tidal volume formula height/weight

[eok361]

does anyone have the formula to determine what your 95% tidal volume be on CPAP machines? I see conflicting info.

thanks

[Crimson Nape]

Here is one that I found:

To determine the adequate tidal volume (Vt) to deliver during protective ventilation, it is necessary to calculate the patient's PBW. This is accomplished by using the Devine's formulas (3) adjusted by gender: Male: PBW = 50 + (0.91 × (height in cm–152.4)) Kg. Female: PBW = 45.5 + (0.91 × (height in cm–152.4)) Kg.

Here is the Devine formula, originally published in 1974:

 -  Male ideal body weight = 50 kilograms (110 lb) + (0.9 kilograms (2.0 lb) × (height (cm) − 152))
 -  Female ideal body weight = 45.5 kilograms (100 lb) + (0.9 kilograms (2.0 lb) × (height (cm) − 152))
Similar to the Hamwi Formula, it was originally intended as a basis for medicinal dosages based on weight and height. Over time, the formula became a universal determinant of IBW.

Volume Calculation:

VT = Tidal Volume (mL)
Wt = Body Weight (kg)
VT = Tidal Volume (mL/kg)
*VT is the volume of air inspired/expired with each breath. (Also, VT= IC-IRV. VT= VC-(IRV+ERV), VT= TLC-(IRV+ERV+RV).

With all that said, here are 2 calculators to make it easy:
Tidal Volume Calculator
Ideal Weight Calculator

- Red

[eok361]

thanks, crimson. very informative.

but this math is above my head, or i'm being generally dense.

that calculator wants the Tidal Volume at input. I don't know what that is, or how to get it from that devine thing.

i'm 6'0" 180 lbs, and i'm stumped. lol

but thanks

[cdplatt]

Are you asking about the 95% value shown in OSCAR statistics?  If so, that number just means that 95% of the tidal volume measurements during the session were at or below that level.  

If you're curious about how a normal tidal volume is calculated for your height and ideal body weight, that is explained well in the OSCAR wiki: 

https://www.apneaboard.com/wiki/index.php?title=OSCAR_-_The_Guide#Tidal_Volume

My calculations suggest a normal tidal volume for you should fall in the range of 466ml - 621ml.

[eok361]

thanks!  and yes.

[Jay51]

The Med (median) tidal volume statistic holds the most weight IMO.  Median means, "denoting or relating to a value or quantity lying at the midpoint of a frequency distribution of observed values or quantities, such that there is an equal probability of falling above or below it."   Median is different from Mean (or average) - "a number expressing the central or typical value in a set of data, in particular the mode, median, or (most commonly) the mean, which is calculated by dividing the sum of the values in the set by their number."

The longer a person sleeps, the more accurate the median tidal volume should be also (more data points to use).  It should be pretty accurate if the person is actually asleep, too, as compared to being awake or transitioning back and forth between wake and sleep.