The study evaluates changes in Pulmonary and extra-pulmonary mechanics in pigs with IAH (standard 12 mmHg pneumoperitineum for laparoscopic surgery) and correlates it with Dynamic CT images.
Obviously the n will depend on your sample size calculations that again depends on your endpoint, expected difference and expected standard deviation. You may want to consider performing a pilot study with 3 animals to be able to do a decent sample size calculation.
If possible I suggest a "trigger free" anesthesia as pigs are more susceptible to getting malignant hyperthermia. So I would avoid inhalational agents.
Dr. Lionetti, Dr. Regli, thank you for your answers. You posted very good advice.
Our study involves ventilating for an hour healthy pigs, establish a 15 mmHg Pneumoperitoneum and try some new experimental diagnostic devices. It's no model for ARDS. Do you think we can expect such a high mortality? Body temperature can be controlled with forced air blanket and we'll choose a PaO2/FiO2 around 0.3-0.5.
Also we are planning on managing hemodynamics guided by VVS and/or PCP (Wedge). We consider it a valid method. I'm very interested in your opinion on this.
I would not expect a high mortality as you are not using an ALI/ARDS model. The problem with experimental studies is that mortality is that not predictable but you still have to factor this in your planning. Depending on your ethics committee they can go ballistic if you say that deaths can occur because they think you are inexperienced.
You may have a good run through your experiment and no deaths occur or you suddenly find pigs dying unexpectedly which can be due to numerous things. Once we experienced a few deaths and found some animals diseased in autopsies.
If everything goes well you will be able to ventilate them for several hours.
I dont understand how you want to control P/F ratio when using healthy lungs.
Sorry for that. It should have said FiO2, not PaO2/FiO2.
Your experience is very helpful we'll definitely have it into account.
We have been mechanically ventilating pigs in our lab for many years. We can ventilate pigs for up to 48hrs without a significant clinical injury. We can also apply preemptive protective ventilation and actually prevent the development of ARDS in septic animals. I have attached our most recent papers for your review.
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