Statistical
Winters formula range comparison and smoking pack-years: spreadsheet examples
Practice a conditional comparison with an expected CO2 range and a separate pack-year calculation using fictional values.
Compare a model range without making an automatic diagnosis
Winters formula estimates an expected PaCO2 range, 1.5*HCO3+8 plus or minus 2 mmHg, when primary metabolic acidosis has already been established clinically. It is not an exact target, and low bicarbonate alone does not establish that condition.
This worksheet labels a fictional measurement as within, above or below the model range. It cannot identify a disease, its cause or a treatment. Interpreting compensation requires the complete clinical context. The example restricts bicarbonate to positive values below 22 as an exercise gate, not a diagnostic criterion.
Pack-years is a separate exposure arithmetic example using 20 cigarettes per pack. For varying smoking intensity, calculate each time segment and sum the results. Pack-years alone does not establish screening eligibility or quantify an individual cancer risk.
| Pulmonary / ABG Assessment | Formula / Inputs | Patient Lab Values | Clinical Finding |
|---|---|---|---|
| Winter's Expected PaCO2 | 1.5 * B2 + 8 | HCO3- B2 = 12 mEq/L | 26.0 mmHg (Range 24–28) |
| Measured PaCO2 = 26 mmHg | ABS(B3 - Exp) <= 2 | Within ±2 mmHg window | "Within expected range" |
| Measured PaCO2 = 34 mmHg | B3 > Exp + 2 | CO2 retention above 28 mmHg | "Above expected range" |
| Smoking Pack-Years | (B4 / 20) * B5 | 30 cigs/day (1.5 pk) x 16 yrs | 24 pack-years (exposure arithmetic) |
Compare fictional PaCO2 with the expected range
Compares measured arterial PaCO2 (B3) against 1.5 * HCO3 (B2) + 8 with the standard ±2 mmHg physiological band.
=IF(COUNT(B2:B3)<>2,"Invalid inputs",IF(OR(B2<=0,B3<=0),"Invalid inputs",IF(B2>=22,"Outside exercise domain",IF(ABS(B3 - (1.5 * B2 + 8)) <= 2, "Within expected range", IF(B3 > (1.5 * B2 + 8) + 2, "Above expected range", "Below expected range")))))Cumulative Smoking Exposure in Pack-Years = (CigsPerDay / 20) * Years
Cigarettes per day and years must be nonnegative. Fractional years and average daily cigarette counts are allowed. This does not cover other tobacco products.
=IF(COUNT(B4:B5)<>2,"Invalid inputs",IF(OR(B4<0,B5<0),"Invalid inputs",ROUND((B4 / 20) * B5, 2)))Try the example
Use the original values or change them to test your understanding.