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- Devaquet, Jerome, et al.
(author)
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Effects of inspiratory pause on CO2 elimination and arterial PCO2 in acute lung injury
- 2008
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In: Journal of Applied Physiology. - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 105:6, s. 1944-1949
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Journal article (peer-reviewed)abstract
- A high respiratory rate associated with the use of small tidal volumes, recommended for acute lung injury (ALI), shortens time for gas diffusion in the alveoli. This may decrease CO2 elimination. We hypothesized that a postinspiratory pause could enhance CO2 elimination and reduce PaCO2 by reducing dead space in ALI. In 15 mechanically ventilated patients with ALI and hypercapnia, a 20% postinspiratory pause (Tp20) was applied during a period of 30 min between two ventilation periods without postinspiratory pause (Tp0). Other parameters were kept unchanged. The single breath test for CO2 was recorded every 5 min to measure tidal CO2 elimination (VtCO(2)), airway dead space (V-Daw), and slope of the alveolar plateau. PaO2, PaCO2, and physiological and alveolar dead space (V-Dphys, V-Dalv) were determined at the end of each 30-min period. The postinspiratory pause, 0.7 +/- 0.2 s, induced on average < 0.5 cmH(2)O of intrinsic positive end-expiratory pressure (PEEP). During Tp20, VtCO(2) increased immediately by 28 +/- 10% (14 +/- 5 ml per breath compared with 11 +/- 4 for Tp0) and then decreased without reaching the initial value within 30 min. The addition of a postinspiratory pause significantly decreased V-Daw by 14% and V-Dphys by 11% with no change in V-Dalv. During Tp20, the slope of the alveolar plateau initially fell to 65 +/- 10% of baseline value and continued to decrease. Tp20 induced a 10 +/- 3% decrease in PaCO2 at 30 min (from 55 +/- 10 to 49 +/- 9 mmHg, P < 0.001) with no significant variation in PaO2. Postinspiratory pause has a significant influence on CO2 elimination when small tidal volumes are used during mechanical ventilation for ALI.
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| 2. |
- Åström, Elisabet, et al.
(author)
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Pattern of inspiratory gas delivery affects CO(2) elimination in health and after acute lung injury.
- 2008
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In: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 34:2, s. 377-384
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Journal article (peer-reviewed)abstract
- Objective To avoid ventilator induced lung injury, tidal volume should be low in acute lung injury (ALI). Reducing dead space may be useful, for example by using a pattern of inspiration that prolongs the time available for gas distribution and diffusion within the respiratory zone, the mean distribution time (MDT). A study was conducted to investigate how MDT affects CO2 elimination in pigs at health and after ALI. Design and setting Randomised crossover study in the animal laboratory of Lund University Biomedical Center. Subjects and intervention Healthy pigs and pigs with ALI, caused by surfactant perturbation and lung-damaging ventilation were ventilated with a computer-controlled ventilator. With this device each breath could be tailored with respect to insufflation time and pause time (T I and T P) as well as flow shape (square, increasing or decreasing flow). Measurements and results The single-breath test for CO2 allowed analysis of the volume of expired CO2 and the volume of CO2 re-inspired from Y-piece and tubes. With a long MDT caused by long T I or T P, the expired volume of CO2 increased markedly in accordance with the MDT concept in both healthy and ALI pigs. High initial inspiratory flow caused by a short T I or decreasing flow increased the re-inspired volume of CO2. Arterial CO2 increased during a longer period of short MDT and decreased again when MDT was prolonged. Conclusions CO2 elimination can be enhanced by a pattern of ventilation that prolongs MDT. Positive effects of prolonged MDT caused by short T I and decreasing flow were attenuated by high initial inspiratory flow. Electronic supplementary material The online version of this article (doi:10.1007/s00134-007-0840-7) contains supplementary material, which is available to authorized users.
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