| 1. |
- Tusman, Gerardo, et al.
(författare)
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Lung recruitment and positive end-expiratory pressure have different effects on CO2 elimination in healthy and sick lungs
- 2010
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Ingår i: Anesthesia and Analgesia. - 0003-2999 .- 1526-7598. ; 111:4, s. 968-977
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: We studied the effects that the lung recruitment maneuver (RM) and positive end-expiratory pressure (PEEP) have on the elimination of CO(2) per breath (Vtco(2,br)). METHODS: In 7 healthy and 7 lung-lavaged pigs at constant ventilation, PEEP was increased from 0 to 18 cm H(2)O and then decreased to 0 in steps of 6 cm H(2)O every 10 minutes. Cycling RMs with plateau pressure/PEEP of 40/20 (healthy) and 50/25 (lavaged) cm H(2)O were applied for 2 minutes between 18-PEEP steps. Volumetric capnography, respiratory mechanics, blood gas, and hemodynamic data were recorded. RESULTS: In healthy lungs before the RM, Vtco(2,br) was inversely proportional to PEEP decreasing from 4.0 (3.6-4.4) mL (median and interquartile range) at 0-PEEP to 3.1 (2.8-3.4) mL at 18-PEEP (P < 0.05). After the RM, Vtco(2,br) increased from 3.3 (3-3.6) mL at 18-PEEP to 4.0 (3.5-4.5) mL at 0-PEEP (P < 0.05). In lavaged lungs before the RM, Vtco(2,br) increased initially from 2.0 (1.7-2.3) mL at 0-PEEP to 2.6 (2.2-3) mL at 12-PEEP (P < 0.05) but then decreased to 2.4 (2-2.8) mL when PEEP was increased further to 18 cm H(2)O (P < 0.05). After the RM, the highest Vtco(2,br) of 2.9 (2.1-3.7) mL was observed at 12-PEEP and then decreased to 2.5 (1.9-3.1) mL at 0-PEEP (P < 0.05). Vtco(2,br) was directly related to changes in lung perfusion, the area of gas exchange, and alveolar ventilation but inversely related to changes in dead space. CONCLUSIONS: CO(2) elimination by the lungs was dependent on PEEP and recruitment and showed major differences between healthy and lavaged lungs.
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| 2. |
- Tusman, Gerardo, et al.
(författare)
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Model fitting of volumetric capnograms improves calculations of airway dead space and slope of phase III
- 2009
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Ingår i: Journal of clinical monitoring and computing. - : Springer Science and Business Media LLC. - 1387-1307 .- 1573-2614. ; 23:4, s. 197-206
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Tidskriftsartikel (refereegranskat)abstract
- Background This study assessed the performance of a Functional Approximation based on a Levenberg-Marquardt Algorithm (FA-LMA) to calculate airway dead space (VDaw) and the slope of phase III (S III) from capnograms. Methods We performed mathematical simulations to test the effect of noises on the calculation of VDaw and S III. Data from ten mechanically ventilated patients at 0, 5 and 10 cmH2O of PEEP were also studied. FA-LMA was compared with the traditional Fowler’s method (FM). Results Simulations showed that: (1) The FM determined VDaw with accuracy only if the capnogram approximated a symmetrical curve (S III = 0). When capnograms became asymmetrical (S III > 0), the FM underestimated VDaw (−3.1% to −0.9%). (2) When adding noises on 800 capnograms, VDaw was underestimated whenever the FM was used thereby creating a bias between −5.54 and −1.28 ml at standard deviations (SD) of 0.1–1.8 ml (P < 0.0001). FA-LMA calculations of VDaw were close to the simulated values with the bias ranging from −0.21 to 0.16 ml at SD from 0.1 to 0.4 ml. The FM overestimated S III and showed more bias (0.0041–0.0078 mmHg/ml, P < 0.0001) than the FA-LMA (0.0002–0.0030 mmHg/ml). When calculating VDaw from patients, variability was less with the FA-LMA leading to mean variation coefficients of 0.0102, 0.0111 and 0.0123 compared to the FM (0.0243, 0.0247 and 0.0262, P < 0.001) for 0, 5 and 10 cmH2O of PEEP, respectively. The FA-LMA also showed less variability in S III with mean variation coefficients of 0.0739, 0.0662 and 0.0730 compared to the FM (0.1379, 0.1208 and 0.1246, P < 0.001) for 0, 5 and 10 cmH2O of PEEP, respectively. Conclusions The Functional Approxi- mation based on a Levenberg-Marquardt Algorithm showed less bias and dispersion compared to the traditional Fowler’s method when calculating VDaw and S III.
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| 3. |
- Tusman, Gerardo, et al.
(författare)
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Monitoring dead space during recruitment and PEEP titration in an experimental model
- 2006
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Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 32:11, s. 1863-1871
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To test the usefulness of dead space for determining open-lung PEEP, the lowest PEEP that prevents lung collapse after a lung recruitment maneuver. Design: Prospective animal study. Setting: Department of Clinical Physiology, University of Uppsala, Sweden. Subjects: Eight lung-lavaged pigs. Interventions: Animals were ventilated using constant flow mode with VT of 6 ml/kg, respiratory rate of 30 bpm, inspiratory-to-expiratory ratio of 1 : 2, and FiO(2) of 1. Baseline measurements were performed at 6 cmH(2)O of PEEP. PEEP was increased in steps of 6 cmH(2)O from 6 to 24 cmH(2)O. Recruitment maneuver was achieved within 2 min at pressure levels of 60/30 cmH(2)O for Peak/PEEP. PEEP was decreased from 24 to 6 cmH(2)O in steps of 2 cmH(2)O and then to 0 cmH(2)O. Each PEEP step was maintained for 10 min. Measurements and results: Alveolar dead space (VDalv), the ratio of alveolar dead space to alveolar tidal volume (VDalv/VTalv), and the arterial to end-tidal PCO2 difference (Pa-ETCO2) showed a good correlation with PaO2, normally aerated areas, and non-aerated CT areas in all animals (minimum-maximum r(2) = 0.83-0.99; p < 0.01). Lung collapse (non-aerated tissue > 5%) started at 12 cmH(2)O PEEP; hence, open-lung PEEP was established at 14 cmH(2)O. The receiver operating characteristics curve demonstrated a high specificity and sensitivity of VDalv (0.89 and 0.90), VDalv/VTalv (0.82 and 1.00), and Pa-ETCO2 (0.93 and 0.95) for detecting lung collapse. Conclusions: Monitoring of dead space was useful for detecting lung collapse and for establishing open-lung PEEP after a recruitment maneuver.
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| 4. |
- Tusman, Gerardo, et al.
(författare)
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Multimodal non-invasive monitoring to apply an open lung approach strategy in morbidly obese patients during bariatric surgery
- 2020
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Ingår i: Journal of clinical monitoring and computing. - : SPRINGER HEIDELBERG. - 1387-1307 .- 1573-2614. ; 34:5, s. 1015-1024
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the use of non-invasive variables for monitoring an open-lung approach (OLA) strategy in bariatric surgery. Twelve morbidly obese patients undergoing bariatric surgery received a baseline protective ventilation with 8 cmH(2)O of positive-end expiratory pressure (PEEP). Then, the OLA strategy was applied consisting in lung recruitment followed by a decremental PEEP trial, from 20 to 8 cmH(2)O, in steps of 2 cmH(2)O to find the lung's closing pressure. Baseline ventilation was then resumed setting open lung PEEP (OL-PEEP) at 2 cmH(2)O above this pressure. The multimodal non-invasive variables used for monitoring OLA consisted in pulse oximetry (SpO(2)), respiratory compliance (Crs), end-expiratory lung volume measured by a capnodynamic method (EELVCO2), and esophageal manometry. OL-PEEP was detected at 15.9 +/- 1.7 cmH(2)O corresponding to a positive end-expiratory transpulmonary pressure (P-L,P-ee) of 0.9 +/- 1.1 cmH(2)O. ROC analysis showed that SpO(2) was more accurate (AUC 0.92, IC95% 0.87-0.97) than Crs (AUC 0.76, IC95% 0.87-0.97) and EELVCO2 (AUC 0.73, IC95% 0.64-0.82) to detect the lung's closing pressure according to the change of P-L,P-ee from positive to negative values. Compared to baseline ventilation with 8 cmH(2)O of PEEP, OLA increased EELVCO2 (1309 +/- 517 vs. 2177 +/- 679 mL) and decreased driving pressure (18.3 +/- 2.2 vs. 10.1 +/- 1.7 cmH(2)O), estimated shunt (17.7 +/- 3.4 vs. 4.2 +/- 1.4%), lung strain (0.39 +/- 0.07 vs. 0.22 +/- 0.06) and lung elastance (28.4 +/- 5.8 vs. 15.3 +/- 4.3 cmH(2)O/L), respectively; all p < 0.0001. The OLA strategy can be monitored using noninvasive variables during bariatric surgery. This strategy decreased lung strain, elastance and driving pressure compared with standard protective ventilatory settings. Clinical trial number NTC03694665.
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| 5. |
- Tusman, Gerardo, et al.
(författare)
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Noninvasive Monitoring of Lung Recruitment Maneuvers in Morbidly Obese Patients : The Role of Pulse Oximetry and Volumetric Capnography
- 2014
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Ingår i: Anesthesia and Analgesia. - : Ovid Technologies (Wolters Kluwer Health). - 0003-2999 .- 1526-7598. ; 118:1, s. 137-144
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: We conducted this study to determine whether pulse oximetry and volumetric capnography (VCap) can determine the opening and closing pressures of lungs of anesthetized morbidly obese patients. METHODS: Twenty morbidly obese patients undergoing laparoscopic bariatric surgery with capnoperitoneum were studied. A lung recruitment maneuver was performed in pressure control ventilation as follows: (1) During an ascending limb, the lungs' opening pressure was detected. After increasing positive end-expiratory pressure (PEEP) from 8 to 16 cm H2O, fraction of inspired oxygen (Fio(2)) was decreased until pulse oximetric arterial saturation (Spo(2)) was <92%. Thereafter, end-inspiratory pressure was increased in steps of 2 cm H2O, from 36 to a maximum of 50 cm H2O. The opening pressure was attained when Spo(2) exceeded 97%. (2) During a subsequent decreasing limb, the lungs' closing pressure was identified. PEEP was decreased from 22 to 10 cm H2O in steps of 2 cm H2O. The closing pressure was determined as the PEEP value at which respiratory compliance decreased from its maximum value. We continuously recorded lung mechanics, Spo(2), and VCap. RESULTS: The lungs' opening pressures were detected at 44 (4) cm H2O (median and interquartile range) and the closing pressure at 14 (2) cm H2O. Therefore, the level of PEEP that kept the lungs without collapse was found to be 16 (3) cm H2O. Using respiratory compliance as a reference, receiver operating characteristic analysis showed that Spo(2) (area under the curve [AUC] 0.80 [SE 0.07], sensitivity 0.65, and specificity 0.94), the elimination of CO2 per breath (AUC 0.91 [SE 0.05], sensitivity 0.85, and specificity 0.98), and Bohr's dead space (AUC 0.83 [SE 0.06], sensitivity 0.70, and specificity 0.95] were relatively accurate for detecting lung collapse during the decreasing limb of a recruitment maneuver. CONCLUSIONS: Lung recruitment in morbidly obese patients could be effectively monitored by combining noninvasive pulse oximetry and VCap. Spo(2), the elimination of CO2, and Bohr's dead space detected the individual's opening and closing pressures.
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| 6. |
- Tusman, Gerardo, et al.
(författare)
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Photoplethysmographic characterization of vascular tone mediated changes in arterial pressure : an observational study
- 2019
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Ingår i: Journal of clinical monitoring and computing. - : SPRINGER HEIDELBERG. - 1387-1307 .- 1573-2614. ; 33:5, s. 815-824
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Tidskriftsartikel (refereegranskat)abstract
- To determine whether a classification based on the contour of the photoplethysmography signal (PPGc) can detect changes in systolic arterial blood pressure (SAP) and vascular tone. Episodes of normotension (SAP 90-140 mmHg), hypertension (SAP > 140 mmHg) and hypotension (SAP < 90 mmHg) were analyzed in 15 cardiac surgery patients. SAP and two surrogates of the vascular tone, systemic vascular resistance (SVR) and vascular compliance (Cvasc = stroke volume/pulse pressure) were compared with PPGc. Changes in PPG amplitude (foot-to-peak distance) and dicrotic notch position were used to define 6 classes taking class III as a normal vascular tone with a notch placed between 20 and 50% of the PPG amplitude. Class I-to-II represented vasoconstriction with notch placed > 50% in a small PPG, while class IV-to-VI described vasodilation with a notch placed < 20% in a tall PPG wave. 190 datasets were analyzed including 61 episodes of hypertension [SAP = 159 (151-170) mmHg (median 1st-3rd quartiles)], 84 of normotension, SAP = 124 (113-131) mmHg and 45 of hypotension SAP = 85(80-87) mmHg. SAP were well correlated with SVR (r = 0.78, p < 0.0001) and Cvasc (r = 0.84, p < 0.0001). The PPG-based classification correlated well with SAP (r = - 0.90, p < 0.0001), SVR (r = - 0.72, p < 0.0001) and Cvasc (r = 0.82, p < 0.0001). The PPGc misclassified 7 out of the 190 episodes, presenting good accuracy (98.4% and 97.8%), sensitivity (100% and 94.9%) and specificity (97.9% and 99.2%) for detecting episodes of hypotension and hypertension, respectively. Changes in arterial pressure and vascular tone were closely related to the proposed classification based on PPG waveform. Clinical Trial Registration NTC02854852.
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| 7. |
- Tusman, Gerardo, et al.
(författare)
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Reference values for volumetric capnography-derived non-invasive parameters in healthy individuals
- 2013
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Ingår i: Journal of clinical monitoring and computing. - : Springer Science and Business Media LLC. - 1387-1307 .- 1573-2614. ; 27:3, s. 281-288
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine typical values for non-invasive volumetric capnography (VCap) parameters for healthy volunteers and anesthetized individuals. VCap was obtained by a capnograph connected to the airway opening. We prospectively studied 33 healthy volunteers 32 +/- A 6 years of age weighing 70 +/- A 13 kg at a height of 171 +/- A 11 cm in the supine position. Data from these volunteers were compared with a cohort of similar healthy anesthetized patients ventilated with the following settings: tidal volume (VT) of 6-8 mL/kg, respiratory rate 10-15 bpm, PEEP of 5-6 cmH(2)O and FiO(2) of 0.5. Volunteers showed better clearance of CO2 compared to anesthetized patients as indicated by (median and interquartile range): (1) an increased elimination of CO2 per mL of VT of 0.028 (0.005) in volunteers versus 0.023 (0.003) in anesthetized patients, p < 0.05; (2) a lower normalized slope of phase III of 0.26 (0.17) in volunteers versus 0.39 (0.38) in anesthetized patients, p < 0.05; and (3) a lower Bohr dead space ratio of 0.23 (0.05) in volunteers versus 0.28 (0.05) in anesthetized patients, p < 0.05. This study presents reference values for non-invasive volumetric capnography-derived parameters in healthy individuals. Mechanical ventilation and anesthesia altered these values significantly.
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| 8. |
- Tusman, Gerardo, et al.
(författare)
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The Sensitivity and Specificity of Pulmonary Carbon Dioxide Elimination for Noninvasive Assessment of Fluid Responsiveness
- 2016
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Ingår i: Anesthesia and Analgesia. - 0003-2999 .- 1526-7598. ; 122:5, s. 1404-1411
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: We sought to determine whether the response of pulmonary elimination of CO2 (Vco(2)) to a sudden increase in positive end-expiratory pressure (PEEP) could predict fluid responsiveness and serve as a noninvasive surrogate for cardiac index (CI). METHODS: Fifty-two patients undergoing cardiovascular surgery were included in this study. By using a constant-flow ventilation mode, we performed a PEEP challenge of 1-minute increase in PEEP from 5 to 10 cm H2O. At PEEP of 5 cm H2O, patients were preloaded with 500 mL IV saline solution after which a second PEEP challenge was performed. Patients in whom fluid administration increased CI by >= 15% from the individual baseline value were defined as volume responders. Beat-by-beat CI was derived from arterial pulse contour analysis, and breath-by-breath Vco(2) data were collected during the protocol. The sensitivity and specificity of Vco(2) for detecting the fluid responders according to CI was performed by the receiver operating characteristic curves. RESULTS: Twenty-one of 52 patients were identified as fluid responders (40%). The PEEP maneuver before fluid administration decreased CI from 2.65 +/- 0.34 to 2.21 +/- 0.32 L/min/m(2) (P = 0.0011) and Vco(2) from 150 +/- 23 to 123 +/- 23 mL/min (P = 0.0036) in responders, whereas the changes in CI and Vco(2) were not significant in nonresponders. The PEEP challenge after fluid administration induced no significant changes in CI and Vco(2), in neither responders nor nonresponders. PEEP-induced decreases in CI and Vco(2) before fluid administration were well correlated (r(2) = 0.75, P < 0.0001) but not thereafter. The area under the receiver operating characteristic curves for a PEEP-induced decrease in Delta CI and Delta Vco(2) was 0.99, with a 95% confidence interval from 0.96 to 0.99 for Delta CI and from 0.97 to 0.99 for Delta Vco(2). During the PEEP challenge, a decrease in Vco(2) by 11% predicted fluid responsiveness with a sensitivity of 0.90 (95% confidence interval, 0.87-0.93) and a specificity of 0.95 (95% confidence interval, 0.92-0.98). CONCLUSIONS: PEEP-induced changes in Vco(2) predicted fluid responsiveness with accuracy in patients undergoing cardiac surgery.
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