Case 3 – Mechanical Ventilation
I recently encountered a challenging clinical case (consented to share here). In the case a patient required a one hour transfer between two hospitals. The young patient had an recessive inherited chronic lung disease and was immunosuppressed They had presented to their local hospital after developing progressive severe shortness of breath over a 24 hour period. This ultimately resulted in the requirement of Rapid Sequence Intubation (RSI) and Mechanical Ventilation. In the Intensive Care Unit (ICU) at the small district hospital the patient was found to be difficult to ventilate on their Puritan Bennett ventilator (pictured).
The Puritan Bennett
Even this high level ICU ventilator was only adequate to maintain a CO2 of around 80 mmHg (with a similar corresponding End Tidal Co2 measurement). In this case there was a significant acute respiratory acidosis and the respiratory rate was set to 30/min in the referring ICU.
On transfer to a portable ventilator, the Oxylog 3000, the CO2 started to gradually rise and the acidosis worsened… Although I was familiar with the device from working in Emergency Departments in the past there appeared to be a significant difference the the set volumes and the received volumes in this (<30kg) Adult patient.
The Oxylog 3000
Emergency Transport Ventilator
The repeat ABGs lead to a CO2 of >100 and worsening acidosis with a conservative lung protective strategy:
Blood Gas 1
With sedation, paralysis and increased minute volume (from respiratory rate) as well as changing the I/E ratio there was some improvement in the blood gas. After planning ongoing transport from the small peripheral hospital to the large tertiary hospital the patient remained stable throughout this process.
While the Oxylog 3000 ventilator continually alarmed due to high peak pressures the measured plateau pressure remained around the 30cmH20 mark. At this point a case conference was initiated and we decided that it was safe to transport the patient with these pressures. In addition, with the appropriate changes described above the ventilation appeared better from the end of the bed and the blood gas improved (with a Co2 around the 90 mark and pH of around 7.1).
A further blood gas was taken on route (in the helicopter) using an I-STAT machine:
Blood Gas 2
The patient improved over the next 24 hours and it was suspected (with hindsight) that she might have Bronchiolitis Obliterans Syndrome Complicating her Lung Transplant.
This case and similar presentations in the past have left me wondering the best ways to ventilate difficult patients in the ED and Pre-hospital environment without high-level ventilators and the immediate expertise of ICU physicians. At the outset I would suggest that early consultation in these cases is extremely useful as is a process of continuous reassessment of the patient from the end of the bed.
In this case it was interesting to note a degree of discrepancy between the settings of the machined and what the patient received. The initial measured lung protective strategy (6-8ml/kg) with a rate of 20/min was inadequate in terms of the measured and observed volumes generated by the Oxylog 3000. Constant reassessment was required and ultimately successful in achieving adequate albeit not optimal ventilation Another issue was that we used the adult hosing system given the age of the patient, although the size of the patient may have indicated using the paediatric apparatus. I would be interested to hear others comments about this – the manuals suggests that paediatric circuits must be used in children but don’t suggest a weight cut off. I will contact a Drager representative to find out their recommendations (see discussion below).
[vimeo http://vimeo.com/37938870 w=640&h=385]
In conclusion, when using transport ventilators knowledge of your machine, adequate analgesia/sedation, constant reassessment and early expert advice can aid in achieving adequate ventilation in difficult cases.
(1) Slutskey A et al. Mechanical ventilation: lessons from the ARDS Net trial. Respir Res. 2000; 1(2): 73–77.
(2) The Acute Respiratory Distress Syndrome Network: Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342:1301–1308
(3) Shirley P et al. Retrieval medicine: a review and guide for UK practitioners. Part 1: Clinical guidelines and evidence base. Emerg Med J. 2006 December; 23(12): 937–942
(4) Oxylog Manual (accessed April 2013) http://www.draeger.com/media/10/08/29/10082917/9066099_Oxylog_3000_plus_EN_170510.pdf
(5) Emergency Care Institute Introduction Video – http://www.ecinsw.com.au/oxylog_ventilators