Skill:
• Monitoring of ventilation in humans at rest and after mild and vigorous exercise
Ventilation in humans changes in response to levels of physical activity, as the body’s energy demands are increased
- ATP production (via cellular respiration) produces carbon dioxide as a waste product (and may consume oxygen aerobically)
- Changes in blood CO2 levels are detected by chemosensors in the walls of the arteries which send signals to the brainstem
- As exercise intensity increases, so does the demand for gas exchange, leading to an increase in levels of ventilation
Exercise will influence ventilation in two main ways:
- Increase ventilation rate (a greater frequency of breaths allows for a more continuous exchange of gases)
- Increase tidal volume (increasing the volume of air taken in and out per breath allows for more air in the lungs to be exchanged)
Trends in Tidal Volume and Breathing Frequency
Measuring Ventilation
Ventilation in humans can be monitored in a number of ways:
- Via simple observation (counting number of breaths per minute)
- Chest belt and pressure meter (recording the rise and fall of the chest)
- Spirometer (recording the volume of gas expelled per breath)
Spirometry involves measuring the amount (volume) and / or speed (flow) at which air can be inhaled or exhaled
- A spirometer is a device that detects the changes in ventilation and presents the data on a digital display
- A more simplistic method involves breathing into a balloon and measuring the volume of air in a single breath
- The volume of air can be determined by submerging the balloon in water and measuring the volume displaced (1ml = 1cm3)
Measuring Ventilation with a Spirometer
