Measuring Lung Volumes

—> it’s important to be able to measure lung volumes as this allows health professionals to monitor lung function

—> this would help diagnose respiratory conditions such as asthma and emphysema

—> and monitor the effectiveness of treatments for these conditions

—> 2 of the most important measurements that can be taken are :

• peak expiratory flow rate (PEFR)
• forced vital capacity (FVC)

—> measured using a peak flow meter

—> maximum speed of expiration

—> measures ability to breath air out fast so monitors degree of obstruction in airways

—> used to determine lung functionality and the severity of asthma and emphysema symptoms

What does PEFR vary with?

• age
• gender
• height
• lung volume = fitness

—> measure using a spirometer

—> volume of air that can be breathed out after the biggest breath in

—> used to diagnose and severity of asthma, bronchitis, emphysema and chronic obstructive pulmonary disease (COPD)

What does FVC vary with?

• gender
• age
• weight
• physical fitness

—> spirometer are used to measure lung function by taking many different lung volumes

—> a ‘closed’ spirometer as the patient breathes medical grade oxygen from a tank floating on water

—> other spirometers can be ‘open’ where the patient breathes in air from the room

Tidal Volume : volume of air moved in and out of the lungs with each resting breath. Approximately 500cm^3 in most adults.

Vital Capacity : the volume of air that can be breathed out after the strongest possible inhalation.

Inspiratory Reserve Volume : maximum volume of air that can be breathed in above the normal breathing rate.

Expiratory Reserve Volume : extra volume of air that can be forced/breathed out above the normal breathing rate.

Residual Volume : the volumes of air left in the lungs when you have exhaled as hard as possible. This can’t be measured directly.

Total Lung Capacity : maximum volume of air that can be in the lungs. Sun oh the vital capacity and the residual volume.

Breathing Rate : number of breaths taken in a minute. Be aware that this will changed with a noticeable change between testing and during exercise.

Respiratory Minute Volume (RMV) : volume of air passing in and out of lungs in one minute.
RMV = tidal volume x number of breaths in a minute.

Oxygen Consumption : volume of oxygen used by patient in one minute. Uses the slope of the trace to calculate.