The future of genetic studies of complex human diseases: an epidemiologic perspective

Every intubated and mechanically-ventilated patient should be clinically evaluated, at least on a daily basis, by a skilled team in order to speed up the weaning process as much as possible. Again, it should be emphasized that the adoption of an active clinical strategy when faced with "difficult" to wean patients is of paramount importance. In one study, performed in Spain, analysing the prevalence of mechanical ventilation in intensive care units [3], reported the mean number of days that patients spent on mechanical ventilation was 27. In a more recent intervention study, in which a specific protocol was followed each day [2], the mean number of days on mechanical ventilation was only 12. These data have been confirmed by several authors [4, 40], and it has also been reported that a protocol-directed weaning strategy leads not only to a significant reduction in the duration of mechanical ventilation but also to a significant decrease in the number of complications and cost [4]. However, even following a protocol-directed weaning strategy, it is possible that weaning duration can be further reduced. In a prospective study performed in our institution [41] during 32 months, we reported that, following an episode of unplanned extubation, the only independent variables associated with the need for reintubation were the number of days of mechanical ventilation and the type of ventilatory support at the time of autoextubation. Indeed, when patients were in the weaning period only 16% (5 out of 32) needed reintubation, whereas reintubation was needed in 82% (22 out of 27) of patients who had an unplanned extubation during full mechanical ventilatory support. These data suggest that there are still some patients being on mechanical ventilation for a longer than necessary period of time. Finally, very recent advances in technological areas such as artificial intelligence, are proving to be useful in the management of the weaning process. When such systems are applied to modern microprocessor-controlled mechanical ventilators they can significantly help in the process of weaning [42] by automatically reducing the ventilatory assistance and by indicating the optimal time to withdraw the patient from the ventilator and proceed with extubation.     

Intergenerational gamete donation: ethical and societal implications

The incidence of hemodynamic and airway complications associated with tracheal reintubation after an unplanned extubation has not been established. Patients whose tracheas were emergently intubated outside the operating room were reviewed over a 27-mo period via a quality improvement vehicle to evaluate hemodynamic and airway complications. Data from a subset of patients (n = 57) who underwent tracheal reintubation after unplanned (self-) extubation were collected for analysis. Of the reintubations, 93% took place within 2 h of self-extubation. Of the patients, 72% had hemodynamic alterations and/or airway-related complications, including hypotension (35%), tachycardia (30%), hypertension (14%), multiple laryngoscopic attempts (22%), difficult laryngoscopy (16%), difficult intubations (14%), hypoxemia (14%), and esophageal intubation (14%). In addition, one surgical airway and one case of "cannot ventilate, cannot intubate" leading to cardiac arrest and death were recorded. These findings suggest that patients requiring reintubation will likely do so soon after self-extubation and that reintubation can be fraught with significant hemodynamic and airway complications. Less than one third of patients undergo a mishap-free reintubation. Strategies to decrease the self-extubation rate in the intensive care unit are needed to improve patient safety and to lessen the potential impact of emergency airway management. Implications: Self-extubation by patients requiring mechanical ventilation can be life-threatening, and replacing the breathing tube often leads to hemodynamic and airway complications. Using this quality improvement audit, 57 self-extubating patients and the complications associated with replacing the breathing tube, which are numerous and can lead to significant morbidity and mortality, were analyzed.     

Effect of spontaneous breathing trial duration on outcome of attempts to discontinue mechanical ventilation. Spanish Lung Failure Collaborative Group

The duration of spontaneous breathing trials before extubation has been set at 2 h in research studies, but the optimal duration is not known. We conducted a prospective, multicenter study involving 526 ventilator-supported patients considered ready for weaning, to compare clinical outcomes for trials of spontaneous breathing with target durations of 30 and 120 min. Of the 270 and 256 patients in the 30- and 120-min trial groups, respectively, 237 (87.8%) and 216 (84.8%), respectively, completed the trial without distress and were extubated (p = 0.32); 32 (13.5%) and 29 (13.4%), respectively, of these patients required reintubation within 48 h. The percentage of patients who remained extubated for 48 h after a spontaneous breathing trial did not differ in the 30- and 120-min trial groups (75.9% versus 73.0%, respectively, p = 0.43). The 30- and 120-min trial groups had similar within-unit mortality rates (13 and 9%, respectively) and in-hospital mortality rates (19 and 18%, respectively). Reintubation was required in 61 (13.5%) patients, and these patients had a higher mortality (20 of 61, 32.8%) than did patients who tolerated extubation (18 of 392, 4.6%) (p < 0.001). Neither measurements of respiratory frequency, heart rate, systolic blood pressure, and oxygen saturation during the trial, nor other functional measurements before the trial discriminated between patients who required reintubation from those who tolerated extubation. In conclusion, after a first trial of spontaneous breathing, successful extubation was achieved equally effectively with trials targeted to last 30 and 120 min.     

Randomised, controlled trial of nasal continuous positive airway pressure in the extubation of infants weighing 600 to 1250 g

AIM: To determine whether extubation to nasal continuous airway pressure (NCPAP) results in a greater proportion of infants remaining free of additional ventilatory support for one week after extubation compared with those extubated directly to headbox oxygen. METHODS: A randomised, controlled, clinical trial was conducted at the neonatal intensive care unit of the Royal Women's Hospital, Melbourne, of infants with birthweights between 600 and 1250 g, ventilated via an endotracheal tube for more than 12 hours, requiring less than 50% oxygen, a ventilator rate < or = 20/minute, considered by the clinical management team to be ready for extubation. Infants were randomly allocated either to NCPAP or to oxygen administered via a headbox. Success was defined by no requirement for additional ventilatory support over the week following extubation. Failure criteria were (i) apnoea; (ii) absolute increase in oxygen requirement greater than 15% above than required before extubation; or (iii) respiratory acidosis (pH < 7.25 with pCO2 > 6.67 kPa). RESULTS: Thirty one of 47 (66%) infants were successfully extubated to NCPAP compared with 18 of 45 (40%) for headbox oxygen. The increase in failure rate in the headbox group was due primarily to increased oxygen requirements in this group. Of the 27 who failed headbox oxygen, 26 were given a trial of NCPAP and 13 did not require endotracheal reintubation. There was no significant difference between the groups in the total number of days of assisted ventilation or the duration of inpatient stay. CONCLUSIONS: NCPAP applied prophylactically after endotracheal extubation reduces the incidence of adverse clinical events that lead to failure of extubation in the seven days after extubation. This reduction is clinically important. The benefits of NCPAP do not seem to be associated with an increased incidence of unwanted side effects.     

Independent effects of etiology of failure and time to reintubation on outcome for patients failing extubation

Patients requiring reintubation after failed extubation have a poor prognosis, with hospital mortality exceeding 30 to 40%, though the reason remains unclear. To examine the impact of etiology of extubation failure and time to reintubation on hospital outcome, we performed a post hoc analysis of prospectively gathered data on 74 MICU patients (47 men, 27 women), 64 +/- 2 yr of age who required reintubation within 72 h of extubation. Cause for reintubation was classified as airway (upper airway obstruction, 11; aspiration/excess pulmonary secretions, 12) or nonairway (respiratory failure, 21; congestive heart failure, 17; encephalopathy, 7; other, 6). The duration of mechanical ventilation prior to extubation was 139 +/- 19 h, and the median time to reintubation was 21 h. Thirty-one of 74 patients (42%) died, with mortality highest for patients failing from nonairway etiologies (27/51, 53% versus 4/23, 17%; p < 0.01). Patients failing from an airway cause tended to be reintubated earlier (21 +/- 4 versus 31 +/- 3 h, p = 0.07). Mortality increased with longer duration of time from extubation to reintubation (<= 12 h, 6/25 versus > 12 h, 25/49; p < 0.05). With multiple logistic regression, both cause for extubation failure and time to reintubation were independently associated with hospital mortality. In conclusion, etiology of extubation failure and time to reintubation are independent predictors of outcome in reintubated MICU patients. The high mortality for those reintubated for nonairway problems indicate that efforts should be preferentially focused on identifying these patients. The effect of time to reintubation suggests that identification of patients early after extubation and timely reinstitution of ventilatory support has the potential to reduce the increased mortality associated with extubation failure.     

Clinical characteristics, respiratory functional parameters, and outcome of a two-hour T-piece trial in patients weaning from mechanical ventilation

The discrepancy in results from different studies regarding outcome of weaning from mechanical ventilation may be due to several factors such as the differences in patient populations and weaning indexes used. In order to analyze the clinical characteristics and weaning indexes in patients undergoing a 2-h T-piece weaning trial and the relationship between the etiology of acute respiratory failure (ARF) and the outcome of this weaning trial, we prospectively studied 217 patients receiving mechanical ventilation who met standard weaning criteria. Successful weaning occurred in 57.6% (125 of 217) of patients: 13 of 33 (39.4%) patients with chronic obstructive pulmonary disease (COPD), 27 of 46 (58.7%) neurologic patients, and 85 of 138 (61.6%) patients with ARF. Ventilatory support was reinstituted in 31.8% (69 of 217) patients: 20 of 33 (60.6%) of patients with COPD, four of 46 (8.7%) neurologic patients, and 45 of 138 (32.6%) patients with ARF (p < 0.001). Reintubation was required in 23 of 148 (15.5%) patients: 15 of 42 (35.7%) neurologic patients, and eight of 93 (8.6%) patients with ARF, whereas no patient with COPD was reintubated (p < 0.001). Using a discriminant analysis, the following variables were selected as the best predictors of outcome: (1) in the whole population, days of mechanical ventilation before weaning trial (DMV), frequency-to-tidal volume ratio (f/VT), maximal inspiratory pressure (MIP), airway occlusion pressure (P0.1), maximal expiratory pressure (MEP), and vital capacity (VC); (2) in patients with ARF, DMV, P0.1/MIP, MIP, f/VT, and age; (3) in patients with COPD, f/VT, P0.1, P0.1/MIP, MIP, age, and DMV; (4) in neurologic patients, MIP, MEP, and f/VT.P0.1. Using these predictors, 74.6% of the whole population, 76.1% of patients with ARF, 93.9% of patients with COPD, and 73.9% of neurologic patients were accurately classified as weaning successes or failures. The highest rate of reintubation occurred in neurologic patients. In this group, the ability to cough and clear respiratory secretions, objectively reflected by MEP, may help in clinical decision-making.     

Contribution of bronchoalveolar lavage and transbronchial biopsy to diagnosis and prognosis of drug-induced pneumopathies

OBJECTIVE: The purpose of this study was to evaluate three ventilator weaning strategies and to evaluate whether the use of continuous positive airway pressure (CPAP) via a nasopharyngeal or endotracheal tube would increase the likelihood of extubation failure in very low birth weight (VLBW) infants. STUDY DESIGN: We studied prospectively 87 preterm infants (mean +/- SD; birth weight: 1078 +/- 188 g; gestational age: 28.8 +/- 2.2 weeks) who were in the process of being weaned from intermittent mandatory ventilation (IMV). Infants were assigned by systematic sampling to one of the following three treatment groups: (1) direct extubation from IMV (D.EXT) (n = 30); (2) preextubation endotracheal CPAP (ET-CPAP) for 12-24 hr (n = 28); or (3) postextubation nasopharyngeal CPAP (NP-CPAP) for 12-24 hr (n = 29). Failure was defined as the need for resumption of mechanical ventilation within 72 hr of extubation due to frequent or severe apnea and/or respiratory failure (pH < 7.25, PaCO2 > 60 mm Hg, and/or requirement for oxygen FiO2 > 60%). RESULTS: There were no significant differences in failure rates among the three procedures. Failures were 2/30 (7%) in D.EXT; 4/28 (14%) in ET-CPAP; and 7/29 (24%) in the NP-CPAP. There were also no differences in FiO2, PaO2, and respiratory rates before and after discontinuation of IMV among the three groups. PaCO2 values were slightly higher in the NP-CPAP group 12-24 hr after weaning from IMV. CONCLUSION: We were unable to demonstrate a clear difference in extubation outcome by use of CPAP administered via an endotracheal or nasopharyngeal tube when compared to direct extubation from low-rate IMV in VLBW infants.     

A randomized, controlled trial of aminophylline in ventilatory weaning of premature infants

OBJECTIVES: To determine whether maximal inspiratory force predicts successful neonatal extubation, and whether aminophylline affects maximal inspiratory force or the success rate of extubation. DESIGN: Double-blind, prospective, randomized, placebo-controlled trial. SETTING: Tertiary level neonatal intensive care unit. PATIENTS: A total of 20 ventilated, preterm, newborn infants: birth weight < 2.5 kg; gestation < 35 wks. INTERVENTIONS: Intravenous aminophylline 4 mg/kg bolus followed by 2.5 mg/kg every 6 hrs x three doses, then 1.5 mg/kg every 6 hrs; or placebo. Drug administration began when infants were receiving an FIO2 of < 0.4 and were progressively weaning from assisted mechanical ventilation. A standardized weaning protocol was instituted, and patients were extubated when they were able to tolerate a mechanical ventilatory rate of < 5 cycles/min. MEASUREMENTS AND MAIN RESULTS: Occlusion pressures, including maximal inspiratory force, were measured before aminophylline and daily until endotracheal extubation. Arterial blood gases were measured every 3 hrs, and 24-hr cardiac and respiratory recordings were performed postextubation. Three of ten aminophylline-treated patients failed extubation compared with two of ten placebo infants (p = nonsignificant). Mean apnea frequency postextubation was 0.02/hr in the aminophylline group compared with 0.3/hr in the placebo group (p < .05). Aminophylline had no effect on successful extubation or on maximal inspiratory force. Maximal inspiratory force was not correlated with the success of extubation. Apnea frequency postextubation was significantly reduced by aminophylline. CONCLUSIONS: Aminophylline is an effective prophylaxis for postextubation apnea in the preterm infant but does not affect maximal inspiratory force or increase the success rate of extubation in this patient population.     

Noninvasive pressure support ventilation in COPD patients with postextubation hypercapnic respiratory insufficiency

Patients with chronic obstructive pulmonary disease (COPD) who have been intubated and mechanically ventilated may prove difficult to wean. Noninvasive ventilation may be used in an attempt to avoid new endotracheal intubation. The efficacy of administration of noninvasive pressure support ventilation was evaluated in 30 COPD patients with postextubation hypercapnic respiratory insufficiency, compared with 30 historically matched control patients who were treated conventionally. Patients were included in the study if, within 72 h postextubation, they presented with respiratory distress, defined as the combination of a respiratory frequency >25 breaths x min(-1), an increase in the arterial carbon dioxide tension (Pa,CO2) of at least 20% compared with the value measured after extubation, and a pH <7.35. Noninvasive pressure support ventilation was effective in correcting gas exchange abnormalities. The use of noninvasive ventilation significantly reduced the need for endotracheal intubation: 20 of the 30 patients (67%) in the control group required endotracheal intubation, compared with only six of the 30 patients (20%) in the noninvasive-ventilation group (p<0.001). In-hospital mortality was not significantly different between the two groups, but the mean duration of ventilatory assistance for the treatment of the postextubation distress, and the length of intensive care unit stay related to this event, were both significantly shortened by noninvasive ventilation (p<0.01). In conclusion, noninvasive ventilation may be used in the management of patients with chronic obstructive pulmonary disease and postextubation hypercapnic respiratory insufficiency.     

Gastric intramucosal pH: an indicator of weaning outcome from mechanical ventilation in COPD patients

The aim of this study was to determine whether gastric intramucosal pH (pHim) and/or gastric intramucosal carbon dioxide tension (PCO2,im) measured by tonometry can be used to predict the success of weaning in chronic obstructive pulmonary disease (COPD) patients. Twenty six consecutive COPD patients, undergoing mechanical ventilation for acute respiratory failure and satisfying the criteria of weaning from mechanical ventilation with nasogastric tonometer in place, were studied. Arterial blood gas values and PCO2,im were measured 24 h before (H-24), just before (H0), and after 20 min of a weaning trial on T-piece (H20min). Weaning failure was defined as the development of respiratory distress and/or arterial blood gas impairments during the first 2 h of spontaneous breathing on T-piece, or reintubation within 24 h after extubation. Between the weaning failure (n = 6) and weaning success (n = 20) groups, there were no differences in blood gas analysis readings at H-24 and H0 before the weaning period, age, Simplified Acute Physiology Score (SAPS) on admission, SAPS on the day of weaning trial, and duration of ventilation. Clinical status, tonometric and arterial gasometric data were similar at H-24 and H0 in all patients. During mechanical ventilation, pHim was < or = 7.30 in patients who failed weaning and > 7.30 in patients who were successfully weaned (p < 0.001; 100% sensitivity and specificity). The threshold value for PCO2,im of 8.0 kPa (60 mmHg) represents a clear demarcation with respect to outcome before the weaning trial. PCO2,im values during mechanical ventilation are significantly different (p < 0.001) between patients who were successfully weaned and those who were not (6.9 +/- 0.9 vs 9.9 +/- 1.1 kPa (51.9 +/- 6.7 vs 74.3 +/- 8.0 mmHg, respectively)). At H20min, pHim and PCO2,im were still statistically different between the weaning failure and the weaning success group. We conclude that measurement of gastric intramucosal pH (or gastric intramucosal carbon dioxide tension) represents a simple and accurate index to predict weaning outcome in chronic obstructive pulmonary disease patients before attempting weaning.     

Noninvasive management of pediatric neuromuscular ventilatory failure

OBJECTIVE: To evaluate the use of mouth piece/nasal intermittent positive-pressure ventilation (IPPV) as an alternative to intubation or to permit extubation for patients with primarily neuromuscular ventilatory impairment and no ventilator-free breathing ability. DESIGN: A case control study. INTERVENTIONS: Using a protocol in which oxyhemoglobin desaturation was prevented or reversed by the continuous use of noninvasive IPPV and manually and mechanically assisted coughing as needed, patients with neuromuscular ventilatory failure and no ventilator-free breathing ability were managed noninvasively or extubated to continuous use of noninvasive IPPV for ventilatory support on room air. MEASUREMENTS AND MAIN RESULTS: Four of ten patients who presented in acute ventilatory failure were managed without intubation, despite becoming dependent on continuous ventilator use. The six intubated patients were extubated successfully to continuous noninvasive IPPV once normal arterial oxygen saturation levels could be maintained on room air, despite their having no ventilator-free breathing ability. CONCLUSIONS: The use of inspiratory and expiratory aids can decrease the need for intubation for patients with neuromuscular ventilatory failure in the absence of significant lung disease. It can also permit extubation, despite the need for continuous ventilatory support and, thereby, decrease the need to resort to tracheostomy.     

Doctoral education in nursing for practitioner knowledge and for academic knowledge: the University of Adelaide, Australia

A retrospective review was made of 49 survivors who were mechanically ventilated for more than 48 hours in the neurosurgical ICU. Thirty-two patients (Gp I) were successfully extubated, 9 patients (Gp II) underwent tracheostomy after one or more failed extubations, and 8 patients (Gp III) underwent elective tracheostomy. Glasgow Coma Scale (GCS) scores at extubation were 11.3 +/- 2.8 (mean (SD) for Gp I vs 7.8 +/- 2.7 for Gp II (P = n.s.) and at elective tracheostomy (Gp III) was 5.4 +/- 2.3. Incidence of ventilator-associated pneumonia were 35% in Gp I vs 100% of patients in Gp II and III (P < 0.05). Reasons for reintubation in 7 of 9 patients (Gp II) were upper airway obstruction and tenacious tracheal secretions while 14 of 17 patients were weaned off the ventilator within 48 hours of tracheostomy. The length of stay in ICU was 16.8 +/- 7.1 days in Gp II vs 11.7 +/- 2.9 days in Gp III (P < 0.05). In our study, elective tracheostomy for selected patients with poor GCS scores and nosocomial pneumonia has resulted in shortened ICU length of stay and rapid weaning from ventilatory support.     

Difficult weaning from mechanical ventilation: a graduated approach and teamwork

Weaning from mechanical ventilation in patients with chronic obstructive pulmonary disease (COPD) or left ventricular failure may be difficult. At the time of intubation and initiation of mechanical ventilatory support, this treatment is usually life-saving in the short term. Only later on, the condition which necessitated such support may prove irreversible. COPD patients often require positive end-expiratory pressure to enable them to trigger the ventilator comfortably. Patients with left ventricular failure need pharmacological support to reduce the circulating volume and to reduce left ventricular afterload because the ventilatory support itself reduces both left ventricular preload and afterload. Gradual withdrawal of pressure support and gradually increasing periods of T-piece weaning are probably equally effective. New methods have been described but have not yet been tested in randomized controlled trials. More important than the method of weaning is the presence of qualified and dedicated nursing support. Not all patients can be weaned; for most of those who cannot, prospects are grim. These patients require optimal palliative support with recognition of their autonomy.     

Determinants of prolonged mechanical ventilation after coronary artery bypass grafting

BACKGROUND: Early extubation of cardiac surgical patients enhances ambulation, improves cardiopulmonary function, and can lead to savings in health care costs. METHODS: We retrospectively examined the role of 48 variables in determining the period of ventilatory support in 507 patients having coronary artery bypass grafting. RESULTS: Fifteen (< 3%) of 507 patients required ventilatory support in excess of 24 hours. Among the remaining patients, extubation was achieved early (< or = 8 hours) (mean time, 5.65 +/- 1.31 hours) in 53% and late (> 8 hours) (mean time, 13.7 +/- 3.4 hours) in 47%. Logistic and linear multivariate regression analyses implicated increased age, New York Heart Association functional class IV, intraoperative fluid retention, postoperative intraaortic balloon pump requirement, and bank blood transfusions as predictors of late extubation. Also, the linear regression linked lower body weight and number of anastomoses (or grafts) to increased mechanical ventilatory support. CONCLUSIONS: Analysis of the fluid balance and cardiopulmonary bypass data suggests that earlier extubation may be achieved by actively reducing fluid retention (eg, by hemoconcentration) and time on bypass (eg, normothermia). Finally, intensive care unit stay and postoperative length of stay were significantly lower in the early versus late extubation groups without an increase in pulmonary complications.     

Change in anaesthesia practice and postoperative sedation shortens ICU and hospital length of stay following coronary artery bypass surgery

We randomized prospectively 144 patients, undergoing elective coronary artery bypass surgery, to either early or to routine extubation [mechanical ventilatory support for 4-7 h (Group A), or 8-14 h (Group B)]. Anaesthesia was modified for both groups. The groups were well matched in terms of sex, age, NYHA class, preoperative left ventricular ejection fraction, bypass time and aortic cross-clamp time, number of grafts used, and blood units transfused. All patients had normal preoperative respiratory, renal, hepatic and cerebral functions. Mechanical ventilatory support (mean +/- SD) was 6.3 +/- 0.7 h for Group A and 11.6 +/- 1.3 h for Group B. Mean ICU stay was 17 +/- 1.3 h for Group A and 22 +/- 1.2 h for Group B, while the mean hospital stay was 7.3 +/- 0.8 days and 8.4 +/- 0.9, respectively. There were no statistically significant differences in the frequency of all postoperative complications among the two groups. There were no reintubation, readmission to the ICU or death in either group. We concluded that change in anaesthesia practice and early postoperative sedation in patients undergoing elective coronary artery bypass graft (CABG) surgery resulted in earlier tracheal extubation, shorter ICU and hospital length of stay without organ dysfunction or postoperative complications. Early extubation was only possible due to the modification of anaesthesia and ICU sedation regime.     

Stellettamide B, a new indolizidine alkaloid from a sponge of the genus Stelletta

BACKGROUND: The availability of nasal mask bi-level positive airway pressure (BiPAP) support in managing respiratory failure following cardiovascular surgery was studied. MATERIALS AND METHODS: BiPAP support was used for eight patients requiring postoperative prolonged respiratory support of 72 hours or longer. Their mean age was 65 years of age and the mean periods of postoperative endotracheal intubation was 12+/-5 days. BiPAP support was removed within 48 hours in six out of eight patients. Reintubation of an endotracheal tube was not necessary in all eight patients after the BiPAP treatment. RESULTS: The respiratory rates during the BiPAP management remained unchanged. The values of the respiratory index significantly (p<0.01) improved after BiPAP management (1.5+/-0.2 --> 0.9+/-0.2). A-aDO2 and Qs/Qt decreased (p<0.1) after the BiPAP management. There were no significant differences in central venous pressure and circulatory states during BiPAP support. CONCLUSIONS: In conclusions, BiPAP support is a noninvasive management technique for postoperative respiratory failure and may also prevent prolonged endotracheal intubation.     

Airway occlusion pressure at 0.1 s (P0.1) after extubation: an early indicator of postextubation hypercapnic respiratory insufficiency

OBJECTIVE: To examine variables associated with postextubation respiratory distress in chronic obstructive pulmonary disease (COPD) patients. DESIGN: Prospective, clinical investigation. SETTING: Intensive care unit of a university hospital. PATIENTS: Forty COPD patients, considered ready for extubation. MEASUREMENTS AND MAIN RESULTS: We recorded, from the digital display of a standard ventilator, breathing frequency (f), tidal volume (VT) and f/VT for the respiratory pattern, airway occlusion pressure at 0.1 s (P0.1) for the respiratory drive and measured blood gases: i) before extubation, following 30 min of a 6 cm H2O pressure support (PS) ventilation trial, ii) 1 h after extubation, at the 30th min of a face mask 4 cm H2O PS ventilation trial. According to the weaning outcome, the patients were divided into two groups: respiratory distress, and non-respiratory distress within 72 h of the discontinuation of mechanical ventilation. The respiratory distress was defined as the combination of f more than 25 breaths/min, an increase in PaCO2 of at least 20% compared with the value measured after extubation, and pH lower than 7.35. We determined whether those patients who developed respiratory distress after extubation differed from those who did not. Respiratory pattern data and arterial blood gases recorded, either before or after extubation, and P0.1 recorded before extubation, were inadequate to differentiate the two groups. Only P0.1 recorded 1 h after the discontinuation of mechanical ventilation differentiated the patients who developed respiratory distress from those who did not (4.2+/-0.9 vs 1.8+/-0.8, p < 0.01). CONCLUSIONS: P0.1 recorded after extubation may be a good indicator of postextubation respiratory distress. Measuring P0.1 and/or the analysis of the evolution of this parameter could facilitate decisions during the period following extubation.     

Predictors of extubation success and failure in mechanically ventilated infants and children

OBJECTIVE: To predict extubation success and failure in mechanically ventilated infants and children using bedside measures of respiratory function. DESIGN: Prospective collection of data. SETTING: A university-affiliated children's hospital with a 51-bed critical care unit. PATIENTS: All infants and children who were mechanically ventilated for at least 24 hrs, except neonates < or = 37 wks gestation and patients with neuromuscular disease. INTERVENTIONS: Bedside measurements of cardiorespiratory function were obtained immediately before extubation. MEASUREMENTS AND MAIN RESULTS: Extubation failure was defined as reintubation within 48 hrs of extubation in the absence of upper airway obstruction. Failure rates were calculated for different ranges (selected a priori) of preextubation measures of breathing effort, ventilatory support, respiratory mechanics, central inspiratory drive, and integrated indices useful in adults. Effort of spontaneous breathing was assessed by the respiratory rate standardized to age, the presence of retractions and paradoxical breathing, inspiratory pressure, maximal negative inspiratory pressure (maximal negative inspiratory pressure), inspiratory pressure/maximal negative inspiratory pressure ratio, and tidal volume indexed to body weight of a spontaneous breath. Ventilatory support was measured by the fraction of inspired oxygen (F10(2)), mean airway pressure, oxygenation index, and the fraction of total minute ventilation provided by the ventilator. Respiratory mechanics were assessed by determination of peak ventilatory inspiratory pressure and dynamic compliance. Central inspiratory drive was assessed by mean inspiratory flow. Frequency to tidal volume ratio and the compliance, rate, oxygenation, and pressure indexed to body weight, the integrated indices useful in predicting extubation failure in adults, were also calculated. Thirty-four of the 208 patients who were studied were reintubated for an overall failure rate of 16.3% (95% confidence interval 11.3% to 21.4%). The reasons for reintubation were poor effort (n = 8), excessive effort (n = 14), altered mental status or absent airway reflexes (n = 2), cardiovascular instability (n = 3), inadequate oxygenation (n = 3), respiratory acidosis (n = 3), and undocumented (n = 1). Extubation failure increased significantly with decreasing tidal volume indexed to body weight of a spontaneous breath, increasing F10(2), increasing mean airway pressure, increasing oxygenation index, increasing fraction of total minute ventilation provided by the ventilator, increasing peak ventilatory inspiratory pressure, or decreasing mean inspiratory flow (p < .05). Dynamic compliance showed a trend of increasing failure rate with decreasing dynamic compliance but did not reach statistical significance (p = .116). Respiratory rate standardized to age, inspiratory pressure, maximal negative inspiratory pressure, inspiratory pressure/maximal negative inspiratory pressure ratio, frequency to tidal volume ratio, and compliance, rate, oxygenation, and pressure did not show any trend in failure rate with increasing or decreasing values. Threshold values that defined a low risk (< or = 10%) and a high risk (> or = 25%) of extubation failure could be determined for tidal volume indexed to body weight of a spontaneous breath, F10(2), mean airway pressure, oxygenation index, fraction of total minute ventilation provided by the ventilator, peak ventilatory inspiratory pressure, dynamic compliance, and mean inspiratory flow. Neither a low nor a high risk of failure could be defined for frequency to tidal volume ratio or the compliance, rate, oxygenation, and pressure (CROP) index. CONCLUSIONS: Bedside measurements of respiratory function can predict extubation success and failure in infants and children. Both a low risk and a high risk of failure can be determined using these measures. Integrated indices useful in adults do not reliably predict extubation success or failure in     

Clinical applications of cardiopulmonary interactions

The hemodynamic consequences of both spontaneous and positive-pressure ventilation may be profound and may have opposite effects on cardiovascular stability in differing patient populations. Thus, no firm rules apply as to the specific response that will be seen in all patients and under all conditions. Some generalities, however, are probably reasonable. In patients with markedly increased work of breathing, hypervolemia, or impaired LV pump function, the institution of mechanical ventilatory support can be lifesaving because of its ability to support the cardiovascular system, independent of any beneficial effects that mechanical ventilation may have on gas exchange. In patients with decreased pulmonary elastic recoil, increased pulmonary vascular resistance, hypovolemia, or airflow obstruction, the institution of mechanical ventilatory support may induce cardiovascular instability, which, if not corrected, can lead to total cardiovascular collapse. Similarly, withdrawal of ventilatory support invariably increases intrathoracic blood volume and LV afterload and can be thought of as a type of cardiovascular stress test. Patients who pass this test easily can usually be successfully weaned from mechanical ventilatory support, whereas those who fail often are not ready to be weaned. Some patients who fail weaning trials do so because of the cardiovascular effects of spontaneous ventilation, not because the work of breathing is too great. Identification of such patients early on may improve their treatment by directing supportive therapies toward cardiovascular rather than ventilatory endpoints. However, in many situations, it will be difficult to single out a primary process determining cardiovascular instability, because multiple factors are compounded to create the observed situation and the patient's response to initiation of ventilatory support or weaning. Thus, the clinician is left with a series of therapeutic options, which if depending on the patient's response, suggest specific origins of the ventilatory and cardiovascular dysfunction. In that regard, the initiation and withdrawal of ventilatory support can be seen as a ventilatory probe into the determinants of cardiovascular homeostasis in the ventilatory-dependent patient.     

Randomised trial of elective continuous positive airway pressure (CPAP) compared with rescue CPAP after extubation

AIM: To determine if a weaning regimen on flow driver continuous positive airway pressure (CPAP) would decrease the number of ventilator days but increase the number of CPAP days when compared with a rescue regimen. METHODS: Fifty eight babies of 24-32 weeks gestation with respiratory distress syndrome (RDS) were studied prospectively. After extubation they were randomly allocated to receive CPAP for 72 hours (n = 29) according to a weaning regimen, or were placed in headbox oxygen and received CPAP only if present "start CPAP" criteria were met (n = 29, rescue group). RESULTS: There was no difference in successful extubation at 72 hours, 1 and 2 weeks, between the groups in terms of the number of reventilation episodes, reventilation days, or in total days of CPAP. Birthweight, gestational age, race, day of first extubation, antenatal or postnatal steroids, patent ductus arteriosus status and maximal mean airway pressure used were of no value in predicting success or failure at 72 hours, 1, or 2 weeks. CONCLUSION: The weaning regimen did not decrease the number of ventilator days or days on CPAP compared with the rescue regimen. The rescue regimen on flow driver CPAP seems to be a safe and effective method of managing a baby of 24-32 weeks gestation who has been ventilated for RDS or immature lung disease.