Skip to content
📢We are still a growing community and would love some help. Want to contribute? Join us by mailing an e-mail of interest to "r6394175@gmail.com"
Start helping our community →
← Theoretical A

Q48 — Helium Dilution Test for Residual Volume

Theoretical A Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Respiratory Physiology

During pulmonary function tests, tidal volume, inspiratory reserve volume, and expiratory reserve volume can be measured directly, but not residual volume (RV). The helium dilution technique estimates RV (Figure 1), by recording Vsf (final spirometer volume) and C2 (final helium concentration). The initial spirometer volume is 5 L with 10% helium. Helium is not exchanged in the lungs, i.e. not absorbed into the blood.

Diagram of the helium dilution test: a patient attached to a spirometer after regular expiration, then performing a full forced expiration, alongside a table of Vsf and final helium concentration for a healthy control and two patients. Figure 1. A In the first stage, the patient is attached to the spirometer after regular expiration and then breathes several times to establish helium equilibrium. Vs - initial spirometer volume. B The patient performs a full forced expiration, and the spirometer is detached. Table 1. Results of the helium dilution test for two male patients and one male control: Vsf (L) / C2 (%) — Healthy control 6.1 / 6.8, Patient 1: 5.6 / 6.5, Patient 2: 5.6 / 8.

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. Vsf equals to Vs plus expiratory reserve volume.
B. Patient 2 has an RV of 750 ml.
C. Given that inspiratory capacity is constant for Patient 1, the increase in RV with respect to the healthy control can be explained by an increase in lung volume.
D. A patient with a single-lung pneumothorax, causing incomplete lung collapse, would likely have results similar to Patient 2.
← Previous: Q47 Next: Q49 →

Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)