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Synchronized Intermittent Mandatory Ventilation (SIMV): In SIMV, the ventilator delivers a set number of mandatory breaths, but the patient can breathe spontaneously between them without assistance. These spontaneous breaths require the patient to use their own respiratory muscles, increasing workload compared with fully controlled modes.

Continuous Positive Airway Pressure (CPAP): CPAP is a spontaneous mode with no mandatory breaths. The patient breathes entirely on their own against continuous airway pressure, maintaining alveolar stability but requiring full respiratory muscle effort.

Pressure Support Ventilation (PSV): In PSV, each breath is patient-initiated and supported by preset pressure from the ventilator. The patient performs most of the work of breathing, and the ventilator simply decreases airway resistance, thus strengthening respiratory muscles during weaning.

Cystic Fibrosis: This chronic genetic disorder leads to the production of thick mucus that obstructs airways, causing severe respiratory infections and hypoventilation. During acute exacerbations or respiratory failure, mechanical ventilation supports oxygenation and CO₂ elimination until the underlying infection or obstruction is managed.

Acute Respiratory Distress Syndrome (ARDS): ARDS results in severe alveolar damage, noncompliant lungs, and refractory hypoxemia, making spontaneous breathing ineffective. Mechanical ventilation with PEEP (positive end-expiratory pressure) is essential to improve oxygenation and prevent alveolar collapse.

Require an artificial airway: Most positive pressure ventilators require an endotracheal or tracheostomy tube to deliver air directly into the lungs. This ensures a sealed system for effective ventilation and prevents aspiration in critically ill patients.

Most frequently used with acutely ill patients: Positive pressure ventilation is the standard of care in intensive care units (ICUs) for patients with acute respiratory failure, ARDS, or those undergoing major surgery. It allows precise control of tidal volume, respiratory rate, and FiO₂.Rationale for Incorrect Answers

Peak inspiratory pressure predetermined: In pressure-controlled ventilation, the ventilator delivers each breath to a preset inspiratory pressure, regardless of the volume achieved. This limits barotrauma risk but allows the delivered volume to fluctuate with compliance.

Increased risk for hyperventilation and hypoventilation: Because patient lung compliance and airway resistance can change, both volume-controlled and pressure-controlled modes may deliver too much or too little ventilation, resulting in hyperventilation or hypoventilation if not closely monitored.

Volume delivered varies based on selected pressure and patient lung compliance: In pressure-controlled modes, tidal volume depends on the set pressure and the compliance of the lungs and chest wall—poor compliance leads to smaller volumes, while improved compliance increases volume.