Page 297 - Clinical Application of Mechanical Ventilation

Monitoring in Mechanical Ventilation 263

50

40 C
B
30 End
Exhalation
20 Normal
Bronchospasm
10
A
Time © Cengage Learning 2014
Beginning
Exhalation
Figure 9-13 The normal capnogram (solid line). (A, phase I) PCO 2 is near zero and it repre-
sents gas in anatomic deadspace; (A to B, phase II) PCO 2 rises rapidly as alveolar gas mixes with
deadspace gas; (B to C, phase III) alveolar plateau shows arrival of gas flow from alveoli; Point
(C) is the end-tidal PCO 2 (PetCO 2 ). Dotted line represents tracing in bronchospasm. (Reference:
Hess, 1990.)

A B

Used with permission from Criticare Systems, Inc.
C D

Figure 9-14 Abnormal capnograms monitored via real time or trend screen. (A) Cardiac
arrest (real time). The PetCO 2 values drop suddenly and proportionally. This condition indicates
lung perfusion is inadequate due to a decreased cardiac output. (B) Effectiveness of external
compressions can be monitored by the resultant rise in PetCO 2 as shown in the trend screen.
(C) Kinked ET tube (trend screen). As the ET tube is obstructed (partially or completely),
the PetCO 2 values reflect the degree of obstruction. With complete obstruction, zero PetCO 2
is seen. (D) Disconnection. Immediate disappearance of the PetCO 2 values and wave form
are observed.

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