Critical Care

, 15:P44 | Cite as

Effect of minute ventilation on central venous-to-arterial carbon dioxide difference

  • S Saengngammongkhol
  • A Wattanathum
  • A Wongsa
Poster presentation


Carbon Dioxide Pilot Study Cardiac Output Mechanical Ventilator Respiratory Rate 
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The central venous-to-arterial carbon dioxide difference (P(cv-a)CO2, dPCO2) is a global index of tissue perfusion. A normal dPCO2 indicates cardiac output (CO) is high enough to wash out CO2 production from peripheral tissues. An increased dPCO2 suggests that CO is not high enough with respect to global metabolic conditions. PCO2 depends on alveolar ventilation. We hypothesized that minute ventilation (MV) has an effect on dPCO2.


A prospective experimental, pilot study was performed on 19 patients admitted to a medical ICU with septic shock between August 2010 and November 2010. All patients were intubated and on a mechanical ventilator with continuously monitoring end-tidal CO2, central venous pressure (CVP), blood pressure (BP), and CO. Mechanical ventilator was set consecutively in three steps every 30 minutes (T0, T30, T60) by increasing the respiratory rate (RR) for MV of 8 l, 15 l, and 8 l, respectively. Tidal volume, RR, MV, auto-PEEP, CO and dPCO2 were recorded at each step of MV changed for all patients.


Patients' age and APACHE II scores were 67.3 ± 13.2 years and 24.4 ± 6.6, respectively. There was a significant difference between the dPCO2 between T0 and T30 (3.5 ± 3.5 vs. 5.9 ± 2.0, P = 0.04) (Table 1). Moreover, there was significantly decreased CO from T0 to T30 (5.1 ± 1.4 vs. 4.5 ± 1.11, P = 0.002) and, also, T30 and T60 (4.5 ± 1.1 vs. 5.0 ± 1.3, P = 0.009). Auto-PEEP values were inversely correlated with decreased CO (P < 0.001) at T30.

Table 1


P value





T0 vs. T30

T30vs. T60

T0 vs. T60


3.5 ± 3.5

5.9 ± 2.0

4.8 ± 2.1





5.1 ± 1.4

4.5 ± 1.1

5 ± 1.3





Minute ventilation had an effect on dPCO2 by reduced CO due to development of auto-PEEP. The dPCO2 should be measured during normal minute ventilation without auto-PEEP.


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Copyright information

© Saengngammongkhol et al. 2011

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Authors and Affiliations

  • S Saengngammongkhol
    • 1
  • A Wattanathum
    • 1
  • A Wongsa
    • 1
  1. 1.Phramongkutklao HospitalBangkokThailand

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