Baseline demographic and clinical characteristics
Table 1 summarizes the clinical characteristics of the hypoxemia group (n = 48) and no hypoxemia group (n = 223). The mean age was 53.4 ± 7.2 and 52.9 ± 6.2 years in the two groups, respectively. The incidence of aortic valve disease, Marfan syndrome, CAD, and history of thoracic surgery were not significantly different between the groups (all p > 0.05). Compared to the control group, the hypoxemia group had significantly greater BMI, SBP, TG and WBC values and a longer length of surgery, ICU stay time, hospital stay time and mechanical ventilation time, and the differences were statistically significant (all P < 0.05). Similarly, there were statistically significant differences in the incidence of HT, T2DM, metabolic syndrome and smoking (all p > 0.05).
Table 1
clinical characteristics in two group.
Variables
|
Hypoxemia group
|
No Hypoxemia group
|
x2/t
|
P Value
|
n = 48
|
n = 223
|
Male,n(%)
|
37(77.1)
|
164(73.5)
|
0.258
|
0.611
|
Age,years
|
53.4 ± 7.2
|
52.9 ± 6.2
|
0.555
|
0.579
|
BMI,Kg/m2
|
29.2 ± 4.1
|
25.8 ± 2.7
|
-7.277
|
< 0.001
|
HT,n(%)
|
32(66.7)
|
113(50.7)
|
4.062
|
0.044
|
T2DM,n(%)
|
19(39.6)
|
26(11.7)
|
22.241
|
< 0.001
|
Aortic valve disease,n(%)
|
4(8.3)
|
16(7.2)
|
0.078
|
0.781
|
Metabolic syndrome,n(%)
|
27(56.3)
|
17(7.6)
|
68.673
|
< 0.001
|
smoker,n(%)
|
31(64.6)
|
96(43.0)
|
7.355
|
0.007
|
Marfan syndrome,n(%)
|
1(2.1)
|
1(0.4)
|
1.441
|
0.230
|
CAD,n(%)
|
7(14.6)
|
34(15.2)
|
0.014
|
0.907
|
History of thoracic surgery,n(%)
|
2(4.2)
|
21(9.4)
|
1.402
|
0.236
|
SBP,mmHg
|
150.5 ± 13.4
|
143.4 ± 13.8
|
-3.264
|
0.001
|
DBP,mmHg
|
80.3 ± 6.2
|
79.1 ± 6.7
|
-1.110
|
0.268
|
HR,bpm
|
70.1 ± 12.3
|
71.7 ± 11.1
|
0.177
|
0.383
|
LVEF,%
|
56.9 ± 6.0
|
57.4 ± 6.5
|
0.480
|
0.632
|
Troponin I, ng/mL
|
0.01(0,0.01)
|
0(0,0.01)
|
-1.103
|
0.270
|
FBG, mmol/L
|
5.0 ± 0.7
|
4.9 ± 0.4
|
-1.229
|
0.220
|
TG, mmol/L
|
1.5(1.1,2.6)
|
1.2(1.0,1.5)
|
-2.620
|
0.009
|
HDL-C, mmol/L
|
1.2(0.9,1.8)
|
1.6(1.1,2.2)
|
-3.925
|
< 0.001
|
WBC,1012/L
|
11.4 ± 1.9
|
10.0 ± 1.4
|
-5.961
|
< 0.001
|
PLT,109/L
|
235.5 ± 67.8
|
217.6 ± 58.9
|
-1.653
|
0.100
|
RBC, 1012/L
|
4.6 ± 0.6
|
4.6 ± 0.5
|
-0.426
|
0.670
|
Cr, µmol/L
|
75.4 ± 16.4
|
76.2 ± 21.3
|
0.246
|
0.806
|
UA, µmol/L
|
349.0 ± 91.9
|
338.6 ± 76.9
|
0.725
|
0.469
|
eGFR, mL/(min·1.73 m2)
|
90.9 ± 14.3
|
90.5 ± 16.2
|
-0.145
|
0.885
|
Length of surgery, min
|
287.3 ± 19.4
|
276.2 ± 24.9
|
-2.913
|
0.004
|
Cardiopulmonary bypass time,min
|
167.5 ± 22.5
|
170.0 ± 23.0
|
0.674
|
0.501
|
Cross-clamp time,min
|
87.7 ± 13.6
|
88.7 ± 13.0
|
0.465
|
0.642
|
Circulatory arrest,min
|
43.4 ± 7.3
|
42.1 ± 7.5
|
-1.076
|
0.283
|
Minimum temperature,°C
|
26.0 ± 0.5
|
26.0 ± 0.5
|
1.105
|
0.270
|
ICU stay time,day
|
6.7 ± 1.6
|
5.4 ± 1.5
|
-5.488
|
< 0.001
|
Hospital stay time,day
|
20.0 ± 3.7
|
17.1 ± 4.2
|
-4.522
|
< 0.001
|
PaO2/FiO2, mmHg
|
256.4 ± 24.4
|
330.8 ± 13.5
|
29.346
|
< 0.001
|
Mechanical ventilation time,hour
|
39.2 ± 21.9
|
21.1 ± 8.2
|
-9.587
|
< 0.001
|
Elevated BMI,n (%)
|
18(37.5)
|
11(4.9)
|
43.839
|
< 0.001
|
Elevated BP,n (%)
|
47(97.9)
|
203(91.0)
|
2.619
|
0.106
|
Elevated FBG,n (%)
|
23(47.9)
|
31(13.9)
|
28.643
|
< 0.001
|
Reduced HDL-C,n (%)
|
25(52.1)
|
42(18.8)
|
23.462
|
< 0.001
|
Elevated TG,n (%)
|
16(33.3)
|
26(11.7)
|
14.168
|
< 0.001
|
BMI: body mass index; HT: Hypertension; T2DM: type 2 diabetes mellitus; SBP: systolic blood pressure; DBP: diastolic blood pressure; HR: heart rate; FBG: Fasting blood glucose; TG: Triglycerides; HDL-C: high-density lipoprotein cholesterol; WBC: white blood cell; PLT: Platelet; Cr: creatinine; UA: Uric acid; LVEF: ventricular ejection fraction. |
METs incidence and clinical characteristics
Participants were divided into six groups according to whether they met 0, 1, 2, 3, 4 or 5 of the METs diagnostic criteria, and there were 10 (3.7%), 136 (50.2%), 81 (29.9%), 33 (12.2%), 10 (3.7%) and 1 (0.3%) individuals in the respective groups. Hypoxemia was present in 0%, 3.7%, 19.8%, 51.5%, 90.0% and 100% of the six groups, with significant differences among groups (P < 0.05, Table 2 Fig. 2). The prevalence of males was the highest in the 0 group. There were significant differences among the six groups in terms of mechanical ventilation time, WBC, PaO2/FiO2, cross-clamp time and LVEF (all P < 0.001). The MetS components BMI, HT, T2DM, SBP, and TG increased with increasing numbers of traits. For comparisons among groups, the greatest difference was in BMI. (P < 0001, Table 2).
Table 2
Baseline characteristics of the number of METs.
Variables
|
the number of the presence of MetS
|
0
|
1
|
2
|
3
|
4
|
5
|
P Value
|
P<0.05
|
n=10
|
n=136
|
n=81
|
n=33
|
n=10
|
n=1
|
Male,n(%)
|
8(80.0)
|
101(74.3)
|
62(76.5)
|
21(63.6)
|
8(80.0)
|
1(100.0)
|
0.723
|
c,e,i,l
|
Age,years
|
52.1±3.9
|
53.1±6.5
|
53.0±5.6
|
52.3±7.7
|
52.9±7.4
|
65
|
0.521
|
e,l
|
BMI,Kg/m2
|
24.3±1.7
|
25.4±2.3
|
26.9±2.9
|
27.2±3.4
|
33.7±5.0
|
35.0
|
<0.001
|
b,c,d,e,f,g,h,i,k,l,m,n
|
HT,n(%)
|
0(0)
|
71(52.5)
|
45(55.6)
|
23(69.7)
|
5(50.0)
|
1(100.0)
|
0.006
|
a,b,c,d,e,i,l,n,o
|
T2DM,n(%)
|
0(0)
|
3(2.2)
|
18(22.2)
|
18(54.5)
|
5(50.0)
|
1(100.0)
|
<0.001
|
b,c,d,e,g,h,i,l,m,n,o
|
Hypoxemia,n(%)
|
0(0)
|
5(3.7)
|
16(19.8)
|
17(51.5)
|
9(90.0)
|
1(100.0)
|
<0.001
|
b,c,d,e,g,h,i,j,k,l,m,n,o
|
SBP,mmHg
|
123.8±6.5
|
144.8±14.8
|
144.7±11.7
|
148.9±13.0
|
149.7±9.4
|
149
|
<0.001
|
a,b,c,d,e
|
DBP,mmHg
|
72.2±6.7
|
79.5±6.4
|
79.3±6.8
|
80.4±6.5
|
81.5±6.6
|
80
|
0.019
|
a,b,c,d
|
HR,bpm
|
68.8±5.3
|
73.3±12.9
|
70.5±9.3
|
69.0±7.9
|
65.2±12.9
|
59
|
0.063
|
|
FBG,mmol/L
|
5.2±0.3
|
4.9±0.4
|
5.0±0.5
|
5.1±0.6
|
5.1±0.8
|
6.3
|
0.002
|
a,e,f,g,i,l,n
|
TG,mmol/L
|
1.2(0.9,1.3)
|
1.2(1.0,1.4)
|
1.3(1.1,1.6)
|
1.5(1.2,2.1)
|
2.7(2.1,3.3)
|
2.4
|
<0.001
|
c,d,e,f,g,h,i,k,m
|
Mechanical ventilation time,hour
|
19.9±7.9
|
21.6±9.2
|
25.2±13.4
|
29.9±12.8
|
40.1±18.8
|
36
|
<0.001
|
d,f,g,h,k
|
WBC,1012/L
|
9.6±2.0
|
10.1±1.4
|
10.0±1.7
|
10.6±1.5
|
11.6±2.2
|
10.3
|
0.024
|
d,h,k
|
PLT,109/L
|
198.5±32.7
|
217.1±56.0
|
225.5±63.0
|
225.0±70.4
|
215.8±77.2
|
372
|
0.118
|
e,i,l
|
PaO2/FiO2,mmHg
|
334.9±12.5
|
328.2±15.9
|
321.2±28.2
|
285.4±43.8
|
243.8±33.8
|
224
|
<0.001
|
d,e,f,g,h,i,j,k,l,m
|
Length of surgery, min
|
293.1±30.7
|
275.1±24.9
|
279.2±23.5
|
281.0±22.3
|
284.8±18.8
|
298
|
0.163
|
a
|
Cardiopulmonary bypass time, min
|
164.4±16.7
|
167.5±21.9
|
172.8±24.3
|
167.4±24.1
|
183.2±23.6
|
163.0
|
0.212
|
h
|
Cross-clamp time, min
|
87.9±10.7
|
88.8±13.3
|
89.4±12.6
|
82.8±11.6
|
95.9±17.0
|
103
|
0.049
|
g,j,m
|
Circulatory arrest, min
|
45.6±5.8
|
42.2±6.9
|
42.2±8.3
|
41.3±6.2
|
46.5±12.1
|
40.6
|
0.333
|
|
Minimum temperature
|
25.9±0.5
|
26.1±0.5
|
26.0±0.5
|
26.0±0.5
|
26.2±0.5
|
25.2
|
0.312
|
|
HDL-C, mmol/L
|
1.5(1.2,2.2)
|
1.8(1.3,2.3)
|
1.3(0.9,1.8)
|
1.0(0.9,1.5)
|
0.9(0.8,1.5)
|
0.8
|
<0.001
|
c,f,g,h,j
|
LVEF,%
|
60.5±7.6
|
57.3±6.2
|
58.0±6.3
|
54.7±6.2
|
57.7±7.6
|
58
|
0.100
|
c,g,j
|
a:0vs1, b:0vs2, c:0vs3, d:0vs4, e:0vs5, f:1vs2, g:1vs3, h:1vs4, i:1vs5, g:2vs3, k:2vs4, l:2vs5, m:3vs4, n:3vs5, o:4vs5.
METs:Metabolic Syndrome;BMI: body mass index; HT:Hypertension; T2DM: type 2 diabetes mellitus; SBP: systolic blood pressure; DBP: diastolic blood pressure;HR: heart rate; FBG:Fasting blood glucose; TG: Triglycerides;HDL-C: high-density lipoprotein cholesterol; LVEF:ventricular ejection fraction.
|
METs components and hypoxemia
After adjustment for some potential risk factors, such as age, male sex, HR, CAD, previous thoracic surgery, and smoking, BMI quartiles (adjusted OR = 2.616, 95% CI 1.743–3.924, P < 0.001), HDL (adjusted OR = 0.560, 95% CI 0.393–0.799, P < 0.001) and SBP (adjusted OR = 1.646, 95% CI 1.145–2.367, P = 0.007) remained independent factors of hypoxemia. People with T2DM had a significantly increased risk of hypoxemia compared with those with no T2DM in all groups (adjusted OR = 5.460, 95% CI 2.211–13.484, P < 0.001). Compared with the first BMI quartile, the second, third and fourth BMI quartiles had ORs of incident hypoxemia of 6.124 (95% CI 1.056–35.493), 6.269 (95% CI 1.142–34.409), and 33.918 (95% CI 6.084–189.102), respectively, after adjusting for potential risk factors (Table 3).
Table 3
Impact of MetS components on patients with hypoxemia.
Variables
|
Quartiles of components
|
All
|
Range
|
n
|
Hypoxemia/No Hypoxemia
|
OR(95%CI)
|
P Value
|
HT,n(%)
|
-
|
145
|
32/113
|
1.827(0.820–4.067)
|
0.140
|
T2DM,n(%)
|
-
|
45
|
19/26
|
5.460(2.211–13.484)
|
< 0.001
|
BMI,Kg/m2
|
Per quartile
|
271
|
48/223
|
2.616(1.743–3.924)
|
< 0.001
|
|
Q1 ≤ 24.44
|
68
|
2/66
|
-
|
-
|
|
24.22 < Q2 ≤ 26.02
|
68
|
8/60
|
6.124(1.056–35.493)
|
0.043
|
|
26.02 < Q3 ≤ 27.88
|
68
|
10/58
|
6.269(1.142–34.409)
|
0.035
|
|
27.88 < Q4
|
67
|
28/39
|
33.918(6.084-189.102)
|
< 0.001
|
TG, mmol/L
|
Per quartile
|
271
|
48/223
|
1.236(0.870–1.756)
|
0.238
|
|
Q1 ≤ 1.04
|
70
|
11/59
|
-
|
-
|
|
1.04 < Q2 ≤ 1.23
|
66
|
9/57
|
1.370(0.411–4.569)
|
0.608
|
|
1.23 < Q3 ≤ 1.49
|
67
|
5/62
|
0.261(0.062–1.091)
|
0.066
|
|
1.69 < Q4
|
68
|
23/45
|
2.268(0.696–7.384)
|
0.174
|
HDL-C,mmol/L
|
Per quartile
|
271
|
48/223
|
0.560(0.393–0.799)
|
0.001
|
|
Q1 ≤ 1.15
|
65
|
23/42
|
-
|
-
|
|
1.15 < Q2 ≤ 1.56
|
71
|
9/62
|
0.517(0.157–1.708)
|
0.279
|
|
1.56 < Q3 ≤ 2.12
|
68
|
10/58
|
0.383(0.126–1.167)
|
0.091
|
|
2.12 < Q4
|
67
|
6/61
|
0.091(0.024–0.351)
|
< 0.001
|
SBP,mmHg
|
Per quartile
|
271
|
48/223
|
1.646(1.145–2.367)
|
0.007
|
|
Q1 ≤ 135
|
66
|
5/61
|
-
|
-
|
|
135 < Q2 ≤ 143
|
70
|
11/59
|
4.178(0.901–19.367)
|
0.068
|
|
143 < Q3 ≤ 153
|
68
|
13/55
|
3.265(0.737–14.462)
|
0.119
|
|
153 < Q4
|
67
|
19/48
|
7.367(1.676–32.377)
|
0.008
|
DBP,mmHg
|
Per quartile
|
271
|
48/223
|
0.988(0.678–1.441)
|
0.952
|
|
Q1 ≤ 75
|
70
|
10/60
|
-
|
|
|
75 < Q2 ≤ 80
|
69
|
10/59
|
0.606(0.153–2.399)
|
0.475
|
|
80 < Q3 ≤ 84
|
62
|
16/46
|
1.148(0.351–4.180)
|
0.834
|
|
84 < Q4
|
70
|
12/58
|
0.557(0.142–2.182)
|
0.401
|
FBG,mmol/L
|
Per quartile
|
271
|
48/223
|
0.976(0.698–1.366)
|
0.889
|
|
Q1 ≤ 4.58
|
66
|
12/54
|
-
|
|
|
4.62 < Q2 ≤ 4.93
|
68
|
13/55
|
0.989(0.312–3.141)
|
0.986
|
|
4.93 < Q3 ≤ 5.29
|
69
|
6/63
|
0.353(0.082–1.522)
|
0.163
|
|
5.29 < Q4
|
68
|
17/51
|
0.951(0.303–2.987)
|
0.932
|
OR:odds ratio;CI:confdence interval; METs:Metabolic Syndrome; BMI: body mass index; HT:Hypertension; T2DM: type 2 diabetes mellitus; HDL-C:high-density lipoprotein cholesterol, TG:Triglycerides, FBG:Fasting blood glucose; SBP: systolic blood pressure; DBP: diastolic blood pressure. |
a Multiple adjustment for Age,Male,HR,CAD,Previous thoracic surgey,Aortic valve disease,Marfan syndrome,smoker,LVEF, Length of surgey,Cardiopulmonary bypass time,Cross-clamp time, Circulatory arrest,Minimum temperature,TroponinI,WBC,PLT,RBC,ICU stay time,Hospital stay time,Mechanical ventilation time,PaO2/FiO2,Cr,eGFR,UA. |
METs and hypoxemia
Table 4 shows the results of multivariate logistic regression analysis of the association between the incidence of hypoxemia and MetS. There were five models that adjusted for age, male sex, HR, CAD, previous thoracic surgery, aortic valve disease, Marfan syndrome, smoking status, LVEF, length of surgery, cardiopulmonary bypass time, cross-clamp time, circulatory arrest, minimum temperature, troponin I, WBCs, PLTs, RBCs, ICU stay time, hospital stay time, mechanical ventilation time, PaO2/FiO2, Cr, eGFR, UA, elevated body mass index, elevated blood pressure, elevated fasting glucose, reduced high-density lipoprotein cholesterol, and elevated triglycerides. The ORs were 17.112, 20.521, 31.229, 40.132, and 68.053 for MetS in Models 1, 2, 3, 4, and 5, respectively (all P < 0.05).
Table 4
Odds ratio and 95% confdence interval for hypoxemia
Models
|
MetS
|
OR(95%CI)
|
P Value
|
Model 1
|
17.112(7.742–37.821)
|
< 0.001
|
Model 2
|
20.521(8.921–47.203)
|
< 0.001
|
Model 3
|
31.229(11.295–86.341)
|
< 0.001
|
Model 4
|
40.132(5.461-294.906)
|
< 0.001
|
Model 5
|
68.053(2.026-2283.417)
|
0.019
|
Model 1:adjusted for Age,Male,HR; |
Model 2:adjusted for Age,Male,HR,CAD,Previous thoracic surgey,Aortic valve disease,Marfan syndrome; |
Model 3:adjusted for Age,Male,HR,CAD,Previous thoracic surgey,Aortic valve disease,Marfan syndrome,smoker,LVEF, Length of surgey,Cardiopulmonary bypass time,Cross-clamp time, Circulatory arrest,Minimum temperature; |
Model 4:adjusted for Age,Male,HR,CAD,Previous thoracic surgey,Aortic valve disease,Marfan syndrome,smoker,LVEF, Length of surgey,Cardiopulmonary bypass time,Cross-clamp time, Circulatory arrest,Minimum temperature,TroponinI,WBC,PLT,RBC,ICU stay time,Hospital stay time,Mechanical ventilation time,PaO2/FiO2,Cr,eGFR,UA; |
Model 5:adjusted for Age,Male,HR,CAD,Previous thoracic surgey,Aortic valve disease,Marfan syndrome,smoker,LVEF, Length of surgey,Cardiopulmonary bypass time,Cross-clamp time, Circulatory arrest,Minimum temperature,TroponinI,WBC,PLT,RBC,ICU stay time,Hospital stay time,Mechanical ventilation time,PaO2/FiO2,Cr,eGFR,UA,elevated body mass index, elevated blood pressure,elevated fasting glucose,reduced high-density lipoprotein cholesterol,elevated triglycerides. |
METs scoring system and ROC curve analysis
Based on the regression coefficient, a point was assigned to each METs component. Elevated BMI was given 2 points, elevated BP was given 2 points, elevated FBG was given 1 point, reduced HDL was given 1 point, and elevated TG was given 1 point (Table 5). ROC curves were constructed to evaluate the scoring system. The AUCs were 0.852 (95% CI: 0.789–0.914) in all patients, 0.728 (95% CI: 0.573–0.882) in patients with METs and 0.744 (95% CI: 0.636–0.853) in patients without METs (Table 6 Fig. 3).
Table 5
Multivariable analysis of the METs components.
Variables
|
OR(95%CI)
|
P Value
|
Regression Coefficeint
|
point
|
Elevated BMI
|
12.084(4.193–34.828)
|
< 0.001
|
2.482
|
2
|
Elevated BP
|
9.829(0.867-111.455)
|
0.065
|
2.285
|
2
|
Elevated FBG
|
5.814(2.538–13.318)
|
< 0.001
|
1.760
|
1
|
Reduced HDL-C
|
5.300(2.358–11.914)
|
< 0.001
|
1.668
|
1
|
Elevated TG
|
2.822(1.100-7.238)
|
0.031
|
1.037
|
1
|
BMI: body mass index; BP: blood pressure; FBG:Fasting blood glucose; HDL-C: high-density lipoprotein cholesterol; TG: Triglycerides. |
Table 6
The ROC Curve analysis of the METs with hypoxemia.
Factors
|
AUC
|
P
|
95%CI
|
Se(%)
|
Sp(%)
|
Cut off point
|
All Patients
|
0.852
|
<0.001
|
0.789–0.914
|
85.40%
|
70.40%
|
4
|
MetS
|
0.728
|
0.012
|
0.573–0.882
|
81.50%
|
52.90%
|
6
|
non-MetS
|
0.744
|
<0.001
|
0.636–0.853
|
76.20%
|
68.40%
|
3
|
Se:sensitive,SP:specifity. |