According to a previous report (Brandolese et al., 1993), artificially-induced intrinsic positive end-expiratory pressure (iPEEP) causes a deterioration of gas exchange in mechanically-ventilated patients with acute respiratory failure, presumably because of a less homogeneous distribution of inspired gas. Objectives This hypothesis was investigated indirectly by measuring the slope of phase III, anatomic and physiologic dead space using volumetric capnography. Methods Measurements were obtained in 11 sedated, mechanically-ventilated paralyzed acute respiratory failure patients with iPEEP<3 cmH2O assessed at zero end-expiratory pressure, and without a known diagnosis of chronic obstructive pulmonary disease. In all experimental conditions, respiratory rate, ventilation and total PEEP (PEEPtot) were the same, but the same PEEPtot was obtained either by applying external PEEP (ePEEP condition) or by shortening the duration of expiration to produce iPEEP. iPEEP was induced either by reducing the inspiratory flow (Fins) and increasing the duration of the inflation (TI) (iPEEP with long TI, iPEEPlongTI condition), or by keeping constant Fins and TI, and introducing a long post-inspiratory pause (pIp) (iPEEP with long pause, iPEEPlongP condition). Results PEEPtot was not significantly different in the three experimental conditions (6.6±1.3, 6.4±1.5 and 6.4±1.2 cmH2O, P=0.474, for ePEEP, iPEEPlongTI and iPEEPlongP, respectively), as was the corresponding end-expiratory volume above equilibrium volume, measured during a deflation to ZEEP (P=0.158). iPEEP was not different between iPEEPlongTI and iPEEPlongP (4.9±1.1 and 5.1±0.9 cmH2O, P=0.453, respectively), but substantially greater than in the ePEEP condition (0.6±0.3 cmH2O, P<0.001). PaO2 was not significantly different among the three conditions (P=0.262), while PaCO2 was lower at iPEEPlongP (35.2±4.7 mmHg) than at ePEEP (38.4±5.2 mmHg, P<0.001) and iPEEPlongTI (38.3±4.2 mmHg, P=0.019). Relative to ePEEP, slope of phase III, anatomic, physiologic and alveolar dead space were not different at iPEEPlongTI (Δ -0.7±1.8 %CO2/L, P=0.655; 1±7 ml, P=1.000, 2±22, P=1.000 and 1±17 ml, P=1.000, respectively). In contrast, the same parameters were significantly lower at iPEEPlongP (Δ -1.6±1.1 %CO2/L, P<0.002, -18±9 ml, P<0.001, -32±19 ml, P<0.001, and -14±13 ml, P=0.017, respectively). Conclusions In these patients, no difference in slope of phase III, anatomic and physiologic dead space were detected between ePEEP and iPEEPlongTI, suggesting that during iPEEPlongTI the effect of iPEEP-induced alterations of ventilation distribution, if any, were completely compensated by the increase of inspiratory duration (Åström et al., 2008). In contrast, prolongation of pIp led to a significant reduction of heterogeneity as indexed by slope of phase III in the iPEEPlongP condition, despite the presence of iPEEP. References Brandolese R, Broseghini C, Polese G, Bernasconi M, Brandi G, Milic-Emili J, Rossi A. Effects of intrinsic PEEP on pulmonary gas exchange in mechanically-ventilated patients. Eur Respir J. 1993 Mar;6(3):358-63. PMID: 8472826. Aström E, Niklason L, Drefeldt B, Bajc M, Jonson B. Partitioning of dead space--a method and reference values in the aw ake human. Eur Respir J. 2000 Oct;16(4):659-64. doi: 10.1034/j.1399-3003.2000.16d16.x. PMID: 11106209.
Effects of artificially‑induced iPEEP and post‑inspiratory pause on dead space and slope of capnographic phase III in acute respiratory failure / C. Zilianti, A. Kyriakoudi, E. Potamianou, C. Karakatsanis, K. Pontikis, A. Koutsoukou, M. Pecchiari. - In: INTENSIVE CARE MEDICINE EXPERIMENTAL. - ISSN 2197-425X. - 12:1(2024 Oct 03), pp. 001542.783-001542.783. (Intervento presentato al 37. convegno ESICM LIVES tenutosi a Barcelona nel 2024).
Effects of artificially‑induced iPEEP and post‑inspiratory pause on dead space and slope of capnographic phase III in acute respiratory failure
C. Zilianti
Primo
;M. PecchiariUltimo
2024
Abstract
According to a previous report (Brandolese et al., 1993), artificially-induced intrinsic positive end-expiratory pressure (iPEEP) causes a deterioration of gas exchange in mechanically-ventilated patients with acute respiratory failure, presumably because of a less homogeneous distribution of inspired gas. Objectives This hypothesis was investigated indirectly by measuring the slope of phase III, anatomic and physiologic dead space using volumetric capnography. Methods Measurements were obtained in 11 sedated, mechanically-ventilated paralyzed acute respiratory failure patients with iPEEP<3 cmH2O assessed at zero end-expiratory pressure, and without a known diagnosis of chronic obstructive pulmonary disease. In all experimental conditions, respiratory rate, ventilation and total PEEP (PEEPtot) were the same, but the same PEEPtot was obtained either by applying external PEEP (ePEEP condition) or by shortening the duration of expiration to produce iPEEP. iPEEP was induced either by reducing the inspiratory flow (Fins) and increasing the duration of the inflation (TI) (iPEEP with long TI, iPEEPlongTI condition), or by keeping constant Fins and TI, and introducing a long post-inspiratory pause (pIp) (iPEEP with long pause, iPEEPlongP condition). Results PEEPtot was not significantly different in the three experimental conditions (6.6±1.3, 6.4±1.5 and 6.4±1.2 cmH2O, P=0.474, for ePEEP, iPEEPlongTI and iPEEPlongP, respectively), as was the corresponding end-expiratory volume above equilibrium volume, measured during a deflation to ZEEP (P=0.158). iPEEP was not different between iPEEPlongTI and iPEEPlongP (4.9±1.1 and 5.1±0.9 cmH2O, P=0.453, respectively), but substantially greater than in the ePEEP condition (0.6±0.3 cmH2O, P<0.001). PaO2 was not significantly different among the three conditions (P=0.262), while PaCO2 was lower at iPEEPlongP (35.2±4.7 mmHg) than at ePEEP (38.4±5.2 mmHg, P<0.001) and iPEEPlongTI (38.3±4.2 mmHg, P=0.019). Relative to ePEEP, slope of phase III, anatomic, physiologic and alveolar dead space were not different at iPEEPlongTI (Δ -0.7±1.8 %CO2/L, P=0.655; 1±7 ml, P=1.000, 2±22, P=1.000 and 1±17 ml, P=1.000, respectively). In contrast, the same parameters were significantly lower at iPEEPlongP (Δ -1.6±1.1 %CO2/L, P<0.002, -18±9 ml, P<0.001, -32±19 ml, P<0.001, and -14±13 ml, P=0.017, respectively). Conclusions In these patients, no difference in slope of phase III, anatomic and physiologic dead space were detected between ePEEP and iPEEPlongTI, suggesting that during iPEEPlongTI the effect of iPEEP-induced alterations of ventilation distribution, if any, were completely compensated by the increase of inspiratory duration (Åström et al., 2008). In contrast, prolongation of pIp led to a significant reduction of heterogeneity as indexed by slope of phase III in the iPEEPlongP condition, despite the presence of iPEEP. References Brandolese R, Broseghini C, Polese G, Bernasconi M, Brandi G, Milic-Emili J, Rossi A. Effects of intrinsic PEEP on pulmonary gas exchange in mechanically-ventilated patients. Eur Respir J. 1993 Mar;6(3):358-63. PMID: 8472826. Aström E, Niklason L, Drefeldt B, Bajc M, Jonson B. Partitioning of dead space--a method and reference values in the aw ake human. Eur Respir J. 2000 Oct;16(4):659-64. doi: 10.1034/j.1399-3003.2000.16d16.x. PMID: 11106209.File | Dimensione | Formato | |
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