Question: AMBU vs. Ventilator

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Specializes in Critical Care.

Hi,

I've been in the ICU for almost a year now, and I recently came across a concept that I am not clear on.

When a ventilated patient's oxygen saturation starts dropping, or if a patient is experiencing respiratory arrest, an important part of our interventions is to immediately disconnect the ETT from the ventilator and connect an AMBU-bag to manually ventilate.

I understand that this is to have more control over the pressure and rate so that we can adequately perfuse the lungs. I am simply not sure how that is the best method, though. It seems to me that a mechanical ventilator would be able to have much more control over a pressure through PEEP/vT.

I guess what I'm asking is: how is AMBU still the best method vs. a mechanical breathing apparatus that can be 'tweaked' to any specification? I understand that before an RT arrives, it would not be appropriate for nurses to try and mess with the settings, so we simply bag. However, once the RT arrives, I believe that's their first move too.

I apologize in advance if I'm a little incorrect about some of this. I'm still trying to completely grasp all of the RT components to the ICU! Hopefully my question makes sense to someone.

If an RT sees this, perhaps if you could briefly compare the difference in pressures between AMBU and typical vent. modes that may clear it up.

Thank you!

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You can read the pressures on the vent, but you can't read them on the bag. :) But an educated hand can feel whether there's an obstruction, when the vent only says "ALARM! PRESSURE EXCEEDED!"

Other than that, I think that if you can't find any info on this in the literature, it would make an interesting study. Another one of those, "Why do we always...?" things. There might be a good reason, or it might just be habit. Do a lit search on Google Scholar and see!

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Specializes in Nurse Scientist-Research.

I work with neonates and they respond very quickly (positively or negatively) to respiratory changes. Bagging is ideal when they are having a real problem because the nurse/RT can quickly adjust the pressure and rate according to the infant's response. HR & sats not coming up? increase your rGood thing is we use anesthesia bags and they also provide peep/cpap.

Love the anesthesia (flow inflating) bags as they can provide almost all forms of support from PPV to CPAP to blow-by.

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.
Hi,

I've been in the ICU for almost a year now, and I recently came across a concept that I am not clear on.

When a ventilated patient's oxygen saturation starts dropping, or if a patient is experiencing respiratory arrest, an important part of our interventions is to immediately disconnect the ETT from the ventilator and connect an AMBU-bag to manually ventilate.

I understand that this is to have more control over the pressure and rate so that we can adequately perfuse the lungs. I am simply not sure how that is the best method, though. It seems to me that a mechanical ventilator would be able to have much more control over a pressure through PEEP/vT.

I guess what I'm asking is: how is AMBU still the best method vs. a mechanical breathing apparatus that can be 'tweaked' to any specification? I understand that before an RT arrives, it would not be appropriate for nurses to try and mess with the settings, so we simply bag. However, once the RT arrives, I believe that's their first move too.

I apologize in advance if I'm a little incorrect about some of this. I'm still trying to completely grasp all of the RT components to the ICU! Hopefully my question makes sense to someone.

If an RT sees this, perhaps if you could briefly compare the difference in pressures between AMBU and typical vent. modes that may clear it up.

Thank you!

If the patient is on the vent...how are they experiencing a respiratory arrest?

The point is that the vent may be faulty...you can deliver 100% 02 quicker....you can synchronize the breaths with CPR and defib...if the patient is on high levels of PEEP you must have a PEEP valve on the vent to prevent lung collapse.

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1. Are there any alarms going off on the ventilator?

2. What are the other vitals?

3. What are the ventilator settings?

4. Was this patient being weaned either on mandatory settings or FiO2?

5. What was just done to the patient?

5. Could hitting the 100% O2 button recover the patient?

6. Could pre-oxygenating the patient before a procedure have prevented a desaturation?

7. Is the patient on vasopressors? Was there a change in BP or CO which affects the SpO2?

8. Respiratory arrest? Was this by an "Apnea Alarm"? Was the patient actually breathing? Were the alarms set tight like 10 or 15 seconds instead of 20? Some critical alarms like "Apnea" require you to acknowledge by a reset much like alarms on the CR monitor. It may not mean the patient is apneic at that moment.

9. If they are on high PEEP settings, breathing the circuit, especially if you do not have a BVM with a proper PEEP valve, might bring more desaturation which might not be able to recover. Even with a PEEP valve on a BVM, this spring valve is not a good substitution for the PEEP delivered by a ventilator.

10. Is the tube still in place?

11. Is it secretions which triggered the lower SpO2 or even Apnea alarm? Can hitting the 100% button and a quick pass of the inline check that without breaking the circuit?

11. Is the pulse ox probe properly placed and a good pleth is showing?

12. What were the breath sounds? Physical assessment of chest? The patient's effort? I probably should have put this at number 1.

13. Remember D-O-P-E. Listen to breath sounds quickly both on and off the ventilator.

The RT might bag because you were bagging. They are also ultimately responsible for the ventilator and its effects on the patient. They will make sure no settings have been changed or tubes out of place before placing it back on the patient. They have to be cautious since someone like a doctor could have made adjustments to the ventilator and did not know the adjustments were not compatible with the given flow or the alarms. They also must make sure the tube is confirmed since connecting a ventilator circuit with an ETT heading toward the stomach can have very bad results.

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We tend to do this when a patient has an acute desaturation on the vent in order to both feel and hyperventilate forgoing any other obvious signs of why they may be desaturating.

Most recently I had a patient plug their airway (unbeknownst to us) and desat into the 60s fairly quickly despite increasing FiO2 and minor PEEP adjustments, so manual bagging was used to assess for stiffness/resistance (possible collapse) and to hyperventilate until we CCM decided it would be a good idea to bronch.

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We tend to do this when a patient has an acute desaturation on the vent in order to both feel and hyperventilate forgoing any other obvious signs of why they may be desaturating.

Most recently I had a patient plug their airway (unbeknownst to us) and desat into the 60s fairly quickly despite increasing FiO2 and minor PEEP adjustments, so manual bagging was used to assess for stiffness/resistance (possible collapse) and to hyperventilate until we CCM decided it would be a good idea to bronch.

Unfortunately when using the BVM, hyperventilating is also a complication and can cause more problems. Oxygenating is normally the goal in a desat situation unless you know what the PaCO2 and pH are. Too often during a desat situation, the first response is to bag fast and hard. Not only can rapid decrease in PaCO2 cause problems but also the hyperinflation of the lungs.

I also will give a reminder to make sure the BVM you are using is connected correctly to Nitric Oxide or Helium if either is being used to ensure the patient still receives the proper amount. Protect yourself from breathing in the medications or gases in the circuit. Always remember to have a filter on your BVM even if the patient is not in isolation. And, be mindful of the spray from the circuit which at 50 - 150 L/M it can cover a long distance. The RTs should teach you have to correctly break a circuit if you have to.

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Never fast and hard, it really gives us quicker control of PEEP adjustment and ability to recruit the lung (by hyperventilating with a larger Vt or slightly faster rate depending on the situation). Yes hyperventilating can cause issues but leaving someone with their Spo2 in the tank can cause issues as well.

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Specializes in cardiac, emergency.

maybe by bagging you are also trying to remove any mucus plugs causing the desaturation?

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Specializes in ICU.

Such an interesting topic. I haven't been in ICU for very long and had a similar situation a couple of weeks ago after turning a pt, they desatted down into the 70s...they had pretty crappy lungs and were already on a lot of PEEP and a high FiO2, so I wasn't really happy to bag, and didn't, but I had wondered later what the right thing to do had been. The Dr was there and the sats came back up to baseline after about 5-10min on 100% o2.

*I'm in Australia and we don't have RTs - RNs are responsible for the vent.

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When you think the pt will desat with a procedure preoxygenate for a few minutes prior and during.

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