Table 2 Ventilation parameters and capnography indices obtained at low, medium and high breathing frequencies in spontaneously breathing subjects (n = 35).

From: Relationships between capnogram parameters by mainstream and sidestream techniques at different breathing frequencies

 

Low

Medium

High

Mainstream

Sidestream

Mainstream

Sidestream

Mainstream

Sidestream

f (bpm)

10

12

20

VT (l)

1.1 ± 0.5*

1.0 ± 0.3#

0.8 ± 0.3*#

MV (l/min)

11.3 ± 3.9*

13.5 ± 3.5#

15.3 ± 5.9*#

ETCO2 (mmHg)

33.3 ± 4.8*

33.4 ± 5.2*

34.7 ± 4.0

35.1 ± 4.8

29.4 ± 4.6*#

28.3 ± 5.0*#

S2T (mmHg/s)

118 ± 26*

101 ± 15$*

138 ± 31#

114 ± 18$#

147 ± 31*

105 ± 16$*#

S2V (mmHg/ml)

221 ± 59

180 ± 58$

233 ± 56

184 ± 57$

191 ± 54*#

104 ± 34$*#

S3T (mmHg/s)

1.8 ± 0.6*

2.2 ± 0.7$*

2.3 ± 0.8#

3.0 ± 0.9$#

3.3 ± 0.9*#

4.6 ± 1.2$*#

S3V (mmHg/ml)

5.5 ± 1.8

7.7 ± 4.5$

5.9 ± 2.6

9.6 ± 5.6$

8.5 ± 7.5*#

11.6 ± 6.0$*#

VDF (ml)

119 ± 49

98 ± 26$

130 ± 37

106 ± 25$

166 ± 44*#

112 ± 35$#

VDB (ml)

189 ± 54

193 ± 57

197 ± 48

194 ± 42

204 ± 60

176 ± 29$

VCO2 (ml)

40.3 ± 13.6*

40.3 ± 13.8*

38.4 ± 12.9#

37.3 ± 12.0#

20.8 ± 8.5*#

19.1 ± 8.1$*#

  1. f: Breathing frequency, VT: Tidal volume, MV: Minute ventilation, ETCO2: End-tidal CO2. Time capnography parameters: S2T: phase 2 slope, S3T: phase 3 slope. Volumetric capnography parameters: S2V: phase 2 slope, S3V: phase 3 slope, VDF: Fowler (anatomical) dead space, VDB: Bohr (physiological) dead space, VCO2: Volume of exhaled CO2 per breath. *: p < 0.05 vs. medium within mainstream or sidestream; #: p < 0.05 vs. low within mainstream or sidestream; $: p < 0.05 mainstream vs. sidestream within a condition.
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