The investigators performed the clinical study on a total of 50 patients in a 14 months period. The median age of the whole group was 53 years (22 - 80). There were 28 males and 22 females. The data presented in Table 1 provides demographic information, co-morbidities, pulmonary function tests of 26 patients with possible moderate to severe lung disorders, as well as surgical approach and type of surgery. Pulmonary function tests were not obtained from all patients due to the COVID-19 pandemic.
Table 1. Demographic Data and Operation Characteristics of Patients undergoing Elective Thoracic Surgery with Open Lung Ventilation.
Age, (year)
|
55.46 ± 13.85
|
Height, (cm)
|
168.5 ± 8.43
|
Weight, (kg)
|
77.76 ± 16.1
|
Body mass index, (kg/m2)
|
27.54 ± 6.17
|
Gender, n (%)
|
|
Female
|
22 (44)
|
Male
|
28 (56)
|
ASA-PS, n (%)
|
|
I
|
5 (10)
|
II
|
27 854)
|
III
|
18 (36)
|
FVC, (mL)
|
2.87 ± 0.68
|
FEV1
|
2.3 ± 0.59
|
Smoking, n (%)
|
34 (68)
|
COPD, n (%)
|
11 (22)
|
Hypertension, n (%)
|
17 (34)
|
Diabetes mellitus, n (%)
|
8 (16)
|
Coronary artery disease, n (%)
|
6 (12)
|
Right side intervention, n (%)
|
24 (48)
|
Surgical approach, n (%)
|
|
Thoracotomy
|
27 (54)
|
VATS
|
23 (46)
|
Type of surgery, n (%)
|
|
Lung biopsy
|
12 (24)
|
Wedge resection
|
19 (38)
|
Lobectomy
|
14 (28)
|
Pneumonectomy
|
5 (10)
|
Duration of operation, (min)
|
71.3 ± 37.59
|
Abbreviations: ASA-PS, American Society of Anesthesiologists-physical status; BMI, body mass index; COPD, chronic obstructive pulmonary disease; FVC, forced vital capacity; FEV1, forced expiratory volume fist second; VATS, video assisted; thoracoscopic surgery.
Hemodynamic and oximeter data were continuously monitored. The investigators collected the data during several phases of the anesthesia and surgery. First, during the patient's arrival to the operating room in the supine position breathing room air (basal), and during preoxygenation with 100% oxygen in the supine position (preoxygenation), 5 minutes after tracheal intubation during two-lung ventilation in the supine position (ORiDS5), 5 minutes after placing the patient in a lateral position with two-lung ventilation (ORiDL5), at 1 minute after OLV placement (OROLV1), 2 minutes after OLV placement (OROLV120), 5 minutes (OROLV5), 10 minutes (OROLV10), 15 minutes (OROLV15), 30 minutes (OROLV30), 45 minutes (OROLV45), and 60 minutes (OROLV60) and 90 minutes (OROLV90). At the time point of five minutes after tracheal intubation in the supine position (ORiDS5), ORi = 0 value was observed in 12 of the 19 patients who presented with SpO2 values of less than 95%, which is defined as hypoxemia. Table 2 shows the diagnostic test for ORi = 0 at different time points during anesthesia induction and maintenance for predicting hypoxemia at a level of SpO2 less than 95% during OLV. At the time point of ORiDS5, which presents five minutes after tracheal intubation in the supine position, recorded ORi equals zero together with a higher incidence of SpO2 values of less than 95%. Therefore, the accuracy for predicting hypoxemia during anesthesia induction showed a sensitivity of 92.3% (95% CI 84.9-99.6), specificity of 81.1% (95% CI 70.2-91.9), and an accuracy of 84.0% (95% CI 73.8- 94.2).
Table 2. The Data Analysis of ORi Equals to Zero and Accuracy for Predicting Hypoxemia During OLV at Different Time Points of Surgery.
|
Sensitivity
|
Specificity
|
PPV
|
NPV
|
PLHR
|
NLHR
|
Accuracy
|
Preoxygenation (95% CI)
|
0.15
(0.1-0.3)
|
91.9
(84.3-99.5)
|
40
(26.4-53.6)
|
75.6
(63.6-87.5)
|
1.9
(1.9-5.7)
|
0.9
(0.8-1)
|
72
(59.6-84.4)
|
ORIDS5 = 0
(95% CI)
|
92.3
(84.9-99.6)
|
81.1
(70.2-.91.9)
|
63.2
(49.8-76.5)
|
96.8
(91.9-100)
|
4.9
(1.1-10.9)
|
0.1
(0.1-0.2)
|
84
(73.8-94.2)
|
ORIDL5 = 0
(95% CI)
|
69.2
(56.4-82)
|
83.3
(73-93.7)
|
81.8
(71.1-92.5)
|
71.4
(58.9-84)
|
4.2
(1.4-9.7)
|
0.4
(0.2-0.5)
|
76
(64.2-87.8)
|
OROLV1 = 0
(95% CI)
|
63.6
(50.3-77)
|
75
(63-87)
|
66.7
(53.6-79.7)
|
72.4
(60-84.8)
|
2.6
(1.8-6.9)
|
0.5
(0.3-0.6)
|
70
(57.3-82.7)
|
OROLV2 = 0 (95% CI)
|
65.2
(52-78.4)
|
70.4
(57.7-83)
|
68.2
(55.3-81.1)
|
70.4
(57.7-83)
|
2.2
(1.9-6.2)
|
0.5
(0.4-0.6)
|
69.4
(56.6-82.2)
|
OROLV5 = 0 (95% CI)
|
56.5
(42.8-70.3)
|
66.7
(53.6-79.7)
|
59.1
(45.5-72.7)
|
64.3
(51-77.6)
|
1.7
(0.7-2.7)
|
0.7
(0.5-0.8)
|
62
(48.5-75.5)
|
OROLV10 = 0 (95% CI)
|
56
(42.2-70)
|
64
(50.7-77.3)
|
60.9
(47.3-74.4)
|
59.3
(50-72.9)
|
1.6
(0.6-2.6)
|
0.7
(0.6-0.8)
|
60
(46.4-73.6)
|
OROLV15 = 0 (95% CI)
|
52.2
(38-66.3)
|
68
(54.8-81.2)
|
60
(46.1-73.9)
|
60.7
(46.9-74.5)
|
1.6
(0.6-2.7)
|
0.7
(0.6-0.8)
|
60.4
(46.6-74.3)
|
OROLV30 = 0 (95% CI)
|
43.8
(29.7-57.8)
|
64
(50.4-77.6)
|
43.8
(29.7-57.8)
|
64
(50.4-77.6)
|
1.2
(0.2-2.2)
|
0.9
(0.8-1)
|
56.1
(42.1-70.1)
|
OROLV45 = 0 (95% CI)
|
40
(23.3-56.7)
|
72.2
(57-87.5)
|
54.5
(37.6-71.5)
|
59.1
(42.3-75.9)
|
1.4
(0.3-2.7)
|
0.8
(0.7-1)
|
57.6
(40.7-74.4)
|
OROLV60 = 0 (95% CI)
|
53.3
(35.8-70.9)
|
68.8
(52.4-85.1)
|
61.5
(44.4-78.7)
|
61.1
(43.9-78.3)
|
1.7
(0.4-3)
|
0.7
(0.5-0.8)
|
61.3
(44.1-78.4)
|
OROLV90 = 0 (95% CI)
|
50
(25.5-75)
|
66.7
(43.6-90)
|
71.4
(49.3-93.6)
|
44.4
(20.1-68.8)
|
1.5
(0.2-4.3)
|
0.8
(0.5-0.9)
|
56.3
(31.9-80.6)
|
Abbreviations: ORi, oxygen reserve index; OR, oxygen reserve; OLV, one-lung ventilation; PPV, positive predictive value; NPV, negative predictive value; PLHR, positive likelihood ratio; NLHR, negative likelihood ratio; CI, confidental interval; ORiDS5, ORi under mechanical ventilation 5 minutes after intubation in supine position; ORiDL5, ORi under mechanical ventilation 5 minutes after positioning in the lateral decubitus position; OROLV1, ORi after 1 minutes of OLV; OROLV2, ORi after 2 minutes of OLV; OROLV5, ORi after 5 minutes of OLV; OROLV10, ORi after 10 minutes of OLV; OROLV15, ORi after 15 minutes of OLV; OROLV30, ORi after 30 minutes of OLV; OROLV45, ORi after 45 minutes of OLV; OROLV60, ORi after 60 minutes of OLV; OROLV90, ORi after 90 minutes of OLV.
In Figure 1, data analysis provides thirteen different time points during the anesthesia induction and maintenance of the surgery. In this analysis, a correlation of ORi and SpO2 values at different time points during the anesthesia induction and maintenance periods are shown in a continuous graph. This correlation shows that a strong correlation between ORi and SpO2 was found at the at time points of DS5; (r = 0.286, p = 0.044), DL5 (r = 0.293, p = 0.039), at OLV10; there is a significant correlation with SpO2 (r = 0.360, p = 0.011) (Figure 1).
Later, we statistically evaluated the representative trends of the oxygen reserve index (ORi) and perfusion index (PI) values and the oxygen reserve index (ORi) and pleth variability index (PVI) values at different time points during anesthesia induction and maintanace of thoracic surgery. These are represented in Figure 2 and 3.
Table 3 shows the median values and interquartile range of PI and PVI values at different measurement points during the study. The analysis of correlations between these PI and PVI values showed a correlation between PI and PVI values at the time point of ORiDL5 (r = -0.284, p = 0.046). In other time points, a correlation was not observed. Table 4 provides time-dependent correlations between ORi with SpO2, PI, and PVI. These correlation analysis provide data that ORi has significant correlations with SpO2, PI and PVI at some specific time points and these include; 1- at time point of DS5; (r = 0.286, p = 0.044), DL5 (r = 0.293, p = 0.039), and OLV10; there is a significant correlation with SpO2 (r = 0.360, p = 0.011), 2- at time point of DLS5; there is a significant negative correlation with PI (r = -0.332, p = 0.019), whereas; 3- no correlations with PVI was noted.
Table 3. The Median Values and Interquartile Range of Perfusion Index (PI) and Pleth Variability Index (PVI) Values at Different Measurement Points of Surgery.
Time (min)
|
Perfusion Index (PI)
|
|
Pleth Variability Index (PVI)
|
Median
|
Interquartile range (IQR)
|
|
Median
|
Interquartile range (IQR)
|
Baseline
|
1.55
|
0.86-2.3
|
|
20.5
|
14-30.25
|
Preoxygenation
|
1.8
|
1.3-2.6
|
|
18.5
|
13-30.25
|
DS5
|
1.6
|
1-2.5
|
|
16
|
11-21
|
DL5
|
1.7
|
1.28-2.3
|
|
17
|
12-26
|
OLV1
|
1.3
|
0.61-1.3
|
|
16.5
|
11.75-23
|
OLV2
|
1.1
|
0.63-1.93
|
|
13.5
|
10-21.25
|
OLV5
|
1.3
|
0.64-1.93
|
|
14
|
10-20.25
|
OLV10
|
1.3
|
0.71-1.7
|
|
17
|
10.5-22.5
|
OLV15
|
1.25
|
0.76-2.1
|
|
15
|
10.25-21
|
OLV30
|
1.1
|
0.66-2
|
|
17
|
10-22
|
OLV45
|
1.3
|
0.82-2.1
|
|
14
|
8.5-20.5
|
OLV60
|
1.2
|
0.63-2.2
|
|
14
|
10-22
|
OLV90
|
1.1
|
0.73-2
|
|
13
|
8.5-18.75
|
Abbreviations: PI, perfusion index; PVI, pleth variability index; IQR, interquartile range; DLV, double-lung ventilation; OLV, one-lung ventilation; DS5, under mechanical ventilation 5 minutes after intubation in supine position; DL5, under mechanical ventilation 5 minutes after positioning in the lateral decubitus position; OLV1, after 1 minutes of OLV; OLV2, after 2 minutes of OLV; OLV5, after 5 minutes of OLV; OLV10, after 10 minutes of OLV; OLV15, after 15 minutes of OLV; OLV30, after 30 minutes of OLV; OLV45, after 45 minutes of OLV; OLV60, after 60 minutes of OLV; OLV90, after 90 minutes of OLV.
Table 4. Time-Dependent Correlations between Oxygen Reserve Index (ORi) with Peripheral Oxygen Saturation (SpO2), Perfusion Index (PI) and Pleth Variability Index (PVI) during Surgery.
Time (min)
|
Peripheral Oxygen Saturation (SpO2)
|
|
Perfusion Index
(PI)
|
|
Pleth Variability Index
(PVI)
|
r
|
p
|
|
r
|
p
|
|
r
|
p
|
Preoxygenation
|
0.121
|
0.404
|
|
0.042
|
0.774
|
|
0.017
|
0.908
|
DS5
|
0.286
|
0.044*
|
|
-0.332
|
0.019*
|
|
0.073
|
0.617
|
DL5
|
0.293
|
0.039*
|
|
-0.010
|
0.947
|
|
0.089
|
0.540
|
OLV1
|
-0.030
|
0.834
|
|
0.020
|
0.888
|
|
-0.013
|
0.984
|
OLV2
|
-0.087
|
0.548
|
|
0.158
|
0.272
|
|
-0.147
|
0.307
|
OLV5
|
-0.249
|
0.081
|
|
0.133
|
0.358
|
|
-0.001
|
0.997
|
OLV10
|
0.360
|
0.011*
|
-0.240
|
0.097
|
-0.058
|
0.692
|
OLV15
|
0.241
|
0.099
|
|
-0,247
|
0.091
|
|
-0.175
|
0.234
|
OLV30
|
-0.162
|
0.313
|
|
0.305
|
0.053
|
|
-0.189
|
0.237
|
OLV45
|
0.270
|
0.129
|
|
-0.115
|
0.529
|
|
0.038
|
0.837
|
OLV60
|
0.092
|
0.630
|
|
-0.179
|
0.344
|
|
-0.036
|
0.850
|
OLV90
|
-0,412
|
0.113
|
|
0.433
|
0.094
|
|
-0.167
|
0.535
|
Abbreviations: ORi, Oxygen Reserve Index; SpO2, peripheral oxygen saturation; PI, perfusion index; PVI, pleth variability index; DLV, double-lung ventilation; OLV, one-lung ventilation; DS5, under mechanical ventilation 5 minutes after intubation in supine position; DL5, under mechanical ventilation 5 minutes after positioning in the lateral decubitus position; OLV1, after 1 minutes of OLV; OLV2, after 2 minutes of OLV; OLV5, after 5 minutes of OLV; OLV10, after 10 minutes of OLV; OLV15, after 15 minutes of OLV; OLV30, after 30 minutes of OLV; OLV45, after 45 minutes of OLV; OLV60, after 60 minutes of OLV; OLV90, after 90 minutes of OLV.
For hemodynamical parameters, as collected as; MAP, SBP, DBP, HR oximeter related SpO2 values, a correlation between these parameters were not found in statistical analysis (p>0.05). In our study, we demonstrated a time-dependent correlation between PVI and MAP at the time point of OLV90, indicating that PVI showed a relation to MAP at a late stage of the thoracic surgical procedure.