On the basis of the data presented below, calculate the time constant.
$\bullet$ Tidal volume (VT) , 600 mL
$\bullet$ Respiratory rate (RR) , 12 breaths per minute
$\bullet$ Lung compliance (C) , 0.2 L/cm H₂O
$\bullet$ Airway resistance (Raw) , 2.5 cm H₂O/L/second
$\bullet$ Peak inspiratory pressure (PIP) , 30 cm H₂O
$\bullet$ Inspiratory time (TI) , 2 seconds
$\bullet$ Expiratory time (TE) , 1 second

Question

On the basis of the data presented below, calculate the time constant.

\bullet

Tidal volume (VT) , 600 mL

\bullet

Respiratory rate (RR) , 12 breaths per minute

\bullet

Lung compliance (C) , 0.2 L/cm H₂O

\bullet

Airway resistance (Raw) , 2.5 cm H₂O/L/second

\bullet

Peak inspiratory pressure (PIP) , 30 cm H₂O

\bullet

Inspiratory time (TI) , 2 seconds

\bullet

Expiratory time (TE) , 1 second

Quizplus · Accepted Answer

Respiratory time constants, tau (F1F1F1S1F1F1F10), are the mathematical product of compliance and resistance expressed as seconds because all the units of pressure and volume measurement cancel out except time. A time constant is an interval over which a given change occurs, as a percentage of total change. Three time constants are required to reach 95% of inflation or exhalation. TI, or inflation time, and TE should be at least three times the respiratory time constants for optimal inspiration or expiration to occur.

On the Basis of the Data Presented Below, Calculate the Time