Page 132 - Basic Monitoring in Canine and Feline Emergency Patients

ETCO 2
VetBooks.ir 60 Note phase II is angled and prolonged while
(mmHg)
phase III is not present

50
40
30
20
10
0
Time

Fig. 6.11. Graphic representation of an obstructed endotracheal tube. In this case, the CO cannot be easily expelled,
2
thus the ascending slope (phase II) is prolonged and there is no alveolar plateau (phase III). There is no obvious
alpha angle. This usually happens when the endotracheal tube obstruction is severe enough to prevent complete
expiration of the gas during the expiratory phase by the time the next inspiratory phase occurs. Due to absence of
phase III, the alpha angle is not obvious either. ETCO , end-tidal carbon dioxide.
2
ETCO 2
(mmHg) The alveolar plateau is blunted and blends
with the downstroke of the capnogram
60
50
40
30
20
10
0
Time
Fig. 6.12. Graphic representation of leak around the endotracheal tube cuff. If air leaks around the cuff, it will dilute
the ETCO making it a lower concentration. This will shorten the alveolar plateau as the CO drops. Note a shorter
2
2
alveolar plateau (phase III) and an undulating shape of phase 0. ETCO , end-tidal carbon dioxide.
2
largely dead-space ventilation. This can be distin- patient’s condition. If the patient is stable clinically,
guished from true decreases in ETCO because the consider the possibility of malfunction of the anes-
2
ETCO will rise again after a deep inspiration thetic circuit or the capnograph or poor connection
2
when full gas exchange occurs. between capnograph and anesthesia circuit/patient.
A flat line may be seen when there is severe bron-
chospasm leading to complete obstruction, tracheal
tube obstruction, obstruction of the sampling tubing, 6.5 Pitfalls of the Monitor
apnea, cardiac arrest, or a disconnected capnograph. General comments
If an abnormal ETCO value is obtained, evalu-
2
ate the patient prior to attributing the abnormal Capnography is valuable for monitoring a patient’s
value to equipment malfunction or a change in the respiratory status. However, capnograms must

124 L.A.M. Ilie