ObjectivesDescribe types of breaths and modes of mechanical ventilationDescribe interactions between ventilatory parameters and modifications needed to avoid harmful effects

Early ventilators

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Ventilator ~ ventilasi

Ventilasi = keluar masuknya udara dari atmosfer ke alveolusVentilator = menghantarkan (delivery) udara/gas TEKANAN POSITIF ke dalam paruVentilasi semenit = TV x RR (frekuensi nafas)TV = 5-7 cc/kgBBRR = 10 12 kali/menitCompliance = Pengukuran dari elastisitas paru dan dinding dadaNilai compliance mengekspresikan adanya perubahan volume akibat perubahan dari tekanan (pressure)Compliance rendah = Stiff lung - edema paru, efusi pleura, obstruksi, distensi abdomen dan pneumotoraksCompliance tinggi = penurunan elastisitas resistensi pada inspirasi dan penurunan kemampuan mengeluarkan udara waktu ekspirasi (COPD)

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Kriteria tradisional untuk bantuan ventilasi mekanik

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TUJUAN KLINIS / INDIKASI PEMAKAIAN VENTILASI MEKANIK

GAGAL 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 chestMENCEGAH ATAU MENGOBATI ATELEKTASIS

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TUJUAN FISIOLOGIS

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

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

Indications for Mechanical VentilationVentilation abnormalitiesRespiratory muscle dysfunctionRespiratory muscle fatigueChest wall abnormalitiesNeuromuscular diseaseDecreased ventilatory driveIncreased airway resistance and/or obstruction

Oxygenation abnormalitiesRefractory hypoxemiaNeed for positive end-expiratory pressure (PEEP)Excessive work of breathingIndications for Mechanical Ventilation

Types of Ventilator BreathsVolume-cycled breathVolume breathPreset tidal volumeTime-cycled breathPressure control breathConstant pressure for preset timeFlow-cycled breathPressure support breathConstant pressure during inspiration

Modes of Mechanical VentilationConsider trial of NPPVDetermine patient needsGoals of mechanical ventilationAdequate ventilation and oxygenationDecreased work of breathingPatient 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 pressurePatient controls rate and tidal volume

Assist-Control VentilationVolume or time-cycled breaths + minimal ventilator rateAdditional breaths delivered with inspiratory effortAdvantages: reduced work of breathing; allows patient to modify minute ventilationDisadvantages: potential adverse hemodynamic effects or inappropriate hyperventilation

Pressure-Support VentilationPressure assist during spontaneous inspiration with flow-cycled breathPressure assist continues until inspiratory effort decreasesDelivered tidal volume dependent on inspiratory effort and resistance/compliance of lung/thorax

Potential advantagesPatient comfort Decreased work of breathingMay enhance patient-ventilator synchronyUsed with SIMV to support spontaneous breathsPressure-Support Ventilation

Potential disadvantagesVariable tidal volume if pulmonary resistance/compliance changes rapidlyIf sole mode of ventilation, apnea alarm mode may be only backupGas leak from circuit may interfere with cyclingPressure-Support Ventilation

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

Potential advantagesMore comfortable for some patientsLess hemodynamic effectsPotential disadvantages Increased work of breathing Synchronized Intermittent Mandatory Ventilation (SIMV)

Controlled Mechanical VentilationPreset rate with volume or time-cycled breathsNo patient interaction with ventilatorAdvantages: rests muscles of respirationDisadvantages: requires sedation/neuro-muscular blockade, potential adverse hemodynamic effects

Inspiratory Plateau Pressure (IPP)Airway pressure measured at end of inspiration with no gas flow presentEstimates alveolar pressure at end-inspirationIndirect indicator of alveolar distensionPeak pressurePlateau pressureInspiration ExpirationPIPPlateau pressure

High inspiratory plateau pressureBarotrauma VolutraumaDecreased cardiac output Methods to decrease IPPDecrease PEEPDecrease tidal volume

Inspiratory Plateau Pressure (IPP)

Inspiratory Time: Expiratory Time Relationship (I:E ratio)Spontaneous breathing I:E = 1:2Inspiratory time determinants with volume breathsTidal volumeGas flow rateRespiratory rateInspiratory pauseExpiratory time passively determined

I:E Ratio during Mechanical VentilationExpiratory time too short for exhalationBreath stackingAuto-PEEPReduce auto-PEEP by shortening inspiratory timeDecrease respiratory rateDecrease tidal volumeIncrease gas flow rate

Permissive HypercapniaAcceptance of an elevated PaCO2, e.g., lower tidal volume to reduce peak airway pressure Contraindicated with increased intracranial pressureConsider in severe asthma and ARDS Critical care consultation advised

Auto-PEEPCan be measured on some ventilatorsIncreases peak, plateau, and mean airway pressuresPotential harmful physiologic effects

Can be measured on some ventilatorsIncreases peak, plateau, and mean airway pressuresPotential harmful physiologic effectsAuto-PEEP

Pediatric ConsiderationsInfants (< 5 kg)Time-cycled, pressure-limited ventilationPeak inspiratory pressure initiated at 1820 cm H2OAdjust to adequate chest movement or exhaled tidal volume ~8 mL/kgLow level of PEEP (24 cm H2O) to prevent alveolar collapse

ChildrenSIMV modeTidal volume 8-10 mL/kgFlow rate adjusted to yield desired inspiratory timeInfants 0.50.6 secsToddlers 0.6-0.8 secsOlder 0.81.0 secsRate