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- Devaquet, Jerome, et al.
(författare)
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Effects of inspiratory pause on CO2 elimination and arterial PCO2 in acute lung injury
- 2008
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Ingår i: Journal of Applied Physiology. - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 105:6, s. 1944-1949
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Tidskriftsartikel (refereegranskat)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. |
- Aboab, Jerome, et al.
(författare)
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Dead space and CO2 elimination related to pattern of inspiratory gas delivery in ARDS patients
- 2012
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Ingår i: Critical Care. - : Springer Science and Business Media LLC. - 1364-8535. ; 16:2
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The inspiratory flow pattern influences CO2 elimination by affecting the time the tidal volume remains resident in alveoli. This time is expressed in terms of mean distribution time (MDT), which is the time available for distribution and diffusion of inspired tidal gas within resident alveolar gas. In healthy and sick pigs, abrupt cessation of inspiratory flow (that is, high end-inspiratory flow (EIF)), enhances CO2 elimination. The objective was to test the hypothesis that effects of inspiratory gas delivery pattern on CO2 exchange can be comprehensively described from the effects of MDT and EIF in patients with acute respiratory distress syndrome (ARDS). Methods: In a medical intensive care unit of a university hospital, ARDS patients were studied during sequences of breaths with varying inspiratory flow patterns. Patients were ventilated with a computer-controlled ventilator allowing single breaths to be modified with respect to durations of inspiratory flow and postinspiratory pause (T-P), as well as the shape of the inspiratory flow wave. From the single-breath test for CO2, the volume of CO2 eliminated by each tidal breath was derived. Results: A long MDT, caused primarily by a long TP, led to importantly enhanced CO2 elimination. So did a high EIF. Effects of MDT and EIF were comprehensively described with a simple equation. Typically, an efficient and a less-efficient pattern of inspiration could result in +/- 10% variation of CO2 elimination, and in individuals, up to 35%. Conclusions: In ARDS, CO2 elimination is importantly enhanced by an inspiratory flow pattern with long MDT and high EIF. An optimal inspiratory pattern allows a reduction of tidal volume and may be part of lung-protective ventilation.
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| 3. |
- Aboab, Jerome, et al.
(författare)
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Effect of inspired oxygen fraction on alveolar derecruitment in acute respiratory distress syndrome
- 2006
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Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 32:12, s. 1979-1986
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Tidskriftsartikel (refereegranskat)abstract
- Objective: High fractions of inspired oxygen (FIO2) used in acute lung injury (ALI) may promote resorption atelectasis. The impact of derecruitment related to high FIO2 in ALI is debated. We evaluated derecruitment with 100% vs. 60% FIO2 at two levels of positive end-expiratory pressure (PEEP). Patients: Fourteen consecutive patients with ALI were studied. Interventions: Recruited volume at two PEEP levels was computed from two pressure-volume curves, recorded from PEEP and from zero end-expiratory pressure, using the sinusoidal flow modulation method. PEEP-induced recruitment was measured during prolonged expiration as the difference between the two curves at a given pressure. PaO2/FIO2 was also measured. PEEP was 5 +/- 1 or 14 +/- 3 cmH(2)O and FIO2 was 60% or 100%, yielding four combinations. We looked for differences between the beginning and end of a 30-min period with each combination. Measurement and results: With low PEEP and 100% FIO2, recruited volume decreased significantly from 68 +/- 53 to 39 +/- 43 ml and PaO2/FIO2 from 196 +/- 104 to 153 +/- 83 mmHg. With the three other combinations (low PEEP and 60% FIO2 or high PEEP and 60% or 100% FIO2) none of the parameters decreased significantly. Conclusion: In mechanically ventilated patients with ALI the breathing of pure oxygen leads to derecruitment, which is prevented by high PEEP.
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| 5. |
- Åström, Elisabet, et al.
(författare)
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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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Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 34:2, s. 377-384
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Tidskriftsartikel (refereegranskat)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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