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Mechanical Ventilation mechanisms of action and complications

Mechanical Ventilation: Mechanisms of Action and Complications Authors: Madison Amyotte Reviewers: Victória Silva, Mao Ding Eric Leung* * MD at time of publication Mechanical ventilation is a form of life support that helps a patient breathe (ventilate) when they cannot breathe on their own. Invasive: Delivery of positive pressure to the lungs via endotracheal or tracheostomy tube Mechanical ventilation Pressure support ventilation (PSV): Set inspiratory pressure & flow. Patient initiates all breaths unassisted Non-invasive: Delivery of oxygen into the lungs via positive pressure through the mouth No endotracheal or tracheostomy tube Assist/control ventilation (AC): Set respiratory rate & tidal volume (amount of air delivered to the lungs with each breath). Patient can trigger additional assisted breaths Synchronized intermittent mandatory ventilation (SIMV): Set tidal volume & respiratory rate. Patient can trigger additional unassisted breaths 02 mask delivery Continuous positive airway pressure (CPAP) Provides continuous positive ventilatory pressure Bilevel positive airway pressure (BIPAP) Provides positive pressure with two different pressure levels for inhalation and exhalation ↑ Swallow non- inspiratory flow Aspiration Acute rise in airway pressure Barotrauma Patient- triggered breath Ventilator senses negative pressure from inflation of the lungs Time-triggered breath Respiratory rate set at x breaths per min Patient-triggered breath Ventilator senses negative pressure from inflation of the lungs Tidal volume determined by patient’s strength & lung compliance Time-triggered breath Respiratory rate set at x breaths per min Delivery of set tidal volume, inspiratory flow rate & pattern Complete patient- triggered breaths Ventilator senses negative pressure from inflation of the lungs Breathes assisted by set inspiratory pressure Inspiratory flow drops below set inhalational negative pressure threshold Pressure support terminates as exhalation cycle begins Combined with SIMV Inspiratory pressure added to patient triggered breaths Patient can overcome resistance of the endotracheal tube or ↑ volume of spontaneous breathes Delivery of set tidal volume, inspiratory flow rate & pattern Airways remain open & clear of obstruction Forced air into nasal passages Nose bleeds (epistaxis) Maximum tidal volume reached Exhale valve opens Patient exhales actively or passively until set end expiratory pressure in the lungs is reached (PEEP) to prevent alveolar collapse Patient exhales until PEEP reached Patient achieves optimal ventilation throughout respiratory cycles Mouth breathing Dry mouth (xerostomia) Increased work of breathing & muscle fatigue Prolonged weaning & extubation Breath stacking ↑ Volume and pressure in lungs Lung tissue injury (barotrauma) Microorganisms colonize artificial airway Ventilator associated pneumonia if ventilation >48 hrs Tachypnea ↓ CO2in circulation Respiratory alkalosis Legend: Pathophysiology Mechanism Sign/symptom/lab finding Complications Published Nov 25, 2023 on www.thecalgaryguide.com