Student question about Tidal Volume!

[ShelbyB]

Hello everyone, I am new to the site and hoping to get some help. I am currently a student and learning about Tidal Volume. I understand the equation for Minute Volume. However, how do you determine Tidal volume in any given patient? Do you use a specialized machine? Do you eyeball it based on breathing regularity/irregularity? What I'm trying to say is that I know the equations and mL rates, I just want to know how to get it during a real situation. I'm sure I will learn this during my clinicals, but I'd like to be prepared in advance.Thank you!

 

[TransportJockey]

Tidal volume is 5-10mL/kg of ideal body weight. Each person has a different tidal volume
Real world? Squeeze the BVM until you get gentle chest rise. A pediatric BVM actually has enough volume to bag most adults too, so you don't risk barotrauma in the event you start squeezing the bag for all its worth.

 

[CALEMT]

A pediatric BVM actually has enough volume to bag most adults too

*providing you have a good face seal of course.

 

[TransportJockey]

That tends to go without saying. No matter what you're doing with a BVM, if you can't make a good face seal, you're shooting yourself in the foot.

*providing you have a good face seal of course.

 

[EpiEMS]

@ShelbyB, if the NREMT exam asks you, ~500mL is your average adult* person's tidal volume. In practice, bag for chest rise.

(@TransportJockey said it better than I did.)

 

[MonkeyArrow]

To accurately determine a person’s tidal volume, one would usually expect the patient to be on a ventilator, or otherwise in an outpatient setting, by a pulmonary function test.

 

[DesertMedic66]

Unless you are dealing with ventilators knowing the tidal volume isn’t going to offer any help. If they need to be bagged just bag until you see the chest start to rise and then stop.

If you really are interested then the normal tidal volume is roughly 5-10mL/KG of their ideal body weight (not actual weight).

 

[VentMonkey]

A pediatric BVM actually has enough volume to bag most adults too, so you don't risk barotrauma in the event you start squeezing the bag for all its worth.

Yep, this is the only BVM we’re carrying in our flight bag now. We still store the adult, and infant BVM’s in our aft compartment for those truly rare baby lungs, or the Andre The Giant-sized patients who may require a tad more than the standard pediatric BVM’s Vt delivery.

To the OP, what they all said. Adequate chest rise and fall should be the main objective along with a targeted end tidal for the specific patient being ventilated. A BVM’s Vt is not quite the same as a ventilators; it’s much less consistently accurate even with skillful hands.

There are certain adult patient populations that may require even smaller Vt’s still (4-6 ml/ kg IBW vs. 5-10 ml/ kg IBW). But again for now, as an EMT focus on adequate chest rise and fall, and compliance.

Also, YouTube search “BLS BVM techniques”, I’m certain you’ll find some decent tutorials on how to accurately deliver said Vt’s. Proper airway management is ever so crucial at the basic level, so kudos for wanting to learn more.

 

[VFlutter]

If you see a patient on a ventilator during your clinicals you will may see "VTe" which is the patient's exhaled tidal volume. It will be slightly lower (~100-150ml) than the ventilators set tidal volume because of dead space ventilation.

 

[ShelbyB]

Yep, this is the only BVM we’re carrying in our flight bag now. We still store the adult, and infant BVM’s in our aft compartment for those truly rare baby lungs, or the Andre The Giant-sized patients who may require a tad more than the standard pediatric BVM’s Vt delivery.

To the OP, what they all said. Adequate chest rise and fall should be the main objective along with a targeted end tidal for the specific patient being ventilated. A BVM’s Vt is not quite the same as a ventilators; it’s much less consistently accurate even with skillful hands.

There are certain adult patient populations that may require even smaller Vt’s still (4-6 ml/ kg IBW vs. 5-10 ml/ kg IBW). But again for now, as an EMT focus on adequate chest rise and fall, and compliance.

Also, YouTube search “BLS BVM techniques”, I’m certain you’ll find some decent tutorials on how to accurately deliver said Vt’s. Proper airway management is ever so crucial at the basic level, so kudos for wanting to learn more.

Thank you for the encouragement! I will look that video up.[/QUOTE]

 

[EpiEMS]

Also, YouTube search “BLS BVM techniques”, I’m certain you’ll find some decent tutorials on how to accurately deliver said Vt’s. Proper airway management is ever so crucial at the basic level, so kudos for wanting to learn more.

@ShelbyB, also take a look at @Brandon O's blog - EMSBasics: he has some great content on BLS airway management.

 

[ThadeusJ]

I have attached a copy of the BVM insert that I deal with (removing any identifying numbers in case I am accused of promoting a brand). You can see that each size has been tested for one-hand and two-hand volume delivery (as per international standards). The only way to determine the actual volume in the field is to measure it using a mechanical or ultrasonic respirometer. I have seen classes where these are used to train students so they can get a feel for proper volume.
Also, the lower volumes of 4-8 mL/kg is being promoted for reducing barotrauma.

 

[EpiEMS]

You can see that each size has been tested for one-hand and two-hand volume delivery (as per international standards).

Very interesting! This'll make me more cautious - 850ml for 1 handed adult-size BVM seems like a tad much for your ideal body weight adult...

 

[ThadeusJ]

I am sure that these standards were created when tidal volumes were 10-15 mL/kg.

Very interesting! This'll make me more cautious - 850ml for 1 handed adult-size BVM seems like a tad much for your ideal body weight adult...

Or put another way, you may recognize that you don't have to squeeze the bejesus out of the bag to make your target (plus it shows that the target can be reached even if you have smaller or weaker hands). Smooth, careful operation will get you there and there is more volume available if you need it for whatever reason. If you're really, really interested in finding the volume, you may want to strike up a conversation with your friendly neighbourhood respiratory therapist at one of the local hospitals and see if one of their team may be interested in working with you with some of their equipment that measures tidal volume. Coffee and donuts also make for a great incentive.

 

[Brandon O]

If you see a patient on a ventilator during your clinicals you will may see "VTe" which is the patient's exhaled tidal volume. It will be slightly lower (~100-150ml) than the ventilators set tidal volume because of dead space ventilation.

Usually more due to leaks in the circuit than dead space. A well-sealed circuit (e.g. an ETT with no cuff leak) should have very little difference in inhaled versus exhaled volumes.