[show abstract][hide abstract] ABSTRACT: To access the effect of propofol administration on sleep quality in critically ill patients ventilated on assisted modes.
This was a randomized crossover physiological study conducted in an adult ICU at a tertiary hospital. Two nights' polysomnography was performed in mechanically ventilated critically ill patients with and without propofol infusion, while respiratory variables were continuously recorded. Arterial blood gasses were measured in the beginning and at the end of the study. The rate of propofol infusion was adjusted to maintain a sedation level of 3 on the Ramsay scale. Sleep architecture was analyzed manually using predetermined criteria. Patient-ventilator asynchrony was evaluated breath by breath using the flow-time and airway pressure-time waveforms.
Twelve patients were studied. Respiratory variables, patient-ventilator asynchrony, and arterial blood gasses did not differ between experimental conditions. With or without propofol all patients demonstrated abnormal sleep architecture, expressed by lack of sequential progression through sleep stages and their abnormal distribution. Sleep efficiency, sleep fragmentation, and sleep stage distribution (1, 2, and slow wave) did not differ with or without propofol. Compared to without propofol, both the number of patients exhibiting REM sleep (p = 0.02) and the percentage of REM sleep (p = 0.04) decreased significantly with propofol.
In critically ill patients ventilated on assisted modes, propofol administration to achieve the recommended level of sedation suppresses the REM sleep stage and further worsens the poor sleep quality of these patients.
European Journal of Intensive Care Medicine 07/2012; 38(10):1640-6. · 5.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: In mechanically ventilated patients with COPD, the response of the expiratory resistance of the respiratory system (expiratory R(RS)) to bronchodilators is virtually unknown.
To examine the effect of inhaled albuterol on expiratory R(RS), and the correlation of albuterol-induced changes in expiratory R(RS) with end-inspiratory resistance and the expiratory flow-volume relationship.
We studied 10 mechanically ventilated patients with COPD exacerbation, before and 30 min after administration of albuterol. We obtained flow-volume curves during passive expiration, divided the expired volume into 5 equal volume slices, and then calculated the time constant and dynamic effective deflation compliance of the respiratory system (effective deflation C(RS)) of each slice via regression analysis of the volume-flow and post-occlusion volume-tracheal pressure relationships, respectively. For each slice we calculated expiratory R(RS) as the time constant divided by the effective deflation C(RS).
Albuterol significantly decreased the expiratory R(RS) (mean expiratory R(RS) 42.68 ± 17.8 cm H(2)O/L/s vs 38.08 ± 16.1 cm H(2)O/L/s) and increased the rate of lung emptying toward the end of expiration (mean time constant 2.51 ± 1.2 s vs 2.21 ± 1.2 s). No correlation was found between the albuterol-induced changes in expiratory R(RS) and that of end-inspiratory resistance. Only at the end of expiration did albuterol-induced changes in the expiratory flow-volume relationship correlate with changes in expiratory R(RS) in all patients.
In patients with COPD, albuterol significantly decreases expiratory resistance at the end of expiration. In mechanically ventilated patients, neither inspiratory resistance nor the whole expiratory flow-volume curve may be used to evaluate the bronchodilator response of expiratory resistance.
Respiratory care 01/2011; 56(5):626-32. · 2.03 Impact Factor
[show abstract][hide abstract] ABSTRACT: The incidence of ventilator-associated pneumonia (VAP) due to multidrug-resistant (MDR) organisms is increasing. Intravenous (IV) colistin or aerosolized (AS) plus IV colistin have been recently used to treat these life-threatening infections. The purpose of this study was to compare the efficacy and safety of AS plus IV colistin versus IV colistin alone for patients with MDR VAP due to gram-negative bacteria.
A retrospective matched case-control study was performed at the Intensive Care Unit of the University Hospital of Heraklion, Greece, from January 2005 through December 2008. Forty-three patients with VAP due gram-negative MDR pathogens received AS plus IV colistin and were matched on the basis of age and Acute Physiology and Chronic Health Evaluation II score with 43 control patients who had received IV colistin alone.
Demographic characteristics, clinical status, and gram-negative isolated pathogens were similar between the 2 treatment groups. Acinetobacter baumannii (66 cases [77%]) was the most common pathogen, followed by Klebsiella pneumoniae (12 cases [14%]) and Pseudomonas aeruginosa (8 cases [9.3%]). No colistin-resistant strains were isolated from patients in either group. No significant differences between the 2 groups were observed regarding eradication of pathogens (P = .679), clinical cure (P = .10), and mortality (P = .289). Eight patients (19%) in each treatment group developed reversible renal dysfunction. No AS colistin-related adverse events were recorded.
Addition of AS colistin to IV colistin did not provide additional therapeutic benefit to patients with MDR VAP due to gram-negative bacteria.
[show abstract][hide abstract] ABSTRACT: Recently, a new technology has been introduced aiming to monitor and improve patient ventilator interaction (PVI monitor). With the PVI monitor, a signal representing an estimation of the patient's total inspiratory muscle pressure (Pmus(PVI)) is calculated from the equation of motion, utilizing estimated values of resistance and elastance of the respiratory system.
The aim of the study was to prospectively examine the accuracy of Pmus(PVI) to quantify inspiratory muscle pressure.
Eleven critically ill patients mechanically ventilated on proportional assist ventilation with load-adjustable gain factors were studied at three levels of assist (30, 50 and 70%). Airway, esophageal, gastric and transdiaphragmatic (Pdi) pressures, volume and flow were measured breath by breath, whereas the total inspiratory muscle pressure (Pmus) was calculated using the Campbell diagram.
For a given assist, Pmus(PVI) throughout inspiration did not differ from the corresponding values calculated using the Pdi and Pmus signals. Inspiratory and expiratory time did not differ among the various methods of calculation. Inspiratory muscle pressure decreased with increasing assist, and the magnitude of this decrease did not differ among the various methods of pressure calculation.
A signal generated from flow, volume and airway pressure may be used to provide breath-by-breath quantitative information of inspiratory muscle pressure.
European Journal of Intensive Care Medicine 04/2010; 36(4):648-55. · 5.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of the study was to investigate Propofol's effect on breathing stability in brain damage patients, as quantified by the Loop Gain (LG) of the respiratory system (breathing stability increases with decreasing LG). In 11 stable brain damage patients full polysomnography was performed before, during and after propofol sedation, titrated to achieve stage 2 or slow wave sleep. During each period, patients were ventilated with proportional assist ventilation and the % assist was increased in steps, until either periodic breathing (PB) occurred or the highest assist (95%) was achieved. The tidal volume amplification factor (VT(AF)) at the highest assist level reached just before PB occurred was used to calculate LG (LG=1/VT(AF)). In all but one patient, PB was observed. With propofol, the assist level at which PB occurred (73 + or - 19%) was significantly higher, than that before (43 + or - 35%) and after propofol sedation (49 + or - 29%). As a result, with propofol LG (0.49 + or - 0.2) was significantly lower than that before (0.74 + or - 0.2) and after propofol sedation (0.69 + or - 0.2) (p<0.05). We conclude that Propofol decreases LG. Therefore it exerts an overall stabilizing effect on control of breathing.
[show abstract][hide abstract] ABSTRACT: Patient-ventilator asynchrony refers to the uncoupling between the mechanically delivered breath and the patient's respiratory effort. It is common during assisted mechanical ventilation and may affect the morbidity of critically ill patients. Close inspection of pressure, volume and flow waveforms - displayed by modern ventilators - may help the physician to recognize and act appropriately to minimize patient-ventilator asynchrony. During the last two decades new modes of assisted mechanical ventilation have been introduced, aiming to improve patient ventilator synchrony by modulating the triggering function and the variables that control the flow delivery and the cycling off.
Expert Review of Respiratory Medicine 06/2009; 3(3):231-43.
[show abstract][hide abstract] ABSTRACT: It is not known if proportional assist ventilation with load-adjustable gain factors (PAV+) may be used as a mode of support in critically ill patients. The aim of this study was to examine the effectiveness of sustained use of PAV+ in critically ill patients and compare it with pressure support ventilation (PS).
Randomized study in the intensive care unit of a university hospital.
A total of 208 critically ill patients mechanically ventilated on controlled modes for at least 36 h and meeting certain criteria were randomized to receive either PS (n = 100) or PAV+ (n = 108). Specific written algorithms were used to adjust the ventilator settings in each mode. PAV+ or PS was continued for 48 h unless the patients met pre-defined criteria either for switching to controlled modes (failure criteria) or for breathing without ventilator assistance.
Failure rate was significantly lower in PAV+ than that in PS (11.1 vs. 22.0%, P = 0.040, OR 0.443, 95% CI 0.206-0.952). The proportion of patients exhibiting major patient-ventilator dyssynchronies at least during one occasion and after adjusting the initial ventilator settings, was significantly lower in PAV+ than in PS (5.6 vs. 29.0%, P < 0.001, OR 0.1, 95% CI 0.06-0.4). The proportion of patients meeting criteria for unassisted breathing did not differ between modes.
PAV+ may be used as a useful mode of support in critically ill patients. Compared to PS, PAV+ increases the probability of remaining on spontaneous breathing, while it considerably reduces the incidence of patient-ventilator asynchronies.
Intensive Care Medicine 08/2008; 34(11):2026-34. · 5.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: In mechanically ventilated patients respiratory system impedance may vary from time to time, resulting, with pressure modalities of ventilator support, in changes in the level of assistance. Recently, implementation of a closed-loop adjustment to continuously adapt the level of assistance to changes in respiratory mechanics has been designed to operate with proportional assist ventilation (PAV+).
The aim of this study was to assess, in critically ill patients, the short-term steady-state response of respiratory motor output to added mechanical respiratory load during PAV+ and during pressure support (PS).
In 10 patients respiratory workload was increased and the pattern of respiratory load compensation was examined during both modes of support.
Airway and transdiaphragmatic pressures, volume and flow were measured breath by breath. Without load, both modes provided an equal support as indicated by a similar pressure-time product of the diaphragm per breath, per minute and per litre of ventilation. With load, these values were significantly lower (p<0.05) with PAV+ than those with PS (5.1+/-3.7 vs 6.1+/-3.4 cmH2O.s, 120.9+/-77.6 vs 165.6+/-77.5 cmH2O.s/min, and 18.7+/-15.1 vs 24.4+/-16.4 cmH2O.s/l, respectively). Contrary to PS, with PAV+ the ratio of tidal volume (VT) to pressure-time product of the diaphragm per breath (an index of neuroventilatory coupling) remained relatively independent of load. With PAV+ the magnitude of load-induced VT reduction and breathing frequency increase was significantly smaller than that during PS.
In critically ill patients the short-term respiratory load compensation is more efficient during proportional assist ventilation with adjustable gain factors than during pressure support.
Intensive Care Medicine 05/2006; 32(5):692-9. · 5.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: The cuff-leak test has been proposed as a simple method to predict the occurrence of post-extubation stridor. The test is performed by cuff deflation and measuring the expired tidal volume a few breaths later (VT). The leak is calculated as the difference between VT with and without a deflated cuff. However, because the cuff remains deflated throughout the respiratory cycle a volume of gas may also leak during inspiration and therefore this method (conventional) measures the total leak consisting of an inspiratory and expiratory component. The aims of this physiological study were, first, to examine the effects of various variables on total leak and, second, to compare the total leak with that obtained when the inspiratory component was eliminated, leaving only the expiratory leak.
In 15 critically ill patients mechanically ventilated on volume control mode, the cuff-leak volume was measured randomly either by the conventional method (Leakconv) or by deflating the cuff at the end of inspiration and measuring the VT of the following expiration (Leakpause). To investigate the effects of respiratory system mechanics and inspiratory flow, cuff-leak volume was studied by using a lung model, varying the cross-sectional area around the endotracheal tube and model mechanics.
In patients Leakconv was significantly higher than Leakpause, averaging 188 +/- 159 ml (mean +/- SD) and 61 +/- 75 ml, respectively. In the model study Leakconv increased significantly with decreasing inspiratory flow and model compliance. Leakpause and Leakconv increased slightly with increasing model resistance, the difference being significant only for Leakpause. The difference between Leakconv and Leakpause increased significantly with decreasing inspiratory flow (V'I) and model compliance and increasing cross-sectional area around the tube.
We conclude that the cross-sectional area around the endotracheal tube is not the only determinant of the cuff-leak test. System compliance and inspiratory flow significantly affect the test, mainly through an effect on the inspiratory component of the total leak. The expiratory component is slightly influenced by respiratory system resistance.
Critical care (London, England) 03/2005; 9(1):R24-31. · 4.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: Angiogenesis is an adaptation mechanism of skeletal muscles to increased load. Animal data have shown increased vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and transforming growth factor-beta(1) (TGF-beta(1)) mRNA levels in the diaphragm as a result of increased minute ventilation, but there are no data concerning the human diaphragm.
The purpose of this study was to investigate the VEGF, bFGF, TGF-beta(1) mRNA levels in the human diaphragm of normal subjects and patients with altered respiratory mechanics.
We studied 9 patients with chronic obstructive pulmonary disease (COPD), 4 obese patients and 12 controls. We performed multiplex semiquantitative reverse transcription polymerase chain reaction to determine the VEGF, bFGF and TGF-beta(1) mRNA levels in specimens taken from their diaphragm.
VEGF mRNA levels were 18% higher in COPD patients compared with controls (p = 0.04), while for the obese patients, these levels were not statistically significantly different. bFGF and TGF-beta(1) mRNA levels in COPD patients or obese individuals compared with controls did not differ significantly either.
The results of our study showed that TGF-beta(1), VEGF and bFGF mRNA was detected in the human diaphragm. The VEGF levels were higher in COPD patients than in normal subjects. This upregulation of VEGF may suggest an enhancement of angiogenesis in the diaphragm in COPD patients.
[show abstract][hide abstract] ABSTRACT: To study the pattern of lung emptying and expiratory resistance in mechanically ventilated patients with chronic obstructive pulmonary disease (COPD).
A prospective physiological study.
A 12-bed Intensive Care Unit.
Ten patients with acute exacerbation of COPD.
At three levels of positive end-expiratory pressure (PEEP, 0, 5 and 10 cm H(2)O) tracheal (Ptr) and airway pressures, flow (V') and volume (V) were continuously recorded during volume control ventilation and airway occlusions at different time of expiration.
V-V' curves during passive expiration were obtained, expired volume was divided into five equal volume slices and the time constant (tau) and dynamic deflation compliance (Crs(dyn)) of each slice was calculated by regression analysis of V-V' and post-occlusion V-Ptr relationships, respectively. In each volume slice the existence or not of flow limitation was examined by comparing V-V' curves with and without decreasing Ptr. For a given slice total expiratory resistance was calculated as tau/Crs(dyn), whereas expiratory resistance (Rrs) and time constant (tau(rs)) of the respiratory system were subsequently estimated taken into consideration the presence of flow limitation. At zero PEEP, tau(rs) increased significantly toward the end of expiration due to an increase in Rrs. PEEP significantly decreased Rrs at the end of expiration and resulted in a faster and relatively constant rate of lung emptying.
Patients with COPD exhibit a decrease in the rate of lung emptying toward the end of expiration due to an increase in Rrs. PEEP decreases Rrs, resulting in a faster and uniform rate of lung emptying.
Intensive Care Medicine 08/2004; 30(7):1311-8. · 5.26 Impact Factor