Abstract
Background: Many successful therapies developed for human medicine involve animal experimentation. With competition for public research funding and career advancement opportunities, animal studies focused on the translational potential may not sufficiently document unexpected outcomes. Such studies often have hastily developed methods with ad hoc modifications including the use of additional animals, leading to considerable amounts of idle, unprocessed data that could be used to advance veterinary science, or to refine the base animal model. Sheep, for example, are poorly understood models of intensive care and therefore, any experimental data arising from them should be interpreted with care. The hypothesis was that there is little information describing the development of methods of physiological data processing in multifaceted sheep models of intensive care and the author aimed to develop a suitable data processing method and to analyse the data, once processed.
Methods: Data from 19 adult mechanically ventilated ewes undergoing intensive care in a previous study evaluating a form of extracorporeal life support (treatment) for acute lung injury were used to develop a comprehensive method for processing manual and electronically gathered clinical observations. Eight sheep were injured by acute smoke inhalation prior to treatment (injured/treated), while another eight were not injured but treated (uninjured/treated). Two sheep were injured but not treated (injured/untreated), while one received room air instead of smoke as the injury, and was not treated (placebo/untreated). The data were then analysed for 11 physiological categories and compared between the two treated groups.
Results: The analysis revealed that compared with the baseline, treatment contributed to and exacerbated the deterioration of pulmonary pathology by reducing lung compliance and PaO2/FiO2 ratio. The oxygen extraction index changes mirrored those of the PaO2/FiO2 ratio. Decreasing coronary perfusion pressure predicted the severity of cardiopulmonary injury.
Conclusions: These novel observations could help in understanding similar pathology such as that which occurs in smoke inhalation animal victims of house and bush fires. A similar data processing method could be used when evaluating the effectiveness of other clinical interventions such as potentially reversible aspiration pneumonia secondary to tick paralysis in veterinary patients.
List of abbreviations
- ANOVA
- Analysis of variance
- C24H
- Control experiment for 24 hours
- CaO2
- Arterial oxygen content
- CCO
- Continuous cardiac output
- CI
- Cardiac index
- CO
- Cardiac output
- CPP
- Coronary perfusion pressure
- [Hb]
- Haemoglobin concentration
- CVP
- Central venous pressure
- DO2I
- Oxygen delivery index
- E24H
- Extracorporeal life support for 24 hours
- E2H
- Extracorporeal life support for 24 hours
- ECLS
- Extracorporeal life support
- ECMO
- Extracorporeal membrane oxygenation
- etCO2
- End tidal carbon dioxide tension
- FCOHb
- Fraction of carboxyhaemoglobin
- FiO2
- Fraction of inspired oxygen
- FO2Hb
- Fraction of oxyhaemoglobin
- HR
- Heart rate
- LVSWI
- Left ventricular stroke work index
- MAP
- Mean arterial pressure
- MERF
- Medical Engineering Facility
- MetHb
- Methaemoglobin
- MPAP
- Mean pulmonary artery pressure
- O2EI
- Oxygen extraction index
- PaO2
- Arterial partial pressure of oxygen
- PAP
- Pulmonary artery pressure
- pCO2
- Partial pressure of carbon dioxide
- PCV
- Packed cell volume
- PEEP
- Positive end-expiratory pressure
- pO2
- Partial pressure of blood oxygen
- PVRI
- Pulmonary vascular resistance index
- QUT
- Queensland University of Technology
- QUT-MERF
- Queensland University of Technology Medical Engineering Research Facility
- SC24
- Smoke control experiment for 24 hours
- SD
- Standard Deviation
- SE24H
- Smoke injury and extracorporeal life support for 24 hours
- SEA24H
- Smoke injury, stored blood transfusion and extracorporeal life support for 24 hours
- SEF24H
- Smoke injury, fresh blood transfusion and extracorporeal life support for 24 hours
- SPO2
- Blood oxygen saturation
- SV
- Stroke volume
- SVI
- Stroke volume index
- SvO2
- Mixed venous oxygen saturation
- SVR
- Systemic vascular resistance
- SVRI
- Systemic vascular resistance index
- TPP
- Total plasma protein
- UQ
- The University of Queensland