Ventilator mode selection, weaning parameters, and alarm troubleshooting concepts tested on respiratory therapist certification exams.
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- What does AC/VC mode stand for in mechanical ventilation?
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Assist/Control, Volume Control. Delivers a set tidal volume with every breath, whether patient-triggered or machine-triggered.- In PC mode, what parameter is set by the clinician?
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Pressure. The ventilator delivers a set inspiratory pressure; tidal volume varies with lung compliance and resistance.- What is PSV (Pressure Support Ventilation)?
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A patient-triggered, pressure-limited mode in which the ventilator augments each spontaneous breath with a preset pressure to ease the work of breathing.- When is SIMV (Synchronized Intermittent Mandatory Ventilation) most commonly used?
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During weaning, to allow gradual transition from machine ventilation to spontaneous breathing while guaranteeing a minimum number of full ventilator-supported breaths.- What is CPAP (Continuous Positive Airway Pressure)?
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A spontaneous mode that maintains constant positive airway pressure throughout the breathing cycle; no mandatory breaths are delivered.- What is BiPAP (Bilevel Positive Airway Pressure)?
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A mode that cycles between two pressure levels: a higher pressure during inspiration and a lower pressure during expiration, assisting spontaneous breathing.- Define the Rapid Shallow Breathing Index (RSBI).
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Respiratory rate divided by tidal volume in liters (f/VT). Values below 100 suggest readiness for weaning; above 100 suggests weaning may fail.- What is Maximum Inspiratory Pressure (MIP) and what value suggests readiness to wean?
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The most negative airway pressure a patient can generate during inhalation. MIP more negative than -20 cm H2O (or -30 in some protocols) suggests adequate respiratory muscle strength for weaning.- What is Maximum Expiratory Pressure (MEP) and why is it assessed?
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The most positive airway pressure a patient can generate during exhalation. It reflects expiratory muscle strength and is used to assess cough effectiveness and airway protection.- What is the significance of a positive Spontaneous Breathing Trial (SBT)?
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The patient tolerates a period of spontaneous breathing (typically on low PSV or CPAP/T-piece for 30-120 minutes) without signs of distress or deterioration, indicating readiness for extubation.- What are three objective criteria used to assess readiness for weaning?
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1. Underlying cause of respiratory failure resolved; 2. Adequate oxygenation (PaO2/FiO2 > 200 or SpO2 > 90% on moderate support); 3. Adequate ventilation (pH > 7.25, PaCO2 < 55).- What does a 'high pressure alarm' on a ventilator usually indicate?
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Obstruction or decreased lung compliance. Causes include secretions, tube obstruction, bronchospasm, pneumothorax, pneumonia, or ventilator malfunction.- What is the first step when a high pressure alarm sounds on the ventilator?
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Check the patient: assess breath sounds, lung compliance, and tube patency. Listen for crackles, wheezes, or unequal air entry. Suction if needed.- What causes a 'low pressure alarm' on the ventilator?
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Inadequate circuit pressure. Common causes include ventilator disconnection, endotracheal tube cuff leak, circuit leak, or ventilator malfunction.- What is the appropriate response to a ventilator disconnect alarm?
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Immediately check the circuit for disconnection. Manually ventilate the patient with a bag-valve-mask if the tube is disconnected, then reconnect or replace the circuit and notify the physician.
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