1. Instruct the patient to begin the procedure by breathing normally.
2. Ask the patient to exhale completely to Residual Volume. ATS-ERS standards recommends that this portion of the
manoeuvre be limited to 6 seconds. In patients with severe obstructive lung disease exhalation to RV may require
additional time.
3. Next, instruct the patient to inhale the DLCO gas mixture to Total Lung Capacity. The inspiration should be rapid since
the calculations assume instantaneous lung filling. ATS and ERS standards state that 85% of the patient’s inspiratory
volume should be inhaled in less than 4 seconds. It should be noted on the post-test notes if longer inspiratory times
are necessary to achieve the recommended 85% VI goal.
4. When the patient completes a full inspiration, instruct him/her to hold their breath for the required apnea time.