BACKGROUND The weaning process from mechanical ventilation is a complicated issue for patients with respiratory failure who require long-term respiratory support. Although the application of weaning protocols reduces weaning time, and enhances patient outcome, little is known about the actual approaches that clinicians use for the weaning of these patients. AIM The purpose of this paper is to explore approaches to weaning of long-term ventilated patients in a Scottish Intensive Care Unit. The findings are part of a larger study on decision-making during the weaning of long-term ventilated patients. METHOD Data were collected through participant observation and follow-up interviews with the nursing staff. Twenty-four-hour chart and medical notes review and informal conversation with the bedside nurse were also used to collect information on the weaning process. FINDINGS Nine patients were recruited to the study. Two patients were extubated and three patients were extubated but then required a tracheostomy. A further four patients had a tracheostomy performed. Thematic analysis of the data showed that weaning was individualized, and physician led, regardless of the existence of the weaning protocol. Six different weaning approaches were identified. Nurses followed a conservative approach to weaning in comparison to doctors who appeared more aggressive. CONCLUSION There are many varieties in the approaches clinicians use when weaning long-term ventilated patients, which acts on the continuity of their care. A shift of focus to identify ways of maintaining continuity of care and a combined 'wake and wean' approach needs to be considered.

AIMS AND OBJECTIVES To provide an analysis of the scope of nursing practice and inter-professional role responsibility for ventilatory decision-making in Australian and New Zealand (ANZ) intensive care units (ICU). BACKGROUND Currently, little empirical data describe nurses' role in decision-making for ventilation and its weaning. Delineation of roles and responsibilities for ventilatory practices vary according to unit structure, staffing and skill-mix, patient case-mix and unit leadership models. METHODS Self-administered questionnaire sent to nurse managers of eligible ICUs within ANZ. Results. Survey responses were available from 54/180 ICUs. The majority (71%) of responding ICUs were located within metropolitan areas and categorised as a tertiary level ICU (50%). The mean number of nurses employed per ICU bed was 4.7 in Australia and 4.2 in NZ, with 69%(IQR: 47-80%) of nurses holding a postgraduate specialty qualification. All units reported a 1:1 nurse-to-patient ratio for ventilated patients with 71% reporting a 1:2 nurse-to-patient ratio for non- ventilated patients. Key ventilator decisions, including assessment of weaning and extubation readiness, were reported as predominantly made by nurses and doctors in collaboration. Overall, nurses described high levels of autonomy and influence in ventilator decision-making. Decisions to change ventilator settings, including FiO(2)(91%, 95% CI: 80-97), ventilator rate (65%, 95% CI: 51-77) and pressure support adjustment (57%, 95% CI: 43-71), were made independently by nurses. CONCLUSIONS The results of this survey suggest, within the ANZ context, nurses participate actively in ventilation and weaning decisions. In addition, the results support an association between the education profile and skill-mix of nurses and the level of collaborative practice in ICU. Relevance to clinical practice. Mechanical ventilation may result in significant complications if not applied appropriately. Collaborative practice that encourages nursing input into decision-making may improve patient outcomes and reduce complications.

Nurse-led weaning can improve patient outcome. Exploration of the factors that influence the commencement of weaning. Themes of decision-making, pathophysiological and multidisciplinary team factors emerged. Experience was a key factor in the decision to wean. The use of protocol-led weaning may not be useful in the decision to wean.

Nine species of Ocimum (Lamiaceae) were surveyed for leaf-surface flavonoids by means of HPLC with diode array detection and atmospheric pressure chemical ionisation (APCI) mass spectrometry. The analysis revealed the presence of 23 different flavones, most of which were identified by comparing their UV and mass spectra with those of standards. Almost all taxa investigated contained flavones methoxylated in the 6- and 8-positions, such as nevadensin, xanthomicrol and gardenin B. The same taxa also produced flavones methoxylated in the 6-position but hydroxylated in the 8-position, including isothymusin (5,8,4'-trihydroxy-6,7-dimethoxyflavone), pedunculin (5,8-dihydroxy-6,7,4'-trimethoxyflavone) and a new flavone, 5,7,8-trihydroxy-6,4'-dimethoxyflavone, which was given the trivial name pilosin. This compound was isolated from O. americanum var. pilosum and also detected as a minor constituent in O. x citriodorum leaf extracts. Its molecular structure was elucidated by means of NMR spectroscopy. 8-Oxygenated flavones were absent only from O. lamiifolium. APCI mass spectrometry of the flavonoids revealed that the product ions formed by collision induced dissociation of the protonated molecule provided structural information about the substitution pattern of the A-ring. The chemotaxonomic and biogenetic implications of the results are discussed.

In 1991, the nursing profession began to pursue the idea of reflective practice with vigour, despite little evidence that reflective practice improved nursing care (Burnard 1991; Hunt 1993). A small qualitative study on the experiences of nurses writing reflective journals was undertaken in the intensive care unit at Newham General Hospital.(A Price 1995). This highlighted the need for clear initial guidance and support when introducing reflective practice. It also demonstrated a lack of knowledge about reflection within the unit. During this time, a group of nurses who were interested in developing clinical supervision as a method of support for staff was formed. Kohner's (1994) definition of clinical supervision, adopted by the group after review of literature, makes it clear that this involves reflection on practice. Johns'(1993) Model of Structured Reflection was amended and used to promote in-depth analysis of situations, and journal writing was encouraged within the group. A continuing process of group clinical supervision was started, initially with the help of a facilitator experienced in it. On the basis of this experience, a strategy for implementation of clinical supervision in the intensive care unit was developed and put into action by the group members. Consideration of the progress and problems experienced leads to the conclusion that continuing staff motivation and commitment, and adequate time are essential for implementation of clinical supervision.

Nonisosmolar solutions were placed in the lumen of the ferret trachea in vitro in an organ bath. Hyposmolar (150 mmol/kg) solutions progressively increased in osmolarity over 1 h. Increases in luminal concentration of impermeant blue dextran occurred only after 5 min, suggesting that the initial changes were due to ion rather than water fluxes. With hyperosmolar solutions the osmolarity decreased over 1 h with no change in blue dextran concentration, indicating that ion but not water fluxes were taking place. Cooling the preparation to 4 degrees C greatly reduced the osmolaity changes with hyperosmolar solutions and halved those with hyposmolar solutions, suggesting that active ion transport was involved. Hyposmolar (75-150 mmol/kg) and hyperosmolar (450-900 mmol/kg) solutions both increased albumin output into the lumen, but the response was prevented by cooling the trachea to 4 degrees C. Hyposmolar and hyperosmolar solutions both increased the output of lysozyme from glandular serous cells into the lumen. The response to hyposmolar solutions was stronger. Cooling the trachea abolished the lysozyme response to hyperosmolar solutions. Thus hypo- and hyperosmolar solutions promote ion transport in directions to restore isosmolarity. Both nonisosmolar solutions promote albumin movement by active transport across the mucosa and lysozyme secretion from submucosal glands, responses inhibited by tracheal cooling and therefore dependent on metabolically active processes.

The rabbit whole trachea was mounted in vitro in an organ bath containing Krebs-Henseleit (KH) solution. When the trachea was air filled there was no resting secretion and none was induced by methacholine (0.02 mM). Histology showed that the trachea has very few submucosal glands. When the trachea was filled with KH, with fluorescent bovine serum albumin in the surrounding KH solution, the rate of transport of albumin into the lumen was measured. Methacholine (0.02 mM) and phenylephrine (0.1 mM) more than doubled the output of albumin, and albuterol (0.1 mM) increased it more than fourfold. Cooling the preparation to 4 degrees C decreased the spontaneous output of albumin to less than one-half control and abolished the increase in output due to albuterol. Addition of sodium cyanide (1 mM) to the preparation abolished the increase in albumin transport due to albuterol. Serosal-to-mucosal transport of fluorescent dextran (mol wt 70,000) was less than one-third that of albumin and was not enhanced by methacholine, phenylephrine, or albuterol. Lysozyme output, an index of serous cell secretion, was barely detectable in controls and was not enhanced by any of the drugs. We conclude that the rabbit trachea has no measurable submucosal gland secretion and that it can actively transport albumin into the lumen via the epithelium. The transport rate is enhanced by methacholine, phenylephrine, and especially by albuterol.

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Between 15% and 35% of mechanically ventilated patients fail an initial spontaneous breathing trial. For these patients, 40% of total time on mechanical ventilation is consumed by the weaning process (60% for patients with chronic obstructive pulmonary disease). Longer duration of mechanical ventilation is associated with higher risk of complications and probably with higher mortality. Noninvasive ventilation (NIV) has been used successfully in some forms of acute respiratory failure. Randomized controlled trials have indicated that, in selected patients with chronic obstructive pulmonary disease and acute-on-chronic respiratory failure, NIV can facilitate weaning, reduce the duration of invasive mechanical ventilation, decrease complications, and reduce mortality, compared to weaning on continued invasive ventilation. However, extubation failure resulting in re-intubation is associated with higher mortality, and this mortality risk increases with delay of re-intubation and may not be prevented by application of NIV. Patients extubated to NIV must have careful monitoring by skilled clinicians able to provide timely re-intubation if the patient shows signs of intolerance or worsening respiratory failure.

BACKGROUND Weaning is the process during which mechanical ventilation is withdrawn and the work of breathing is transferred from the ventilator back to the patient. Prolonged weaning is associated with development of ventilator-related complications and longer stays in the Intensive Care Unit (ICU). Computerized or Automated Weaning is a novel weaning strategy that continuously measures and adapts ventilator support (by frequently measuring and averaging three breathing parameters) and automatically conducts Spontaneous Breathing Trials to ascertain whether patients can resume autonomous breathing. Automated Weaning holds promise as a strategy to reduce the time spent on the ventilator, decrease ICU length of stay, and improve clinically important outcomes. METHODS/DESIGN A pilot weaning randomized controlled trial (RCT) is underway in the ICUs of 8 Canadian hospitals. We will randomize 90 critically ill adults requiring invasive ventilation for at least 24 hours and identified at an early stage of the weaning process to either Automated Weaning (SmartCare) or Protocolized Weaning. The results of a National Weaning Survey informed the design of the Protocolized Weaning arm. Both weaning protocols are operationalized in Pressure Support mode, include opportunities for Spontaneous Breathing Trials, and share a common sedation protocol, oxygen titration parameters, and extubation and reintubation criteria. The primary outcome of the WEAN study is to evaluate compliance with the proposed weaning and sedation protocols. A key secondary outcome of the pilot RCT is to evaluate clinician acceptance of the weaning and sedation protocols. Prior to initiating the WEAN Study, we conducted a run-in phase, involving two patients per centre (randomizing the first participant to either weaning strategy and assigning the second patient to the alternate strategy) to ensure that participating centres could implement the weaning and sedation protocols and complete the detailed case report forms. DISCUSSION Mechanical ventilation studies are difficult to implement; requiring protocols to be operationalized continuously and entailing detailed daily data collection. As the first multicentre weaning RCT in Canada, the WEAN Study seeks to determine the feasibility of conducting a large scale future weaning trial and to establish a collaborative network of ICU clinicians dedicated to advancing the science of weaning. TRIAL REGISTRATION NUMBER ISRCTN43760151.

INTRODUCTION Tolerance of a spontaneous breathing trial is an evidence-based strategy to predict successful weaning from mechanical ventilation. Some patients may not tolerate the trial because of the respiratory load imposed by the endotracheal tube, so varying levels of respiratory support are widely used during the trial. Automatic tube compensation (ATC), specifically developed to overcome the imposed work of breathing because of artificial airways, appears ideally suited for the weaning process. We further evaluated the use of ATC in this setting. METHODS In a prospective study, patients who had received mechanical ventilation for more than 24 hours and met defined criteria for a weaning trial, underwent a one-hour spontaneous breathing trial with either ATC (n = 87) or pressure support ventilation (PSV; n = 93). Those tolerating the trial were immediately extubated. The primary outcome measure was the ability to maintain spontaneous, unassisted breathing for more than 48 hours after extubation. In addition, we measured the frequency/tidal volume ratio (f/VT) both with (ATC-assisted) and without ATC (unassisted-f/VT) at the start of the breathing trial as a pretrial predictor of extubation outcome. RESULTS There were no significant differences in any of the baseline characteristics between the two groups apart from a significantly higher Acute Physiology and Chronic Health Evaluation (APACHE) II score in the ATC group (p = 0.009). In the PSV group, 13 of 93 (14%) patients failed the breathing trial compared with only 6 of 87 (6%) in the ATC group; this observed 8% difference, however, did not reach statistical significance (p = 0.12). The rate of reintubation was not different between the groups (total group = 17.3%; ATC = 18.4% vs. PSV = 12.9%, p = 0.43). The percentage of patients who remained extubated for more than 48 hours was similar in both groups (ATC = 74.7% vs. PSV = 73.1%; p = 0.81). This represented a positive predictive value for PSV of 0.85 and ATC of 0.80 (p = 0.87). Finally, the ATC-assisted f/VT was found to have a significant contribution in predicting successful liberation and extubation compared with the non-significant contribution of the unassisted f/VT (unassisted f/VT, p = 0.19; ATC-assisted f/VT, p = 0.005). CONCLUSIONS This study confirms the usefulness of ATC during the weaning process, being at least as effective as PSV in predicting successful extubation outcome and significantly improving the predictive value of the f/VT. TRIAL REGISTRATION Current Controlled Trials ISRCTN16080446.

PURPOSE OF REVIEW In intubated patients, mechanical ventilation offers essential ventilatory support, while the respiratory system recovers from acute respiratory failure. Yet, invasive mechanical ventilation is associated with risks and complications that prolong the duration of mechanical ventilation and increase the risk for death. Therefore, safely weaning the patient from the ventilator as soon as possible is paramount. Recent randomized trials have addressed a number of key areas of interest. RECENT FINDINGS Determining readiness for spontaneous breathing, the first step in weaning, is best achieved using liberal oxygenation criteria; does not require routine use of weaning predictors; and can be conducted, in certain patient populations, using protocols driven by respiratory therapists or ICU nurses. Spontaneous breathing trials can be conducted on low levels of pressure support, continuous positive airway pressure, or T-piece. Weaning failure often results from an imbalance between respiratory load and capacity. There is increasing appreciation that cardiac dysfunction can limit weaning. Recent randomized trials suggest that noninvasive ventilation (in patients with chronic obstructive pulmonary disease) and computer-driven approaches show promise as weaning strategies. New techniques have been employed to identify patients at increased risk for extubation failure. Noninvasive ventilation, when used in high-risk patients, can decrease extubation failure. SUMMARY Weaning from mechanical ventilation continues to be an area of considerable importance. Recent randomized controlled trials provide high-level evidence for the best approaches to weaning and extubation.

Noninvasive ventilation (NIV) successfully treats primary respiratory failure in chronic obstructive pulmonary disease (COPD), acute pulmonary edema, and, in some patients, hypoxemic respiratory failure. Increasingly clinicians have applied NIV in an effort to shorten the duration of mechanical ventilation by facilitating weaning and preventing or treating post-extubation respiratory failure. Randomized controlled trials (RCTs) indicate that NIV may be an effective weaning tool in a subset of patients with acute-on-chronic respiratory failure from COPD, and that applying immediate NIV to extubated patients at high risk for extubation failure improves outcome by decreasing the need for reintubation. In contrast, there is mixed evidence about the effectiveness of NIV to treat established post-extubation respiratory failure. NIV appeared to be ineffective in heterogeneous patient populations in some randomized trials that enrolled relatively few patients with COPD, and a case-control study found that NIV decreased the need for reintubation in this group. Therefore, as with primary therapy, NIV should be considered for patients with COPD and post-extubation respiratory distress.

ABSTRACT: INTRODUCTION: Automatic pressure support reduction based on a target respiratory frequency or mandatory rate ventilation (MRV) is available in the Taema-Horus ventilator for the weaning process in the ICU setting. We hypothesized that MRV is as effective as manual weaning in post-operative ICU patients. METHODS: There were 106 patients selected in the post-operative period in a prospective, randomized, controlled protocol. When the patients arrived at the ICU after surgery, they were randomly assigned to traditional weaning, consisting of the manual reduction of pressure support every thirty minutes, keeping the respiratory rate/tidal volume (RR/TV)(L)< 80 until 5-7 cmH20 of pressure support ventilation (PSV). Alternatively, they were assigned to automatic weaning, referring to MRV set with a respiratory frequency target of 15 breaths per minute (the ventilator automatically decreased the PSV level by 1 cmH20 every 4 respiratory cycles, if the patient's RR was less than 15 per minute). The primary endpoint of the study was the duration of the weaning process. Secondary endpoints were levels of pressure support, respiratory rate, tidal volume (mL), RR/VT (L), PEEP levels FiO2 and SpO2 required during the weaning process, the need for reintubation and the need for non-invasive ventilation in the 48 hours after extubation. RESULTS: In the intention to treat analysis there were no statistically significant differences between the 53 patients selected for each group regarding gender (p=0.541), age (p=0.585) and type of surgery (p=0.172). Nineteen patients presented complications during the trial (4 in the PSV group and 15 in the MRV group, p<0.05. Nine patients in the automatic group did not adapt to the MRV mode. The mean duration of the weaning process was 221+/- 192 for the manual group, and 271+/- 369 minutes for the automatic group.(p=0.375). PSV levels were significantly higher in MRV compared to that of the PSV manual reduction (p<0.05). Reintubation was not required in either group. Non-invasive ventilation was necessary for two patients, in the manual group after cardiac surgery (p=0.51). CONCLUSIONS: The duration of the automatic reduction of pressure support was similar to the manual one in the post-operative period in the ICU, but presented more complications, especially no adaptation to the MRV algorithm. Trial registration number: ISRCTN37456640.

BACKGROUND Adaptive-support ventilation (ASV) is a minute ventilation-controlled mode governed by a closed-loop algorithm. With ASV, tidal volume and respiratory rate are automatically adjusted to minimize work of breathing. Studies indicate that ventilation in ASV enables more rapid weaning. The authors conducted a randomized controlled trial to determine whether ventilation in ASV results in a shorter time to extubation than pressure-regulated volume-controlled ventilation with automode (PRVCa) after cardiac surgery. METHODS Fifty patients were randomly assigned to ASV or PRVCa after elective coronary artery bypass grafting. Respiratory weaning progressed through three phases: phase 1 (controlled ventilation), phase 2 (assisted ventilation), and phase 3 (T-piece trial), followed by extubation. The primary outcome was duration of intubation (sum of phases 1-3). Secondary outcomes were duration of mechanical ventilation (sum of phases 1 and 2), number of arterial blood gas samples, and manual ventilator setting changes made before extubation. RESULTS Forty-eight patients completed the study. The median duration of intubation was significantly shorter in the ASV group than in the PRVCa group (300 [205-365] vs. 540 [462-580] min; P < 0.05). This difference was due to a reduction in the duration of mechanical ventilation (165 [120-195] vs. 480 [360-510] min; P < 0.05). There were no significant differences between the ASV and PRVCa groups in the number of arterial blood gas samples taken or manual ventilator setting changes made. CONCLUSIONS ASV is associated with earlier extubation, without an increase in clinician intervention, when compared with PRVCa in patients undergoing uncomplicated cardiac surgery.

OBJECTIVE Preliminary assessment of an automated weaning system (SmartCare/PS) compared to usual management of weaning from mechanical ventilation performed in the absence of formal protocols. DESIGN AND SETTING A randomised, controlled pilot study in one Australian intensive care unit. PATIENTS A total of 102 patients were equally divided between SmartCare/PS and Control. INTERVENTIONS The automated system titrated pressure support, conducted a spontaneous breathing trial and provided notification of success ("separation potential"). MEASUREMENTS AND RESULTS The median time from the first identified point of suitability for weaning commencement to the state of "separation potential" using SmartCare/PS was 20 h (interquartile range, IQR, 2-40) compared to 8 h (IQR 2-43) with Control (log-rank P = 0.3). The median time to successful extubation was 43 h (IQR 6-169) using SmartCare/PS and 40 (14-87) with Control (log-rank P = 0.6). Unadjusted, the estimated probability of reaching "separation potential" was 21% lower (95% CI, 48% lower to 20% greater) with SmartCare/PS compared to Control. Adjusted for other covariates (age, gender, APACHE II, SOFAmax, neuromuscular blockade, corticosteroids, coma and elevated blood glucose), these estimates were 31% lower (95% CI, 56% lower to 9% greater) with SmartCare/PS. The study groups showed comparable rates of reintubation, non-invasive ventilation post-extubation, tracheostomy, sedation, neuromuscular blockade and use of corticosteroids. CONCLUSIONS Substantial reductions in weaning duration previously demonstrated were not confirmed when the SmartCare/PS system was compared to weaning managed by experienced critical care specialty nurses, using a 1:1 nurse-to-patient ratio. The effect of SmartCare/PS may be influenced by the local clinical organisational context. DESCRIPTOR 28. Mechanical ventilation: weaning.

BACKGROUND Prolonged mechanical ventilation is associated with lung injury in preterm infants. In these infants, weaning from synchronized intermittent mandatory ventilation may be delayed by their inability to cope with increased respiratory loads. The addition of pressure support to synchronized intermittent mandatory ventilation can offset these loads and may facilitate weaning. OBJECTIVE The purpose of this work was to compare synchronized intermittent mandatory ventilation and synchronized intermittent mandatory ventilation plus pressure support in weaning from mechanical ventilation and the duration of supplemental oxygen dependency in preterm infants with respiratory failure. METHODS Preterm infants weighing 500 to 1000 g at birth who required mechanical ventilation during the first postnatal week were randomly assigned to synchronized intermittent mandatory ventilation or synchronized intermittent mandatory ventilation plus pressure support. In both groups, weaning followed a set protocol during the first 28 days. Outcomes were assessed during the first 28 days and until discharge or death. RESULTS There were 107 infants enrolled (53 synchronized intermittent mandatory ventilation plus pressure support and 54 synchronized intermittent mandatory ventilation). Demographic and perinatal data, mortality, and morbidity did not differ between groups. During the first 28 days, infants in the synchronized intermittent mandatory ventilation plus pressure support group reached minimal ventilator settings and were extubated earlier than infants in the synchronized intermittent mandatory ventilation group. Total duration of mechanical ventilation, duration of oxygen dependency, and oxygen need at 36 weeks' postmenstrual age alone or combined with death did not differ between groups. However, infants in synchronized intermittent mandatory ventilation plus pressure support within the 700- to 1000-g birth weight strata had a shorter oxygen dependency. CONCLUSIONS The results of this study suggest that the addition of pressure support as a supplement to synchronized intermittent mandatory ventilation during the first 28 days may play a role in reducing the duration of mechanical ventilation in extremely low birth-weight infants, and it may lead to a reduced oxygen dependency in the 700- to 1000-g birth weight strata.