Best Ventilator Mode for Permissive Tachypnea

Understanding Permissive Tachypnea

Permissive tachypnea is a ventilation strategy that allows for an elevated respiratory rate while maintaining adequate minute ventilation and preventing ventilator-associated lung injury 1
This approach is similar to permissive hypercapnia strategies used in acute lung injury, where pressure-limited small volume ventilation is preferred 2
The goal is to minimize ventilator-induced lung injury while allowing the patient to maintain their own respiratory drive 3

Bi-level pressure support ventilators using IPAP (inspiratory positive airway pressure) and EPAP (expiratory positive airway pressure) are recommended as first-line for permissive tachypnea 2, 3
These ventilators are simpler to use, more flexible, and provide better leak compensation compared to volume-controlled ventilators 3
The de-accelerating flow profile of pressure-controlled breaths results in better distribution of ventilation 2

Initial IPAP should be 8-15 cmH2O and EPAP 4-8 cmH2O 4, 5
Pressure support (difference between IPAP and EPAP) should be at least 5 cmH2O 5
Increase pressure support if tidal volume is low (<6-8 mL/kg) 4, 5
For patients with COPD or obstructive disease, use shorter inspiratory time (approximately 30% of cycle time) to allow adequate time for exhalation 6, 7

Add a backup rate (ST mode) if the patient has an inappropriately low respiratory rate or fails to trigger the ventilator reliably 5, 7
Set the backup rate equal to or slightly less than the patient's spontaneous sleeping respiratory rate (minimum 10 breaths/min) 6
Adjust inspiratory time based on respiratory rate to provide an I:E ratio of approximately 1:2 for patients with obstructive disease 6, 7

Consider volume-controlled ventilation for difficult-to-manage patients where ensuring consistent alveolar ventilation is crucial 1, 2
Some patients who fail on pressure support may be successfully treated with volume control 2

Monitor work of breathing - higher values indicate increased patient effort and potential need for ventilator adjustment 8
If rebreathing is suspected (especially with increasing respiratory rate), ensure proper function of exhalation valves and consider increasing EPAP 1

Inadequate expiratory time for tachypneic patients can lead to air trapping and auto-PEEP 1, 6
Rebreathing can occur during bi-level pressure support, especially with increasing respiratory frequency, if EPAP is too low 1
Occlusion of exhaust ports by secretions can exacerbate hypercapnia through rebreathing 1

If the patient complains that pressures are too high, lower them to a level comfortable enough to allow continued ventilation 5
Adjust ventilator parameters such as pressure relief, rise time, and IPAP duration to optimize patient comfort and synchrony 5