Since the patients are from highland area,we analyzed the patients enrolled and characteristics, blood gas and mechanical ventilation data based on the Berlin definition plateau criteria .
Patients enrolled and characteristics
There was 512 with invasive mechanical ventilation admissions during the study period. Of this group, 253 patients met the Berlin definition, 229 with ARDS by Berlin Definition Plateau Criteria and 204 patients meet the Zhang criteria.( figure 1)
General Information
There were 229 patients that meet plateau criteria, 107(46.72%) were mild ARDS, 84(36.68%) were moderate ARDS and 38(16.59%) were severe ARDS.
Patients with severe ARDS have fewer chronic hepatic dysfunctions than mild to moderate patients (P=0.017), APACHE II scores at presentation were slightly higher for patients with severe ARDS (P<0.001); the most common risk factors were infection, pneumonia, aspiration and trauma.
(TABLE 1).TABLE 1 General Information of 229 meet Berlin Definition Plateau Criteria
|
Mild
|
Moderate
|
Severe
|
P values
|
No(%)
|
107(46.72%)
|
84(36.68%)
|
38(16.59%)
|
|
Age (years ,±s)
|
50.45±15.40
|
56.85±16.83
|
59.05±14.64
|
0.290
|
Male (n,%)
|
74(69.16%)
|
55(65.47%)
|
26(68.42%)
|
0.859
|
Source of entry ICU (n,%)
|
|
|
|
|
Surgery
|
39(36.45%)
|
40(47.62%)
|
10(26.32%)
|
0.064
|
Internal Medicine
|
10(9.35%)
|
10(11.90%)
|
12(31.58%)
|
0.003
|
Emergency
|
58(54.21%)
|
34(40.47%)
|
16(42.11%)
|
0.134
|
ARDS risk factors (n,%)
|
|
|
|
|
Pneumonia
|
16(14.95%)
|
18(21.43%)
|
8(21.05%)
|
0.463
|
Infection
|
37(34.58%)
|
35(41.67%)
|
11(28.95%)
|
0.355
|
Misprision
|
15(14.02%)
|
12(14.29%)
|
5(13.16%)
|
0.986
|
Trauma
|
22(20.56%)
|
15(17.86%)
|
4(10.53%)
|
0.383
|
Basic diseases (n,%)
|
|
|
|
|
Hypertension
|
33(30.84%)
|
27(32.14%)
|
8(21.05%)
|
0.434
|
Diabetes mellitus
|
15(14.02%)
|
15(17.86%)
|
1(2.63%)
|
0.073
|
Chronic pulmonary disease
|
14(13.08%)
|
21(25.00%)
|
6(15.79%)
|
0.096
|
Chronic cardiac insufficiency
|
25(23.36%)
|
25(29.76%)
|
9(23.68%)
|
0.574
|
Chronic renal dysfunction
|
19(17.76%)
|
15(17.86%)
|
2(5.26%)
|
0.153
|
Chronic liver dysfunction
|
29(27.10%)
|
17(20.24%)
|
2(5.26%)
|
0.017
|
APACHE II score
|
12.45±5.11
|
13.24±5.28
|
17.55±5.52
|
<0.001
|
PaO2/FiO2 (±s)
|
183.49±20.04
|
118.15±20.97
|
52.31±12.39
|
<0.001
|
pH (±s)
|
7.37±0.31
|
7.29±0.81
|
7.37±0.11
|
0.572
|
PaCO2(mmHg,±s)
|
36.52±18.21
|
41.17±18.26
|
42.10±12.03
|
0.098
|
PaO2(mmHg,±s)
|
82.25±35.70
|
66.2±22.92
|
43.86±14.28
|
<0.001
|
FiO2(%,±s)
|
63.92±22.37
|
71.87±21.41
|
89.47±15.93
|
<0.001
|
PEEP (cmH2O,±s)
|
5.11±0.86
|
5.36±1.59
|
5.26±0.86
|
0.358
|
Lac (mmol/L, median IQR)
|
1.90(1.30-3.40)
|
2.40(1.40-4.85)
|
3.30(2.05-5.63)
|
0.030
|
APACHE II, Acute Physiology and Chronic Health Evaluation II;PaO2,partial pressure of arterial oxygen;FiO2,fraction of inspired oxygen; PaO2, arterial oxygen partial pressure; PaCO2, arterial carbon dioxide partial pressure; FiO2,fraction of inspired oxygen; PEEP, positive end-expiratory pressure.Lac, lactic.
Blood gas and Mechanical Ventilation Practice
In the indicators of pH and arterial carbon dioxide partial pressure (PaCO2) the three groups have similar values. Arterial partial pressure of oxygen (PaO2) and PaO2/FiO2 significantly decreased with increasing ARDS severity (P <0.001), and increasing severity of ARDS was associated with higher lactate (Lac) values (TABLE 1).
The ventilator parameters were recorded during the first 24 hours which the patients fulfilled the Plateau criteria (TABLE 1). Most doctors use lung protective ventilation strategies. In order to prevent ventilator-related lung injury, PEEP have not increased with the severity of ARDS.However,the oxygen concentration fraction of inhalation (FiO2) was associated with a worse prognosis and the difference was statistically significant (P <0.001).
Outcomes in Patients with ARDS
The Berlin definition plateau criteria
Among the 229 meet Berlin Definition Plateau Criteria patients ,107(46.72%) patients diagnosed with mild ARDS , 84(36.68%) patients meet criteria for moderate ARDS, and 38(16.59%) were severe ARDS. ICU mortality increased with stages of ARDS from mild 17.76% to moderate 21.43% to severe 47.37%. 28-days mortality increased with worsen of ARDS (mild 23.36% VS moderate 44.05% VS severe 63.16%) (P<0.001). Median (IQR) 28-days ventilator free days declined with stages of ARDS from mild 21.42(3.75-26.50) days to moderate 16.53(0.00-24.28) days to severe 0.0(0.00-16.02) days (P<0.001).
Median (IQR) duration of mechanical ventilation in survivors slightly increased with stages of ARDS from mild 3.88(1.04-9.13) days to moderate 4.46 (1.40-9.45) days to severe 5.11 (2.73-11.85)days, but the difference was not statistically significant (P=0.132).Differences of between ICU length of stay and the hospital length of stay across categories of Berlin Definition (mild, moderate, and severe) were statistically significant.
The Berlin definition
253 patients meet the Berlin definition, of whom 49(19.37%) were mild,148(58.50%) were moderate and 56(22.13%) were severe ARDS.The ICU mortality of mild, moderate and severe ARDS patients were 6.12%,18.92%,42.86%,(P<0.001). With worsen of ARDS, 28-days mortality increases(mild 6.12% VS moderate 33.11% VS severe 60.71%) and median (IQR)28-days ventilator free days drops, which from mild 26.17 (20.00-27.21) days , moderate ARDS 18.73 (0.00-25.30) days to severe ARDS 0.00(0.00-18.26) days.
Diagnostic Criteria of ALI/ARDS at high altitudes in Western China
There are 204 patients that meet Zhang criteria, among the 204 enrolled patients, 87(42.65%) were ALI and 117(57.35%) were ARDS. The ICU mortality was ALI 18.39% VS ARDS 30.77%, ( P=0.045), and the 28 days mortality ARDS (51.28%) was higher than ALI (26.44%),( P<0.001).28-days ventilator free days median from ALI [19.50 (0.00-26.04)] to ARDS [4.21(0.00-23.31)] (P=0.03). There is no statistical difference between the ICU length of stay, duration of invasive ventilation and hospital length of stay. ( TABLE 2)
TABLE 2 Comparison of three criteria outcomes
|
Berlin Definition (253 cases)
|
Plateau criteria (229 cases)
|
Zhang criteria (204 cases)
|
|
Mild
|
Moderate
|
Severe
|
P values
|
Mild
|
Moderate
|
Severe
|
P values
|
ALI
|
ARDS
|
P values
|
No(%)
|
49(19.37)
|
148(58.50)
|
56(22.13)
|
|
107(46.72)
|
84(36.68)
|
38(16.59)
|
|
87(42.65)
|
117(57.35)
|
|
ICU mortality: NO(%)
|
3(6.12)
|
28(18.92)
|
24(42.86)
|
<0.001
|
19(17.76)
|
18(21.43)
|
18(47.37)
|
0.001
|
16(18.39)
|
36(30.77)
|
0.045
|
28-days mortality No(%)
|
3(6.12)
|
49(33.11)
|
34(60.71)
|
<0.001
|
25(23.36)
|
37(44.05)
|
24(63.16)
|
<0.001
|
23(26.44)
|
60(51.28)
|
<0.001
|
28-days ventilator free days median (IQR)
|
26.17
(20.00-27.21)
|
18.73
(0.00-25.30)
|
0.0
(0.00-18.26)
|
<0.001
|
21.42
(3.75-26.50)
|
16.53
(0.00-24.28)
|
5.60
(0.00-16.02)
|
<0.01
|
19.50
(0.00-26.04)
|
4.21
(0.00-23.31)
|
0.03
|
ICU length of stay, d, median (IQR)
|
6.00
(2.23-12.32)
|
8.71
(4.63-18.10)
|
6.69
(3.53-14.18)
|
0.024
|
7.67
(3.67-14.92)
|
8.23
(3.71-16.96)
|
7.69
(4.30-14.77)
|
0.929
|
8.08
(4.63-16.42)
|
7.79
(3.63-15.17)
|
0.246
|
Duration of invasive ventilation, d, median (IQR)
|
1.79
(0.73-4.98)
|
4.75
(1.50-10.62)
|
4.23
(2.16-9.92)
|
0.003
|
3.88
(1.04-9.13)
|
4.46
(1.40-9.45)
|
5.11
(2.73-11.85)
|
0.132
|
5.08
(1.46-9.83)
|
4.67
(2.15-10.63)
|
0.945
|
Hospital length of stay, d, median (IQR)
|
24.00
(19.00-38.00)
|
22.00
(13.25-35.75)
|
16.00
(6.00-25.75)
|
0.001
|
23.00
(14.00-37.00)
|
18.50
(9.25-30.00)
|
18.00
(8.00-26.00)
|
0.036
|
23.00
(14.00-38.00)
|
18.00
(9.00-29.50)
|
0.059
|
The AUROC of the Berlin Definition, the Plateau criteriaand Zhang criteria were 0.6675 (95% CIPower0.5866-0.7484), 0.6216 (95% CIPower0.5317-0.7116) and 0.6050 (95% CIPower0.5084-0.7016). There was no significant difference among the three groups.