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Table 1 Measures of R/I ratio with 5 ventilators according to theoretical R/I ratio equal to 0.0, 0.5 and 1.0

From: Recruitment-to-inflation ratio measured with modern intensive care unit ventilators: How accurate is it?

Theoretical R/I ratio

Ventilator

PEEP 5 cmH2O

PEEP 15 cmH2O

PEEP 15-to-5

Calculated values

VTe (ml)

PPlat (cmH2O)

PEEPt (cmH2O)

VTe (ml)

PPlat (cmH2O)

PEEPt (cmH2O)

EELV (ml)

Vrec (ml)

R/I

Error in R/I

0.0

A

428

14

5

412

23

15

921

33

0.07

+ 0.07

  

429

14

5

413

24

15

921

28

0.06

+ 0.06

 

B

397

14

5

386

23

15

831

4

0.01

+ 0.01

  

385

14

5

381

23

15

825

16

0.04

+ 0.04

 

C

404

14.3

5.2

407

23.8

15.2

898

47

0.11

+ 0.11

  

402

14.4

5.3

397

24.2

15.4

877

34

0.08

+ 0.08

 

D

350

14.9

5.4

353

24.5

15.3

747

29

0.08

+ 0.08

  

358

14.7

5.4

354

24.2

15.4

776

37

0.10

+ 0.10

 

E

370

14

6

380

24

15

797

1

0.00

+ 0.00

  

385

14

6

381

24

15

790

− 24

− 0.05

− 0.05

0.5

A

420

14

5

419

21

15

1172

286

0.61

+ 0.11

  

429

14

5

414

21

15

1162

271

0.57

+ 0.07

 

B

397

14

5

392

21

15

1060

227

0.51

+ 0.01

  

385

14

5

384

21

15

1045

223

0.55

+ 0.05

 

C

404

14.3

5.2

405

21.8

15.6

1144

277

0.60

+ 0.10

  

402

14.4

5.3

398

21.0

15.1

1121

290

0.67

+ 0.17

 

D

350

14.9

5.4

350

22.5

15.9

977

230

0.59

+ 0.09

  

358

14.7

5.4

355

22.0

15.9

951

192

0.47

− 0.03

 

E

370

14

6

365

22

16

950

123

0.26

− 0.24

  

385

14

6

385

22

16

1010

144

0.30

− 0.20

1.0

A

428

14

5

416

20

16

1408

471

0.90

− 0.10

  

429

14

5

415

20

16

1406

467

0.89

− 0.11

 

B

397

14

5

393

20

15

1269

435

0.99

− 0.01

  

385

14

5

385

20

15

1258

445

1.04

+ 0.04

 

C

404

14.3

5.2

397

20.4

15.9

1365

493

1.03

+ 0.03

  

402

14.4

5.3

394

20.6

15.9

1322

460

0.98

− 0.02

 

D

350

14.9

5.4

353

22.1

16.4

1140

382

0.94

− 0.06

  

358

14.7

5.4

351

21.0

16.5

1137

359

0.84

− 0.16

 

E

370

14

6

387

21

16

1220

370

0.80

− 0.20

  

385

14

6

385

20

16

1220

353

0.73

− 0.27

  1. Values are expressed as number and reported as displayed by the ventilator (i.e. with or without a decimal expansion). The ventilators were set in volume control mode with a tidal volume of 400 ml. Two independent set of measures are reported for each of the 5 ventilators (A: Carestation, B: Servo I, C: Hamilton C5, D: Infinity C500; E: EVITA XL)
  2. R/I, recruitment-to-inflation ratio; PEEP, positive end-expiratory pressure; PEEP 15-to-5, decrease in PEEP from 15 to 5 cmH2O on a single breath; VTe, expired tidal volume; PPlat, plateau pressure; PEEPt, total PEEP; EELV, end-expiratory lung volume; Vrec, recruited lung volume