Modes of Ventilation Dr Eugenia Mahamid Rambam Medical

Modes of Ventilation Dr. Eugenia Mahamid Rambam Medical Center 1

Modes of Ventilation The main indication for ventilatory support is Respiratory Failure 2

Categories of Respiratory Failure HYPOXEMIC • • ARDS PULMONARY EDEMA PULMONARY HEMORRHAGE PNEUMONIA Low compliance lung disease: Low PO 2, Low Sa. O 2 3

Categories of Respiratory Failure HYPERCARBIC • • OBSTRUCTION TO AIRFLOW NEUROMUSCULAR DISORDERS DRUG OVERDOSE ENDOCRINOPATHIES Increase in PCO 2 Respiratory acidosis Decrease in p. H 4

Categories of Respiratory Failure E CENTRAL C • DECREASED LEVEL OF E CONSCIOUSNESS ACUTE MEDICAL AND SURGICAL CONDITIONS • MECHANICAL VENTILATION IS USED TO DECREASE WORK OF BREATHING 5

A MECHANICAL VENTILATOR is mp providing an external source of energy to push the lungs and allow for passive exhalation (CO 2 elimination). Ventilator’s Changeable parameters Vt = Tidal Volume FIO 2 = Fraction of Inspired Oxygen RR = Respiratory Rate I: E = Inspiratory to Expiratory ratio EEP = End Expiratory Pressure PIP = Peak Inspiratory Pressure Inspiratory Flow Rate 6

OTHER MEANS AFFECTING VENTILATION • NO = Nitric Oxide • Orientation of patient’s body in gravitational field 7

GENERAL CLASSES OF VENTILATORS Negative pressure application of negative pressure at the chest wall and upper abdomen Positive pressure application of positive pressure at airway opening 8

Negative Pressure Ventilators Perithoracic pump for replacement failing patients’ muscles, wide-spread use for polio epidemics • Manually operated ventilator (Woillez, 1876) • Tank respirator “iron lung”, cuirass, body suits (1930 - 1950) Patient care problems: airway obstruction, low efficacy in interstitial lung diseases, patient’s discomfort 9

Negative Pressure Ventilators 1876 1960 1930 -1950 10

Positive pressure ventilators Volume-cycled Delivers set Vt at specified RR and terminates respiration when Vt is delivered. Airway pressures are determined by respiratory system impedance (risk of barotrauma). Pressure-cycled Limits flow, when set pressure is delivered (may decrease minute ventilation) 11

Positive pressure ventilators Evita 2 Dragger Germany 12

VENTILATOR SETTINGS OXYGEN THERAPY O 2 delivery = Qt (1. 39 x Sa. O 2 x Hb + 0. 0031 x Pa. O 2) FIO 2 1 0. 4 Adjustment of oxygen percent to achieve Sa. O 2 > 90% potential oxygen toxicity (pulmonary fibrosis ) FIO 2 > 0. 6 13

VENTILATOR SETTINGS MINUTE VENTILATION (VOLUME) = Vt x RR Physiologic Vt Mechanical Vt 5 m. L/kg 7 – 10 m. L/kg Limitation of Vt in cases of: • airway obstruction • one lung patient • PIP > 40 cm H 2 O RESPIRATORY RATE 10 -12 /min or more to match metabolic needs of the patient 14

VENTILATOR SETTINGS Inspiratory Flow Rate and Inspiratory to Expiratory Ratio IFR L/min: rapidity of airflow in airways Ti = Inspiratory Time: the time to complete inspiration Ti = Vt / Flow Rate TE = Expiratory Time: time to complete exhalation Ti + TE = T total: respiratory cycle 15

CONVENTIONAL VENTILATION CMV : Controlled Mandatory Ventilation Full mechanical support § Maintaining full V min. § Reduction of oxygen and energy consumption Indications: Following intubation Respiratory muscle fatigue ( for muscle rest) Poor cardiac output ( VO 2 of respiratory muscles) 16

CONVENTIONAL VENTILATION CMV Airway pressure Flow inspirium expirium fixed rate fixed Vt Patient’s spontaneous effort fixed flow rate FIO 2 Disadvantages: • need for sedatives + relaxants • unresponsiveness to the changing V min. of patient • muscle atrophy 17

CONVENTIONAL VENTILATION ASSIST / CONTROL Mechanical breath initiated by patient’s negative pressure. Every breath is machine supported (set Vt) Airway pressure Flow inspirium expirium Disadvantages: • alkalosis Patient’s spontaneous effort • intrinsic PEEP • barotrauma: pneumothorax, pneumomediastinum, subcutaneous emphysema, tension air cyst 18

CONVENTIONAL VENTILATION IMV INTERMITTENT MANDATORY VENTILATION combined mechanical and spontaneous breathing (CMV + spontaneous) 5 0 expirium inspirium Spontaneous ventilation 5 0 IMV 5 0 Patient’s spontaneous effort CMV 19

CONVENTIONAL VENTILATION SIMV SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION Synchronization of the ventilator delivered Vt with the patient’s spontaneous breathing. Prevention of ventilator stacking by timing window. Pressure Timing window cm H 2 O A B PEEP Patient’s spontaneous effort 20 Time (sec)

CONVENTIONAL VENTILATION Controlled FIO 2 Gas source Reservoir bag Conventional ventilator IMV CIRCUIT 21 One-way valve PEEP and Exhalation Valves

CONVENTIONAL VENTILATION IMV / SIMV Advantages decreased need in sedatives prevention of muscle atrophy lower airway pressure and intrathoracic pressure hemodynamic stability reduction in alkalosis patient’s ability to regulate his rate and Vt according to metabolic requirements 22

CONVENTIONAL VENTILATION IMV / SIMV Disadvantages respiratory muscle fatigue increased work of breathing due to highly resistant respiratory circuit, small diameter (ETT) possibility of respiratory acidosis risk of cardiac decompensation in patient with heart disease 23

PEEP and CPAP During continuous mechanical ventilation PEEP Positive End Expiratory Pressure 50 CMV cm H 2 O 40 30 PEEP 20 10 0 50 CMV Patient triggered 40 cm H 2 O 30 20 10 0 24 PEEP

PEEP and CPAP During spontaneous breathing with or without inspiratory support CPAP Continuous Positive Airway Pressure 15 expiration 10 5 0 -5 25 inspiration PEEP

NON PEEP & CPAP Mechanism 80% - Decreases Qs/Qt without reducing edema 20 % Qs / Qt 23. 8 % 5. 1 % 146. 8 μ 78. 6 μ - Reduces number of flooded alveoli - Redistributes edema to peribroncho vascular interstitial spaces - Decreases work of breathing - Decreases preload 26

PEEP and CPAP Goals Reduction of shunt recruitment of previously collapsed alveoli ventilation of non-ventilated zones continuous gas exchange (during expiration) Prevention of atelectasis prevention of brisk alveolar inflation and deflation > protection of surfactant and pulmonary parenchyma 27

PEEP and CPAP Complications increased intrathoracic pressure decrease of venous returns decrease of cardiac output EFFECT of PEEP venous 28 compression

PEEP and CPAP Complications Increased ADH secretion, decrease of renal artery perfusion pressure decrease of urinary output and creatinine clearance decreased venous return from brain increased ICP decrease of CPP barotrauma – induced by PEEP ≈ 20% 29

PEEP / CPAP Therapy Titrate EEP until: PO 2 ≈ 60 mm. Hg (Sat O 2 ≈ 90%) on FIO 2 < 60% Qs / Qt < 15% Best PEEP on volume-pressure loop Volume (m. L) provided cardiac output is maintained D C 500 B 250 A 0 30 Upper deflection point Lower inflection point 15 30 Pressure cm. H 20

PRESSURE SUPPORT VENTILATION (PS) patient triggered, patient-controlled (flow-time), pressure limited interactive ventilation with clinicianselected level of positive pressure (2 -50 cm H 2 O) C Proximal Airway Pressure cm. H 20 20 D B 15 10 5 A time 31

PRESSURE SUPPORT VENTILATION (PS) Synchrony PS interaction with ventilatory muscles PS adds to the patient’s effort to deliver Vt Overload of ventilatory muscles tachypnea, small Vt PS Vt, Vt m. L/kg 12 RR 8 4 Muscle tension 32 Ventilator pressure

PRESSURE SUPPORT VENTILATION (PS) Synchrony Patient interaction with ventilator: Trigger (prompt breath initiation, ventilator sensitivity and responsiveness) Flow adjustment of the gas delivery to the patient’s effort Cycling ventilator breath termination with the end of patient’s effort 25 -30% of peak flow 33

PRESSURE SUPPORT VENTILATION (PS) Titration of PS to overcome endotracheal tube resistance (6 -10 cm. H 2 O) to achieve effective Vt and V min without causing respiratory overload non-invasive application BIPAP* = CPAP + Pressure Support *Bi-level Positive Airway Pressure 34

NON CONVENTIONAL VENTILATION PRESSURE CONTROL VENTILATION Time and pressure controlled Exhalation is passive Vt and V min determined by respiratory system impedance (compliance and resistance) pressure Inverse ratio ventilation (IRV) Mandatory BIPAP I : E 3: 1 T- inspiratory P. inspiratory Tidal volume 35 volume PEEP T- expiratory

NON CONVENTIONAL VENTILATION pressure Airway pressure release ventilation (APRV) Spontaneous breathing P. inspiratory volume PEEP time Spontaneous tidal volume Tidal volume 36

NON CONVENTIONAL VENTILATION Indication: severe hypoxemic respiratory failure ARDS ( CT ) Breathing lung (baby lung) Edema Pleural effusion 37

NON CONVENTIONAL VENTILATION Open Lung Conception Pressure controlled, Inverse ratio ventilation with permissive hypercapnia: Permissive hypercapnia = increase of PCO 2 until p. H reaches 7. 2 at p. H < 7. 2 give bicarbonate Prone position Nitric Oxide Selective pulmonary vasodilator 38 Gravitational force

NON CONVENTIONAL VENTILATION Proportional assist ventilation for spontaneously breathing patients gives maximal Vt with minimal inspiratory pressure, by measuring lung compliance and resistance Perflubron liquid ventilation injection of perfluorocarbon into the trachea aiming to recruiting collapsed alveoli. ECMO Extra Corporeal Membrane Oxygenator IVOX Intra. Venous Oxygenator (membrane “lung” inserted in inferior vena cava 39

NON CONVENTIONAL VENTILATION HIGH FREQUENCY VENTILATION RR 60 – 3600 / min CONVECTION DIFFUSION TYPES I. HFPPV high frequency positive pressure ventilation II. III. HFO HFJT high frequency oscillation high frequency jet ventilation INDICATIONS I. II. Broncho-pleural fistula Hypoxemic respiratory failure 40

VEANING FROM MECHANICAL VENTILATION Necessary conditions for considering discontinuation from Mechanical Ventilation: Stable circulation and absence of myocardial ischemia, sepsis and uncontrolled acidosis Adequate pulmonary O 2 exchange as evidenced by Sa. O 2 > 90% with FIO 2 < 0. 4 and PEEP < 7. 5 cm H 2 O Adequate ability to ventilate spontaneously (Vt > 5 m. L/Kg, VC = 3 x Vt, NIF > 30 cm. H 2 O, and f < 36 /min) 41

VEANING FROM MECHANICAL VENTILATION CMV > SIMV + PS (15 cm. H 2 O) CPAP + PS (8 cm H 2 O) Disconnection + T Tube 42 Extubation + O 2 mask