El-Manshawi et al developed an equation for predicting the level of breathlessness experienced by a person during exercise. The authors are from McMaster University in Hamilton, Ontario.
Parameters:
(1) duration of inspiration in seconds
(2) total duration of breath in seconds
(3) esophageal pressure in cm H2O
(4) frequency of breathing in breaths per minute
(5) inspiratory flow rate in liters per second
(6) breathlessness on the Borg scale (see previous section)
intensity of breathlessness on the Borg scale =
= (0.11 * (esophageal pressure)) + (0.61 * (inspiratory flow rate)) + (1.99 * (duration of inspiration) / (total duration of breath)) + (0.04 * (number of breaths per minute)) - 2.60
where
• The velocity of muscle shortening was proportional to the inspiratory flow rate.
• The ratio of duration of inspiration to total breath duration is called the duty cycle.
• The total duration of a breath in seconds should = 60 / (breaths per minute).
estimated peak esophageal pressure in cm H2O =
= (pressure at the mouth in cm H2O) + ((inspiratory flow rate) * (resistance)) + (0.8 * (tidal volume) * (dynamic elastance of the lung))
