DASAR VENTILASI MEKANIK

ANANG ACHMADI, SpAn ICU Bedah RS Jantung Pusat Nasional Harapan Kita - Jakarta

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Objectives Describe types of breaths and modes of mechanical ventilation Describe interactions between ventilatory parameters and modifications needed to avoid harmful effects

Early ventilators

Ventilator ~ ventilasi Ventilasi = keluar masuknya udara dari atmosfer ke alveolus Ventilator = menghantarkan (delivery) udara/gas TEKANAN udara/gas POSITIF ke dalam paru Ventilasi semenit = TV x RR (frekuensi nafas ) (frekuensi nafas) TV = 5-7 cc/ kgBB cc/kgBB RR = 10 12 kali/ menit kali/menit

Compliance = Pengukuran dari elastisitas paru dan dinding dada Nilai compliance mengekspresikan adanya perubahan volume akibat perubahan dari tekanan (pressure) Compliance rendah = Stiff lung - edema paru, efusi pleura, paru, obstruksi, obstruksi, distensi abdomen dan pneumotoraks Compliance tinggi = penurunan elastisitas resistensi pada inspirasi dan penurunan kemampuan mengeluarkan udara waktu ekspirasi (COPD)

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Kriteria tradisional untuk bantuan ventilasi mekanikPARAMETER Mekanik (RR) TV (cc/kg) Oksigenasi (PaO2mmHg) P(A-aDO2) mmHg Ventilasi (PaCO2mmHg) INDIKASI VENTILASI > 35x/m 60 NORMAL RANGE 10-20x/m 5-7 75-100 (air) 25-65(FiO2 1.0) 35-45

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TUJUAN KLINIS / INDIKASI PEMAKAIAN VENTILASI MEKANIKGAGAL NAFAS HIPOKSEMIK: Reverse hypoxemia dgn pemberian PEEP dan konsentrasi O2 tinggi (ARDS,edema paru atau pneumonia akut) GAGAL NAFAS VENTILASI: Reverse acute respiratory acidosis - Koma : trauma kepala, encefalitis, overdosis, CPR - Trauma med spinalis, polio, motor neuron disease - Polineuropati, miastenia gravis - Anesthesia (relaksan u/operasi, tetanus, epilepsi) STABILISASI DINDING DADA: Flail chest MENCEGAH ATAU MENGOBATI ATELEKTASIS

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TUJUAN FISIOLOGISMEMPERBAIKI VENTILASI ALVEOLAR MEMPERBAIKI OKSIGENASI ALVEOLAR (FiO2, FRC,V'A) MEMBERIKAN PUMP SUPPORT ( ME WOB)

Consensus conference on mechanical ventilation, Int Care Med 1994, 20:64-79

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Indications for Mechanical Ventilation

Ventilation abnormalities Respiratory muscle dysfunction Respiratory muscle fatigue Chest wall abnormalities Neuromuscular disease

Decreased ventilatory drive Increased airway resistance and/or obstruction

Indications for Mechanical Ventilation Oxygenation abnormalities Refractory hypoxemia

Need for positive endexpiratory pressure (PEEP) Excessive work of breathing

Types of Ventilator Breaths Volume-cycled breath Volume breath Preset tidal volume

Time-cycled breath Pressure control breath Constant pressure for preset time

Flow-cycled breath Pressure support breath Constant pressure during inspiration

Modes of Mechanical Ventilation

Consider trial of NPPV Determine patient needs Goals of mechanical ventilation Adequate ventilation and oxygenation Decreased work of breathing Patient comfort and synchrony

Modes of Mechanical VentilationPoint of Reference: Spontaneous Ventilation

Continuous Positive Airway Pressure (CPAP) No machine breaths delivered

Allows spontaneous breathing at elevated baseline pressure Patient controls rate and tidal volume

Assist-Control Ventilation Volume or time-cycled breaths + minimal ventilator rate Additional breaths delivered with inspiratory effort Advantages: reduced work of breathing; allows patient to modify minute ventilation Disadvantages: potential adverse hemodynamic effects or inappropriate hyperventilation

Pressure-Support Ventilation Pressure assist during spontaneous inspiration with flow-cycled breath Pressure assist continues until inspiratory effort decreases Delivered tidal volume dependent on inspiratory effort and resistance/compliance of lung/thorax

Pressure-Support Ventilation Potential advantages Patient comfort Decreased work of breathing May enhance patient-ventilator synchrony Used with SIMV to support spontaneous breaths

Pressure-Support Ventilation Potential disadvantages Variable tidal volume if pulmonary resistance/compliance changes rapidly

If sole mode of ventilation, apnea alarm mode may be only backup Gas leak from circuit may interfere with cycling

Synchronized Intermittent Mandatory Ventilation (SIMV) Volume or time-cycled breaths at a preset rate Additional spontaneous breaths at tidal volume and rate determined by patient Used with pressure support

Synchronized Intermittent Mandatory Ventilation (SIMV) Potential advantages More comfortable for some patients Less hemodynamic effects

Potential disadvantages Increased work of breathing

Controlled Mechanical Ventilation Preset rate with volume or time-cycled breaths No patient interaction with ventilator Advantages: rests muscles of respiration Disadvantages: requires sedation/neuromuscular blockade, potential adverse hemodynamic effects

Inspiratory Plateau Pressure (IPP) Airway pressure measured at end of inspiration with no gas flow present Estimates alveolar pressure at end-inspiration Indirect indicator of alveolar distensionPIP Plateau pressure

Peak pressure

Plateau pressure

Inspiration

Expiration

Inspiratory Plateau Pressure (IPP) High inspiratory plateau pressure Barotrauma Volutrauma Decreased cardiac output

Methods to decrease IPP Decrease PEEP Decrease tidal volume

Inspiratory Time: Expiratory Time Relationship (I:E ratio) Spontaneous breathing I:E = 1:2 Inspiratory time determinants with volume breaths Tidal volume Gas flow rate Respiratory rate Inspiratory pause

Expiratory time passively determined

I:E Ratio during Mechanical Ventilation Expiratory time too short for exhalation Breath stacking Auto-PEEP

Reduce auto-PEEP by shortening inspiratory time Decrease respiratory rate Decrease tidal volume Increase gas flow rate

Permissive Hypercapnia Acceptance of an elevated PaCO2, e.g., lower tidal volume to reduce peak airway pressure

Contraindicated with increased intracranial pressure Consider in severe asthma and ARDS Critical care consultation advised

Auto-PEEP Can be measured on some ventilators Increases peak, plateau, and mean airway pressures Potential harmful physiologic effects

Auto-PEEP Can be measured on some ventilators Increases peak, plateau, and mean airway pressures Potential harmful physiologic effects

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Pediatric Considerations Infants (< 5 kg) Time-cycled, pressure-limited ventilation

Peak inspiratory pressure initiated at 1820 cm H2O Adjust to adequate chest movement or exhaled tidal volume ~8 mL/kg Low level of PEEP (24 cm H2O) to prevent alveolar collapse

Pediatric Considerations Children SIMV mode Tidal volume 8-10 mL/kg Flow rate adjusted to yield desired inspiratory time Infants 0.50.6 secs Toddlers 0.6-0.8 secs Older 0.81.0 secs

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