| 1. |
- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 2. |
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| 3. |
- Acosta, Cecilia M., et al.
(författare)
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Doppler images of intra-pulmonary shunt within atelectasis in anesthetized children
- 2016
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Ingår i: Critical Ultrasound Journal. - : Springer Science and Business Media LLC. - 2036-3176 .- 2036-7902. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Background: Doppler images of pulmonary vessels in pulmonary diseases associated with subpleural consolidations have been described. Color Doppler easily identifies such vessels within consolidations while spectral Doppler analysis allows the differentiation between pulmonary and bronchial arteries. Thus, Doppler helps in diagnosing the nature of consolidations. To our knowledge, Doppler analysis of pulmonary vessels within anesthesia-induced atelectasis has never been described before. The aim of this case series is to demonstrate the ability of lung ultrasound to detect the shunting of blood within atelectatic lung areas in anesthetized children.Findings: Three anesthetized and mechanically ventilated children were scanned in the supine position using a high-resolution linear probe of 6-12 MHz. Once subpleural consolidations were detected in the most dependent posterior lung regions, the probe was rotated such that its long axis followed the intercostal space. In this oblique position, color Doppler mapping was performed to detect blood flow within the consolidation. Thereafter, pulsed waved spectral Doppler was applied in the previously identified vessels during a short expiratory pause, which prevented interferences from respiratory motion. Different flow patterns were identified which corresponded to both, pulmonary and bronchial vessels. Finally, a lung recruitment maneuver was performed which leads to the complete resolution of the aforementioned consolidation thereby confirming the pathophysiological entity of anesthesia-induced atelectasis.Conclusions: Lung ultrasound is a non-invasive imaging tool that not only enables the diagnosis of anesthesia-induced atelectasis in pediatric patients but also analysis of shunting blood within this consolidation.
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| 4. |
- Borges, João Batista, et al.
(författare)
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Regional Lung Perfusion estimated by Electrical Impedance Tomography in a piglet model of lung collapse
- 2011
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 112:1, s. 225-236
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Tidskriftsartikel (refereegranskat)abstract
- The assessment of the regional match between alveolar ventilation and perfusion in critically ill patients requires simultaneous measurements of both parameters. Ideally, assessment of lung perfusion should be performed in real-time with an imaging technology which provides, through fast acquisition of sequential images, information about the regional dynamics or regional kinetics of an appropriate tracer. We present a novel electrical impedance tomography (EIT) based method that quantitatively estimates regional lung perfusion based on first-pass kinetics of a bolus of hypertonic saline contrast. Pulmonary blood flow was measured in six piglets during control and unilateral or bilateral lung collapse conditions. The first-pass kinetics method showed good agreement with the estimates obtained by single-photon-emission computerized tomography (SPECT). The mean difference (SPECT minus EIT) between fractional blood flow to lung areas suffering atelectasis was -0.6 %, with a standard deviation of 2.9 %. This method outperformed the estimates of lung perfusion based on impedance-pulsatility. In conclusion, we describe a novel method based on Electrical Impedance Tomography for estimating regional lung perfusion at the bedside. In both, healthy and injured lung conditions, the distribution of pulmonary blood flow as assessed by EIT agreed well with the one obtained by SPECT. The method proposed in this paper has the potential to contribute to a better understanding of the behavior of regional perfusion under different lung and therapeutic conditions.
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| 5. |
- Costa, Eduardo L V, et al.
(författare)
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Bedside estimation of recruitable alveolar collapse and hyperdistension by electrical impedance tomography
- 2009
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Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 35:6, s. 1132-1137
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To present a novel algorithm for estimating recruitable alveolar collapse and hyperdistension based on electrical impedance tomography (EIT) during a decremental positive end-expiratory pressure (PEEP) titration. DESIGN: Technical note with illustrative case reports. SETTING: Respiratory intensive care unit. PATIENT: Patients with acute respiratory distress syndrome. INTERVENTIONS: Lung recruitment and PEEP titration maneuver. MEASUREMENTS AND RESULTS: Simultaneous acquisition of EIT and X-ray computerized tomography (CT) data. We found good agreement (in terms of amount and spatial location) between the collapse estimated by EIT and CT for all levels of PEEP. The optimal PEEP values detected by EIT for patients 1 and 2 (keeping lung collapse <10%) were 19 and 17 cmH2O, respectively. Although pointing to the same non-dependent lung regions, EIT estimates of hyperdistension represent the functional deterioration of lung units, instead of their anatomical changes, and could not be compared directly with static CT estimates for hyperinflation. CONCLUSIONS: We described an EIT-based method for estimating recruitable alveolar collapse at the bedside, pointing out its regional distribution. Additionally, we proposed a measure of lung hyperdistension based on regional lung mechanics.
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| 6. |
- Solà, Josep, et al.
(författare)
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Non-invasive monitoring of central blood pressure by electrical impedance tomography : first experimental evidence
- 2011
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Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 49:4, s. 409-415
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Tidskriftsartikel (refereegranskat)abstract
- There is a strong clinical demand for devices allowing continuous non-invasive monitoring of central blood pressure (BP). In the state of the art a new family of techniques providing BP surrogates based on the measurement of the so-called pulse wave velocity (PWV) has been proposed, eliminating the need for inflation cuffs. PWV is defined as the velocity at which pressure pulses propagate along the arterial wall. However, no technique to assess PWV within central arteries in a fully unsupervised manner has been proposed so far. In this pilot study, we provide first experimental evidence that electrical impedance tomography (EIT) is capable of measuring pressure pulses directly within the descending aorta. To obtain a wide range of BP values, we administrated noradrenalin and nitroglycerine to an anesthetized pig under mechanical ventilation. An arterial line was inserted into the ascending aorta for measuring reference BP. EIT images were generated from 32 impedance electrodes placed around the chest at the level of the axilla. Regions of Interest (ROI) such as the descending aorta and the lungs were automatically identified by a novel time-based processing algorithm as the respective EIT pixels representing these structures. The correct positions of these ROIs were confirmed by bolus injections of highly conductive concentrated saline into the right heart and into the ascending aorta. Aortic pulse transit time (PTT) values were determined as the delay between the opening of the aortic valve (obtained from arterial line) and the arrival of pressure pulses at the aortic ROI within the EIT plane. For 11 experimental conditions, with mean BP ranging from 73 to 141 mmHg, strongly significant correlation (r = -0.97, P < 0.00001) between central BP and aortic PTT was observed, suggesting that EIT-derived aortic PTT is a potential non-invasive surrogate of central BP.
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| 7. |
- Suarez-Sipmann, Fernando, et al.
(författare)
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Recruit the lung before titrating the right positive end-expiratory pressure to protect it
- 2009
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Ingår i: Critical Care. - : Springer Science and Business Media LLC. - 1364-8535 .- 1466-609X. ; 13:3, s. 134-
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Tidskriftsartikel (refereegranskat)abstract
- The optimal level of positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome patients is still controversial and has gained renewed interest in the era of 'lung protective ventilation strategies'. Despite experimental evidence that higher levels of PEEP protect against ventilator-induced lung injury, recent clinical trials have failed to demonstrate clear survival benefits. The open-lung protective ventilation strategy combines lung recruitment maneuvers with a decremental PEEP trial aimed at finding the minimum level of PEEP that prevents the lung from collapsing. This approach to PEEP titration is more likely to exert its protective effects and is clearly different from the one used in previous clinical trials.
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| 8. |
- Suarez-Sipmann, Fernando, et al.
(författare)
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Volumetric capnography : the time has come
- 2014
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Ingår i: Current Opinion in Critical Care. - 1070-5295 .- 1531-7072. ; 20:3, s. 333-339
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Forskningsöversikt (refereegranskat)abstract
- Purpose of review This review article summarizes the recent advances in electrical impedance tomography (EIT) related to cardiopulmonary imaging and monitoring on the background of the 30-year development of this technology. Recent findings EIT is expected to become a bedside tool for monitoring and guiding ventilator therapy. In this context, several studies applied EIT to determine spatial ventilation distribution during different ventilation modes and settings. EIT was increasingly combined with other signals, such as airway pressure, enabling the assessment of regional respiratory system mechanics. EIT was for the first time used prospectively to define ventilator settings in an experimental and a clinical study. Increased neonatal and paediatric use of EIT was noted. Only few studies focused on cardiac function and lung perfusion. Advanced radiological imaging techniques were applied to assess EIT performance in detecting regional lung ventilation. New approaches to improve the quality of thoracic EIT images were proposed. EIT is not routinely used in a clinical setting, but the interest in EIT is evident. The major task for EIT research is to provide the clinicians with guidelines how to conduct, analyse and interpret EIT examinations and combine them with other medical techniques so as to meaningfully impact the clinical decision-making.
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| 9. |
- Tusman, Gerardo, et al.
(författare)
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Advanced Uses of Pulse Oximetry for Monitoring Mechanically Ventilated Patients
- 2017
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Ingår i: Anesthesia and Analgesia. - 0003-2999 .- 1526-7598. ; 124:1, s. 62-71
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Tidskriftsartikel (refereegranskat)abstract
- Pulse oximetry is an undisputable standard of care in clinical monitoring. It combines a spectrometer to detect hypoxemia with a plethysmograph for the diagnosis, monitoring, and follow-up of cardiovascular diseases. These pulse oximetry capabilities are extremely useful for assessing the respiratory and circulatory status and for monitoring of mechanically ventilated patients. On the one hand, the key spectrography-derived function of pulse oximetry is to evaluate a patient's gas exchange that results from a particular ventilatory treatment by continuously and noninvasively measuring arterial hemoglobin saturation (Spo(2)). This information helps to maintain patients above the hypoxemic levels, leading to appropriate ventilator settings and inspired oxygen fractions. However, whenever higher than normal oxygen fractions are used, Spo(2) can mask existing oxygenation defects in ventilated patients. This limitation, resulting from the S shape of the oxyhemoglobin saturation curve, can be overcome by reducing the oxygen fraction delivered to the patient in a controlled and stepwise manner. This results in a Spo(2)/Fio(2) diagram, which allows a rough characterization of a patient's gas exchange, shunt, and the amount of lung area with a low ventilation/perfusion ratio without the need of blood sampling. On the other hand, the photoplethysmography-derived oximeter function has barely been exploited for the purpose of monitoring hemodynamics in mechanically ventilated patients. The analysis of the photoplethysmography contour provides useful real-time and noninvasive information about the interaction of heart and lungs during positive pressure ventilation. These hemodynamic monitoring capabilities are related to both the assessment of preload dependency mainly by analyzing the breath-by-breath variation of the photoplethysmographic signals and the analysis of arterial impedance, Which examines the changes in the plethysmographic amplitude, contour, and derived indexes. In this article, we present and describe these extended monitoring capabilities and propose a more holistic monitoring concept that takes advantage of these advanced uses of pulse oximetry in the monitoring of ventilated patients. Today's monitors need to be improved if such novel functionalities were to be offered for clinical use. Future developments and clinical evaluations are needed to establish the true potential of these advanced monitoring uses of pulse oximetry.
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| 10. |
- Tusman, Gerardo, et al.
(författare)
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Bohr Dead Space Calculation In Response
- 2012
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Ingår i: Anesthesia and Analgesia. - 0003-2999 .- 1526-7598. ; 115:6, s. 1472-1473
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Tidskriftsartikel (refereegranskat)
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| 11. |
- 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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| 12. |
- 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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| 13. |
- Tusman, Gerardo, et al.
(författare)
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Pulmonary blood flow generates cardiogenic oscillations
- 2009
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Ingår i: Respiratory Physiology & Neurobiology. - : Elsevier BV. - 1569-9048 .- 1878-1519. ; 167:3, s. 247-254
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Tidskriftsartikel (refereegranskat)abstract
- Cardiogenic oscillations are small waves produced by heartbeats, which are superimposed on the pressure and flow signals at the airway opening. The aim of this study was to investigate the role of the two main factors believed to generate these oscillations: (1) contact between heart and lungs and (2) pulmonary blood flow. We studied 15 heart surgery patients on cardiopulmonary bypass so both factors could be manipulated independently. At minimal heart–lung contact pressure and flow oscillations were larger than during maximal contact (1.20 ± 0.17 cmH2O and 2.36 ± 0.08 L min−1 vs 0.92 ± 0.15 cmH2O and 1.78 ± 0.26 L min−1, mean ± SD, p < 0.05). Cardiogenic oscillations for pressure and flow were smaller at 50% compared to 100% pulmonary blood flow (0.80 ± 0.12 cmH2O and 1.56 ± 0.34 L min−1 vs 1.19 ± 0.14 cmH2O and 2.38 ± 0.19 L min−1). We conclude that the amount of pulmonary blood flow and not the contact between heart and lungs is the main factor determining the amplitude of cardiogenic oscillations.
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| 14. |
- Tusman, Gerardo, et al.
(författare)
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Rationale of Dead Space Measurement by Volumetric Capnography
- 2012
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Ingår i: Anesthesia and Analgesia. - 0003-2999 .- 1526-7598. ; 114:4, s. 866-874
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Tidskriftsartikel (refereegranskat)abstract
- Dead space is the portion of a tidal volume that does not participate in gas exchange because it does not get in contact with blood flowing through the pulmonary capillaries. It is commonly calculated using volumetric capnography, the plot of expired carbon dioxide (CO2) versus tidal volume, which is an easy bedside assessment of the inefficiency of a particular ventilatory setting. Today, Bohr's original dead space can be calculated in an entirely noninvasive and breath-by-breath manner as the mean alveolar partial pressure of CO2 (PAco(2)) which can now be determined directly from the capnogram. The value derived from Enghoff's modification of Bohr's formula (using Paco(2) instead of PAco(2)) is a global index of the inefficiency of gas exchange rather than a true "dead space" because it is influenced by all causes of ventilation/perfusion mismatching, from real dead space to shunt. Therefore, the results obtained by Bohr's and Enghoff's formulas have different physiological meanings and clinicians must be conscious of such differences when interpreting patient data. In this article, we describe the rationale of dead space measurements by volumetric capnography and discuss its main clinical implications and the misconceptions surrounding it.
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| 15. |
- Tusman, Gerardo, et al.
(författare)
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Real-time images of tidal recruitment using lung ultrasound
- 2015
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Ingår i: Critical Ultrasound Journal. - : Springer Science and Business Media LLC. - 2036-3176 .- 2036-7902. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Background: Ventilator-induced lung injury is a form of mechanical damage leading to a pulmonary inflammatory response related to the use of mechanical ventilation enhanced by the presence of atelectasis. One proposed mechanism of this injury is the repetitive opening and closing of collapsed alveoli and small airways within these atelectatic areas-a phenomenon called tidal recruitment. The presence of tidal recruitment is difficult to detect, even with high-resolution images of the lungs like CT scan. The purpose of this article is to give evidence of tidal recruitment by lung ultrasound. Findings: A standard lung ultrasound inspection detected lung zones of atelectasis in mechanically ventilated patients. With a linear probe placed in the intercostal oblique position. We observed tidal recruitment within atelectasis as an improvement in aeration at the end of inspiration followed by the re-collapse at the end of expiration. This mechanism disappeared after the performance of a lung recruitment maneuver. Conclusions: Lung ultrasound was helpful in detecting the presence of atelectasis and tidal recruitment and in confirming their resolution after a lung recruitment maneuver.
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| 16. |
- 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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| 17. |
- Tusman, Gerardo, et al.
(författare)
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States of low pulmonary blood flow can be detected non-invasively at the bedside measuring alveolar dead space
- 2012
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Ingår i: Journal of clinical monitoring and computing. - : Springer Science and Business Media LLC. - 1387-1307 .- 1573-2614. ; 26:3, s. 183-190
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Tidskriftsartikel (refereegranskat)abstract
- We tested whether the ratio of alveolar dead space to alveolar tidal volume (VDalv/VTalv) can detect states of low pulmonary blood flow (PBF) in a non-invasive way. Fifteen patients undergoing cardiovascular surgeries with cardiopulmonary bypass (CPB) were studied. CPB is a technique that excludes the lungs from the general circulation. The weaning of CPB is a model that manipulates PBF in vivo because each time blood flow through the CPB decreases, expected PBF (ePBF) increases. Patients were liberated from CPB in steps of 20 % every 2' starting from 100 % CPB (very low ePBF) to 0 % CPB (100 % ePBF). During constant ventilation, volumetric capnograms were recorded and Bohr's dead space ratio (VDBohr/VT), VDalv/VTalv and the ratio of airway dead space to tidal volume (VDaw/VT) were calculated. Before CPB, VDBohr/VT was 0.36 +/- A 0.05, VDaw/VT 0.21 +/- A 0.04 and VDalv/VTalv 0.18 +/- A 0.06 (mean +/- A SD). During weaning from CPB, VDaw/VT remained unchanged while VDBohr/VT and VDalv/VTalv decreased with increasing ePBF. At CPB of 80, 60, 40 and 20 % VDBohr/VT was 0.64 +/- A 0.06, 0.55 +/- A 0.06, 0.47 +/- A 0.05 and 0.40 +/- A 0.04, respectively; < 0.001 and VDalv/VTalv 0.53 +/- A 0.07, 0.40 +/- A 0.07, 0.29 +/- A 0.06 and 0.25 +/- A 0.04, respectively; < 0.001). After CPB, VDBohr/VT and VDalv/VTalv reached values similar to baseline (0.37 +/- A 0.04 and 0.19 +/- A 0.06, respectively). At constant ventilation the alveolar component of VDBohr/VT increased in proportion to the deficit in lung perfusion.
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| 18. |
- 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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| 19. |
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| 20. |
- Tusman, Gerardo, et al.
(författare)
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Validation of Bohr dead space measured by volumetric capnography
- 2011
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Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 37:5, s. 870-874
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Tidskriftsartikel (refereegranskat)abstract
- Bohr's dead space (VDBohr) is commonly calculated using end-tidal CO2 instead of the true alveolar partial pressure of CO2 (PACO(2)). The aim of this work was to validate VDBohr using PACO(2) derived from volumetric capnography (VC) against VDBohr with PACO(2) values obtained from the standard alveolar air formula. Expired gases of seven lung-lavaged pigs were analyzed at different lung conditions using main-stream VC and multiple inert gas elimination technique (MIGET). PACO(2) was determined by VC as the midpoint of the slope of phase III of the capnogram, while mean expired partial pressure of CO2 (PeCO(2)) was calculated as the mean expired fraction of CO2 times the barometric minus the water vapor pressure. MIGET estimated expired CO2 output (VCO2) and PeCO(2) by its V/Q algorithms. Then, PACO(2) was obtained applying the alveolar air formula (PACO(2) = VCO2/alveolar ventilation). We found close linear correlations between the two methods for calculating both PACO(2) (r = 0.99) and VDBohr (r = 0.96), respectively (both p < 0.0001). Mean PACO(2) from VC was very similar to the one obtained by MIGET with a mean bias of -0.10 mmHg and limits of agreement between -2.18 and 1.98 mmHg. Mean VDBohr from VC was close to the value obtained by MIGET with a mean bias of 0.010 ml and limits of agreement between -0.044 and 0.064 ml. VDBohr can be calculated with accuracy using volumetric capnography.
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| 21. |
- Waldmann, Andreas D., et al.
(författare)
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Position-dependent distribution of lung ventilation - A feasability study
- 2015
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Ingår i: 2015 IEEE Sensors Applications Symposium (SAS). - 9781479961177 ; , s. 429-434
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Konferensbidrag (refereegranskat)abstract
- The aim of this feasibility study was to determine whether the measurement setup and study protocol were able to show the effect that lung disease, body position and different levels of positive end expiratory pressure (PEEP) have on lung function. By means of a motorized rotation table and gravity sensors six pigs were rotated in steps of 30 degrees from left to right lateral position. Regional ventilation distributions, measured by electrical impedance tomography (EIT), oxygenation and compliance measurements were performed at each position. Both, experimental and measurement setup as well as the parameters chosen to characterize lung function appear suitable for analyzing the effects of PEEP and rotation in healthy and injured lungs. The initial results show that the distribution of regional ventilation was highly gravity-dependent especially in sick lungs. Furthermore lateral rotation showed significant recruitment effects on previously collapsed lung tissue as witnessed by the increases in oxygenation at all PEEPs.
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