Measure physiological dead space from common respiratory inputs. Compare Bohr, Enghoff, and estimated anatomical values. Get clear results, export data, and study examples easily.
| Case | VT (mL) | RR | PaCO2 | PECO2 | PACO2 | Weight (kg) | Enghoff VD/VT | Enghoff VD (mL) |
|---|---|---|---|---|---|---|---|---|
| Example 1 | 500 | 14 | 40 | 28 | 38 | 70 | 0.3000 | 150.00 |
| Example 2 | 450 | 16 | 45 | 30 | 42 | 60 | 0.3333 | 150.00 |
| Example 3 | 600 | 12 | 50 | 35 | 47 | 80 | 0.3000 | 180.00 |
Enghoff dead space fraction: VD/VT = (PaCO2 - PECO2) / PaCO2
Enghoff dead space volume: VD = VT × (VD/VT)
Bohr dead space fraction: VD/VT = (PACO2 - PECO2) / PACO2
Bohr dead space volume: VD = VT × (VD/VT)
Estimated anatomical dead space: VD anat = 2.2 × weight in kg
Minute ventilation: VE = VT × RR / 1000
Estimated alveolar minute ventilation: VA = (VT - VD) × RR / 1000
The Enghoff method uses arterial CO2. The Bohr method uses alveolar CO2. The two methods answer slightly different clinical questions.
Enter tidal volume in milliliters. Add respiratory rate in breaths per minute.
Type the arterial CO2 value and the mixed expired CO2 value. These are required for the Enghoff calculation.
Add alveolar CO2 if you want the Bohr calculation. Leave it blank if that value is unavailable.
Enter body weight if you want an anatomical dead space estimate. The estimate uses 2.2 mL per kg.
Press the calculate button. The result appears above the form, directly below the header section.
Use the CSV button to export the current result. Use the PDF button to save or print the page.
This dead space calculator helps estimate how much of each breath does not take part in gas exchange. It focuses on respiratory dead space, physiological dead space, and estimated anatomical dead space. The page uses common bedside inputs. It then returns ratios, volumes, and ventilation values that are easier to interpret.
Dead space matters because effective ventilation depends on how much fresh air reaches functioning alveoli. A patient may have an acceptable tidal volume, but alveolar ventilation can still be low when dead space is high. That pattern may appear in lung injury, pulmonary vascular disease, severe ventilation perfusion mismatch, or some ventilator problems.
The Enghoff equation uses arterial carbon dioxide and mixed expired carbon dioxide. It is widely used because arterial values are often easier to obtain in clinical settings. The Bohr equation uses alveolar carbon dioxide instead. That makes it more specific to true physiological dead space when alveolar data are available. The calculator shows both values when possible, so you can compare them on one page.
The dead space fraction shows the share of each tidal breath that is not effectively clearing carbon dioxide. The dead space volume converts that fraction into milliliters. Minute ventilation shows total airflow per minute. Estimated alveolar minute ventilation shows the portion that may actually contribute to gas exchange. These outputs are useful for respiratory review, education, and clinical discussion.
No calculator should replace a full patient assessment. Measurements depend on sampling quality, timing, ventilator settings, and the clinical condition. Always review trends, arterial blood gas data, capnography, and the patient’s overall status. This tool is best used for learning, quick estimation, and structured bedside review.
Dead space is the part of inhaled air that does not participate in gas exchange. It includes conducting airways and poorly perfused or nonfunctioning alveoli.
Bohr uses alveolar CO2 and reflects physiological dead space more directly. Enghoff uses arterial CO2 and often captures dead space plus broader gas exchange impairment.
It can rise with pulmonary embolism, lung overdistension, low perfusion states, severe ventilation perfusion mismatch, or advanced lung disease.
Not always. It depends on the patient, trend, cause, and clinical setting. Still, a clearly rising value deserves prompt review.
Mixed expired CO2 reflects the average carbon dioxide in exhaled gas. It is needed to estimate how much ventilation is effectively clearing CO2.
Yes, as an educational or review tool. Make sure the measurements are accurate and interpret results with ventilator settings and blood gas data.
It is a rough estimate of conducting airway volume. This page uses 2.2 mL per kg as a simple reference value.
No. It provides computed values only. Diagnosis requires history, examination, monitoring, imaging, and clinical judgment.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.