Assembly and Troubleshooting of IPPB Equipment

IPPB equipment varies primarily varies with regard to the number of drive lines. The two most commonly used IPPB machines, the Bird respirators and the Bennett respirators, have different drive line configurations. Most "universal" disposable IPPB circuits are designed to fit either one. The following instructions refer to this type of circuit.

Assembly

1. Locate the attachments for the main breathing hose, exhalation valve drive line, and nebulizer drive line on the respirator. The main breathing hose will be a large-bore tube, and there will be one or two smaller connections for the drive lines. If there are two connections, they will not be the same size to avoid mixing up the drive lines.

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a. Bennett PR-1 and PR-2: These have three connections on the bottom of the respirator: one large-bore tube connection for the main breathing hose and two small lines. The larger of these two lines is to drive the nebulizer; the smaller is the exhalation valve drive line.

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b. Bird Mark 7 (and other Bird Mark models): These have two connections on the right side of the machine (the pressure side): a large-bore connection for the main breathing hose and one small connection for a single drive line. This line splits at the nebulizer to power both the nebulizer and the exhalation valve. A splitting device fits over the connection on the nebulizer. The drive line connects to this device, and the short piece of tubing connects to the exhalation valve.

2. Attach the tubings to the appropriate connections on the respirator, making sure all connections are tight. The connections and tubings are sized so that only the correct tubing will fit on the connector.

3. Attach the tubings to the nebulizer and exhalation valve assembly. Again the tubings and connections are sized to prevent incorrect assembly.

a. Bennett PR series IPPB Machines: These have a connection for the large-bore tubing, which is usually attached before being packaged; a connection for the larger of the small-bore tubings on the nebulizer; and a connection for the smaller on the exhalation valve.

b. Bird IPPB Machines: These have a connection for the large-bore tubing, which is usually attached before being packaged, and a connection on the nebulizer for the line splitter. The small drive line is attached to the line splitter. The short piece of tubing on the line splitter connects to the exhalation valve.

4. Attach the patient connection to the nebulizer assembly. Most disposable circuits come with a six-inch length of large-bore tubing which provides a reservoir for medication and connects the mouthpiece or other device to the nebulizer.

5. Connect the machine to a 50 psig gas source with high-pressure hose.

6. Set initial parameters.

a. Pressure limit: On both types, the pressure limit is determined by the operator and should be set according to the physician's order or department protocol, usually between 10 and 20 cmH2O

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b. Flow:

Bird: The numbers on the flow control knob (5) have no units. It is generally recommended to set the flow at 15, or midrange on the Mark 7a.

Bennett: There is no direct flow control on the Bennett PR series. Set the Peak Flow fully counterclockwise (open) and the Terminal Flow fully clockwise (off).

c. Sensitivity: This should be adjusted so that the patient does not have to work to initiate a breath, yet the machine does not self-trigger into inspiration. Initially, adjust the sensitivity so that no more than -2 cmH2O is required to trigger a breath. On the Bird, the numerals (1) indicate degree of sensitivity; with the lower the number, the more sensitive the machine. It is recommended that this be initially set between 10-15. On the Bennett PR-2, the sensitivity control is labeled with an arrow to indicate increased sensitivity. Initially turn the control fully counterclockwise (off) and adjust to patient effort; the greater the sensitivity, the easier it is to trigger a breath.

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d. Air mix:

Bird: The air mix control should be OUT (engaged).

Bennett: The air dilution control should be pushed IN (on).

e. Rate controls: These allow the respirators to be used as ventilators and have no use in routine IPPB therapy. Bird: Expiratory time control should be completely off. Bennett: Rate and expiration time controls should be turned completely counterclockwise (off).

f. Negative pressure: These are found on the PR-2 and the Bird Mark 8. They have no function in routine IPPB therapy and should be completely off.

g. Inspiration nebulizer control: Found on the Bennett respirators, this control should be set about one half turn counterclockwise (on).

7. Place the ordered medication in the nebulizer cup. Manually trigger the machine and check nebulization output. Adjust the expiration nebulizer control on the PR-2 until mist is just visible coming out of the mouthpiece.

8. Instruct the patient on the machine's use.

9. The key to successful IPPB therapy is careful patient instruction and adjustment of the machine once therapy has begun based on exhaled tidal volumes and patient's tolerance.

Troubleshooting

1. If the machine won't trigger on:

a. Check sensitivity control
b. If the manometer needle is not moving, check for large leak
c. Check gas supply for 50 psig.
d. Check to see if the breathing valve is sticking (should manually activate with ease)

2. If the manometer registers high level of negative pressure after the machine triggers on:

a. Inadequate flow may be causing flow starvation. Increase the flow rate
b. The patient is actively inhaling. Coach the patient to passively allow the machine to fill the lungs.

3. If the machine won't cycle off:

a. Check for system leaks (exhalation valve, lines, connections, nebulizer, patient connection. Tighten all connections. Coach the patient to keep a tight seal with the lips or use a lip seal.
b. Check for sticking breathing valve
c. Add terminal flow gradually to compensate for small leaks (Bennett).

4. If the machine auto-triggers on, check for the following:

a. Too sensitive. Adjust the sensitivity control to make ii more difficult to initiate a breath.
b. Rate control on. Make sure the expiratory timers are off.

5. If the pressure manometer needle is very slow to return to baseline, check for the following:

a. Sticking valve
b. Retard device in place
c. Patient forcefully exhaling. Instruct the patient to passively exhale

6. If there is very little gas flow, check for the following:

a. Gas source for 50 psig.
b. Inlet filter dirty.
c. Occluded breathing hose.
d. Gas leak.

7. If the machine cycles off prematurely:

a. Check for/correct any circuit occlusion
b. Flow may be too high. Adjust the gas flow to a lower setting (Bird)
c. Patient may be "stuffing" tongue into mouthpiece or "blowing" back into machine. Instruct the patient in the proper use of the machine again.
d. Pressure may be too low to achieve desired tidal volumes. Set pressure higher as needed

8. If there is prolonged inspiration:

a. Check for leaks in the circuit and around the mouthpiece.
b. Increase the flow rate (Bird).
c. Decrease pressure, remembering this will decrease tidal volume.
d. Check that the Peak flow control is fully on (Bennett).

9. If there is no mist coming out of nebulizer, check for the following:

a. Gas flow to nebulizer.
b. Adequate solution in nebulizer.
c. Nebulizer positioned properly.
d. Capillary tubes open.
e. Nebulizer jets opened.

Modified from Blazer, C: Quick reference to respiratory therapy equipment assembly and troubleshooting, St. Louis, Mosby, 1994.