Early and continuous weaning from mechanical ventilation without formal protocols in a university hospital

Introduction

There is evidence that formal weaning protocols can reduce the duration of mechanical ventilation (MV) and complications of prolonged unnecessary ventilation [1]. In our ICU we do not employ a formal protocol, but have a standard practice where patients with spontaneous respiratory efforts on pressure-controlled ventilation (PCV) have a trial of assisted spontaneous breathing (ASB). Patients on ASB with pressure support ≤ 10 cmH₂O will then have a trial of unassisted continuous positive airway pressure (CPAP) with high-flow oxygen.

Methods

A retrospective audit was conducted on 47 patients in a 13-bed general medical and surgical ICU of a university hospital. The length of time between first spontaneous breaths while on PCV and a trial of ASB was recorded. The length of time from achieving pressure support ≤ 10 cmH₂O on ASB to a trial of unassisted CPAP was recorded. A retrograde step was defined as going back on to PCV from ASB, or to ASB from unassisted CPAP. If the trial of weaning was repeated within 12 hours of a retrograde step, this was noted as a continuous attempt at weaning. Similar data were collected for subsequent retrograde steps.

Results

The median duration of MV from initiation to discontinuation was 85 hours (range 1 to 345 hours), with a median time of 37 hours (range 1 to 245 hours) on PCV and 32 hours (range 0 to 264 hours) on ASB. The median time from recorded spontaneous breaths on PCV to ASB was 1 hour (range 0 to 34 hours). Twenty-nine (62%) patients on PCV progressed on ASB without any retrograde steps. The median time from having pressure support ≤ 10 cmH₂O on ASB to unassisted CPAP was 2 hours (range 0 to 41 hours). Thirty-one (66%) patients on ASB progressed on CPAP without any retrograde steps. Forty-one patients (87.2%) had a first attempt to wean from PCV to ASB and 40 patients (85%) from ASB to CPAP within 10 hours of eligibility. Maximum delay in initiating first attempts to ASB was 34 hours, and 41 hours to CPAP. Reasons for retrograde steps included respiratory instability (n = 19), signs of poor tolerance or haemodynamic instability on ASB/unassisted CPAP (n = 18) and interventions, for example bronchoscopy, imaging, theatre, and so forth (n = 13).

Conclusion

The median duration on MV in our unit compares favourably with a large randomised controlled trial with a similar patient population [1]. Most patients had their first attempt to wean within 10 hours from eligibility. A significant number of patients may have weaned more quickly if a formal protocol was in place.