PaCO₂ Adjustment Calculator

Practice using current PaCO₂, desired PaCO₂, respiratory rate, and tidal volume to estimate ventilation adjustments.

Clinical Notes and Source

Clinical notes

Clinical Note: PaCO₂ is inversely proportional to alveolar ventilation. To decrease PaCO₂, increase ventilation by increasing VT, RR, or both. To increase PaCO₂, decrease ventilation by decreasing VT, RR, or both.

Disclaimer: Patient response will be unique. Review chest x-ray for V/Q defects if changes do NOT improve PaCO₂.

Source: H. R. Wexler & Peter Lok, A simple formula for adjusting arterial carbon dioxide tension, Canadian Anaesthetists' Society Journal, 28, 370-372 (1981).

Current Ventilation Parameters

Current PaCO₂ (mmHg) 40

Desired PaCO₂ (mmHg) 35

Respiratory Rate 12

Normal range: 12-20 breaths/min

Tidal Volume (mL) 500

Typical range: 6-8 ml/kg IBW

VT Disclaimer

Tidal volumes should always be within 6-8 mL/kg of the patient's predicted normal. Overdistension risk increases as VT increases. Ranges over 8 mL/kg are used with caution.

Example Calculation Based on Sliders

Step 1 of 4

Step 1: Current Minute Ventilation

Minute Ventilation (VE) = Tidal Volume (VT) x Respiratory Rate (RR)

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Step 2: New Minute Ventilation Required

New VE = Current PaCO₂ x current VE ÷ desired PaCO₂

This calculates the exact minute ventilation needed to achieve your desired PaCO₂.

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Step 2, Option 1: Adjust Respiratory Rate Only

New RR = Current PaCO₂ x current RR ÷ desired PaCO₂

Keeps tidal volume constant while adjusting rate. Round the final RR to a whole number at the end.

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Step 2, Option 2: Adjust Tidal Volume Only

New VT = Current PaCO₂ x current VT ÷ desired PaCO₂

Keeps respiratory rate constant while adjusting volume. Round the final VT to a whole mL at the end.

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Practice Scenario

Current PaCO₂ 40 mmHg

Desired PaCO₂ 35 mmHg

RR 12/min

VT 500 mL

Calculate the current VE, the new VE target, and the RR-only or VT-only adjustment. Enter VE answers in L/min rounded to the first decimal place. Round final RR and VT answers at the end.

New VE L/min RR-only breaths/min VT-only mL

Post Test Access Answer 10 practice questions correctly to open the Post Test.

0 / 10 correct

Source: H. R. Wexler & Peter Lok, A simple formula for adjusting arterial carbon dioxide tension, Canadian Anaesthetists' Society Journal, 28, 370-372 (1981).