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OBJECTIVE To investigate, in restrictive patients, the influence of pressure ramp slope values on the efficacy of pressure support ventilation. DESIGN Prospective study. SETTING A university hospital medical intensive care unit. PATIENTS Twelve intubated restrictive patients. INTERVENTIONS Patients were randomly assigned to four sequences in which the values of the slope of the pressure ramp increase were modulated so that the plateau pressure was reached within a predetermined time: 0.1, 0.50, 1, or 1.50 secs. The more rapidly the pressure plateau was achieved, the higher was the initial flow rate. For convenience, these four different ventilatory settings were termed T 0.1, T 0.5, T 1, and T 1.5. MEASUREMENTS AND MAIN RESULTS We measured the following parameters 10 mins after application of each pressure ramp slope: inspiratory work of breathing, breathing pattern, and intrinsic PEEP (PEEPi). Work of breathing was evaluated using Campbell's diagram, and expressed as a percentage of the values observed under spontaneous ventilation. A marked interindividual variation of the values for work of breathing was observed under spontaneous ventilation; the mean value for work of breathing was 1.97 +/- 0.82 joule/L, with a range of 1.22 to 4.10 joule/L. Comparison between the means for each sequence and each variable measured was performed by two-way analysis of variance with internal comparisons between sequences by Duncan's test. Between the first (T 0.1) and the last (T 1.5) sequence, the reduction of values of the pressure ramp slope induced a progressive increase in the values for work of breathing, regardless of the mode of expression (in joule, joule/L, or joule/min). The values for work of breathing (joule/ L), expressed as a percentage of the values observed under spontaneous ventilation, increased from 44.2 +/- 14.4% to 78.3 +/- 17.8% (p < .001). In contrast, the reduction of the pressure ramp slope values and initial flow rate did not induce any significant change in tidal volume, respiratory frequency, and PEEPi. CONCLUSION Among the four tested slope values, the steepest was that which induced the lowest possible work of breathing in restrictive patients ventilated by pressure support ventilation. In this type of patient, we therefore suggest that the programmed pressure value should be reached by using a steep pressure ramp slope.

Prolonged duration of endotracheal mechanical ventilation (ETMV) is associated with an increased morbidity and mortality in intensive care unit (ICU) patients. The aim of this study was to assess the usefulness of noninvasive ventilation (NIV) as a systematic extubation and weaning technique to reduce the duration of ETMV in acute-on-chronic respiratory failure (ACRF). Among 53 consecutively intubated patients admitted for ACRF, we conducted a prospective, randomized controlled trial of weaning in 33 patients who failed a 2-h T-piece weaning trial (2 h-WT) although they met simple criteria for weaning. Conventional invasive pressure support ventilation (IPSV) was used as the control weaning technique in 16 patients (IPSV group), and NIV was applied immediately after extubation in 17 patients (NIV group). The two weaning groups were similar for type of chronic respiratory failure (CRF), pulmonary function data, age, Simplified Acute Physiology Score (SAPS II), and severity of ACRF on admission. The characteristics of the two groups were also similar at randomization. In the IPSV group, 12 of 16 patients (75%) were successfully weaned and extubated, versus 13 of 17 (76.5%) in the NIV group (p = NS). NIV like IPSV significantly and similarly improved gas exchange in relation to that achieved during 2 h-WT (p < 0.05). The duration of ETMV was significantly shorter in the NIV (4.56 +/- 1.85 d) than in the IPSV group (7.69 +/- 3.79 d) (p = 0. 004). NIV also reduced the mean period of daily ventilatory support, but increased the total duration of ventilatory support related to weaning (3.46 +/- 1.42 d, versus 11.54 +/- 5.24 d with NIV; p = 0. 0001). Most patients in the IPSV group developed complications related to ETMV and/or the weaning process, but the difference was not significant (nine of 16 versus six of 17). The durations of ICU and hospital stays and the 3-mo survival were similar in the two groups. In conclusion, NIV permits earlier removal of the endotracheal tube than with conventional IPSV, and reduces the duration of daily ventilatory support without increasing the risk of weaning failures. NIV should be considered as a new and useful systematic approach to weaning in patients with ACRF who are difficult to wean.

To define patients at risk for unplanned extubation; to assess the influence of nursing workload on the incidence of unplanned extubation; and to determine predictive criteria for patients requiring reintubation.A prospective, case-control study, with 10 and 15 mos of data collection.University medical intensive care department.In the first study, which lasted 10 mos, unplanned extubation occurred in 40 (14%) of 281 ventilated and intubated patients; 36 cases were sufficiently documented to be compared with 74 intubated and ventilated controls. In the second study, which lasted 15 mos, the reintubated patients (n=23) of a series of 62 unplanned extubation patients were compared with those who were not reintubated (n=39).None.The following parameters were recorded: gender, age, main reason for admission, Simplified Acute Physiology Score II, route of intubation (oral or nasotracheal), tube diameter, ventilatory mode, FiO2, frequency and tidal volume delivered by the ventilator immediately before unplanned extubation, arterial blood gases performed 24 hrs before unplanned extubation, the presence of any sedation with, in this case, the last Ramsay score, the presence of hand restraints, the presence of weaning of ventilation, the accidental or deliberate nature of unplanned extubation, the Glasgow Coma Score at the time of unplanned extubation, the duration of ventilation before unplanned extubation, total duration of ventilation and stay in the intensive care unit, and the patient's survival or death. The nursing workload was evaluated using a score derived from the Projet de Recherche en Nursing and adapted to intensive care. Unplanned extubation patients were more frequently intubated orally than controls (33.3% vs. 14.9%, respectively; p.05). In the population of sedated patients, unplanned extubation patients were more frequently agitated than controls (60% vs. 19%, respectively; p.05). The nursing workload did not differ between days with and days without unplanned extubation. Twenty-three (37%) of the 62 cases of documented unplanned extubation were reintubated. Predictive factors of reintubation are, in decreasing order of importance: Glasgow Coma Score of11, accidental nature of unplanned extubation, and a PaO2/FiO2 ratio200 torr (26.7 kPa).Patients at risk for unplanned extubation are characterized by oral intubation and insufficient sedation. In the department studied, and with the specific score used, we did not observe a relationship between the nursing workload and the incidence of unplanned extubation. A Glasgow Coma Score of11, the accidental nature of unplanned extubation, and a PaO2/FiO2 ratio200 torr (26.7 kPa) are factors associated with a risk of reintubation.

To compare the effects of noninvasive assist-control ventilation (ACV) and pressure support ventilation (PSV) by nasal mask on respiratory physiologic parameters and comfort in acute hypercapnic respiratory failure (AHRF).A prospective randomized study.A medical ICU.Fifteen patients with COPD and AHRF were consecutively and randomly assigned to two noninvasive ventilation (NIV) sequences with ACV and PSV mode, spontaneous breathing (SB) via nasal mask being used as control. ACV and PSV settings were always subsequently adjusted according to patient's tolerance and air leaks. Fraction of inspired oxygen did not change between the sequences.ACV and PSV mode strongly decreased the inspiratory effort in comparison with SB. The total inspiratory work of breathing (WOBinsp) expressed as WOBinsp/tidal volume (VT) and WOBinsp/respiratory rate (RR), the pressure time product (PTP), and esophageal pressure variations (deltaPes) were the most discriminant parameters (p0.001). ACV most reduced WOBinsp/VT (p0.05), deltaPes (p0.05), and PTP (0.01) compared with PSV mode. The surface diaphragmatic electromyogram activity was also decreased32% as compared with control values (p0.01), with no difference between the two modes. Simultaneously, NIV significantly improved breathing pattern (p0.01) with no difference between ACV and PSV for VT, RR, minute ventilation, and total cycle duration. As compared to SB, respiratory acidosis was similarly improved by both modes. The respiratory comfort assessed by visual analog scale was less with ACV (57.23+/-30.12 mm) than with SB (75.15+/-18.25 mm) (p0.05) and PSV mode (81.62+/-25.2 mm) (p0.01) in our patients.During NIV for AHRF using settings adapted to patient's clinical tolerance and mask air leaks, both ACV and PSV mode provide respiratory muscle rest and similarly improve breathing pattern and gas exchange. However, these physiologic effects are achieved with a lower inspiratory workload but at the expense of a higher respiratory discomfort with ACV than with PSV mode.