Mechanics (continued)
P
tp
PEEP
The difference between the corresponding airway and esophageal
pressures at the end of the expiratory hold during
an AutoPEEP maneuver. Requires an inspiratory hold and
esophageal catheter.
MIP
The maximum negative airway pressure that is achieved by the
patient, during an expiratory hold maneuver.
P
100
The negative pressure that occurs 100 ms after an inspiratory
effort has been detected.
WOB
V
Ventilator work of breathing (WOB
V
) is defined as the summation
of airway pressure (PAW) minus the baseline airway pressure
(PEEPAW) times the change in tidal volume to the patient (-V)
during inspiration, and normalized to the total inspiratory tidal
volume (Vti).
WOB
P
Patient work of breathing (WOB
P
), normalized to the total
inspiratory tidal volume. Patient work of breathing is defined as
the summation of two work components: Work of the lung and
work of the chest wall. Requires an esophageal balloon.
WOB
I
Imposed work of breathing (WOBI) is defined as the work
performed by the patient to breathe spontaneously through the
breathing apparatus, (i.e., the E.T. tube), the breathing circuit and
the demand flow system. Requires a tracheal catheter.
Note:
Monitored values are displayed as BTPS.
Capnography
EtCO
2
The patient’s peak expired CO
2
as measured and reported by the
CO
2
sensor in the airway, calculated for each breath then averaged
as specified by set EtCO
2
averaging time.
VCO
2
Minute volume of exhaled CO
2
measured continuously and
averaged over a user-selectable time. Requires flow measurement
at the wye or circuit compliance active.
VtCO
2
Tidal volume of exhaled CO
2
, measured for each breath and then
averaged over the set VCO
2
averaging time. Requires flow mea-
surement at the wye or circuit compliance active.
Vd ana
The volume of dead space in the patient’s conducting airways
from the nose to the level of the terminal bronchioles measured
for each breath, then averaged over the set CO
2
averaging time.
Also includes any mechanical dead spaces added to the ventila-
tor circuit between the CO
2
sensor and the patient. Requires flow
measurement at the wye or circuit compliance active.
Vd/Vt ana
Anatomic Vd/Vt is averaged over the set VCO
2
averaging
time. Requires flow measurement at the wye or circuit
compliance active.
Vd phy
Comprises Vd ana as well as the volume of the respiratory zone
(respiratory bronchioles, alveolar ducts and alveoli) not participat-
ing in gas exchange. Requires an arterial blood gas sample.
Vd/Vt phy
Physiologic Vd/Vt is averaged over the set VCO
2
averaging time.
Requires an arterial blood gas sample.
Vd alv
Alveolar dead space is the difference between physiological
dead space and anatomical dead space. It represents the volume
of the respiratory zone that is from ventilation of relative
under-perfused or non-perfused alveoli. Requires an arterial
blood gas sample.
Monitors and definitions (continued)
