Original Research Article



Short Report

A 3 year retrospective audit on the use of non invasive positive pressure ventilation (NIPPV) via the Oxylog 3000 transport ventilator during aeromedical retrievals.

Abstract

Objective: To describe the overall clinical efficacy of non invasive positive pressure ventilation (NIPPV) using the Oxylog 3000 transport ventilator by aeromedical retrieval teams from the Queensland Section of the Royal Flying Doctor Service of Australia.

Method: Over a 3 year period, patients identified in clinical transport records to have NIPPV via the Oxylog 3000 Transport Ventilator during aeromedical transfer were systematically reviewed on the clinical indication and side effects.

Results: A total of 29 patients were identified to have had treatment with non invasive positive pressure ventilation (NIPPV) during aeromedical retrieval. 3 patients suffered serious adverse effects of cardiorespiratory arrest during treatment. The main reported adverse event was intolerance of the face mask. There were no documented episodes of vomiting.

Conclusion: The use of non invasive positive pressure ventilation (NIPPV) via the Oxylog 3000 transport ventilator during aeromedical retrieval is safe and well tolerated. The application and management does not differ from standard hospital based practice.

Keywords: non invasive; ventilation; aeromedical; retrieval; Oxylog 3000

Financial disclosures: None declared

Introduction

Although published research and guidelines exist for provision of non invasive positive pressure ventilation (NIPPV) in ground based ambulance services (1,2,3), the optimal strategy for the use of NIPPV during aeromedical transport of patients suffering acute respiratory distress remains unclear. The Queensland Section of The Royal Flying Doctor Service (RFDS) of Australia’s services an area the combined size of Germany, France, Spain and United Kingdom.The Oxylog 3000 transport ventilator (Drager Medical, Germany) has been in operational use on aeromedical missions since early 2005. A RFDS (Qld Section) clinical practice guideline to provide non invasive positive pressure ventilation via the Oxylog 3000 transport ventilator was developed and implemented in 2008. This study sought to review the use of the NIPPV during aeromedical retrieval in terms of safety and appropriate patient selection.

Materials and Methods

Between January 2008 and January 2011, the RFDS Queensland bases transferred 324 patients with a circulatory or respiratory diagnosis as per The International Statistical Classification of Diseases and Related Health Problems, Tenth Edition, Australian Modification (ICD-10-AM). From the sourced charted a screening process to identify for use of non invasive positive pressure ventilation via the Oxylog 3000 transport ventilator occurred. For the purpose of this audit, the mode of application was via a face mask applied positive pressure using either positive end expiratory pressure alone or in combination with positive inspiratory pressure. The records were finally reviewed for primary diagnosis, basic patient demographics and adverse events associated with NIPPV.

The severity category of the sample group was rated either critical or high dependency. This clinical severity indicated a crew configuration of a medical officer and flight nurse escort team. This team ensures the provision of critical care interventions including mechanical ventilation and/or circulatory support infusion based therapies.

Ethics approval for the study was granted from Queensland Health Human Research Ethics Committee (Cairns).

Results

Demographics and Diagnosis- Refer to Table A

From the 324 patients with a circulatory or respiratory ICD-10-AM code, twenty nine (29) retrieval cases were identified to have required non invasive positive pressure ventilation during the study period. The average age of the study group was 66 years old. There were 13 females (45%) and 16 males (55%). Twenty eight percent (28%) or 8 patients had a primary retrieval diagnosis of pneumonia with the second most frequent diagnosis being chronic obstructive pulmonary disease (COPD) at 6 (20%) patients. Combined, the diagnoses of heart failure or pulmonary oedema accounted for 7 (24%) patients. Two patients (7%) was documented to have a primary diagnosis of severe asthma which responded favourably to the NIPPV and standard medical treatment prior to boarding the aircraft.

Adverse events – Refer to Table B

From the data collected and audited, the most common problem encountered was a combination of fatigue and intolerance of the NIPPV face mask (6 patients or 19%). A total of three (3) patients suffered a cardio respiratory arrest (1 cardiac and 2 respiratory arrest) but were all successfully resuscitated during the retrieval. There was only one case of hypotension (3%) yet no cases of vomiting.

Discussion

The use of non invasive positive pressure ventilation via the Oxylog 3000 transport ventilator was generally well tolerated and safe. From the clinical information extracted from the medical documentation, the three (3) patients that suffering a cardiorespiratory arrest should not have been trialled on this therapeutic modality. In retrospect worsening respiratory distress and increasing fatigue were evident and traditional intubation would have been appropriate. In other words the NIPPV was initiated too late in the course of the illness in these patients and persisted with for too long.

The application of non invasive positive pressure ventilation in the aeromedical setting is no different to application in hospital. Appropriately selected patients with pneumonia, exacerbations of chronic obstructive airways disease and cardiogenic pulmonary oedema ensure that no specific issues with the application and management throughout aeromedical transfer should occur. Inappropriate patient selection either in the hospital or the aeromedical environment leads to disastourous results such as respiratory and cardiopulmonary arrest.

The low rate of hypotension and absence of vomiting in the sample group is reassuring.

In conclusion, we found the ability to provide NIPPV during retrieval and inflight to be useful and effective. It should reduce the need to resort to measures such as tracheal intubation and general anaesthesia in this setting.

References

1) L Ducros et al. CPAP for acute cardiogenic pulmonary oedema from out-of- hospital to cardiac intensive care unit: a randomised multicentre study. Intensive Care Med, 2011,37:1501-1509.

2) J Daily, H Wang. Noninvasive Positive Pressure Ventilation: Resource document for the National Association of EMS Physicians position statement. Prehosp Emerg Care, 2011, 15:432-438.

3) W Schmidbauer et al. Early prehospital use of non-invasive ventilation improves acute respiratory failure in acute exarcebation of chronic obstructive pulmonary disease. Emerg Med J, 2011, 28(7) :626-7.

Table A- Primary Diagnosis

|Diagnosis |Heart failure |Pulmonary oedema|Asthma |COPD |Pneumonia |Respiratory |Pulmonary |

| | | | | | |failure/distress |embolism |

|Number of patients|3 |4 |2 |6 |8 |4 |2 |

(COPD = chronic obstructive pulmonary disease, AMI = acute myocardial infarction)

Table B- Documented Adverse Effects

|Adverse effects|Intolerance of mask |Fatigue |Vomiting |Hypotension |Respiratory arrest |Cardiac arrest|Total adverse |

| | | | | | | |events |

|Number of |4 |2 |0 |1 |2 |1 |10 |

|patients | | | | | | | |

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