Measuring Lung Capacity

Learning Intentions Explain the meaning of the terms tidal volume and vital capacity. Describe how a spirometer can be used to measure vital capacity, tidal volume, breathing rate and oxygen uptake. Analyse and interpret data from a spirometer.

Vital Capacity Is the maximum volume of air that a person can breathe in or out in one breath.

Tidal volume is the volume of air breathed in or out of the lungs in one normal breath at rest.

Spirometer Is a high-tech piece of equipment used to measure vital capacity, tidal volume, breathing rate and oxygen uptake.

Spirometer A spirometer consists of a chamber filled with oxygen on a tank of water. A person breaths in the oxygen from the tank causing the lid to sink. Breathing out causes the lid to float up The movement of the chamber is recorded using a data logger so that a spirometer trace can be produced.

Spirometer Trace

Explanation of the trace Residual volume: is the volume of air that always remains in the lungs even after the biggest exhalation Dead space: is the air in the bronchioles, bronchi and trachea. There is no gas exchange between this air and the blood. Inspiratory reserve volume: is how much more air can be breathed in over and above the normal tidal volume. You use this when exercising. Expiratory reserve volume: Is how much more air can be breathed out over and above the normal tidal volume.

Interpreting a spirometer trace Measurement Male Female Tidal Volume dm3 Vital Capacity Breathing rate breaths/min Oxygen uptake dm3/s Answer the questions on the worksheet

Plenary