Gastrointestinal hormones and short-term nutritional schedules in critically ill patients.

BACKGROUND/AIMS: The purpose of the study is to evaluate the gastrointestinal hormone response in critically ill patients under different nutritional schedule (enteral vs. total parenteral) of short duration. METHODOLOGY: Twenty-one sedated and mechanically ventilated patients were nourished with continuous nasogastric schedule (Group A, 11 patients), or with total parenteral nutrition (Group B, 10 patients). Serum concentrations of gastrin, cholecystokinin, vasoactive intestinal peptide, neurotensin, and bombesin, were measured on the 2nd, 3rd and the 5th day of patients' admission, with radioimmunoassay methods. RESULTS: Changes of hormones concentrations were not significant either between the three measurements in each group or between the two groups at the same hospitalization day. CONCLUSIONS: The short-term parenteral nutrition in critically ill patients does not exert a different influence on the serum concentrations of gastrin, cholecystokinin, vasoactive intestinal peptide, neurotensin, and bombesin, compared to enteral nutrition. This conclusion is of clinical interest since the short-term administration of total parenteral nutrition is very often necessary during hospitalization in the intensive care unit.

Non-linear evaluation of respiratory mechanics during laparoscopic cholecystectomy.

BACKGROUND/AIMS: Laparoscopic cholecystectomy is accompanied by significant increase of the respiratory system elastic and resistive properties. These changes are completely abolished after peritoneal deflation. In the present study we examine the volume and flow dependence of respiratory mechanics during four operation phases. METHODOLOGY: Airway pressure and flow were recorded from 17 patients undergoing laparoscopic cholecystectomy. Measurements were done at 4 distinct phases: 1) Before the induction of pneumoperitoneum. 2) Five minutes after pneumoperitoneum induction at Trendelenburg position. 3) Five minutes after positioning the patient at reverse. Trendelenburg. 4) Five minutes after the peritoneal deflation. Data of airway pressure, flow and volume were treated according to the non-linear regression model: Paw = E1.V + E2.V2 + k1.V' + k2.V'. |V'| + k3.V.V' + EEP. RESULTS: The induction of pneumoperitoneum results in: Significant increase of linear elastance and resistance and significant decrease of flow and volume dependence of resistance. No significant changes are noted in volume dependence of elastance and end-expiratory pressure. CONCLUSIONS: The pneumoperitoneum and not the body position causes the changes in respiratory mechanics and their dependencies during laparoscopic cholecystectomy, which, although important, do not predispose to major risks (lung overdistension, alveolar collapse) and they are reversed after peritoneal deflation.

Effects of PEEP on inspiratory and expiratory mechanics in adult respiratory distress syndrome.

The purpose of the present study was to assess the mechanical behavior of the respiratory system separately during inspiration and expiration in adult respiratory distress syndrome (ARDS) and the influence of PEEP on any phasic variations ofthe mechanical respiratory parameters. Airways pressure (P), flow (V), and volume (V) signals were recorded in nine patients with ARDS and 10 patients without known respiratory disorder (control group). All patients were artificially ventilated at three levels of positive end-expiratory pressure (PEEP): 0, 5, and 10 hPa. Data were analyzed separately for inspiratory and expiratory records using multiple linear regression analysis (MLRA) according to the equation: P=Ers V+Rrs V'+P0, where Ers and Rrs represent, respectively, the intubated respiratory system elastance and resistance, and P0 the end-expiratory pressure. In the ARDS group expiratory Ers (ErsEXP=45.58 +/- 4.24 hPa/L) was substantially higher (p<0.01) than inspiratory Ers (ErsINSP=36.76 +/- 2.55) with a marked effect of applied PEEP in diminishing the difference between ErsEXP and ErsINSP (p<0.01). For the ARDS group inspiratory Rrs (RrsINSP) decreased significantly with increasing PEEP (PEEP=0: RrsINSP=16.43, PEEP=10: RrsINSP=13.28, p<0.01). The found differences between ErsEXP and ErsINSP could be attributable to an influence of mechanical ventilation by positive airway pressure on pulmonary edemaand interstitial fluid during the inspiratory phase of the respiratory cycle.

Evaluation of the end-expiratory pressure by multiple linear regression and Fourier analysis in humans.

This study was designed to compare the end-expiratory pressure (EEP) during mechanical ventilation (MV) measured dynamically (EEPdyn), by multiple linear regression (MLR) of the airway pressure (Pao) vs volume (V) and flow (V') and after Fourier analysis (FA) of the Pao and V'. Pao and V' were recorded from 32 ICU patients (II without respiratory disease, 10 COPD, II ARDS) under MV, at three levels of PEEPe (0, 5 and 10 hPa). Volume was calculated by numerical integration of V'. Data were analysed by MLR and FA, while the actual value of EEPdyn was recognised on the Pao signal at zero V' and V. EEPdyn, EEPMLR and EEPFA were compared for all patients, for each group of patients and for every level of applied PEEPe. Despite the different evaluation of respiratory mechanics between MLR and FA, the EEP values were always not significantly different between the three applied methods (P > 0.05). A high degree of correlation was found between them, taken two at a time (r > 0.99, P < 0.001). Two non-invasive analytical methods for the evaluation of respiratory mechanics during MV, MLR and FA offer a reliable and clinically useful estimation of EEP during MV.

Respiratory system mechanics during laparoscopic cholecystectomy.

The influence of laparoscopic cholecystectomy (LC) on the mechanical properties of the respiratory system (RS) was examined using multiple regression analysis (MRA). Measurements of airway pressure (PaO) and flow (V') were obtained from 32 patients at four distinct stages of the LC procedure: 1) Immediately before the application of pneumoperitoneum (PP) at supine position, 2) 5 min after the induction of PP at Trendelenburg position, 3) 5 min after the patients position at reverse Trendelenburg, and 4) 5 min after the end ofthe surgical procedure with the patient again in supine position. Evaluated parameters were the RS elastance (Ers), resistance (Rrs), impedance (Zrs), the angle theta indicating the balance between the elastic and resistive components of the impedance, as well as the end-expiratory elastic recoil pressure (EEP). Ers and Zrs increased considerably during PP and remained elevated immediately after abolishing PP Rrs, on the contrary, returned to pre-operative levels right after the operation. Change of body position from Trendelenburg (T) to reverseTrendelenburg (rT) mainly induced a significant change in theta, thus indicating an increased dominance of the elastic component of Zrs on changing fromT to rT. There was no evidence of increased End-Expiratory Pressure during PP

Linear and nonlinear analysis of pressure and flow during mechanical ventilation.

OBJECTIVE: Linear modeling as a method of exploring respiratory mechanics during mechanical ventilation, was compared to nonlinear modeling for flow dependence of resistance in three distinct groups of patients, those with: (a) normal respiratory function (NRF), (b) chronic obstructive pulmonary disease (COPD), or (c) adult respiratory distress syndrome (ARDS). DESIGN AND PATIENTS: Airways opening pressure (Pao), flow (V'), and volume (V) signals were recorded in 32 ICU mechanically ventilated patients, under sedation and muscle relaxation (10 NRF, 11 COPD, 11 ARDS). All patients were ventilated with controlled mandatory ventilation mode at three levels of end-expiratory pressure (PEEPe): 0, 5, and 10 hPa. Data were analyzed according to: (a) Pao = PE + Ers V + Rrs V' and (b) Pao = PE + Ers V + k1V' + k2¿V'¿V'; where Ers and Rrs represent the intubated respiratory system (RS) elastance and resistance, k1 and k2 the linear and the nonlinear RS resistive coefficients, and PE the end-expiratory pressure. The model's goodness of fit to the data was evaluated by the root mean square difference of predicted minus measured Pao values. RESULTS: NRF data fit both models well at all PEEPe levels. ARDS and particularly COPD data fit the nonlinear model better. Values of k2 were often negative in COPD and ARDS groups, and they increased in parallel with PEEPe. A gradual increase in PEEPe resulted in better fit of ARDS and COPD data to both models. CONCLUSIONS: The model of V' dependence of resistance is more suitable for the ARDS and particularly the COPD groups. PEEP tends to diminish the V' dependence of respiratory resistance during the respiratory cycle, particularly in the COPD group, probably through an indirect effect of the increased lung volume.