Instellen van beademingsparameters bij de obese pa3ent. MDO Nynke Postma

Transcription

1 Instellen van beademingsparameters bij de obese pa3ent MDO Nynke Postma

2 1. Altered respiratory mechanics in obese 2. Transpulmonary pressure 3. PEEP volume 5. Effects of 6. Key messages

3 Obesity & respiratory mechanics Baseline in respiratory mechanics of the obese Decrease in TLC Decrease in FRC and VC Increase in pleural pressure Increase of upper and lower airway resistance.

4 Obesity: Increased weight of the chest wall Increased abdominal pressure } decrease in respir. system compliance

5 Obesity & respiratory mechanics of the small airways & expiratory flow PEEP i at rest Air trapping during exercise Intrinsic mechanical loading of inspiratory muscles Work of breathing & VO 2

6 Obesity & gas exchange Atelectasis with V/Q mismatch due to airway narrowing and in lung perfusion Arterial hypoxemia Elevated A- a gradient

7 Transpulmonary pressure (P L ) Distending pressure across the lung P L =P A - P pl Obesity: P pl - - > P L - - > collapsing pressure - - > ATELECTASIS impaired gas exchange decreased lung compliance

8 Transpulmonary pressure (P L ) Hogere P pl ó lagere P L

9 Transpulmonary pressure (P L ) Safe upper limit: 25 cm H2O

10 Obesity & ARDS Obesity Heterogenic lung ARDS Heterogenic lung Obesity + ARDS Heterogenic lung +++

11 Obesity & ARDS Atelectasis & ARDS VALI Shear stresses at the of open and closed alveoli

12 Open lung strategy Agempts to create parenchymal homogeneity by: 1. Recruitment maneuvers 2. PEEP to respiratory mechanics 3. Minimize airway pressures

13 New focus: Reducing transpulmonary pressure Obese P pl à PEEP to overcome collapse and prevent derecruitment. High P peak ( 30 cmh2o) can be applied without lung overdisten@on P L <25 cmh2o at end inspira@on is considered safe (Mead J, Takishima T, Leith D. Stress distribu7on in lungs: a model of pulmonary elas7city. J Appl Physiol ; 28 ( 5 ): )

14 PEEP level? of PEEP: Collapse of alveoli during Atelectrauma lung injury. of PEEP: Hemodynamic compromise Increased dead space Overdistension of the lungs at end-

15 Methods of PEEPlevel 1. Using transpulmonary pressure by measuring P es 2. Using the airway curve profile (stress index) 3. compliance

16 PEEP level: esophageal pressure (P es ) P esophageal (P es ) es@mates P pl P L can be es@mated PEEP can be to achieve a posi@ve P L at end- exhala@on. Talmor et al. N Engl J Med : improvement of gas exchange and trend to improved 28- day mortality a primarily surgical ARDS popula7on

17 Obesity and Pes

18 Measurement of P es Lower 1/3 of oesofagus In sedated, paralyzed mechanically ven@lated pa@ents: cm distance from the nares transmission of the heartbeat

19 Effects of P es (supine) > P es (upright) (~5cmH2O) Medias@nal weight Much more fluctua@on in P es from cardiac ac@vity in supine posi@on compared with upright posi@on

20 PEEP with use of P es Technique: Increase PEEP un@l P L (end- expira@on) > 0 Goal: Preven@on of atelectrauma by preven@ng lung collapse Talmor et al. N Engl J Med : improvement of gas exchange and trend to improved 28- day mortality a primarily surgical ARDS popula7on

21 PEEP with use of P es Assump@ons: P es approximates P pl Expiratory airway collapse is not occurring in the lung regions in which local P pl < P es measured Risk: Severe overdistension in lung regions where P es overes@mates P pl (ventral regions) Talmor et al. N Engl J Med : improvement of gas exchange and trend to improved 28- day mortality a primarily surgical ARDS popula7on

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23 Piralls Inter- individual variable of weight to P es Increasing PEEP to a target may cause injurious overdistension of other lung regions

24 PEEP compliance receiving a set V t, P plat is measured as PEEP is increased. 1. Pplat increase in PEEP : improved lung compliance and an element of recruitable lung. 2. Pplat increase in PEEP : no recruitment; areas of overdisten@on or hyperinfla@on

25 Tidal volume Based on ideal body weight 6 ml/kg IBW Hypercapnia Acute illness Chronic hypoven@la@on

26 prone Pro Allows the weight to be supported by the sternum Decrease of lung collapse Improvement of V/Q matching Decrease of shunt. Con Futher increase abdominal pressure Pressure ulcera Further studies in obese needed

27 Prone

28 reverse trendelenburg of weaning from the unloading: in trans - diaphragma@c pressure Decreased atelectasis, Improved gas exchange

29 Key messages Obese Altered respiratory mechanics Increased heterogeneity of the lung strategies that focus on P L as a measure of lung stress show promise in pilot studies

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31 Literature