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Background: PEEP decreases intrinsic PEEP (PEEPi) in COPD patients. However, the best PEEP for someone with COPD is unclear. Methods: Ten COPD patients who received invasive mechanical ventilation were enrolled. Before PEEP titration, subjects were sedated and received mandatory ventilation. PEEP increased from 0 to 15 cmH2O. At each PEEP, peak pressure (Ppeak), plateau pressure (Pplat), PEEPi, and other variables were recorded. Increment of Pplat (ΔPplat) and PEEPi were plotted against PEEP applied. The best PEEP was recorded at the cross of the two curves. Results: From PEEP = 0 cmH2O to best PEEP, Ppeak (37.4 ± 5.1 vs. 38.4 ± 4.9 cmH2O) and Pplat (18.7 ± 3.3 vs. 20.4 ± 3.2 cmH2O) increased slightly, resistance (28.1 ± 5.6 vs. 26.6 ± 5.0 cmH2O/l/s) decreased slightly, and PEEPi (7.9 ± 2.3 vs. 1.5 ± 0.4 cmH2O) decreased sharply. Compliance, heart rate, blood pressure, and SpO2 did not change. However, from best PEEP to PEEP = 15 cmH2O, Ppeak (38.4 ± 4.9 vs. 44.9 ± 4.3 cmH2O) and Pplat (20.4 ± 3.2 vs. 27.6 ± 3.3 cmH2O) increased sharply, and systolic blood pressure (116 ± 13 vs. 99 ± 14 mmHg) and compliance (46.1 ± 18.1 vs. 37.7 ± 10.6 mL/cmH2O) decreased sharply. At the same time, PEEPi (1.5 ± 0.4 vs. 0.7 ± 0.8 cmH2O) decreased only slightly, and resistance, heart rate, and SpO2 did not change. Conclusions: It is feasible to use Pplat as a simple way of determining the best PEEP in COPD patients. [ABSTRACT FROM AUTHOR]

Study Objective: To assess the safety of mechanical ventilation and effectiveness of extrinsic positive end-expiratory pressure (PEEP) (PEEPe) in improving peripheral oxygen saturation (SpO2) during direct microlaryngeal laser surgery; to assess the incidence, amount, and nature (dynamic hyperinflation or airflow obstruction) of ensuing intrinsic PEEP (PEEPi); and to find a surrogate PEEPi indicator.Design: Quasiexperimental.Setting: S. Raffaele Hospital (Milano), November 2009 to December 2010.Patients: Fifty-two adults scheduled for direct microlaryngeal laser surgery. Exclusion criterion is pregnancy.Interventions: Twenty-one percent O2 mechanical ventilation through 4.5- to 5.5-mm internal diameter endotracheal tubes; in 29 patients, after measurement of PEEPi, an identical amount of PEEPe was added; and PEEPi.Measurements: SpO2, peak (Pawpeak) and plateau (Pawplateau) airway pressure, and end-expiratory carbon dioxide were measured every 5 minutes. Respiratory compliance (Crs) was computed. PEEPi was measured (end-expiratory occlusion method).Main Results: PEEPi ≥5 cm H2O occurred in 14 patients (27%) after intubation, in 16 (30%) at the beginning, and in 14 (27.3%) at the end of surgery. Thirty-one patients (59.4%) exhibited PEEPi ≥5 cm H2O on at least 1 time point. PEEPi at the beginning of surgery was positively correlated with Pawplateau, Crs, tidal volume, and body mass index. Body mass index was the only predictor for the occurrence of PEEPi ≥5 cm H2O. At the beginning of surgery, the Pawplateau receiver operating characteristic curve predicting PEEPi ≥5 cm H2O had area under the receiver operating characteristic curve of 0.85; best cutoff value of 15.5 cm H2O (sensitivity, 88.9%; specificity, 75%; correctly classified cases, 86.1%). When PEEPe was applied, in 23 cases (82.1%), total PEEP equaled PEEPe+ PEEPi; in 3 (10.7%), it was lower; and in 2 (7.1%), it was higher. Application of PEEPe increased SpO2 (P< .05) and Crs (P< .05).Conclusions: During ventilation through small endotracheal tubes, PEEPi (mostly due to dynamic hyperinflation) is common. Hemodynamic complications, barotrauma, and O2 desaturation (reversible with PEEPe) are rare. Pawplateau provided by ventilators is useful in suspecting and monitoring the occurrence of PEEPi and allows detection of lung overdistension as PEEPe is applied. [ABSTRACT FROM AUTHOR]

Background: Double-lumen tubes (DLT) are routinely used to enable one-lung-ventilation (OLV) during thoracic anaesthesia. The flow-dependent resistance of the DLT's bronchial limb may be high as a result of its narrow inner diameter and length, and thus potentially contribute to an unintended increase in positive end-expiratory pressure (auto-PEEP). We therefore studied the impact of adult sized DLTs on the dynamic auto-PEEP during OLV.Methods: In this prospective clinical study, dynamic auto-PEEP was determined in 72 patients undergoing thoracic surgery, with right- and left-sided DLTs of various sizes. During OLV, air trapping was provoked by increasing inspiration to expiration ratio from 1:2 to 2:1 (five steps). Based on measured flow rate, airway pressure (Paw) and bronchial pressure (Pbronch), the pressure gradient across the DLT (ΔPDLT) and the total auto-PEEP in the respiratory system (i.e. the lungs, the DLT and the ventilator circuit) were determined. Subsequently the DLT's share in total auto-PEEP was calculated.Results: ΔPDLT was 2.3 (0.7) cm H2O over the entire breathing cycle. At the shortest expiratory time the mean total auto-PEEP was 2.9 (1.5) cm H2O (range 0-5.9 cm H2O). The DLT caused 27 to 31% of the total auto-PEEP. Size and side of the DLT's bronchial limb did not impact auto-PEEP significantly.Conclusions: Although the DLT contributes to the overall auto-PEEP, its contribution is small and independent of size and side of the DLT's bronchial limb. The choice of DLT does not influence the risk of auto-PEEP during OLV to a clinically relevant extent.Clinical Trial Registration: DRKS00005648. [ABSTRACT FROM AUTHOR]

Background: Tidal expiratory flow limitation (EFLT) promotes intrinsic PEEP (PEEPi) in patients with chronic obstructive pulmonary disease (COPD). Applying non-invasive ventilation (NIV) with an expiratory positive airway pressure (EPAP) matching PEEPi improves gas exchange, reduces work of breathing and ineffective efforts. We aimed to evaluate the effects of a novel NIV mode that continuously adjusts EPAP to the minimum level that abolishes EFLT.Methods: This prospective, cross-over, open-label study randomized patients to one night of fixed-EPAP and one night of EFLT-abolishing-EPAP. The primary outcome was transcutaneous carbon dioxide pressure (PtcCO2). Secondary outcomes were: peripheral oxygen saturation (SpO2), frequency of ineffective efforts, breathing patterns and oscillatory mechanics.Results: We screened 36 patients and included 12 in the analysis (age 72 ± 8 years, FEV1 38 ± 14%Pred). The median EPAP did not differ between the EFLT-abolishing-EPAP and the fixed-EPAP night (median (IQR) = 7.0 (6.0, 8.8) cmH2O during night vs 7.5 (6.5, 10.5) cmH2O, p = 0.365). We found no differences in mean PtcCO2 (44.9 (41.6, 57.2) mmHg vs 54.5 (51.1, 59.0), p = 0.365), the percentage of night time with PtcCO2 > 45 mm Hg was lower (62(8,100)% vs 98(94,100)%, p = 0.031) and ineffective efforts were fewer (126(93,205) vs 261(205,351) events/hour, p = 0.003) during the EFLT-abolishing-EPAP than during the fixed-EPAP night. We found no differences in oxygen saturation and lung mechanics between nights.Conclusion: An adaptive ventilation mode targeted to abolish EFLT has the potential to reduce hypercapnia and ineffective efforts in stable COPD patients receiving nocturnal NIV.Trial Registration: ClicalTrials.gov, NCT04497090. Registered 29 July 2020-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04497090 . [ABSTRACT FROM AUTHOR]