Low Peak Inspiratory Pressures (PIP) during Adaptive Pressure Control (APC) may be a sign of distress in patients with increased inspiratory efforts (e.g. high metabolic rate, sepsis, and hypercapnea) [1], or may be a sign that the patient is ready for spontaneous breathing trials.
In the patient that is not in distress and the PIP is low (≤ 15 cmH20) consider evaluation for liberation. If the PIP is low one can presume that the patients’ pulmonary mechanics have improved or within the normal range and that the workload imposed by low compliances or high resistances have decreased.
Example Case
80 female patient with the following ventilator settings:
Mode- APC, Rate- 12, Vt- 500, Fio2- 35%, PEEP- +5 cmH2O
Discovered from the ventilator patient assessment that the patient’s PIP was only 13 cmH2O and the patient was resting comfortably. At this institution spontaneous breathing trials are performed with CSV-PS, Pressure Support of 7 cmH2O & a PEEP +5 (PIP total 12 cmH2O).
The measured PIP over the previous 48 hours was a ~ mean of 13 cmH2O.
This was significant, the patient was basically on the same control pressure as what this facility does SBT’s on, indicating that the patient should have been weaned or liberated 48 hours earlier.
After this finding the patient was immediately placed on a Trach collar trial. The trial was successful with no complications and the patient was transferred to a general medical floor within 48 hours.
Conclusion
Low PIP during APC ventilation should always be evaluated further for the potential for liberation from mechanical ventilation or the need for adjusting ventilator settings to decrease the work of breathing.
[1] The Problem With Adaptive Pressure Control Modes of Ventilation: a Case Study.