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Mechanical. Ventilation. PATRICK GERARD L. MORAL, M.D. I NTUBATION. Prevention of upper airway obstruction Protection against aspiration Facilitating tracheobronchial toilet Providing a closed system for mechanical ventilation. EXCESSIVE RESPIRATORY WORKLOAD. REDUCED CENTRAL DRIVE.
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Mechanical Ventilation PATRICK GERARD L. MORAL, M.D.
INTUBATION • Prevention of upper airway obstruction • Protection against aspiration • Facilitating tracheobronchial toilet • Providing a closed system for mechanical ventilation
EXCESSIVE RESPIRATORY WORKLOAD REDUCED CENTRAL DRIVE VENTILATORY FAILURE IMPAIRED INSPIRATORY MUSCLE PERFORMANCE
PHYSIOLOGICAL OBJECTIVES • To support pulmonary gas exchange • alveolar ventilation • arterial oxygenation • To increase lung volume • To reduce or manipulate work of breathing
CLINICAL OBJECTIVES • To reverse hypoxemia • To reverse acute respiratory acidosis • To relieve respiratory distress • To prevent / reverse atelectasis • To reverse ventilatory muscle fatigue • To permit sedation / neuromuscular blockade • To decrease myocardial oxygen consumption • To reduce intracranial pressure • To stabilize chest wall
AMBUBAG VENTILATION • 700 - 900 mL • 15 LPM (self-inflating) • augment VT
MODES • Assist - Control • SIMV • PSV • CPAP • Servo-controlled
BASIC VA = VT - VD VA = VE - VD VT VA
ORDERS • Hook to mechanical ventilator with the following set-up: • mode: assist - control • VT: 500 mL • BUR: 15/ minute • FiO2: 100 % • ABG 30 minutes after hooking to MV • In-line nebulization q 6
FiO2 • 100 % • dependent on target PaO2, hemodynamic status, MAP, PEEP level
OXYGEN CONTENT CaO2 = 1.34 mL x Hgb x SaO2 + .OO3 mL O2 x PaO2
TIDAL VOLUME • Physiologic: 5 - 7 mL / Kg • MV: 10 - 15 mL / Kg • alveolar distending pressure: 35 cm H2O
BASIC VA = VT - VD VA = VE - VD mechanical anatomic alveolar VA VD
CARDIAC OUTPUT hyperinflation Increased pulmonary vascular resistance Increased RV afterload Decreased RV output Decreased LV preload Decreased LV output
RESPIRATORY RATE • 4 to 20 / minute • 8 to 12 / minute • dependent on: • delivered VT • metabolic rate • target PaCO2 • level of spontaneous ventilation
FLOW RATE • 40 to 100 L/ minute • determined by level of spontaneous breathing effort
INSPIRATORY TIME / I:E RATIO • Inspiratory time: 0.8 to 1.2 s • I:E 1:2 to 1:1.5
INSPIRATORY TIME / I:E RATIO • Respiratory rate: 20 / minute 60 seconds / 20 = 3 seconds = Ttot at an I:E ratio of 1:2: TI = 1 second TE = 2 seconds
INSPIRATORY TIME / I:E RATIO • Respiratory rate: 30 / minute 60 seconds / 30 = 2 seconds = Ttot at an I:E ratio of 1:1: TI = 1 second TE = 1 second
SENSITIVITY • -0.5 to 1.5 cm H20 • most sensitive level that prevents self-cycling
PRESSURE ALARMS • High pressure • Low pressure
PRESSURE ALARMS • Low pressure • check connections between tubings and patient • deflated cuff • extubation
PRESSURE ALARMS • High pressure • bronchoconstriction • airway obstruction • barotrauma • right main bronchus obstruction • kinked endotracheal tube
HUMIDIFICATION • Cascade humidifier • heats carrier gas to 37 C • holds 44 mg H20 / L gas • water replacement • increases volume and decreases viscosity of the sputum
ANCILLARY • Chest radiograph • Arterial blood gas • Oximetry • Capnography
COMPLICATIONS • Barotrauma • Oxygen toxicity • Patient-ventilator asynchrony • Cardiovascular • Renal • Gastrointestinal