Per Henrik Lambert

Does a positive end-expiratory pressure-induced reduction in stroke volume indicate preload responsiveness? An experimental study

Background:  Increases in positive end‐expiratory pressure (PEEP) are often associated with cardiovascular depression, responding to fluid loading. Therefore, we hypothesized that if stroke volume (SV) is reduced by an increase in PEEP this reduction is an indicator of hypovolemia or preload responsiveness, i.e. that SV would increase by fluid administration at zero end‐expiratory pressure (ZEEP). The relationship between the cardiovascular response to different PEEP levels and fluid load as well as the relation between change in SV as a result of change in preload (Frank–Starling relationship) were evaluated in a porcine model. In addition, other measures of fluid status were assessed.

Prediction of hemodynamic changes towards PEEP titrations at different volemic levels using a minimal cardiovascular model

A cardiovascular system model and parameter identification method have previously been validated for porcine experiments of induced pulmonary embolism and positive end-expiratory pressure (PEEP) titrations, accurately tracking all the main hemodynamic trends. In this research, the model and parameter identification process are further validated by predicting the effect of intervention. An overall population-specific rule linking specific model parameters to increases in PEEP is formulated to predict the hemodynamic effects on arterial pressure, pulmonary artery pressure and stroke volume. Hemodynamic changes are predicted for an increase from 0 to 10 cm H(2)O with median absolute percentage errors less than 7% (systolic pressures) and 13% (stroke volume). For an increase from 10 to 20 cm H(2)O median absolute percentage errors are less than 11% (systolic pressures) and 17% (stroke volume). These results validate the general applicability of such a rule, which is not pig-specific, but holds over for all analyzed pigs. This rule enables physiological simulation and prediction of patient response. Overall, the prediction accuracy achieved represents a further clinical validation of these models, methods and overall approach to cardiovascular diagnosis and therapy guidance.

Model-based identification of PEEP titrations during different volemic levels

A cardiovascular system (CVS) model has previously been validated in simulated cardiac and circulatory disease states. It has also been shown to accurately capture all main hemodynamic trends in a porcine model of pulmonary embolism. In this research, a slightly extended CVS model and parameter identification process are presented and validated in a porcine experiment of positive end-expiratory pressure (PEEP) titrations at different volemic levels. The model is extended to more physiologically represent the separation of venous and arterial circulation. Errors for the identified model are within 5% when re-simulated and compared to clinical data. All identified parameter trends match clinically expected changes. This work represents another clinical validation of the underlying fundamental CVS model, and the methods and approach of using them for cardiovascular diagnosis in critical care.

Selective recruitment maneuvers for lobar atelectasis: effects on lung function and central hemodynamics: an experimental study in pigs

We investigated whether selective lung recruitment of a lobar collapse would improve oxygenation and lung volume as well as a general (global) lung recruitment maneuver, with fewer circulatory side effects. In 10 ventilated, anesthetized pigs, a bronchial blocker was inserted in the right lower lobe, which was selectively lavaged to create a dense lobar collapse. The pigs were randomized into two orders of lung recruitment maneuvers (40 cm H2O airway pressure for 30 s): either a selective lung recruitment maneuver (using the inner lumen of the bronchial blocker) followed by a general lung recruitment maneuver, or vice versa. Median end-expiratory lung volume and median Pao2 increased significantly by approximately 100 mL and 16 kPa, respectively, with no significant differences between the two recruitment methods. There were no circulatory changes during the selective lung recruitment maneuver, but during the general lung recruitment maneuver, mean arterial blood pressure decreased significantly by 36 (21, 41) mm Hg (median, 25th and 75th percentiles), cardiac output by 2.1 (1.6, 2.5) L/min and left ventricular end-diastolic area by 4.4 (3.5, 4.5) cm2. In conclusion, a selective recruitment maneuver improved lung function similar to a general lung recruitment maneuver but without any circulatory side effects.

Impact of Bispectral Index for monitoring propofol remifentanil anaesthesia. A randomised clinical trial

Previous research has shown that the use of the bispectral index (BIS) monitor to measure the depth of anaesthesia reduces the amount of anaesthetics administered and the recovery time from general anaesthesia. The effect of BIS on recovery from anaesthesia and consumption of anaesthetics in a paediatric population receiving total intravenous anaesthesia (TIVA) with propofol and remifentanil has not been studied.

Simulation based teaching of paramedics in endotracheal intubation: a mannequin study

Background Previous studies have shown a steep learning curve in endotracheal intubation using the Airtraq(R) for non skilled personnel. We examined 16 Danish paramedics’ ability to intubate by using the Airtraq(R). The paramedics went through a 1-day course at CeMS (Centre for Medical Simulation, the department of Anaesthesia, Aalborg, Denmark) with skill training and simulation based teaching with the Airtraq(R). The objective of the course was that the paramedics should be able to intubate in less than 30 seconds.