Which ventilation mode allows the patient to breathe spontaneously at their own rate while the ventilator provides a preset pressure support with each breath?

Explanation

## Pressure Support Ventilation (PSV): Definition and Mechanism **Key Point:** PSV is a **spontaneous breathing mode** in which every patient-initiated breath receives a preset pressure boost from the ventilator. There is no mandatory backup rate — the patient controls both rate and inspiratory time. ### How PSV Works 1. Patient initiates a breath (triggers the ventilator) 2. Ventilator delivers a preset inspiratory pressure (e.g., 10 cm H₂O) 3. Breath cycles off when inspiratory flow falls below a threshold (typically 25% of peak flow) 4. Patient exhales passively 5. **No mandatory breaths** if patient does not trigger ### Key Features | Feature | PSV | |---------|-----| | **Mandatory breaths** | None | | **Patient controls** | Rate, inspiratory time, effort | | **Ventilator delivers** | Preset pressure support per breath | | **Backup rate** | None (apnea alarm only) | | **Triggering** | Patient-initiated only | | **Weaning tool** | Yes — pressure can be gradually reduced | **High-Yield:** PSV is the **mode of choice for weaning** from mechanical ventilation. Pressure support is progressively reduced as the patient's respiratory muscle strength improves. ### Distinction from Other Modes **PSV vs. SIMV:** - SIMV = hybrid mode with **mandatory breaths** (set rate) + spontaneous breaths with or without pressure support - PSV = **purely spontaneous** — no mandatory breaths **PSV vs. CPAP:** - CPAP = maintains positive airway pressure throughout the breath cycle; no pressure boost during inspiration - PSV = pressure boost **only during inspiration**; exhalation is at baseline (usually 0 or low PEEP) **Clinical Pearl:** In PSV, always set an **apnea alarm** (e.g., 10–15 seconds) because there is no mandatory backup rate. If the patient stops breathing, the ventilator will not deliver breaths. **Mnemonic:** **PSV = Patient-driven, Spontaneous, Variable rate** — remember that the patient is in control.