how to calculate minute volume

The minute ventilation is the amount of air a person breaths in a minute. The minute ventilation is calculated by the multiplication of the tidal volume and the respiratory rate.

What is minute ventilation?

The normal tidal volume of a person is around 8- 10 ml per kg of weight. That is for a 70 kg person the tidal volume would be 700 ml. The tidal volume is actually the amount of air a person takes during each breath at rest.

The normal respiratory rate is about 14- 18 breaths per minute.

Hence, Minute ventilation = Tidal Volume X Respiratory rate.

So what is minute ventilation of a 70kg person. Minute ventilation for a 70 kg person would be 700 X 15 which would be approximately 10500ml.

A person requires a minimum of 6 to 8 litres of minute volume for the proper oxygenation of the tissues and the removal of carbon dioxide from the lungs. The minute volume increases at times of stress and exercise. This increase compensates for the increase in the demand of oxygen and the increased production of Carbon dioxide. This minimum volume of air required to be breathed every minute is also called as the minute volume. The question of what is minute volume is very important for an anesthetist which he had to calculate for every individual patient separately.

Hence, the simplest answer to the question of what is minute ventilation is that it is the amount of air a person inspires in a minute.


The assessment of minute volume during anaesthesia is the same describe as fresh gas flow as following:
1. Mapleson A
FGF should be equal to or greater than MV. ~ 80ml/kg x 70kg = ~6l/min

2. Mapleson B and C
Total ventilation must be greater than or equal to TWICE MV to avoid rebreathing. Or perhaps 2.5 x MV

3.Mapleson D
during Spontious Ventilation there is a degree of rebreathing

To absolutely remove any rebreathing you need THREE times MV

4.The Bain modification
Can safely be used during spontaneous respiration with a FGF = 100 ml.kg.min
5.Mapleson E and F
Provided the FGF > Vmin, efficiency of CO2 washout is entirely dependant on FGF In SV, PaCO2 increases unless FGF > 2.5-3x Vmin.