Early Diagnosis of Ventilator-Associated Pneumonia (Results)

22 Dec
2013

Early Diagnosis of Ventilator-Associated Pneumonia (Results)Patients

One hundred thirty-two patients (mean age, 52±19 years; mean simplified acute physiologic score,14±4; 85 men and 47 women) were included. All were suspected of presenting nosocomial bacterial pneumonia: 163 BALs and PSBs were performed. The mean duration of mechanical ventilation was 15±4 days.

The following were primary indications for ventilatory support: postoperative respiratory failure (n=40), exacerbation of COPD (n=19), other pulmonary diseases (n=10), neurologic emergencies (n=8), head injuries (n=8), multiple organ failure (n=13), severe sepsis (n=17), multisystem trauma patients (n=45), and miscellaneous (n=3).The diagnosis of bacterial pneumonia was established in 56 cases; polymicrobial growth was seen in 48.2% of the cases (27/56). There was no bacterial pneumonia in 107 cases.

Tolerance of Bronchoscopy

All the bronchoscopies were accomplished without complications (no hypoxemia, no pneumothorax, no hemorrhage); we have not observed any major hemodynamic difficulties during or following the procedure in any of the patients.

Cytology

Squanwus Epithelial Cells: None of the samples had more than 1% of squamous epithelial cells (Table 1).

Count of Total Cells: The count of total cells was significantly higher in control patients: 6,684±27,826 vs 5,113±4,983xl03/mL (p<0.001).

Count of PMNs: The count of PMNs in BAL fluid was significantly higher in the group with nosocomial pneumonia: 85±13% versus 73±24% (p<0.01).

Infected Cells: The count of ICs was made on 100 cells (Figs 1 and 2). The percentage of ICs was significantly higher in nosocomial pneumonia: 12.6±12% (95% confidence interval [Cl], 9.3 to 16) vs 1.1±3.4 (95% Cl, 0.49 to 1.8) (p<0.0001). An ROC curve was plotted: the AUC was 0.888; the curve was homogeneous without break.

The presence of ICs in 2% or more on the Giemsa stain corresponded to a sensitivity of 84%, a specificity of 80%, a positive predictive value of 69%, and a negative predictive value ot 90%. There was no correlation (Fig 3) between the percentage of ICs and quantitative cultures of PSB (r=0.25; p=0.06). Concordance between final diagnosis and IC count was 0.82 (Cohen kappa=0.063). Among the patients receiving antibiotics, sensitivity and specificity were, respectively, 82% and 77%; among the patients without antibiotics, 85% and 83%.

Bacteriology

Microscopic Examination: A Gram’s stain was performed on all BAL samples. The sensitivity and the specificity of the presence of bacteria in BAL fluid for the diagnosis were, respectively, 92% and 76.5%; the positive and negative predictive values were, respectively, 69% and 91%. However, in terms of qualitative agreement, the concordance was poor: in 44% of the cases, Gram’s stain was partially right (for example, gram-negative bacilli on Gram’s stain and Staphylococcus aureus plus Pseudomonas aeruginosa on PSB cultures) or totally false (gram-negative bacilli on Gram’s stain and gram-positive on PSB cultures).

Final Diagnosis: In 163 procedures, we noted 107 cases without pneumonia and 56 cases with pneumonia (Table 2): 18 cases with gram-negative bacilli, 11 cases with gram-positive cocci (principally S aureus), and 27 were polymicrobial infections (gram-negative bacilli and gram-positive cocci).

Table 1—Analysis of Cellularity

Group Without Pneumonia (n=107)Group With Pneumonia (n=56)p Value
ICs, %1.1±3.412.6±12<0.0001
Total cells, xl03/mL6,684 ±27,8265,113±4,983<0.001
PMNs, %73±2485 ±13<0.01

Table 2—Main Bacteriologic Results in Infected Patients (continued)

Patient

No.

BacteriaPSB Cultures, cfu/mLIC, %PMN, %Cells, 103/mL
1Escherichia coli500109517,280
Enterococcus faecalis103
M morganii500
2E coli10312754,500
P aeruginosa30
3S aureus10625904,370
Haemophilus influenzae104
Citrobacter spp100
4S aureus2xl0315753,430
P aeruginosa5xl03
5S aureus10011852,150
Klebsiella pneumoniae2.4xl03
Enterobacter spp40
6S aureus5xl065853,000
7H influenzae10635852,640
Enterobacter spp107
8H influenzae10614802,000
9E coli5 x10s29013,320
10S aureus5 x10s2901,568
11P aeruginosa10525959,200
Proteus vulgaris5xl04
S pneumoniae103
12Proteus mirabilis1072952,480
13S aureus1050804,480
14S aureus1033803,500
15H influenzae6xl03195640
H hemolyticus6xl03
S aureus3xl04
16P aeruginosa4xl038902,088
17E coli105508516,000
K pneumoniae103
H influenzae109
18Enterobacter spp10315851,480
N meningitidis106
19P aeruginosa1034595580
E cloacae100
S aureus105
20P aeruginosa1063901,300
21H influenzae1044836,300
22Proteus vulgaris4025802,380
S aureus5×10s
H influenzae103
23S pneumoniae104760500
H influenzae104
24S aureus10312805,760
25S aureus1054905,300
26E coli10510904,560
S aureus105
27M morganii1031905,100
28E coli1040803,120
29H influenzae108189519,600
S pneumoniae108
30S aureus1056902,020
31H influenzae10411951,820
S pneumoniae103
32S aureus1055952,170
E coli4xl03
33S aureus1034080280
34P aeruginosa1054856,120
35P aeruginosa10413851,338
Serratia sdd104
36P aeruginosa10309515,000
P mirabilis100
S epidermidis100
37P aeruginosa19xl0386518
S aureus103
38S aureus10479510,240
39H influenzae108259015,400
Enterobacter spp103
S aureus107
40H influenzae104035236
S epidermidis104
41K pneumoniae105485600
S aureus105
42P aeruginosa1054551,024
43K pneumoniae104309010,910
S aureus104
Candida albicans105
44H alvei5xl077854,290
S aureus5xl03
45S aureus103249510,400
E coli4xl03
46S aureus10420952,120
P vulgaris5xl03
C itrobacter freundii500
47S aureus5xl03070440
P vulgaris104
48S aureus2xl030904,000
B cepacia103
49P aeruginosa5xl04109011,760
50S aureus5xl0622952,176
51E coli1061853,600
S epidermidis100
52S aureus5xl0619903,104
H influenzae5xl06
53S aureus5xl04259811,000
Lactobacillus5xl04
E coli103
54P aeruginosa1075801,020
55S aureus5xl0415907,400
Enterobacter spp103
56Streptococcus B10540959,440

figure-1

Figure 1. ROC curve for the ICs count.

figure-2

Figure 2. Comparison of the percentage of ICs between patients with and without YAP (mean and 95% Cl).

figure-3

Figure 3. Correlation between the percentage of ICs (% of IC) and PSB cultures (log10 cfu/mL) in case of pneumonia.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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