for seconds High PEEP cmh2o- then titrate down Proning + Higher PEEP Initial High Paw on HFOV for 60 seconds then back to transitioning Paw

15 LUNG RECRUITMENT initial inspiratory pressure recruit collapse alveoli, then minimal pressure prevent lung from collapsing Intrapulmonary suction renewed collapse of alveoli PaO2,secretion management must be balance with alveolar recruitment Early OLC ( < 72hrs ) higher response rate, this probably related to the change from exudate to a fibroproliferative process

19 Appropriate Ventilatory Strategy Systematic Evaluation Identify the pathophysiology of the patient Evaluate available modes based on physiology, advantages, & disadvantages Pathophysiology directed therapy: hypothesis testing take your best guess Monitor for effects / side-effects of therapy non-invasive: exam, CXR, graphics invasive: ABG, SVO2, lactates

20 Practical Clinical Guide Initiating Ventilation Open lungs first: Recruit!!! Sustained Inflation; PEEP Titration; High Paw on HFOV Volume limited: TV = 4-6 ml/kg ; PEEP = 8-10 ; FIO2 =1.0 Rate: physiological limits for age Pressure Limited PIP = 20 ; PEEP = 8-10 ; FIO2 = 1.0 Rate: physiological limits for age PSV: PEEP = 8-10; PS to give TV 6-8ml/kg

21 Monitoring Ventilatory Therapy Clinical Evaluation Blood Gases Pulse Oximetry End Tidal CO2 Airway Graphics Radiologic studies

22 Weaning Meet weaning criteria Primary condition reversed/improved ideally no other organ support Normal metabolic profile Decreased need for sedatives/relaxants A-aDO2 less than 100 OI less than 13 Transitioning devises What is comfortable for the patient

23 LUNG PROTECTIVE STRATEGIES UNDERSTAND MODES OF VENTILATION OPEN LUNG APPROACH LOW TIDAL VOLUME STRATEGY HIGH PEEP LOW PIP PERMISSIVE HYPERCAPNIA IF POSSIBLE LOW FIO 2 ASAP!

24 Consider Non Conventional Modes High Frequency Oscillation Partial Liquid Lung Ventilation ECMO Negative Pressure Ventilation

25 NON CONVENTIONAL MODES

26 CONCLUSION Conventional Ventilation: Tried & tested- still mainstay of vent support Familiar with it Adverse effects; Failure Quest for Zero Lung Damage Smarter ventilatory protocols Don t chase normal physiologic values in a diseased lung

27 ADIOS: I WILL BE BACK L HITRAOT SIZOBONANA FUTHI TILL WE MEET AGAIN GO YA KA MAGORO GA SE GO TSWANA LATER DUDES AND DUDDETTES Au Revoir RI do VHONANA HASTA LA VISTA

3100A Competency Exam

NAME DATE (Circle the appropriate answer) 3100A Competency Exam 1. Of the following, which best describes the mechanics of ventilation used by the 3100A? a. Active inspiration with passive exhalation b.