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1.
J Clin Monit Comput ; 34(2): 233-243, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31089844

RESUMO

Evaluation of a new Windkessel model based pulse contour method (WKflow) to calculate stroke volume in patients undergoing intra-aortic balloon pumping (IABP). Preload changes were induced by vena cava occlusions (VCO) in twelve patients undergoing cardiac surgery to vary stroke volume (SV), which was measured by left ventricular conductance volume method (SVlv) and WKflow (SVwf). Twelve VCO series were carried out during IABP assist at a 1:2 ratio and seven VCO series were performed with IABP switched off. Additionally, SVwf was evaluated during nine episodes of severe arrhythmia. VCO's produced marked changes in SV over 10-20 beats. 198 paired data sets of SVlv and SVwf were obtained. Bland-Altman analysis for the difference between SVlv and SVwf during IABP in 1:2 mode showed a bias (accuracy) of 1.04 ± 3.99 ml, precision 10.9% and limits of agreement (LOA) of - 6.94 to 9.02 ml. Without IABP bias was 0.48 ± 4.36 ml, precision 11.6% and LOA of - 8.24 to 9.20 ml. After one thermodilution calibration of SVwf per patient, during IABP the accuracy improved to 0.14 ± 3.07 ml, precision to 8.3% and LOA to - 6.00 to + 6.28 ml. Without IABP the accuracy improved to 0.01 ± 2.71 ml, precision to 7.5% and LOA to - 5.41 to + 5.43 ml. Changes in SVlv and SVwf were directionally concordant in response to VCO's and during severe arrhythmia. (R2 = 0.868). The SVwf and SVlv methods are interchangeable with respect to measuring absolute stroke volume as well as tracking changes in stroke volume. The precision of the non-calibrated WKflow method is about 10% which improved to 7.5% after one calibration per patient.


Assuntos
Pressão Arterial , Débito Cardíaco , Monitorização Hemodinâmica/métodos , Balão Intra-Aórtico , Idoso , Arritmias Cardíacas/fisiopatologia , Simulação por Computador , Feminino , Monitorização Hemodinâmica/estatística & dados numéricos , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Cardiovasculares , Análise de Regressão , Volume Sistólico , Veias Cavas/fisiopatologia
2.
J Clin Monit Comput ; 27(2): 163-70, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23143501

RESUMO

External leg compression (ELC) may increase cardiac output (CO) in fluid-responsive patients like passive leg raising (PLR). We compared the hemodynamic effects of two methods of ELC and PLR measured by thermodilution (COtd), pressure curve analysis Modelflow™ (COmf) and ultra-sound HemoSonic™ (COhs), to evaluate the method with the greatest hemodynamic effect and the most accurate less invasive method to measure that effect. We compared hemodynamic effects of two different ELC methods (circular, A (n = 16), vs. wide, B (n = 13), bandages inflated to 30 cm H2O for 15 min) with PLR prior to each ELC method, in 29 post-operative cardiac surgical patients. Hemodynamic responses were measured with COtd, COmf and COhs. PLR A increased COtd from 6.1 ± 1.7 to 6.3 ± 1.8 L·min(-1) (P = 0.016), and increased COhs from 4.9 ± 1.5 to 5.3 ± 1.6 L·min(-1) (P = 0.001), but did not increase COmf. ELC A increased COtd from 6.4 ± 1.8 to 6.7 ± 1.9 L·min(-1) (P = 0.001) and COmf from 6.9 ± 1.7 to 7.1 ± 1.8 L·min(-1) (P = 0.021), but did not increase COhs. ELC A increased COtd and COmf as in PLR A. PLR B increased COtd from 5.4 ± 1.3 to 5.8 ± 1.4 L·min(-1) (P < 0.001), and COhs from 5.0 ± 1.0 to 5.4 ± 1.0 L·min(-1) (P = 0.013), but not COmf. ELC B increased COtd from 5.2 ± 1.2 to 5.4 ± 1.1 L·min(-1) (P = 0.003), but less than during PLR B (P = 0.012), while COmf and COhs did not change. Bland-Altman and polar plots showed lower limits of agreement with changes in COtd for COmf than for COhs. The circular leg compression increases CO more than bandage compression, and is able to increase CO as in PLR. The less invasive Modelflow™ can detect these changes reasonably well.


Assuntos
Débito Cardíaco/fisiologia , Bandagens Compressivas , Hemodinâmica , Monitorização Fisiológica/instrumentação , Pressão Sanguínea , Procedimentos Cirúrgicos Cardíacos , Desenho de Equipamento , Feminino , Humanos , Perna (Membro) , Masculino , Pessoa de Meia-Idade , Monitorização Fisiológica/métodos , Pressão , Termodiluição
3.
Front Physiol ; 13: 1041730, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36523553

RESUMO

Background: A decade ago, it became possible to derive mean systemic filling pressure (MSFP) at the bedside using the inspiratory hold maneuver. MSFP has the potential to help guide hemodynamic care, but the estimation is not yet implemented in common clinical practice. In this study, we assessed the ability of MSFP, vascular compliance (Csys), and stressed volume (Vs) to track fluid boluses. Second, we assessed the feasibility of implementation of MSFP in the intensive care unit (ICU). Exploratory, a potential difference in MSFP response between colloids and crystalloids was assessed. Methods: This was a prospective cohort study in adult patients admitted to the ICU after cardiac surgery. The MSFP was determined using 3-4 inspiratory holds with incremental pressures (maximum 35 cm H2O) to construct a venous return curve. Two fluid boluses were administered: 100 and 500 ml, enabling to calculate Vs and Csys. Patients were randomized to crystalloid or colloid fluid administration. Trained ICU consultants acted as study supervisors, and protocol deviations were recorded. Results: A total of 20 patients completed the trial. MSFP was able to track the 500 ml bolus (p < 0.001). In 16 patients (80%), Vs and Csys could be determined. Vs had a median of 2029 ml (IQR 1605-3164), and Csys had a median of 73 ml mmHg-1 (IQR 56-133). A difference in response between crystalloids and colloids was present for the 100 ml fluid bolus (p = 0.019) and in a post hoc analysis, also for the 500 ml bolus (p = 0.010). Conclusion: MSFP can be measured at the bedside and provides insights into the hemodynamic status of a patient that are currently missing. The clinical feasibility of Vs and Csys was judged ambiguously based on the lack of required hemodynamic stability. Future studies should address the clinical obstacles found in this study, and less-invasive alternatives to determine MSFP should be further explored. Clinical Trial Registration: ClinicalTrials.gov Identifier NCT03139929.

4.
Eur J Anaesthesiol ; 28(11): 802-6, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21799416

RESUMO

BACKGROUND AND OBJECTIVE: In pharmacological research, arm occlusion pressure is used to study haemodynamic effects of drugs. However, arm occlusion pressure might be an indicator of static filling pressure of the arm. We hypothesised that arm occlusion pressure can be used to predict fluid loading responsiveness. METHODS: Twenty-four patients who underwent cardiac surgery were studied during their first 2 h in the ICU. The lungs were ventilated mechanically and left ventricular function was supported as necessary. Arm occlusion pressure was defined as the radial artery pressure after occluding arterial flow for 35 s by a blood pressure cuff inflated to 50 mmHg above SBP. The cuff was positioned around the arm in which a radial artery catheter had been inserted. Measurements were performed before (baseline) and after fluid loading (500 ml hydroxyethyl starch 6%). Patients whose cardiac output increased by at least 10% were defined as responders. RESULTS: In responders (n = 17), arm occlusion pressure, mean arterial pressure and central venous pressure increased and stroke volume variation and pulse pressure variation decreased. In non-responders (n = 7), arm occlusion pressure and central venous pressure increased, and pulse pressure variation decreased. Mean arterial pressure, stroke volume variation and heart rate did not change significantly. The area under the curve to predict fluid loading responsiveness for arm occlusion pressure was 0.786 (95% confidence interval 0.567-1.000), at a cut-off of 21.9 mmHg, with sensitivity of 71% and specificity of 88% in predicting fluid loading responsiveness. Prediction of responders with baseline arm occlusion pressure was as good as baseline stroke volume variation and pulse pressure variation. CONCLUSION: Arm occlusion pressure was a good predictor of fluid loading responsiveness in our group of cardiac surgery patients and offers clinical advantages over stroke volume variation and pulse pressure variation.


Assuntos
Braço/irrigação sanguínea , Pressão Sanguínea/efeitos dos fármacos , Débito Cardíaco/efeitos dos fármacos , Procedimentos Cirúrgicos Cardíacos , Hidratação , Derivados de Hidroxietil Amido/administração & dosagem , Substitutos do Plasma/administração & dosagem , Artéria Radial/efeitos dos fármacos , Idoso , Determinação da Pressão Arterial/métodos , Pressão Venosa Central/efeitos dos fármacos , Procedimentos Cirúrgicos Eletivos , Feminino , Humanos , Unidades de Terapia Intensiva , Masculino , Pessoa de Meia-Idade , Países Baixos , Sistemas Automatizados de Assistência Junto ao Leito , Valor Preditivo dos Testes , Respiração Artificial , Fatores de Tempo
5.
J Clin Monit Comput ; 25(3): 193-201, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21830048

RESUMO

OBJECTIVE: The volemic status of a patient can be determined by measuring mean systemic filling pressure (Pmsf). Pmsf is obtained from the venous return curve, i.e. the relationship between central venous pressure (Pcv) and blood flow. We evaluated the feasibility and precision of Pmsf measurement. METHODS: In ten piglets we constructed venous return curves using seven 12 s inspiratory holds transiently increasing Pcv to seven different steady state levels and monitored the resultant blood flow, by pulse contour (COpc) and by flow probes around the pulmonary artery (COr) and aorta (COl). Pmsf is obtained by extrapolation of the venous return curve to zero flow. Measurements were repeated to evaluate the precision of Pmsf. RESULTS: During the inspiratory holds, 133 paired data points were obtained for COr, COl, COpc and Pcv. Bland-Altman analysis showed no difference between COr and COl, but a small significant difference was present between COl and COpc. All Pcv versus flow (COl or COpc) relationships were linear. Mean Pmsf was 10.78 with COl and 10.37 mmHg with COpc. Bland-Altman analysis for Pmsf with COl and with COpc, showed a bias of 0.40  ±  0.48 mmHg. The averaged coefficient of variation for repeated measurement of Pmsf with COl was 6.2% and with COpc 6.1%. CONCLUSIONS: During an inspiratory hold pulmonary flow and aortic flow equilibrate. Cardiac output estimates by arterial pulse contour and by a flow probe around the aorta are interchangeable. Therefore, the venous return curve and Pmsf can be estimated accurately by pulse contour methods.


Assuntos
Débito Cardíaco/fisiologia , Pressão Venosa Central/fisiologia , Animais , Feminino , Pulso Arterial , Volume Sistólico/fisiologia , Suínos , Função Ventricular Esquerda/fisiologia
6.
Curr Opin Crit Care ; 16(3): 231-6, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20168223

RESUMO

PURPOSE OF REVIEW: The physiology of the venous part of the human circulation seems to be a forgotten component of the circulation in critical care medicine. One of the main reasons, probably, is that measures of right atrial pressure (Pra) do not seem to be directly linked to blood flow. This perception is primarily due to an inability to measure the pressure gradient for venous return. The upstream pressure for venous return is mean systemic filling pressure (Pmsf) and it does not lend itself easily to be measured. Recent clinical studies now demonstrate the basic principles underpinning the measure of Pmsf at the bedside. RECENT FINDINGS: Using routinely available minimally invasive monitoring of continuous cardiac output and Pra, one can accurately construct venous return curves by performing a series of end-inspiratory hold maneuvers, in ventilator-dependent patients. From these venous return curves, the clinician can now finally obtain at the bedside not only Pmsf but also the derived parameters: resistance to venous return, systemic compliance and stressed volume. SUMMARY: Measurement of Pmsf is essential to describe the control of vascular capacitance. It is the key to distinguish between passive and active mechanisms of blood volume redistribution and partitioning total blood volume in stressed and unstressed volume.


Assuntos
Cuidados Críticos/métodos , Hemodinâmica , Sistemas Automatizados de Assistência Junto ao Leito , Pressão Sanguínea , Humanos , Pessoa de Meia-Idade
7.
J Appl Physiol (1985) ; 129(2): 311-316, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32614685

RESUMO

Potentially, mean circulatory filling pressure (Pmcf) could aid hemodynamic management in patients admitted to the intensive care unit (ICU). However, data regarding the normal range for Pmcf do not exist challenging its clinical use. We aimed to define the range for Pmcf for ICU patients and also calculated in what percentage of cases equilibrium between arterial blood pressure (ABP) and central venous pressure (CVP) was reached. In patients in whom no equilibrium was reached, we corrected for arterial-to-venous compliance differences. Finally, we studied the influence of patient characteristics on Pmcf. We hypothesized fluid balance, the use of vasoactive medication, being on mechanical ventilation, and the level of positive end-expiratory pressure would be positively associated with Pmcf. We retrospectively studied a cohort of 311 patients that had cardiac arrest in ICU while having active recording of ABP and CVP 1 min after death. Median Pmcf was 15 mmHg [interquartile range (IQR) 12-18]. ABP and CVP reached an equilibrium state in 52% of the cases. Correction for arterial-to-venous compliances differences resulted in a maximum alteration of 1.3 mmHg in Pmcf. Fluid balance over the last 24 h, the use of vasoactive medication, and being on mechanical ventilation were associated with a higher Pmcf. Median Pmcf was 15 mmHg (IQR 12-18). When ABP remained higher than CVP, correction for arterial-to-venous compliance differences did not result in a clinically relevant alteration of Pmcf. Pmcf was affected by factors known to alter vasomotor tone and effective circulating blood volume.NEW & NOTEWORTHY In a cohort of 311 intensive care unit (ICU) patients, median mean circulatory filling pressure (Pmcf) measured after cardiac arrest was 15 mmHg (interquartile range 12-18). In 48% of cases, arterial blood pressure remained higher than central venous pressure, but correction for arterial-to-venous compliance differences did not result in clinically relevant alterations of Pmcf. Fluid balance, use of vasopressors or inotropes, and being on mechanical ventilation were associated with a higher Pmcf.


Assuntos
Volume Sanguíneo , Hemodinâmica , Pressão Venosa Central , Humanos , Unidades de Terapia Intensiva , Estudos Retrospectivos
8.
Crit Care Med ; 37(3): 912-8, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19237896

RESUMO

OBJECTIVE: To measure the relationship between blood flow and central venous pressure (Pcv) and to estimate mean systemic filling pressure (Pmsf), circulatory compliance, and stressed volume in patients in the intensive care unit. DESIGN: Intervention study. SETTING: Intensive care unit of a university hospital. PATIENTS: Twelve mechanically ventilated postoperative cardiac surgery patients. INTERVENTIONS: Inspiratory holds were performed during normovolemia in supine position (baseline), relative hypovolemia by placing the patients in 30 degree head-up position (hypo), and relative hypervolemia by volume loading with 0.5 L colloid (hyper). MEASUREMENTS AND MAIN RESULTS: We measured the relationship between blood flow and Pcv using 12-second inspiratory-hold maneuvers transiently increasing Pcv to three different steady-state levels and monitored the resultant blood flow via the pulse contour method during the last 3 seconds. The Pcv to blood flow relation was linear for all measurements with a slope unaltered by relative volume status. Pmsf decreased with hypo and increased with hyper (18.8 +/- 4.5 mm Hg, to 14.5 +/- 3.0 mm Hg, to 29.1 +/- 5.2 mm Hg [baseline, hypo, hyper, respectively, p < 0.05]). Baseline total circulatory compliance was 0.98 mL x mm Hg x kg and stressed volume was 1677 mL. CONCLUSIONS: Pmsf can be determined in intensive care patients with an intact circulation with use of inspiratory pause procedures, making serial measures of circulatory compliance and circulatory stressed volume feasible.


Assuntos
Procedimentos Cirúrgicos Cardíacos , Hemodinâmica , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
9.
Eur J Anaesthesiol ; 26(11): 954-60, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19652601

RESUMO

BACKGROUND: Mathematical coupling may explain in part why cardiac filling volumes obtained by transpulmonary thermodilution may better predict and monitor responses of cardiac output to fluid loading than pressures obtained by pulmonary artery catheters (PACs). METHODS: Eleven consecutive patients with hypovolaemia after coronary surgery and a PAC, allowing central venous pressure (CVP) and continuous cardiac index (CCIp) measurements, received a femoral artery catheter for transpulmonary thermodilution measurements of global end-diastolic blood volume index (GEDVI) and cardiac index (CItp). One to five colloid fluid-loading steps of 250 ml were done in each patient (n = 48 total). RESULTS: Fluid responses were predicted and monitored similarly by CItp and CCIp, whereas CItp and CCIp correlated at r = 0.70 (P < 0.001) with a bias of 0.40 l min(-1) m(-2). Changes in volumes (and not in CVP) related to changes in CItp and not in CCIp. Changes in CVP and GEDVI similarly related to changes in CItp, after exclusion of two patients with greatest CItp outliers (as compared to CCIp). Changes in GEDVI correlated better to changes in CItp when derived from the same thermodilution curve than to changes in CItp of unrelated curves and changes in CCIp. CONCLUSIONS: After coronary surgery, fluid responses can be similarly assessed by intermittent transpulmonary and continuous pulmonary thermodilution methods, in spite of overestimation of CCIp by CItp. Filling pressures are poor monitors of fluid responses and superiority of GEDVI can be caused, at least in part, by mathematical coupling when cardiac volume and output are derived from the same thermodilution curve.


Assuntos
Débito Cardíaco/fisiologia , Ponte de Artéria Coronária , Hidratação , Termodiluição/métodos , Idoso , Idoso de 80 Anos ou mais , Cateterismo de Swan-Ganz , Pressão Venosa Central/fisiologia , Feminino , Artéria Femoral , Humanos , Hipovolemia/etiologia , Masculino , Pessoa de Meia-Idade , Volume Sistólico/fisiologia
10.
J Clin Anesth ; 46: 17-22, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29367093

RESUMO

STUDY OBJECTIVE: The mini-fluid challenge may predict fluid responsiveness with minimum risk of fluid overloading. However, the amount of fluid as well as the best manner to evaluate the effect is unclear. In this prospective observational pilot study, the value of changes in pulse contour cardiac output (CO) measurements during mini-fluid challenges is investigated. DESIGN: Prospective observational study. SETTING: Intensive Care Unit of a university hospital. PATIENTS: Twenty-one patients directly after elective cardiac surgery on mechanical ventilation. INTERVENTIONS: The patients were subsequently given 10 intravenous boluses of 50mL of hydroxyethyl starch with a total of 500mL per patient while measuring pulse contour CO. MEASUREMENTS: We measured CO by minimal invasive ModelflowR (COm) and PulseCOR (COli), before and one minute after each fluid bolus. We analyzed the smallest volume that was predictive of fluid responsiveness. A positive fluid response was defined as an increase in CO of >10% after 500mL fluid infusion. MAIN RESULTS: Fifteen patients (71%) were COm responders and 13 patients (62%) COli responders. An increase in COm after 150mL of fluid >5.0% yielded a positive and negative predictive value (+PV and -PV) of 100% with an area under the curve (AUC) of 1.00 (P<0.001). An increase in COli >6.3% after 200mL was able to predict a fluid response in COli after 500mL with a +PV of 100% and -PV of 73%, with an AUC of 0.88 (P<0.001). CONCLUSION: The use of minimal invasive ModelflowR pulse contour CO measurements following a mini-fluid challenge of 150mL can predict fluid responsiveness and may help to improve fluid management.


Assuntos
Débito Cardíaco , Procedimentos Cirúrgicos Cardíacos/efeitos adversos , Hidratação/efeitos adversos , Monitorização Fisiológica/instrumentação , Substitutos do Plasma/administração & dosagem , Idoso , Pressão Sanguínea , Dióxido de Carbono/análise , Dióxido de Carbono/sangue , Feminino , Hidratação/métodos , Humanos , Derivados de Hidroxietil Amido/administração & dosagem , Infusões Intravenosas , Masculino , Pessoa de Meia-Idade , Monitorização Fisiológica/métodos , Projetos Piloto , Estudos Prospectivos , Curva ROC , Respiração Artificial/efeitos adversos
11.
Ann Intensive Care ; 7(1): 20, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28233196

RESUMO

BACKGROUND: Although oxygen is generally administered in a liberal manner in the perioperative setting, the effects of oxygen administration on dynamic cardiovascular parameters, filling status and cerebral perfusion have not been fully unraveled. Our aim was to study the acute hemodynamic and microcirculatory changes before, during and after arterial hyperoxia in mechanically ventilated patients after coronary artery bypass grafting (CABG) surgery. METHODS: This was a single-center physiological study in a tertiary care ICU in the Netherlands. Twenty-two patients scheduled for ICU admission after elective CABG were enrolled in the study between September 2014 and September 2015. In the ICU, patients were exposed to a fraction of inspired oxygen (FiO2) of 90% allowing a 15-min wash-in period. Various hemodynamic parameters were measured using direct pressure signals and continuous arterial waveform analysis at three sequential time points: before, during and after hyperoxia. RESULTS: During a 15-min exposure to a fraction of inspired oxygen (FiO2) of 90%, the partial pressure of arterial oxygen (PaO2) and arterial oxygen saturation (SaO2) were significantly higher. The systemic resistance increased (P < 0.0001), without altering the heart rate. Stroke volume variation and pulse pressure variation decreased slightly. The cardiac output did not significantly decrease (P = 0.08). Mean systemic filling pressure and arterial critical closing pressure increased (P < 0.01whereas the percentage of perfused microcirculatory vessels decreased (P < 0.01). Other microcirculatory parameters and cerebral blood flow velocity showed only slight changes. CONCLUSIONS: We found that short-term hyperoxia affects hemodynamics in ICU patients after CABG. This was translated in several changes in central circulatory variables, but had only slight effects on cardiac output, cerebral blood flow and the microcirculation. Clinical trial registration Netherlands Trial Register: NTR5064.

12.
Intensive Care Med ; 31(3): 424-30, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15660244

RESUMO

OBJECTIVE: To assess the value of monitoring abdominal and rib cage tidal displacement as an indicator of optimal mean airway pressure (Paw) during high-frequency oscillatory ventilation (HFOV). DESIGN AND SETTING: Prospective observational study in a university research laboratory. ANIMALS: Eight piglets weighing 12.0+/-0.5 kg, surfactant depleted by lung lavage. INTERVENTIONS: Compliance of the respiratory system (C(rs)) was calculated from a quasistatic pressure volume loop. After initiation of HFOV lung volume was recruited by increasing Paw to 40 cmH(2)O. Then mean Paw was decreased in steps until PaO(2)/FIO(2) was below 100 mmHg. Proximal pressure amplitude remained constant. MEASUREMENTS AND RESULTS: Abdominal and rib cage tidal displacement was determined using respiratory inductive plethysmography. During HFOV there was maximum in tidal volume (Vt) in seven of eight piglets. At maximal mean Paw abdominal and rib cage displacement were in phase. Phase difference between abdominal and rib cage displacement increased to a maximum of 178+/-28 degrees at minimum mean Paw. A minimum in abdominal displacement and a maximum of Vt was found near the optimal mean Paw, defined as the lowest mean Paw where shunt fraction is below 0.1. CONCLUSIONS: During HFOV abdominal and rib cage displacement displayed mean Paw dependent asynchrony. Maximal Vt and minimal abdominal displacement coincided with optimal C(rs), oxygenation, and ventilation, suggesting potential clinical relevance of monitoring Vt and abdominal displacement during HFOV.


Assuntos
Ventilação de Alta Frequência/métodos , Pletismografia/métodos , Surfactantes Pulmonares/metabolismo , Mecânica Respiratória/fisiologia , Abdome/fisiologia , Animais , Modelos Animais de Doenças , Monitorização Fisiológica , Cavidade Pleural/fisiologia , Costelas/fisiologia , Sus scrofa , Volume de Ventilação Pulmonar
13.
Intensive Care Med ; 29(2): 233-40, 2003 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-12594585

RESUMO

OBJECTIVE: To assess the degree of linearity between lung volume and impedance change by electrical impedance tomography (EIT) in pigs with acute lung injury and to investigate regional impedance changes during a pressure-volume maneuver. DESIGN AND SETTING: Experimental animal study in a university research laboratory. PATIENTS AND PARTICIPANTS: Nine pigs with lung injury induced by lung lavage. INTERVENTIONS: The lungs were insufflated to four different lung volumes. Next the lungs were inflated in steps up to 40 cm H(2)O and then in steps deflated. MEASUREMENTS AND RESULTS: EIT measurements were performed. Impedance was highly linear with lung volume ( r(2)=0.97). From the pressure-volume maneuver regional pressure-impedance (P-I) curves were obtained in the upper half (ventral) and lower half (dorsal) of the thoracic cross-section. Excellent fit was found of the regional P-I curves with a predefined sigmoid equation ( r(2)=0.998). The P-I curves after lavage were markedly different than before lavage. The P-I curves recorded after lavage displayed a strong heterogeneity on the inflation limb: Lower corner pressure (traditionally lower inflection point) was significantly higher in the dorsal (28.3+/-4.1 cm H(2)O) than in the ventral region (17.5+/-4.3 cm H(2)O). The deflation limb displayed a more homogeneous pattern. Upper corner pressure and true inflection point, where the curve slope is maximal, in the dorsal region were only slightly higher than in the ventral region (1-2 cm H(2)O). CONCLUSIONS: EIT and automated curve fitting provide information on regional lung inflation and deflation which may be of clinical use for optimizing ventilator settings.


Assuntos
Modelos Animais de Doenças , Impedância Elétrica , Modelos Lineares , Medidas de Volume Pulmonar/métodos , Síndrome do Desconforto Respiratório/diagnóstico , Síndrome do Desconforto Respiratório/terapia , Tomografia/métodos , Resistência das Vias Respiratórias , Animais , Gasometria , Monitorização Fisiológica/métodos , Monitorização Fisiológica/normas , Seleção de Pacientes , Sistemas Automatizados de Assistência Junto ao Leito , Respiração Artificial/efeitos adversos , Respiração Artificial/métodos , Síndrome do Desconforto Respiratório/etiologia , Síndrome do Desconforto Respiratório/fisiopatologia , Cloreto de Sódio/efeitos adversos , Suínos , Irrigação Terapêutica , Tomografia/normas
14.
Intensive Care Med ; 28(8): 1151-6, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12185440

RESUMO

OBJECTIVE: To test the hypothesis that, during high-frequency oscillatory ventilation (HFOV) of pigs with acute lung injury, the oxygenation index (OI = Paw*FIO(2)*100/PaO(2)) is minimal at the lowest continuous distending pressure (Paw), where the physiological shunt fraction is below 0.1 (Paw(optimal)). DESIGN AND SETTING: Prospective, observational study in a university research laboratory. SUBJECTS: Eight Yorkshire pigs weighing 12.0+/-0.5 kg, with lung injury induced by lung lavage. INTERVENTIONS: After initiation of HFOV, the pigs were subjected to a stepwise increase of Paw to obtain under-inflation, optimal inflation and over-distension of the lungs (inflation) in series, followed by a similar decrease of Paw (deflation). MEASUREMENTS AND RESULTS: At each Paw level, the OI and physiological shunt fraction were determined. The OI reached a minimum of 6.2+/-1.4 at Paw 30+/-4 cmH(2)O during inflation and a minimum of 2.4+/-0.3 at Paw 13+/-2 cmH(2)O during deflation. Paw(optimal) was 32+/-6 cmH(2)O on the inflation limb and 14+/-2 cmH(2)O on the deflation limb. The difference between the Paw at minimal OI and Paw(optimal) was -1.9+/-4.2 cmH(2)O (NS) during inflation and -1.5+/-1.6 cmH(2)O (p<0.05) during deflation. In 15 out of the 16 comparisons, the difference in Paw was within one step (+/-3 cmH(2)O). CONCLUSION: The minimal OI is indicative for the Paw where oxygenation is optimal during HFOV in surfactant-depleted pigs.


Assuntos
Ventilação de Alta Frequência , Oxigênio/provisão & distribuição , Animais , Estudos Prospectivos , Síndrome do Desconforto Respiratório , Suínos
15.
J Appl Physiol (1985) ; 92(3): 1223-31, 2002 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-11842062

RESUMO

The hemodynamic effects of increases in airway pressure (Paw) are related in part to Paw-induced increases in right atrial pressure (Pra), the downstream pressure for venous return, thus decreasing the pressure gradient for venous return. However, numerous animal and clinical studies have shown that venous return is often sustained during ventilation with positive end-expiratory pressure (PEEP). Potentially, PEEP-induced diaphragmatic descent increases abdominal pressure (Pabd). We hypothesized that an increase in Paw induced by PEEP would minimally alter venous return because the associated increase in Pra would be partially offset by a concomitant increase in Pabd. Thus we studied the acute effects of graded increases of Paw on Pra, Pabd, and cardiac output by application of inspiratory-hold maneuvers in sedated and paralyzed humans. Forty-two patients were studied in the intensive care unit after coronary artery bypass surgery during hemodynamically stable, fluid-resuscitated conditions. Paw was progressively increased in steps of 2 to 4 cmH(2)O from 0 to 20 cmH(2)O in sequential 25-s inspiratory-hold maneuvers. Right ventricular (RV) cardiac output (CO(td)) and RV ejection fraction (EF(rv)) were measured at 5 s into the inspiratory-hold maneuver by the thermodilution technique. RV end-diastolic volume and stroke volume were calculated from EF(rv) and heart rate data, and Pra was measured from the pulmonary artery catheter. Pabd was estimated as bladder pressure. We found that, although increasing Paw progressively increased Pra, neither CO(td) nor RV end-diastolic volume changed. The ratio of change (Delta) in Paw to Delta Pra was 0.32 +/- 0.20. The ratio of Delta Pra to Delta CO(td) was 0.05 +/- 00.15 l x min(-1) x mmHg(-1). However, Pabd increased such that the ratio of Delta Pra to Delta Pabd was 0.73 +/- 0.36, meaning that most of the increase in Pra was reflected in increases in Pabd. We conclude that, in hemodynamically stable fluid-resuscitated postoperative surgical patients, inspiratory-hold maneuvers with increases in Paw of up to 20 cmH(2)O have minimal effects on cardiac output, primarily because of an in-phase-associated pressurization of the abdominal compartment associated with compression of the liver and squeezing of the lungs.


Assuntos
Volume Sanguíneo , Ponte de Artéria Coronária , Respiração com Pressão Positiva , Veias/fisiopatologia , Abdome/fisiopatologia , Função do Átrio Direito , Débito Cardíaco , Hidratação , Humanos , Inalação , Período Pós-Operatório , Pressão , Sistema Respiratório/fisiopatologia , Ressuscitação
16.
Pediatr Pulmonol ; 33(6): 429-36, 2002 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12001275

RESUMO

We tested the hypothesis that during high-frequency oscillatory ventilation, the oscillatory pressure ratio (OPR) is minimal at the optimal mean airway pressure (Paw). OPR is defined as the ratio of pressure swings at the distal end and the proximal opening of the endotracheal tube. Optimal Paw was assumed to be the lowest Paw at which the physiological shunt fraction was below 0.1. Acute lung injury was produced by saline lung lavage of pigs who were then subjected to a stepwise increase of Paw to impose underinflation, optimal inflation, and overdistention (inflation phase), followed by a stepwise decrease of Paw (deflation phase). OPR reached a minimum of 0.10 +/- 0.01 at Paw = 31 +/- 4 cm H(2)O during the inflation phase and a minimum of 0.04 +/- 0.01 at Paw = 18 +/- 1 cm H(2)O during the deflation phase. Optimal Paw was 31 +/- 4 cm H(2)O on the inflation limb and 14 +/- 2 cm H(2)O on the deflation limb. Paw at the minimal OPR was not significantly different from the optimal Paw during the inflation phase, and slightly but significantly higher (4.1 +/- 1.6 cm H(2)O) during the deflation phase. In conclusion, a consistent relationship was found between OPR and Paw, with a minimum in all animals. The minimal OPR coincides fairly well with the Paw where oxygenation is optimal.


Assuntos
Ventilação de Alta Frequência , Intubação Intratraqueal , Pneumopatias/fisiopatologia , Traqueia/fisiopatologia , Animais , Modelos Animais de Doenças , Pneumopatias/terapia , Pressão , Suínos
18.
J Clin Anesth ; 24(8): 668-74, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23228872

RESUMO

Hypovolemia is a common clinical problem. The Trendelenburg position and passive leg raising (PLR) are routinely used in the initial treatment while awaiting fluid resuscitation. In this meta-analysis, we evaluated the hemodynamic effects of PLR and Trendelenburg positioning to determine which position had the most optimal effect on cardiac output (CO). Databases were searched for prospective studies published between 1960 and 2010 in normovolemic or hypovolemic humans; these studies had to investigate the hemodynamic effects within 10 minutes of a postural change from supine. Twenty-one studies were included for PLR (n=431) and 13 studies for Trendelenburg position (n=246). Trendelenburg position increased mean arterial pressure (MAP). Cardiac output increased 9%, or 0.35 L/min, at one minute of head-down tilt. Between 2 and 10 minutes, this increase in CO decreased to 4%, or 0.14 L/min, from baseline. Cardiac output increased at one minute of leg elevation by 6%, or 0.19 L/min. The effect persisted after this period by 6%, or 0.17 L/min. Both Trendelenburg and PLR significantly increased CO, but only PLR seemed to sustain this effect after one minute. Although the Trendelenberg position is a common maneuver for nurses and doctors, PLR may be the better intervention in the initial treatment of hypovolemia.


Assuntos
Decúbito Inclinado com Rebaixamento da Cabeça/fisiologia , Hipovolemia/terapia , Postura/fisiologia , Pressão Sanguínea/fisiologia , Débito Cardíaco/fisiologia , Hemodinâmica/fisiologia , Humanos , Perna (Membro) , Posicionamento do Paciente , Fatores de Tempo
19.
J Appl Physiol (1985) ; 111(3): 853-60, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21700890

RESUMO

Cardiac output measurement from arterial pressure waveforms presumes a defined relationship between the arterial pulse pressure (PP), vascular compliance (C), and resistance (R). Cardiac output estimates degrade if these assumptions are incorrect. We hypothesized that sepsis would differentially alter central and peripheral vasomotor tone, decoupling the usual pressure wave propagation from central to peripheral sites. We assessed arterial input impedance (Z), C, and R from central and peripheral arterial pressures, and aortic blood flow in an anesthetized porcine model (n = 19) of fluid resuscitated endotoxic shock induced by endotoxin infusion (7 µg·kg⁻¹·h⁻¹ increased to 14 and 20 µg·kg⁻¹·h⁻¹ every 10 min and stopped when mean arterial pressure <40 mmHg or Sv(O2) < 45%). Aortic, femoral, and radial artery pressures and aortic and radial artery flows were measured. Z was calculated by FFT of flow and pressure data. R and C were derived using a two-element Windkessel model. Arterial PP increased from aortic to femoral and radial sites. During stable endotoxemia with fluid resuscitation, aortic and radial blood flows returned to or exceeded baseline while mean arterial pressure remained similarly decreased at all three sites. However, aortic PP exceeded both femoral and radial arterial PP. Although Z, R, and C derived from aortic and radial pressure and aortic flow were similar during baseline, Z increases and C decreases when derived from aortic pressure whereas Z decreases and C increases when derived from radial pressure, while R decreased similarly with both pressure signals. This central-to-peripheral vascular tone decoupling, as quantified by the difference in calculated Z and C from aortic and radial artery pressure, may explain the decreasing precision of peripheral arterial pressure profile algorithms in assessing cardiac output in septic shock patients and suggests that different algorithms taking this vascular decoupling into account may be necessary to improve their precision in this patient population.


Assuntos
Aorta/fisiopatologia , Artéria Femoral/fisiopatologia , Hemodinâmica , Artéria Radial/fisiopatologia , Choque Séptico/fisiopatologia , Doença Aguda , Algoritmos , Animais , Velocidade do Fluxo Sanguíneo , Pressão Sanguínea , Débito Cardíaco , Cateterismo , Complacência (Medida de Distensibilidade) , Modelos Animais de Doenças , Feminino , Análise de Fourier , Lipopolissacarídeos , Modelos Cardiovasculares , Monitorização Fisiológica , Valor Preditivo dos Testes , Fluxo Sanguíneo Regional , Ressuscitação , Choque Séptico/induzido quimicamente , Choque Séptico/terapia , Suínos , Fatores de Tempo , Resistência Vascular
20.
Interact Cardiovasc Thorac Surg ; 9(1): 4-8, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19383638

RESUMO

Residual left-sided valvular insufficiencies after valvular surgery may confound transpulmonary thermodilution cardiac output (COtp). We compared the technique with the continuous right-sided thermodilution technique (CCO) after valvular surgery (n=8) and coronary artery surgery (n=8). Patients with pulmonary and femoral artery catheters in the intensive care unit (ICU) were included. After valvular surgery, there was minimal aortic insufficiency in four patients and minimal to moderate mitral valve insufficiency in six. Five fluid loading steps (250 ml) were done in each patient. CCO and COtp were measured prior to and 15 min after each step. The cardiac output was lower after valvular than coronary artery surgery but responses to fluid loading steps were similar among surgery types and techniques. After valvular and coronary artery surgery, cardiac output was lower prior to responses than in non-responses to fluids, by either technique. After valvular surgery, COtp and CCO correlated (r=0.64, P<0.001, n=48) but fluid-induced changes did not. After coronary artery surgery, COtp and CCO correlated (r=0.81, P<0.001) and changes also did (r=0.55, P<0.001). At fluid-induced CCO increases <20%, the r for changes in cardiac output measured by both techniques was similar after valvular and coronary artery surgery. Thus, COtp and CCO were of similar value in predicting and monitoring fluid responses after both surgery types. This argues against left-sided valvular insufficiencies confounding COtp.


Assuntos
Débito Cardíaco , Procedimentos Cirúrgicos Cardíacos , Cateterismo de Swan-Ganz , Doença da Artéria Coronariana/cirurgia , Doenças das Valvas Cardíacas/cirurgia , Monitorização Fisiológica/métodos , Artéria Pulmonar/fisiopatologia , Termodiluição/métodos , Idoso , Idoso de 80 Anos ou mais , Procedimentos Cirúrgicos Cardíacos/efeitos adversos , Doença da Artéria Coronariana/fisiopatologia , Cuidados Críticos , Feminino , Doenças das Valvas Cardíacas/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Período Pós-Operatório , Valor Preditivo dos Testes
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