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For cleaning use warm soapy water or a 50/50 alcohol and water solution. DO NOT use any solvents.
We can answer this question by weight. For complete descriptions of all the machines please see their pages in the product catalog.
For the largest animals ranging from 80 lbs to 2000 lbs.
Some examples would be sheep, foals, horses, cows, and camels.
Model 2000 and Model 2002:
These ventilators have three different bellows available. The smallest with a range of 0 to 300 mL of tidal volume and an affective weight range form 2 lbs to 40 lbs. The next size up our adult bellows has a range of 300mL to 1600mL of tidal volume with weights of 40 lbs 220 lbs. Lastly we have our XL bellows, 1600mL to 3000mL ranging from 200lbs to 440 lbs.
Anesthesia WorkStation (AWS):
The solution for supplying both gas anesthetic delivery and ventilatory support for pocket pets, avian, exotics and laboratory animal applications in one easy to use package. Can be used for animals ranging from 150 grams to 7 kilos.
MicroVent I & II:
This ventilator operates in the very small range mice, small birds and the like, with a tidal volume from 1 to 10 CCs.
All gas anesthetics and most injectable anesthetics are respiratory depressants. As the animal reaches deeper levels of anesthesia respirations will become more depressed. This can result in the patient moving up to a lighter plane of anesthesia. The ventilator will deliver a constant supply of anesthetic gas maintaining a constant plane of anesthesia. Due to the constant delivery of gas concentration by the ventilator the patient responds more rapidly to changes in vaporizer settings and a lower vaporizer setting will maintain the same surgical plane of anesthesia. Lower vaporizer settings mean less anesthetic gas, lower cost and less environmental pollution. The ventilator will provide more control over the patient's depth and smoothness of anesthesia. In other words, because of anesthetic induced respiratory depression hypercapnia often results. The consistent ventilation by the ventilator maintains normocapnia and minimizes respiratory acidosis.
Many lectures now recommend putting all surgical patients on a ventilator. This is especially true for anything brachiocephalic, obese, geriatric, any PU or perianal surgeries where the rear is elevated and the gut is compressing the diaphragm.
In cases which require mechanical ventilation, such as thoracotomies, obese patients, critical care or emergency cases, the technician is much more valuable monitoring the patient and assisting the surgeon rather than just bagging the patient.
The ventilator may be utilized in any one of three sizes, or volume capabilities.
Extra Large 1600-3000ml
All three size clear acrylic housings are attached by placing them over the base assembly O-Ring, pushing straight down, and turning CLOCKWISE (as viewed from the top) until the tabs are locked into two of the bayonet locks. Removal is the reverse of this operation.
The ADULT and EXTRA LARGE Bellows fit on the outside ring (commonly called the bellmouth), with the first convolute over the ring. Holding the Bellows by the white top and extending and lowering the Bellows will eliminate any folds, creases, and ensure a tight seal.
The PEDIATRIC Bellows requires the use of an Adapter, P/N 000A0486, which decreases the ring size down to accommodate the smaller Bellows. The Adapter is placed inside the Base Assembly by placing it O-Ring down into the cavity and pushing straight down. This Bellows is also placed on the ring with the first convolute over the ring.
For cleaning of the Pop-Off Valve as outlined in the CLEANING & STERILIZATION section of this manual, remove the clear acrylic housing, the Bellows, and in the case of PEDIATRIC use, the Adapter, (which pulls straight up). The three red thumbscrews of the Pop-Off Valve are now exposed.
Deciding what bellows to use will become intuitive after you have used the ventilator for a little while. The rule of thumb for the tidal volume requirements of an animal is 10 to 20 ml/kg (4.5 to 9 ml/lb). This is a very wide range as a 20 kg animal could require a TV any where between 200 and 400 ml. The TV deliverable from the small bellows is 350 ml because the bellows bottoms out at that point. By the rule of thumb 350 ml / 20 ml/kg would dictate that the absolute maximum would be 17.5 kg (38.5 lbs).
Please see: Choosing the Correct Bellows Housing
You will start by selecting the proper sized bellows and housing for the patient depending on their weight. Small bellows 1 to 40 lbs, adult bellows 40 to 220 lbs, and the XL bellows will do 200 to 440 lbs.
Next you will set the mean airway pressure limit a few cmH2O above what you expect your working airway pressure to be during the case. This is a safety measure in the event that they airway pressure rises to the limit you set the machine will terminate the breath and start the exhalation.
Turn the volume control(s) all the way down to ensure you have control of the initial tidal volume delivered on the first breaths. Set the rate in breaths per minute to something that is appropriate for that particular case.
Connect the patient and turn the Hallowell Ventilator on, you will hear the low pressure alarm because you are not delivering any tidal volume. Slowly increase the volume breath by breath as you watch the airway pressure gauge rise to and appropriate airway pressure somewhere around 10 to 15 cmH2O.
You will be in the ballpark in about a minute. Now you can fine-tune your ventilator settings as you assess the patient’s needs and the information your monitoring equipment gives you.
Please see your owner’s manual for more information.
The controller, (blue box) provides the driving air from the driving gas port and out the black corrugated hose. This air is what drives the bellows in the down position INHALE, and allows the air to be exhausted in reverse out the exhaust (the chrome one) during EXHALE. This is the only air the controller supplies to the base assembly.
(The word air will be used regardless of the type of gas you are supplying to the SUPPLY GAS connection)
The controller also provides for volume control, settings for Maximum Working Pressure Limit, Rate or speed, and an INSP HOLD function, which is great for X-Ray operations.
The pressure transducer luer port on the back feeds into an electronic pressure monitoring device which controls:
Stopping the controller cycling and returning the bellows to the full up position while triggering an alarm (and LED) if the MWPL set pressure is exceeded.
Issuing a “low breathing alarm” if the INHALE pressure does not exceed 5.5cm/H2O in any cycle, and also acts as a disconnect alarm.
Ceasing the INHALE cycle if any cycle exceeds 70cm/H2O, and the controller will reset.
Bellows which are not mounted correctly will allow the patient breathing gas, mixed with anesthesia gas, to escape from under the bellows and into the clear acrylic housing surrounding the bellows exterior. This gas is exhausted through the chrome plated exhaust port at the rear of the control unit.
A properly mounted bellows retains all patient and anesthesia gas within the confines of the bellows, and normally escaping gas exits through the Pop-Off-Valve and out the exhaust port on the black base of the unit (the center port) and out of the area utilizing the scavenging system.
The scavenging system should be at a negative pressure, thus removing all exhausted patient and anesthesia gases from the area.
As part of the quality control process and to ensure proper operation of your ventilator, Hallowell EMC has cleaned and adjusted the base and Pop-Off-Valve assemblies and has operated the unit in a “user setup” with a test lung for 48 hours without leaks or other anomalies.
The symptom mentioned is generally a result of a low-pressure value of the Pop-Off-Valve due to contamination:
The Pop-Off-Valve (POV) can be located by removing the clear acrylic housing by twisting counter clockwise (from the top) until the locking tabs are revealed, and pulling upward until free. Removal of the adult bellows requires only a gentle tug vertically. The pediatric bellows is removed in much the same manner, and also requires the removal of the adaptor, (shaped like a bell mouth) by pulling straight up. The POV can now be seen as the round black plastic device held in place by three red thumbscrews. Remove the thumbscrews and the POV.
The POV consists of two plastic housings, a rubber diaphragm, and a stainless steel puck, which rests on a plastic seat. Generally, after repeated use with patients, a breathing condensate will form on both the puck and seat. This will appear as a ring on the puck, and a shiny, glazed residue on the seat. This condensate can be removed from both surfaces with the gentle use of a cotton swab moistened in isopropyl alcohol and dried with clean air. Assembly is the reverse of the above.
THEORY OF OPERATION
During the end of the Expiratory Phase of the ventilator cycle, when the bellows reaches the top of the housing, the patient circuit gas exits through the POV and out the exhaust port of the unit base. This is a controlled escape of air, and is designed to hold the patient circuit system to a PEEP pressure of 1.8 cmH2O minimum to 2.6 cmH2O maximum.
By controlling the weight and surface finish of the stainless puck, as well as the thickness and durometer hardness of the rubber diaphragm, this pressure condition can be maintained.
Cleaning operations may be scheduled on an individual basis, depending on condensate build up, frequency of use, and length of down time between operations.
The base houses the bellows, clear acrylic housings, adaptors, and the Pop-Off-Valve (POV). There are three connections for the drive gas tube (black), the breathing system tube (translucent), and the exhaust of anesthetic gases through your SCAV system.
The Pop-Off valve is technically a controlled leak, which provides the bellows with enough pressure (using the anesthesia air it gets from the anesthesia machine). This pressure is maintained at 1.8-2.6 cm/H2O, enough to keep the bellows and in turn the patient lungs inflated during the end of the EXHALE cycle. During the INHALE cycle, the POV seals shut to allow the pressure to build and inflate the patient lungs. In between cycles, any excess anesthesia air is allowed to escape out the center exhaust port of the base and into the house SCAV system.
If you run into the condition that the bellows is not maintaining a full inflation condition try these steps:
Turn the controller OFF.
Ensure that the 50PSI air (or oxygen) is ON to the anesthesia machine.
Verify that the patient connector is occluded or replaced with a breathing bag.
Set the flow meter on the anesthesia machine to 0.5 l/min
Allow the system to “fill” with air (a few minutes)
If the bellows partially fills, or rises to the top and then decreases slightly, remove the hose on the EXHAUST PORT OF THE BASE (SCAV system) and hold your finger over the port on the base to seal it. If the bellows continues rising to a full inflated condition, the POV is dirty and requires cleaning or other maintenance.
The two surfaces which control the pressure maintained by the POV are the stainless steel puck, on the underside of the POV, and the POV seat, the surface upon which the puck sits. Both of these surfaces MUST be clean and free of fibers, dirt, and condensate residue.
For the puck, you can use 91% isopropyl alcohol and a cotton swab to clean, blown dry with clean compressed air.
For the seat, (the object that looks like a black chimney), you can also utilize the alcohol and swab, but since this surface is made of ULTEM (a high temperature plastic) extreme care must be used to not scratch or dent this surface. The top surface of the seat should be matte finish, black or gray in color, and with no shiny spots.
The settings vary with the setup, They especially depend on what you use for an ET tube. You can start out by opening the PAW valve on the side of the ventilator completely.
Connect the intubated mouse to the breathing system with the ventilator off and oxygen flowing at the slowest rate you feel comfortable running through your vaporizer; they all work differently at low flow rates.
Slowly start to close the PAW valve until you observe the mean airway pressure you desire, generally around 5 to 7 cmH2O.
Ensure that the Amplitude is turned all the way down and turn on the machine in IPPV mode. Slowly bring the amplitude up until the oscillation of the airway pressure increases as desired, perhaps down to 0 and up to 10.
You will need to ventilate a few mice, observe them, check a blood gas after a while to see how you are doing and adjust the settings accordingly.
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