Rationale and study design for an Individualized PeriopeRative Open lung VEntilatory approach in Emergency Abdominal Laparotomy/scopy: study protocol for a prospective international randomized controlled trial.

BACKGROUND: Postoperative pulmonary complications (PPC) are the most frequent postoperative complications, with an estimated prevalence in elective surgery ranging from 20% in observational cohort studies to 40% in randomized clinical trials. However, the prevalence of PPCs in patients undergoing emergency abdominal surgery is not well defined. Lung-protective ventilation aims to minimize ventilator-induced lung injury and reduce PPCs. The open lung approach (OLA), which combines recruitment manoeuvres (RM) and positive end-expiratory pressure (PEEP) titration, aims to minimize areas of atelectasis and the development of PPCs; however, there is no conclusive evidence in the literature that OLA can prevent PPCs. The purpose of this study is to compare an individualized perioperative OLA with conventional standardized lung-protective ventilation in patients undergoing emergency abdominal surgery with clinical signs of intraoperative lung collapse. METHODS: Randomized international clinical trial to compare an individualized perioperative OLA (RM plus individualized PEEP and individualized postoperative respiratory support) with conventional lung-protective ventilation (standard PEEP of 5 cmH2O and conventional postoperative oxygen therapy) in patients undergoing emergency abdominal surgery with clinical signs of lung collapse. Patients will be randomised to open-label parallel groups. The primary outcome is any severe PPC during the first 7 postoperative days, including: acute respiratory failure, pneumothorax, weaning failure, acute respiratory distress syndrome, and pulmonary infection. The estimated sample size is 732 patients (366 per group). The final sample size will be readjusted during the interim analysis. DISCUSSION: The Individualized Perioperative Open-lung Ventilatory Strategy in emergency abdominal laparotomy (iPROVE-EAL) is the first multicentre, randomized, controlled trial to investigate whether an individualized perioperative approach prevents PPCs in patients undergoing emergency surgery.

Clinical validation of a capnodynamic method for measuring end-expiratory lung volume in critically ill patients.

RATIONALE: End-expiratory lung volume (EELV) is reduced in mechanically ventilated patients, especially in pathologic conditions. The resulting heterogeneous distribution of ventilation increases the risk for ventilation induced lung injury. Clinical measurement of EELV however, remains difficult. OBJECTIVE: Validation of a novel continuous capnodynamic method based on expired carbon dioxide (CO2) kinetics for measuring EELV in mechanically ventilated critically-ill patients. METHODS: Prospective study of mechanically ventilated patients scheduled for a diagnostic computed tomography exploration. Comparisons were made between absolute and corrected EELVCO2 values, the latter accounting for the amount of CO2 dissolved in lung tissue, with the reference EELV measured by computed tomography (EELVCT). Uncorrected and corrected EELVCO2 was compared with total CT volume (density compartments between - 1000 and 0 Hounsfield units (HU) and functional CT volume, including density compartments of - 1000 to - 200HU eliminating regions of increased shunt. We used comparative statistics including correlations and measurement of accuracy and precision by the Bland Altman method. MEASUREMENTS AND MAIN RESULTS: Of the 46 patients included in the final analysis, 25 had a diagnosis of ARDS (24 of which COVID-19). Both EELVCT and EELVCO2 were significantly reduced (39 and 40% respectively) when compared with theoretical values of functional residual capacity (p < 0.0001). Uncorrected EELVCO2 tended to overestimate EELVCT with a correlation r2 0.58; Bias - 285 and limits of agreement (LoA) (+ 513 to - 1083; 95% CI) ml. Agreement improved for the corrected EELVCO2 to a Bias of - 23 and LoA of (+ 763 to - 716; 95% CI) ml. The best agreement of the method was obtained by comparison of corrected EELVCO2 with functional EELVCT with a r2 of 0.59; Bias - 2.75 (+ 755 to - 761; 95% CI) ml. We did not observe major differences in the performance of the method between ARDS (most of them COVID related) and non-ARDS patients. CONCLUSION: In this first validation in critically ill patients, the capnodynamic method provided good estimates of both total and functional EELV. Bias improved after correcting EELVCO2 for extra-alveolar CO2 content when compared with CT estimated volume. If confirmed in further validations EELVCO2 may become an attractive monitoring option for continuously monitor EELV in critically ill mechanically ventilated patients. TRIAL REGISTRATION: clinicaltrials.gov (NCT04045262).

Photoplethysmography waveform analysis for classification of vascular tone and arterial blood pressure: Study based on neural networks.

BACKGROUND: To test whether a Shallow Neural Network (S-NN) can detect and classify vascular tone dependent changes in arterial blood pressure (ABP) by advanced photopletysmographic (PPG) waveform analysis. METHODS: PPG and invasive ABP signals were recorded in 26 patients undergoing scheduled general surgery. We studied the occurrence of episodes of hypertension (systolic arterial pressure (SAP) >140 mmHg), normotension and hypotension (SAP < 90 mmHg). Vascular tone according to PPG was classified in two ways: 1) By visual inspection of changes in PPG waveform amplitude and dichrotic notch position; where Classes I-II represent vasoconstriction (notch placed >50% of PPG amplitude in small amplitude waves), Class III normal vascular tone (notch placed between 20-50% of PPG amplitude in normal waves) and Classes IV-V-VI vasodilation (notch <20% of PPG amplitude in large waves). 2) By an automated analysis, using S-NN trained and validated system that combines seven PPG derived parameters. RESULTS: The visual assessment was precise in detecting hypotension (sensitivity 91%, specificity 86% and accuracy 88%) and hypertension (sensitivity 93%, specificity 88% and accuracy 90%). Normotension presented as a visual Class III (III-III) (median and 1st-3rd quartiles), hypotension as a Class V (IV-VI) and hypertension as a Class II (I-III); all p < .0001. The automated S-NN performed well in classifying ABP conditions. The percentage of data with correct classification by S-ANN was 83% for normotension, 94% for hypotension, and 90% for hypertension. CONCLUSIONS: Changes in ABP were correctly classified automatically by S-NN analysis of the PPG waveform contour.

Ultrasound-guided brachiocephalic vein access in neonates and pediatric patients.

Central venous accesses in neonates and pediatric patients represent a common and important procedure for both, intraoperative and postoperative care. Point-of-care ultrasound-guided technique has been proposed to increased success rate and efficiency, as well as to decrease the number of complications. Ultrasound-guided internal jugular vein cannulation is considering the "gold standard" in children. Another central venous cannulation option in neonates and children has been supraclavicular ultrasound-guided cannulation of the brachiocephalic vein using the in-plane approach. This article gives a review of the current evidence, the basic knowledge of the technique and the structured approach to follow for supraclavicular ultrasound-guided brachiocephalic vein access in children and neonates.

Ultrasound-guided brachiocephalic vein access in neonates and pediatric patients. / Accesos vasculares ecoguiados de la vena braquiocefálica en neonatos y pacientes pediátricos.

Central venous accesses in neonates and pediatric patients represent a common and important procedure for both, intraoperative and postoperative care. Point-of-care ultrasound-guided technique has been proposed to increased success rate and efficiency, as well as to decrease the number of complications. Ultrasound-guided internal jugular vein cannulation is considering the "gold standard" in children. Another central venous cannulation option in neonates and children has been supraclavicular ultrasound-guided cannulation of the brachiocephalic vein using the in-plane approach. This article gives a review of the current evidence, the basic knowledge of the technique and the structured approach to follow for supraclavicular ultrasound-guided brachiocephalic vein access in children and neonates.

[COVID-19: how to transform a noninvasive ventilation device in a critical care ventilator]. / COVID-19: cómo transformar un ventilador de no invasiva en un ventilador de críticos.

COVID-19 pandemic caused not only many deaths around the world but also made evident technical limitations of hospital and intensive care units (ICU). The growing demand of ICU ventilators in a short lapse of time constitutes one of the main community concerns. The main goal of this communication is to give simple solutions to transform a noninvasive ventilator in an invasive one for intubated patients. The proposal can be applied in two well defined strategies for the COVID-19 pandemic: To replace anesthesia workstations, leaving those machines to be used in patients. To apply this option in COVID-19 patients by way of a therapeutic "bridge", waiting for the release of a ventilator in the ICU.

[Volumetric capnography for analysis and optimization of ventilation and gas exchange]. / Volumetrische Kapnographie zur Analyse und Optimierung von Ventilation und Gasaustausch.

Capnography as the graphical representation of the expiratory carbon dioxide (CO2) concentration, is an essential component of monitoring of every ventilated patient, in addition to pulse oximetry. Capnography demonstrates the kinetics of CO2 in a noninvasive way and in real time. In the daily routine anesthesia, it mainly serves for identification of the correct intubation and adaptation of the respiratory minute volume to be applied; however, capnography can also provide much more far-reaching and clinically particularly valuable information, especially in the form of volumetric capnography (VCap) that is not yet so widely clinically available. These include monitoring and optimization of ventilation and assessment of gas exchange. This article presents parameters for making decisions at the bedside, which could previously only be obtained by extensive, more invasive, nonautomated procedures.

[Foundations of Volumetric capnography : Principles of monitoring of metabolism and hemodynamics]. / Grundlagen der Volumetrischen Kapnographie : Prinzipien der Überwachung von Stoffwechsel und Hämodynamik.

Capnography is the graphical representation of the carbon dioxide (CO2) concentration in expired air. Using this monitoring procedure, the kinetics of CO2 of mechanically ventilated patients can be assessed in a noninvasive way and in real time. This article highlights the importance, particularly of volumetric capnography (VCap), for clinical monitoring of mechanically ventilated patients. The procedure provides important information on the breathing, ventilation, metabolism and hemodynamics of patients.

Estudio sonográfico del diafragma. Una nueva herramienta diagnóstica para el anestesiólogo / Diafragmatic Ultrasound, a new tool for the anesthesiologist

Point-of-care ultrasonography has become a widely used diagnostic tool in the intensive care units and during perioperative settings. Nowadays, ultrasound has been also employed to evaluate diaphragmatic function. Some advantages of this method include safety, absence of ionizing radiation, and availability of real-time bedside examinations. The aim of this review is to promote the use of diaphragmatic ultrasound assessment among anesthesiologists and intensive care physicians. This article describes the standard diaphragmatic ultrasound technique and the knowledge required in order to monitor and diagnose diaphragmatic dysfunction; emphasizing its use in the operating room and in the different fields of clinical application.

El ultrasonido point-of-care se ha convertido en una herramienta diagnóstica ampliamente utilizada en unidades de cuidados intensivos y durante el período peri-operatorio. En la actualidad, el ultrasonido esta siendo empleado además para evaluar la función diafragmática. Las ventajas de este método incluyen seguridad, ausencia de radiación ionizante y posibilidad de realizar examinación en tiempo real a la cabecera del paciente. El objetivo de esta revisión es promover el uso de la evaluación sonográfica del diafragma para médicos anestesiólogos e intensivistas. Este artículo describe la técnica estándar de la evaluación sonográfica del diafragma y el conocimiento requerido para el diagnóstico y monitorización de la disfunción diafragmática, enfatizando el uso en quirófano y en los diferentes campos de aplicación clínica.

Individualized lung recruitment maneuver guided by pulse-oximetry in anesthetized patients undergoing laparoscopy: a feasibility study.

BACKGROUND: We conducted this study to test whether pulse-oximetry hemoglobin saturation (SpO2 ) can personalize the implementation of an open-lung approach during laparoscopy. Thirty patients with SpO2  ≥ 97% on room-air before anesthesia were studied. After anesthesia and capnoperitoneum the FIO2 was reduced to 0.21. Those patients whose SpO2 decreased below 97% - an indication of shunt related to atelectasis - completed the following phases: (1) First recruitment maneuver (RM), until reaching lung's opening pressure, defined as the inspiratory pressure level yielding a SpO2 ≥ 97%; (2) decremental positive end-expiratory (PEEP) titration trial until reaching lung's closing pressure defined as the PEEP level yielding a SpO2  < 97%; (3) second RM and, (4) ongoing ventilation with PEEP adjusted above the detected closing pressure. RESULTS: When breathing air, in 24 of 30 patients SpO2 was < 97%, PaO2 /FIO2  Ë‚ 53.3 kPa and negative end-expiratory transpulmonary pressure (PTP-EE ). The mean (SD) opening pressures were found at 40 (5) and 33 (4) cmH2 O during the first and second RM, respectively (P < 0.001; 95% CI: 3.2-7.7). The closing pressure was found at 11 (5) cmH2 O. This SpO2 -guided approach increased PTP-EE (from -6.4 to 1.2 cmH2 O, P < 0.001) and PaO2 /FIO2 (from 30.3 to 58.1 kPa, P < 0.001) while decreased driving pressure (from 18 to 10 cmH2 O, P < 0.001). SpO2 discriminated the lung's opening and closing pressures with accuracy taking the reference parameter PTP-EE (area under the receiver-operating-curve of 0.89, 95% CI: 0.80-0.99). CONCLUSION: The non-invasive SpO2 monitoring can help to individualize an open-lung approach, including all involved steps, from the identification of those patients who can benefit from recruitment, the identification of opening and closing pressures to the subsequent monitoring of an open-lung condition.

Alveolar recruitment improves ventilation during thoracic surgery: a randomized controlled trial.

BACKGROUND: This study was conducted to determine whether an alveolar recruitment strategy (ARS) applied during two-lung ventilation (TLV) just before starting one-lung ventilation (OLV) improves ventilatory efficiency. METHODS: Subjects were randomly allocated to two groups: (i) control group: ventilation with tidal volume (VT) of 8 or 6 ml kg(-1) for TLV and OLV, respectively, and (ii) ARS group: same ventilatory pattern with ARS consisting of 10 consecutive breaths at a plateau pressure of 40 and 20 cm H(2)O PEEP applied immediately before and after OLV. Volumetric capnography and arterial blood samples were recorded 5 min (baseline) and 20 min into TLV, at 20 and 40 min during OLV, and finally 10 min after re-establishing TLV. RESULTS: Twenty subjects were included in each group. In all subjects, the airway component of dead space remained constant during the study. Compared with baseline, the alveolar dead space ratio (VD(alv)/VT(alv)) increased throughout the protocol in the control but decreased in the ARS group. Differences in VD(alv)/VT(alv) between groups were significant (P<0.001). Except for baseline, all values in kPa (sd) were higher in the ARS than in the control group (P<0.001), respectively [70 (7) and 55 (9); 33 (9) and 24 (10); 33 (8) and 22 (10); 70 (7) and 55 (10)]. CONCLUSIONS: Recruitment of both lungs before instituting OLV not only decreased alveolar dead space but also improved arterial oxygenation and the efficiency of ventilation.

Capnography reflects ventilation/perfusion distribution in a model of acute lung injury.

BACKGROUND: Changes in the shape of the capnogram may reflect changes in lung physiology. We studied the effect of different ventilation/perfusion ratios (V/Q) induced by positive end-expiratory pressures (PEEP) and lung recruitment on phase III slope (S(III)) of volumetric capnograms. METHODS: Seven lung-lavaged pigs received volume control ventilation at tidal volumes of 6 ml/kg. After a lung recruitment maneuver, open-lung PEEP (OL-PEEP) was defined at 2 cmH(2)O above the PEEP at the onset of lung collapse as identified by the maximum respiratory compliance during a decremental PEEP trial. Thereafter, six distinct PEEP levels either at OL-PEEP, 4 cmH(2)O above or below this level were applied in a random order, either with or without a prior lung recruitment maneuver. Ventilation-perfusion distribution (using multiple inert gas elimination technique), hemodynamics, blood gases and volumetric capnography data were recorded at the end of each condition (minute 40). RESULTS: S (III) showed the lowest value whenever lung recruitment and OL-PEEP were jointly applied and was associated with the lowest dispersion of ventilation and perfusion (Disp(R-E)), the lowest ratio of alveolar dead space to alveolar tidal volume (VD(alv)/VT(alv)) and the lowest difference between arterial and end-tidal pCO(2) (Pa-ETCO(2)). Spearman's rank correlations between S(III) and Disp(R-E) showed a ρ=0.85 with 95% CI for ρ (Fisher's Z-transformation) of 0.74-0.91, P<0.0001. CONCLUSION: In this experimental model of lung injury, changes in the phase III slope of the capnograms were directly correlated with the degree of ventilation/perfusion dispersion.

Effects of prone position on alveolar dead space and gas exchange during general anaesthesia in surgery of long duration.

BACKGROUND AND OBJECTIVE: We investigated the effects of prone position on respiratory dead space and gas exchange in 14 anaesthetized healthy patients undergoing elective posterior spinal surgery of more than 3 h of duration. METHODS: The patients received a total intravenous anaesthetic with propofol/remifentanil/cisatracurium. They were ventilated at a tidal volume of 8-10 mL kg(-1), zero positive end-expiratory pressure and an inspired oxygen fraction of 0.4. Physiological, airway and alveolar dead spaces were calculated by analysis of the volumetric capnography waveform. Measurements were made in supine position (20 min after the beginning of mechanical ventilation) and 30, 120 and 180 min after turning to prone position. RESULTS: We found that the alveolar dead space/tidal volume ratio did not change. PaO(2)/F(i)O(2) increased, although not statistically significantly. Dynamic compliance was reduced due to a reduction in tidal volume and an increase in plateau pressure. CONCLUSIONS: Patients undergoing surgery in prone position for a duration of 3 h under general anaesthesia including muscle relaxation and mechanical ventilation without positive end-expiratory pressure have stable haemodynamics and no significant changes in the alveolar dead space to tidal volume ratio. Oxygenation tended to improve.

Effect of pulmonary perfusion on the slopes of single-breath test of CO2.

The objective of this study was to evaluate the effects of lung perfusion on the slopes of phases II (S(II)) and III (S(III)) of a single-breath test of CO(2) (SBT-CO(2)). Fourteen patients submitted to cardiac surgery were studied during weaning from cardiopulmonary bypass (CPB). Pump flow was decreased in 20% steps, from 100% (total CPB = 2.5 l.min(-1).m(-2)) to 0%. This maneuver resulted in a progressive and opposite increase in pulmonary blood flow (PBF) while maintaining ventilator settings constant. SBT-CO(2), respiratory, and hemodynamic variables remained unchanged before and after CPB, reflecting a constant condition at those stages. S(III) was similar before and after CPB (19.6 +/- 2.8 and 18.7 +/- 2.1 mmHg/l, respectively). S(III) was lowest during 20% PBF (8.6 +/- 1.9 mmHg/l) and increased in proportion to PBF until exit from CPB (15.6 +/- 2.2 mmHg/l; P < 0.05). Similarly, S(II) and the CO(2) area under the curve increased from 163 +/- 41 mmHg/l and 4.7 +/- 0.6 ml, respectively, at 20% PBF to 313 +/- 32 mmHg/l and 7.9 +/- 0.6 ml (P < 0.05) at CPB end. When S(II) and S(III) were normalized by the mean percent expired CO(2), they remained unchanged during the protocol. In summary, the changes in PBF affect the slopes of the SBT-CO(2). Normalizing S(II) and S(III) eliminated the effect of changes in the magnitude of PBF on the shape of the SBT-CO(2) curve.

[Effects of the alveolar recruitment manoeuver and PEEP on arterial oxygenation in anesthetized obese patients]. / Efectos de la maniobra de reclutamiento alveolar y la PEEP sobre la oxigenación arterial en pacientes obesos anestesiados.

BACKGROUND: Diminished functional residual capacity and pulmonary collapse during general anesthesia lead to alterations in respiratory mechanics and gas exchange. Such phenomena are more pronounced in obese patients. We recently demonstrated the beneficial effects of the alveolar recruitment strategy on oxygenation in anesthetized patients of normal body mass index (BMI). The aim of the present study was to evaluate whether obese patients also benefit from the alveolar recruitment strategy and to determine the level of positive end-expiratory pressure (PEEP) that prevents recollapse in obese patients. METHODS: Three groups of 30 patients each were studied: patients with normal BMI (control group) and obese patients to whom we applied PEEP at 5 and 10 cm H2O (obese-5 and obese-10 groups, respectively) after the recruitment maneuver. We studied respiratory mechanics (respiratory distensibility, airway pressures and flow volume) and arterial oxygenation (PaO2) before and after the recruitment. RESULTS: PaO2 at baseline was higher in the control group (174 +/- 44 mm Hg) than in either the obese-5 or obese-10 group (108 +/- 24 and 114 +/- 22 mm Hg, respectively, p < 0.001). Oxygenation improved in all groups after recruitment (p < 0.001), and PaO2 in the obese-10 group was similar to that of the control group (218 +/- 25 mm Hg and 259 +/- 80 mm Hg, respectively, p > 0.05). Oxygenation in the obese-5 group, however, was worse (153 +/- 41 mm Hg) than that of either of the other groups (p < 0.001). CONCLUSIONS: We conclude that the alveolar recruitment strategy was effective for increasing PaO2 in anesthetized patients, regardless of body mass. The oxygenation of obese patients receiving the higher level of PEEP was similar to that of non-obese patients.

'Alveolar recruitment strategy' improves arterial oxygenation during general anaesthesia.

Abnormalities in gas exchange during general anaesthesia are caused partly by atelectasis. Inspiratory pressures of approximately 40 cm H2O are required to fully re-expand healthy but collapsed alveoli. However, without PEEP these re-expanded alveoli tend to collapse again. We hypothesized that an initial increase in pressure would open collapsed alveoli; if this inspiratory recruitment is combined with sufficient end-expiratory pressure, alveoli will remain open during general anaesthesia. We tested the effect of an 'alveolar recruitment strategy' on arterial oxygenation and lung mechanics in a prospective, controlled study of 30 ASA II or III patients aged more than 60 yr allocated to one of three groups. Group ZEEP received no PEEP. The second group received an initial control period without PEEP, and then PEEP 5 cm H2O was applied. The third group received an increase in PEEP and tidal volumes until a PEEP of 15 cm H2O and a tidal volume of 18 ml kg-1 or a peak inspiratory pressure of 40 cm H2O was reached. PEEP 5 cm H2O was then maintained. There was a significant increase in median PaO2 values obtained at baseline (20.4 kPa) and those obtained after the recruitment manoeuvre (24.4 kPa) at 40 min. This latter value was also significantly higher than PaO2 measured in the PEEP (16.2 kPa) and ZEEP (18.7 kPa) groups. Application of PEEP also had a significant effect on oxygenation; no such intra-group difference was observed in the ZEEP group. No complications occurred. We conclude that during general anaesthesia, the alveolar recruitment strategy was an efficient way to improve arterial oxygenation.