Biology Reference
In-Depth Information
aerated (
101 HUs), and nonaerated (atelectasis; -100 to +100). The total
area that each compartment occupied within the entire lung was computed and then
expressed as the percentage of the entire lung area. Gas exchange was evaluated for
each patient by measuring the arterial partial pressure of oxygen (PaO
2
) and carbon
dioxide (PaCO
2
). All data are expressed as mean
500 to
standard deviation, and normal
distribution was tested with the Kolmogorow-Smirnow test. Data related to gas
exchange and pulmonary aeration (% of hyperinflated, normally aerated, poorly
aerated, and nonaerated compartments) were compared between the two groups
with the one-way analysis of variance (ANOVA) test (
P
<
0.05).
24.3 Results
The two groups were similar in terms of body weight (NS
21.4
4.2 kg;
¼
S
6.3 months).
The study was conducted without any complications, and none of the dogs were
excluded. The median duration of surgery in the S group was 46.2
20.6
7.2 kg) and age (NS
35.3
6.3 months; S
38.2
¼
¼
¼
7.7 min; thus,
in all dogs of the group, it was possible to perform the CT study. Compared to the
NS group, the S group had a significantly greater amount of nonaerated (atelectatic;
NS
3.9
1.3%; S
12.8
3.7%) and poorly aerated (NS
20.4
7.2%;
¼
¼
¼
S
5.3%) lung compartments and a smaller amount of the normally
aerated lung compartment (NS
26.7
¼
74.4
7.8%; S
58.9
8.1%; Fig.
24.1
).
¼
¼
The percentage of hyperinflated lung compartment (NS
1.1
0.8%; S
1.2
¼
¼
0.8%), the mean value of PaO
2
(NS
499.2
65.3 mmHg; S
491.2
49.2
¼
¼
mm Hg), and PaCO
2
(NS
¼
38.3
4.2 mmHg; S
¼
37.1
3.5 mmHg) were
similar in both groups.
24.4 Discussion
The main result of this study is that in healthy dogs under general anesthesia,
abdominal surgery interferes with pulmonary aeration, promoting the formation of
atelectatic and poorly aerated lung compartments and reducing the normally aerated
lung area. We can speculate that the increased intra-abdominal pressure induced by
the surgical procedures promotes the cranial displacement of the diaphragmwith the
consequent reduction of the pulmonary functional residual capacity, and conse-
quently promotes airway closure and alveolar collapse (Duggan and Kavanag
2005
;
Hedenstierna
2003
). Despite the greater impairment of lung aeration, arterial
oxygenation was not significantly affected in dogs of the S group compared to
dogs of the NS group. The apparently discordant results can be justified by two
theories: the use of high FiO
2
compensated for the greater impairment of lung
aeration, assuring similar arterial oxygenation in dogs of the S group; we can also
speculate that dogs of the S group had a lower cardiac output as a result of the deeper
