Going crazy over here

[jhall98]

stuck on minute ventilation, so confusing, so i guess tidal volume is the amount of mls in the lungs? and Minute ventilation is the amount of respirations per minute? .... and all these formulas and stuff... how would you know how many mls is in someones lungs??? going crazy over here if someone could help me out that would be great!

 

[gotbeerz001]

Tidal volume x RR = minute volume

Tidal volume is not lung capacity, simply the amount of air moving per breath. Without instruments to measure tidal volume, you will simply have your best guesstimate as to whether they are moving enough. 500 mLs seems to be a number that sticks with me as a per-breath volume for a healthy average adult at rest.

In the field, you place them on ETCO2 cannula if there is any question about quality of ventilation.

 

[Scmedic08]

Tidal volume is basically the volume of air displaced in the lungs with each breath. This isn't something that your going to be measuring in the field. But more so, have an understanding of average T.V. for adults, pediatrics etc.
As far as minute volume ( or minute ventilation) the formula if I remember is MV=TV x RR. Right now you should just focus on the understanding of what they are and what changes in each will present. Ex. A lower minute volume could mean shallow respirations (smaller T.V.) and slow respirations, which means a higher concentration of CO2 present in the lungs than normal. Or visversa. May have not helped a bit as I'm getting off a long shift

 

[chaz90]

Don't confuse tidal volume with vital capacity. Vital capacity is the amount of air that one can forcibly inspire, and is typically much larger than total volume. As mentioned above, tidal volume is just the amount of air exchanged in a normal breath.

@Remi may have more input, but I've been told 6-8 mL/kg of ideal body weight is a pretty reasonable starting point to calculate tidal volume.

 

[Carlos Danger]

[

Don't confuse tidal volume with vital capacity. Vital capacity is the amount of air that one can forcibly inspire, and is typically much larger than total volume. As mentioned above, tidal volume is just the amount of air exchanged in a normal breath.

@Remi may have more input, but I've been told 6-8 mL/kg of ideal body weight is a pretty reasonable starting point to calculate tidal volume.

That's exactly right. I just read another study recently that showed fewer pulmonary complications (in post-op ICU patients) associated with lower tidal volumes.

There's still a lot of dinosaurs who like to ventilate everyone with 10-12 cc/kg at a rate of 8 per minute and no PEEP, but that's probably not the best practice, at least in sick patients.

 

[jhall98]

alright thanks everyone. Still a little confusing but I do have a better understanding of it now.

 

[SeeNoMore]

stuck on minute ventilation, so confusing, so i guess tidal volume is the amount of mls in the lungs? and Minute ventilation is the amount of respirations per minute? .... and all these formulas and stuff... how would you know how many mls is in someones lungs??? going crazy over here if someone could help me out that would be great!

It might be helpful in the future to post more specific / detailed questions. This would hopefully occur after a serious effort at obtaining a working knowledge of basic definitions and concepts. What do you mean you are "stuck on" minute ventilation? What exactly is confusing you? Which formulas are you finding challenging, and what type of student are you? What are you asking with "how many mls is in someones lungs?" - I'm not trying to be difficult but I think you'll get way more out of these threads if you refine your approach. It's worth the time as you have some very knowledgeable folks here.

 

[jhall98]

It might be helpful in the future to post more specific / detailed questions. This would hopefully occur after a serious effort at obtaining a working knowledge of basic definitions and concepts. What do you mean you are "stuck on" minute ventilation? What exactly is confusing you? Which formulas are you finding challenging, and what type of student are you? What are you asking with "how many mls is in someones lungs?" - I'm not trying to be difficult but I think you'll get way more out of these threads if you refine your approach. It's worth the time as you have some very knowledgeable folks here.

Alright, sorry let me rephrase my question. I'll pretty much say what the book says because I really dont understand it.
"frequency of ventilation is calculated as number of ventilations in one minute"(prehospital care 10th edition). Okay so I get that frequency of ventilation is it pretty much just the respirations in one minute? e.g the resting rate for an adult is 12-20. So 12-20 respirations would be frequency of ventilations correct? Okay If that's correct then I have no problem with that.. This is where it starts to get confusing. "Minute volume is amount of air moved in and out of lungs in one minute, determined by multiplying the tidal volume by the frequency of ventilation in one minute(prehospital care 10th) "Tidal volume is volume of air breathed in with each individual breath" formula is minute ventilation=tidal volume x frequency of ventilation. My question is how do I know how much someone's tidal volume is. Like how do you measure it. That's probably what the most confusing for me is. I also do appreciate everyone's time and effort on here. Sorry I came off a little rude, not my intentions, everyones answers are very helpful and much appreciated.

 

[jhall98]

It might be helpful in the future to post more specific / detailed questions. This would hopefully occur after a serious effort at obtaining a working knowledge of basic definitions and concepts. What do you mean you are "stuck on" minute ventilation? What exactly is confusing you? Which formulas are you finding challenging, and what type of student are you? What are you asking with "how many mls is in someones lungs?" - I'm not trying to be difficult but I think you'll get way more out of these threads if you refine your approach. It's worth the time as you have some very knowledgeable folks here.

I am also an emt-basic student, working out of prehospital emergency care 10th edition

 

[SeeNoMore]

I didn't think you were being rude, your posts were just a little confusing. In any event, I am assuming you are referring to the tidal volume of a spontaneously breathing individual not a ventilator.

As you may have gathered , tidal volume is not a fixed value but will vary amongst individuals. It is measured as part of pulmonary function tests. You are unlikely to be measuring it prehospitally. Instead you will be assessing the adequacy of ventilation with respiratory rate, depth and evidence of perfusion.

 

[Carlos Danger]

This is where it starts to get confusing. "Minute volume is amount of air moved in and out of lungs in one minute, determined by multiplying the tidal volume by the frequency of ventilation in one minute(prehospital care 10th) "Tidal volume is volume of air breathed in with each individual breath" formula is minute ventilation=tidal volume x frequency of ventilation. My question is how do I know how much someone's tidal volume is. Like how do you measure it. That's probably what the most confusing for me is. I also do appreciate everyone's time and effort on here. Sorry I came off a little rude, not my intentions, everyones answers are very helpful and much appreciated.

OK, let me take a stab:

"Ventilation frequency (FV)", or as it is more commonly termed, "respiratory rate (RR)", is simply the number of times you breath in one minute. The normal rate for an adult at rest varies from person to person and is affected by many factors, but is usually somewhere between 10-20 times per minute. You can count the number of breaths per minute just by watching someone breath.

"Tidal volume (VT)" is how big those breaths are. That is, the volume (how many ml's) of air that goes in and out with each breath. Just like FV, this varies from person to person and is affected by many factors. There are weight-based formulas to estimate a person's expected tidal volume, but just keep in mind 500ml for a normal-sized adult at rest. You can't measure tidal volume unless the patient is on a ventilator or spirometer of some type. You just know what normal is (about 500ml) and, once you gain some experience, you know what it looks like.

"Minute volume (MV)" is simply FV x RR, and it reflects the volume (in ml's or liters) of air that goes in and out over one minute. You cannot measure MV just by looking at a patient because you don't know their tidal volume. It is just an important concept to understand, because the amount of air that is exchanged over a minute is what determines whether or not someone is breathing adequately and is more important than either the FV or VT by themselves.

For instance, if I have what appears to be a normal tidal volume and I am only breathing about 5 times a minute, then my minute volume is too low. But if I am only breathing 5 times a minute, yet my tidal volume appears much larger than normal, I may have an adequate minute volume.

Does that make sense?