Small Animal Ventilator

Ferret On Vetronics Ventilator

Medical Engineering distributes the new Vetronics Small Animal Ventilator which provides a reliable method for controlling ventilation in small patients by employing a T-piece breathing circuit.

This ventilator requires that all patients be intubated as the unit uses the pressure of the incoming gases as the driving force to inflate the patient's chest while at the same time continuously monitoring airway pressure.

Medical Engineering added this relatively inexpensive product to our line because it addresses two major needs that we identified for exotic species veterinarians.

First, it allows a practice which currently is without a ventilator to perform any open chest procedure which would have previously been referred to another practice or university. This ventilator can increase your revenue significantly with a relatively small investment in equipment!

Second, it permits proper anesthesia protocol to be practiced rather than simply immobilizing a patient with an injectable anesthetic where there can be significant uncertainty as to the dosage needed for the patient. It also eliminates the expense of a technician to bag the patient during the procedure. This ventilator improves the quality of medicine practiced while reducing the cost of the surgery!

How the Ventilator Works

Once the airway pressure reaches a user-defined limit in the range of 1 to 40 cm H2O, the expiratory valve opens, allowing the patient to exhale. There is then a timed delay (again user-controlled) before the valve closes and inspiration begins again. The delay time can be any value between 1 and 30 seconds. 

When ventilating very small creatures, however, care must be taken to set the oxygen flow rates to values in the range of 50 to 250 ml/min.  If the oxygen flow rate is set at very high rates, it may be possible to overpressure very small patients such as mice or small birds, during the period the valve is shutting off flow after reaching the pressure setpoint.

The unit thus behaves as a simple pressure cycled device. The ability to vary the maximum airway pressure and the expiratory delay means that a wide variety of animals may be ventilated easily and safely with this unit.

IPPV

By means of a valve by-pass switch the unit may be used as a normal T-piece assembly until such time as IPPV is needed. In this way unaided respiration may occur right up to the point of the chest being opened or the administration of muscle relaxants. Status indicators on the front of the unit show clearly the valve position i.e. open or closed to indicate expiration or inspiration respectively.

The front panel has a clear 2-digit display, which provides two functions: At rest and during the expiratory phase the display shows the maximum inspiratory pressure allowed before the valve opens; and During the inspiratory phase the display shows the difference in pressure between the airway pressure and the target pressure. This is helpful to identify system leaks or causes of insufficient ventilation.

Technical Information On Calculating Trigger Values

Due to the wide diversity of species this Ventilator was designed for, it is difficult to produce a formula for calculating trigger value settings. In these cases proceed as follows:

Start IPPV at a 3cm H20 trigger value every 1-2 seconds. The short breathing interval is only temporary but helps to quickly assess breathing depths (once set, the frequency can be reduced to normal). Increase the pressure setting until normal chest excursions are seen.  Remember to use low oxygen flow rates (50 to 250 ml/min) for the smallest patients such as finches and white mice.

The pressure setting required will depend upon the weight of the animal, degree of obesity, and functional resistance in the airway circuit. Functional resistance is higher in very small animals and a higher trigger pressure setting will be needed in these.

This usually takes a matter of only seconds after gaining experience in the operation of the ventilator. Adjust the incoming gas flow rate to control the duration of inspiration; faster flow rates will give shorter inspiratory times. Again, with a little practice this can be assessed and set within seconds.

Feel free to contact Keith Simpson at ksimpson@vetronic.co.uk or visit his web page at www.vetronic.co.uk.

Keith Simpson qualified from the Bristol University Vet School in 1986 and since that time has been in first opinion veterinary practice. For the first 4 years he worked in a mixed veternary practice but since 1990 has been almost exclusively a small animal clinician. Keith is also a professional electronics engineer and a member of the Institute of Incorporated Engineers which he joined in 1994.

Suggested Values for Ventilation of Some Exotic Species

There is no formula for determining the pressure setting of the Vetronics ventilator since the pressure and resulting volume are dependant fully on the compliance of the respiratory system of the animal being ventilated.

Some average values are provided as guides. There is no danger in using the upper value in any of the ranges provided, but the operator must assess the degree of ventilation by observation and adjust for normal chest excursions or limb movements.

Iguanas/lizards Small/ thin 5cm H2O -- large/fat 10cm H2O

Set pressure for normal chest excursion.

Snakes Small 6 cm H2O -- large 10cmH2O

Set pressure for normal chest excursion. Note that the long trachea may require a higher pressure setting than above to achieve full ventilation.

Tortoises/turtles Normal range 8 -- 10 cm H2O

Set the pressure to produce small outward movements of the hind limbs as an indicator of intra-coelomic pressure.

Birds Tracheal or air-sac ventilation. Normal range 4 -- 12 cm H2O

Set the pressure for normal chest movements. In use, observe the patient before induction and mimic the respiratory rate and movements during anaesthesia.

Specifications

  • Size of animal: Up to 22 lbs. (10 Kg) and down to 10g.
  • Anesthetic Apparatus Configuration: Standard T-piece with Halothane/N20/02 mixture
  • Mode of Operation: IPPV by outlet occlusion
  • Preset Trigger Range: 0 - 40 centimeters water pressure
  • Resolution: 1 centimeter water
  • Expiratory Phase Range: 1 to 30 seconds
  • Respiratory Rate Range: 2 to 60 breaths per minute (depending on inspiratory flow rate)
  • Supply Voltage: 100-240 volts 50/60 Hz AC only
  • Power Consumption: 60 VA
  • Rear Panel Fuse Rating: 1 AMP 250 Volt Slow Blow Only

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For more information:
Medical Engineering & Development
4910 Dancer Rd
Horton, Mi 49246 US
Email: info@med-engrg.com
(800) 784-9060

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