“Cycling Down” PRVC
PRVC can become problematic in patients with increased ventilatory demand and respiratory drive (febrile peds, sepsis, DKA, neuro, etc.).
As these patients’ respiratory drive increases, they drop their diaphragm more forcefully, reducing intrathoracic pressure and increasing inspiratory flow. The ventilator misinterprets this as improved lung compliance and decreases the pressure it delivers to maintain the target volume. This is commonly referred to as “cycling down" PRVC.
The result? Inadequate support, increased work of breathing, and reduced mean airway pressure (potentially leading to atelectasis).
What to watch for:
- Unusually low PIPs
- Signs of increased work of breathing (retractions, tachypnea, nasal flaring, head bobbing in peds, accessory muscle use)
- Sharp negative pressure inflection before inspiratory pressure waveform indicating increased effort (show in white on the graphic).
- Pt. pulling tidal volumes significantly larger than what is set.
- Be cautious using PRVC in conditions that increase ventilatory demand.
- Signs of increased work of breathing (retractions, tachypnea, nasal flaring, head bobbing in peds, accessory muscle use)