Basics for mechanical ventilation Lorx András Semmelweis University Dept. of Anaesthesiology and Intensive Therapy 1
Normal breathing negativ pressure during inspiration zero EEP or 3-4 H2Ocm dynamic PEEP Exspiration: passive 1/Compliance = 1/C lung + 1/C chest wall I : E ratio 1:2-1:3 2
Compliance The volume change per change in distending pressure C Dinamic Static rs, stat = P rs, plato 1800 1600 1400 1200 1000 800 600 400 200 0 ΔV C PEEP 0 10 20 30 40 50 60 70 Tubus C dyn = P peak ΔV PEEP 3
Compliances Circuit Airways Thorax Lung Abdomen 1 C rs 1 1 = + C TOT = Crs + Ccirc C C L cw Series Parallel system 4
Resistance Pressure drop occurring when a unit of flow is maintained Depend on: Diameter of the lumen Flow Density (of the moving material) Type of flow Smaller during inspiration Higher during expiration Normally caused by the big airways R + rs RL= (Pao-Palv)/ V = RL Rcw R L = Raw + Rt R TOT = Rrs + RTubus 5
W = Force* V W = P dv V 0 Mechanical work of breathing Distance V (WOB) W = Pressure*Area*Distance = V * Wvent = Paw * dvw pat = Pmusc * dv V 0 V Wrez = ( Paw P )* alv dv V 0 Pressure*Volume V V 0 P 6
Other measurements.. O 2 -COB Oxygen costs of breathing ineffective muscle constriction metabolic activity of the muscles (sympatic tone fever) TTP Tension- time product For one second Effective action of the muscles 7
The definition of respiratory insuff. Partial: PaO 2 under 60 Hgmm or under predicted value: (100-(Year/10*5)) PaCO 2 under 45 Hgmm (compensatory hyperventilation!) Global: PaO 2 under 60 Hgmm or under predicted value: (100-(Year/10*5)) PaCO 2 over 45 Hgmm Definition: The respiratory system is unable to supply the tissue s oxygen demand and to eliminate the carbon-dioxide production 8
Pump function insuff. CO2 (Hgmm) 100 90 80 70 60 50 40 30 20 pco2 increase severe hypercapnia comes first, then the severe hypoxia severe hypoxaemia can be compensated with elevation of FiO2 PaCO 2 = 0.863 V& E VCO & (1 V D 2 / V T ) Underlying disease: Pump func. insuff. central drive neuro-muscle dysfunc. increased work of breathing Resp. system mechanics Airway Elevated CO 2 production Ventilation/perfusion mismatch Elevated dead space anatomic physiologic 10 0 0 5 10 15 20 25 30 35 40 45 50 MV (L/min) 9
Lung tissue damage/dysfunction Leading sign: Hypoxaemia Shunt O 2 refracter Low FiO 2 Severe hypoventilation dv/dq mismatch Incomplete diffusion O 2 sensitive 100 P a O 2 (Hgmm) egészséges beteg 0.25 0.5 0.75 Tranzitidő 10 (s)
FRC changes FRC Decreases Maintains Increases Pneumonia Cardial Oedema ARDS PTX HTX STX Neurogn Toxic Neuromusculosceletal diseases COPD Asthma 11
Targets of ventilatory support: Temporary supply of impaired respiratory organ function. Long term support of respiratory organ failure. Full support (neuromuscular disorders). Intermittently, to improve life quality. 12
Indication of mechanical ventilation: To overcome the critical phase of a curable disease Irreversible muscle failure (Preventive ventilation) 13
Indication of mechanical ventilation: Respiratory therapy is usually symptomatic therapy The etiology of resp. insuff. makes the indication for MV The pathology of resp. insuff. rules the mode for MV 14
Making the indication for MV: Anamnesis Suffering from Dyspnoe Orthopnoe Paroxysmal nocturnal dyspnoe Headache in the mornings Somnolentia Progressive cough, wheezing Signs Tachypnoe Long exspiratory phase Use of accessory resp. muscles The paradox movement of the abdomen Cyanosis, edema 15
Making the indication for MV: Physical examination: inspection (accessory muscles, jugulum, paradox breathing), percussion auscultation (stridor, wheezing, crepitation) Labs: Arterial blood gas C-X-ray Spirometry MIP Lung volume Lung mechanics 16
Indication for intubation or tracheostomy Free airways Severe upper airway stenosis can be compensated for a long time mild progression leads to severe complication Mucus management Helps only if the mucus is in the trachea Mucus plugged in the distal airways can be mobilized with cough (sedation relaxation) Tracheostomy is preferred instead of ET Avoiding aspiration Avoids only food (solid) aspiration To hence MV Tracheostomy, mask, ET 17
Goal of the respiratory therapy Appropriate gas exchange CO 2 (minute ventilation), O 2 (MAP) Reduce or take the WoB Open the area with atelectasis (ΔV/ ΔQ mismatch) Mucus management Airway protection 18
Contra-indication for MV: Incurable state: End-stage disease End-stage pulmonary disease Pt. refuges Tension PTX 19
Costs a lot The MV: Machine Nurses Doctors Single-use equipments Bed (usage) Quality of life? Suffering? 20
Modes of MV: Negative pressure ventillation Iron lung more physiological, BUT maintenance AND nursing is difficult Needs relative good lungs Homodynamic effect Airway problems 21
Modes of MV: Positive pressure ventilation less physiological technically easier effective for diseased lungs as well 22
Modes positive pressure MV: Invasive ET or tracheostomy Efficient, but dangerous, high rate for complication MV in severe cases Non-invasive Nasal-mask, (Full)-facemask Efficient, less complication Before or after invasive support Avoiding intubation When invasive support is contraindicated 23
The mechanical cycle; breath Plato Inspiratory Trigger Expiratory Trigger Inspiration (I) Expiration (E) 24
Control The inspiratory cycle is totally controlled. (frequency, mode of breath delivery). The expiration is passive. No triggering. Assist/control Controlled mode where trigger is allowed. The preset frequency is the minimum. The triggered breath is controlled in the same way as the mandatory. In case of high frequency triggering the expiratory time shortens (danger of DH) Assist Not controlled, just supported mode. Inspiration starts just after triggering (no minimum rate) Inspiratory time is not controlled, depends on the patient demand. ETS 25
CMV (Volume control) Flow control Time cycled MAP< PAP, Pplat Tplato Preset: Flow Volume RR I/E Insp time Pause time 26
PCV (Pressure control) Pressure control Time cycled Volume Flow pattern MAP, PAP = PC Presets: Pressure RR I/E Insp. time 27
PSV Flow (lpm) 60 40 20 0-20 10 20 30 Assist Pressure target Flow cycled -40 24 Pressure (cmh2o) 20 16 12 8 4 0 0 800 10 20 30 Volume I/E RR 600 Volume (ml) 400 200 0 0 10 20 Time (seconds) 30 Presets: Pressure ETS Trigger 28
(S)IMV + (PSV) Pressure/Volume preset PEEP PS Airway pressure not stable Tidal volume dependent Use: Weaning Minimalized MV As sigh 29
PEEP FRC increase Compliance (?) O 2 (?) Deadspace (?) Haemodynamic effects Shunt WOB VILI Optimal PEEP Obstructive: Auto-PEEPx0.85 ALI/ARDS LIP 30
IRV IRV = Inverse Ratio Ventilation NORMAL: IRV: Inspir. Exspiration Inspiration Exspir. 1 : 2 1 : 1 (or 2:1 ; 3:1 ) Maintains auto-peep 31
Weaning Weaning starts with ventilation! For primary mode, chose the least invasive way of ventilation Decrease the invasivity step-by-step Extubate as soon as possible or Convert to non-invasive mode as possible. But Don not hesitate to be invasive enough Too early extubation leads to atelectatsis, mucus retention and reintubation, etc. 32
Weaning Depends on the underlying disease PEEP (2 H 2 Ocm) I/E PC PS SIMV: rate, control level, support level BIPAP APRV ASV Traditional Extubation from: PS 10, PEEP 4-5, SIMV rate 2-3, support 10 Exceptions! COPD Surfactant disorders Etc. 33
Classical forecast for successful weaning (Lemaire és Meakins 1991.) Criterion Value Tidal volume VT > 5 ml/ttkg Vital capacity VC > 10-15 ml/ttkg Respiratory rate f < 35/min Minute ventilation VE <10 l/min Maximal VE 2 VE at rest Maximal inspiratory pressure (Pimax) > 25-30 (>60) vízcm Airway occlusion pressure (p 0,1) < 7 vízcm PaO2 (FiO2 < 0,4) > 60 Hgmm PaCO2 increase < 8 Hgmm ph > 7,30 34
Diagnosing the weaning failure Cardiogenic Acute left heart failure Circulatory failure (sympathetic tone, low extra pulmonary organ perfusion) Neuromuscular Paradox breathing movements, RSB, hypoventilation, tachypnoe (relative restriction) Fatigue Pulmonary Atelectasis, FRC decrease, mucus retention Hypoxaemia, hypercapnia 35
Just look at the patient Sternocleidomastoid muscle activation Sweating Suprasternal and supraclavicular hole Intercostal swing during inspiration Paradox abdominal pattern Tachycardia 36
Postorerative respiratory failure 37
Perioperative pulmonary complications (PPC) No exact definition Pneumonia Resp. Insuff. Bronchospazm Fever Mucus retention Wheezing Hypoxia After elective abdominal surgery: Cardial complications: 5,7% Pulmonary complications: 9,6% 38
Causes of PPC: Hypoventilation Impaired respiratory muscle function Anesthesia Direct injury Anesthetics: Higher dose: Central drive damage (decreased output) Effects all respiratory muscles Mid dose: The pattern of the neural drive deteriorates Effects muscle groups differently (Uncoordinated) 39
Causes of PPC: Hypoventilation Hypoventilation and chest wall deformation 40
Postop. complications Muscle injury Direct injury Pain Motion disability Reflexes Not only vagal Hypoventilation and chest wall deformity 41
Causes of PPC: Mechanical Chest wall deformity FRC decreases Atelectasis Impaired gas exchange During anesthesia and remains postoperatively as well. 42
Causes of PPC: Mechanical Increased airway resistance Airway manipulation Inflammatory mediators Increased mucus production Impaired mucocilliar function Impaired lung immunity 43
Risk factors Site of operation Time of anesthesia Smoking Lung disease Other disease Preoperative check Anesth. ambulance Preoperative treatment, preparation 44
PPC prevention Avoiding irritation bronchial reflexes Preoperative ß-2 agonist or cholinerg blockade Regional anesthesia if acceptable Postoperative analgesia Pain relief (reflexes) Hence motor function Posztop. RESPIRATORY PHYSIOTHERAPY!! 45
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Noninvasive ventilation 47
BIRD (IPPB) Active training Mucus management Recruitment of atelectasis Special techniques 48