Adjusting the Small Animal Bellows - Step-by-Step Guide

Step-by-Step Guide: Adjusting Small Animal Bellows

1. Initial Setup:
   • Ensure you have a functional small animal ventilator setup with a flow control and bellows.
   • Set the flow control to a desired level, such as 5 liters per minute.
   • Adjust the bellows to approximately three-quarters of its full capacity.
2. Check PEEP:
   • Observe the gauge reading for PEEP (Positive End-Expiratory Pressure) in centimeters of water.
   • The target PEEP range is usually between 5 and 7 centimeters of water.
3. Check for Bellows Leak:
   • Turn the flow control knob all the way down to zero.
   • Monitor the bellows to ensure it stays steady and does not drop. This indicates a good seal without leaks.
4. Adjusting the Bellows:
   • If you suspect a leak or need to adjust the bellows, follow these steps:
     • Loosen the four knobs on the back of the bellows and remove them.
     • Use a three-eighths-inch wrench to loosen the nut on the back of the bellows' adjustment rod.
     • Counterclockwise rotation loosens the nut, enabling adjustments.
5. Determining Adjustment Direction:
   • Turn the adjustment rod clockwise to open the bellows more (increasing the leak).
   • Turn the adjustment rod counterclockwise to close the bellows (decreasing the leak).
6. Adjustment Process:
   • Begin with small adjustments, as they can have a noticeable effect on the bellows' performance.
   • Make minor adjustments to the rod's position to achieve the desired level of sealing.
7. Checking Bellows Suction:
   • While adjusting, test the bellows suction by gently pulling it up.
   • You should feel resistance indicating a proper seal; minimal resistance suggests a potential leak.
8. Tightening the Nut:
   • Once the desired adjustment is reached, tighten the nut on the back of the adjustment rod.
   • Avoid overtightening to prevent damage.
9. Reassembly:
   • Reattach the bellows onto the ventilator.
   • Tighten the four knobs on the back of the bellows evenly.
10. Testing the Adjusted Bellows:
    • Reconnect the hose to the back of the bellows.
    • Fill the bag and the bellows to observe if the bellows drop when the flow control is turned down to zero.
    • Verify that there are no significant leaks and that the bellows maintain their position.
11. PEEP Adjustment Verification:
    • Set the flow control to the desired level (e.g., 5 liters per minute).
    • Observe the gauge reading for PEEP.
    • Adjust the bellows' position if necessary to achieve the target PEEP range.
12. Final Checks:
    • Ensure that the bellows don't drop with the flow control at zero.
    • Verify that the PEEP is within the desired range (5-7 centimeters of water).
13. Completion:
    • You have successfully adjusted the small animal bellows to ensure a proper seal and achieve the desired PEEP level.

Note: Adjustments may require multiple iterations to achieve the desired outcome. Always prioritize safety and careful adjustments to prevent equipment damage.