Cough peak flows and extubation outcomes

Cough strength, secretions and extubation outcome in burn patients who have passed a spontaneous breathing trial

The aim of this study was to develop a clinical prediction model to inform decisions about the timing of extubation in burn patients who have passed a spontaneous breathing trial (SBT). Rapid shallow breathing index, voluntary cough peak flow (CPF) and endotracheal secretions were measured after each patient had passed a SBT and just prior to extubation. We used multiple logistic regression analysis to identify variables that predict extubation outcome. Seventeen patients failed their first trials of extubation (14%). CPF and endotracheal secretions are strongly associated with extubation outcome (p<0.0001). Patients with CPF ≤60 L/min are 9 times as likely to fail extubation as those with CPF >60 L/min (risk ratio=9.1). Patients with abundant endotracheal secretions are 8 times as likely to fail extubation compared to those with no, mild and moderate endotracheal secretions (risk ratio=8). Our clinical prediction model combining CPF and endotracheal secretions has strong predictive capacity for extubation outcome (area under receiver operating characteristic curve=0.96, 95% confidence interval 0.91-0.99) and therefore may be useful to predict which patients will succeed or fail extubation after passing a SBT.

The use of a weaning and extubation protocol to facilitate effective weaning and extubation from mechanical ventilation in patients suffering from traumatic injuries: a non-randomized experimental trial comparing a prospective to retrospective cohort

PURPOSE

Many patients who have suffered traumatic injuries require mechanical ventilation (MV). Weaning is the transition from ventilatory support to spontaneous breathing. The purpose of this study was to determine whether the use of a nurse and a physiotherapist-driven protocol to wean and extubate patients from MV resulted in decreased MV days and intensive care unit (ICU) length of stay (LOS).

METHODS

A prospective cohort of 28 patients (Phase I), weaned according to the protocol developed for the Union Hospital Trauma Unit, was matched retrospectively with a historical cohort of 28 patients (Phase II), weaned according to physician preference. Pairs in the two groups were matched for gender, age, type, and severity of injury.

RESULTS

For mean MV days, the groups did not differ statistically significantly (p 0.3; 14.4 days vs. 16.3 days), although the reduction in MV is clinically significant in view of the complications of additional MV days. The difference of 0.2 days for ICU LOS was not statistically significant (p = 0.9; 20.8 days vs. 21.0 days) demonstrating that the reduction in MV days may not result in the reduction of ICU LOS. The rate of re-intubation was similar between the groups (Phase I = 3/28 vs. Phase II = 4/24).

CONCLUSION

The use of a weaning and extubation protocol led by nursing staff and physiotherapists resulted in a clinically significant reduction in MV time, reducing risk of ventilator-associated complications. The role of physiotherapists and nursing staff in weaning and extubation from MV could be greatly expanded in South African ICUs.

Endoscopic assessment of vocal fold movements during cough

OBJECTIVES

Little is known about the function of the true vocal folds (TVFs) during cough. The objective of this study was to determine the reliability of measuring TVF movements during cough and to obtain preliminary normative data for these measures.

METHODS

Sequential glottal angles associated with TVF adduction and abduction across the phases of cough were analyzed from laryngeal videoendoscopy records of 38 young healthy individuals.

RESULTS

The intraobserver and interobserver reliability of 3 experienced measurers was high (intraclass correlation of at least 0.97) for measuring sequential and maximum glottal angles. The TVF abduction velocity during expulsion was significantly higher than the precompression adduction velocity (p = 0.002), but there were no significant differences in maximum angle. No statistically significant differences were seen in maximum TVF angle and velocity when they were compared between the sexes and between the levels of cough strength. True vocal fold closure following expulsion occurred in 42% of soft coughs and in 57% of moderate to hard coughs.

CONCLUSIONS

The TVF abduction angles during cough can be reliably measured from laryngeal videoendoscopy in young healthy individuals. The TVF movements are faster for expulsion abduction than for precompression adduction, but the extents of abduction are similar. To validly determine the cough phase duration, simultaneous measures of airflow are needed.

Outcomes of extubation failure in medical intensive care unit patients

OBJECTIVE

Extubation failure is associated with a poor prognosis, but the respective roles for reintubation per se and underlying disease severity remain unclear. Our objectives were to evaluate the impact of failed extubation, whether planned or unplanned, on patient outcomes and to identify a patient subset at risk for extubation failure.

DESIGN

Prospective 1-yr observational study with daily data collection.

SETTING

: Thirteen-bed medical intensive care unit in a teaching hospital.

PATIENTS

Consecutive patients requiring invasive mechanical ventilation were screened and followed until discharge or death.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 168 planned extubations in 340 patients, 26 (15%) failed. Of these 26 patients, seven (27%) had pneumonia and 13 (50%) died after reintubation. Compared with successfully extubated patients, the patients with failed extubation were not significantly different regarding disease severity, mechanical ventilation duration, or blood gas values. Age and underlying diseases were the only factors associated with extubation failure, and extubation failure occurred in 34% of patients >65 yrs with chronic cardiac or respiratory disease compared with only 9% of other patients (p < .01). Unplanned extubation occurred in 9% of patients, and inadequate endotracheal tube position was a risk factor. Failure of both planned and unplanned extubation was specifically associated with significant rapid worsening of daily organ dysfunction scores.

CONCLUSIONS

Patients >65 yrs with underlying chronic cardiac or respiratory disease are at high risk for extubation failure and subsequent pneumonia and death. Contrasting with successful extubation, failed planned or unplanned extubation was followed by marked clinical deterioration, suggesting a direct and specific effect of extubation failure and reintubation on patient outcomes.

Noninvasive work of breathing improves prediction of post-extubation outcome

PURPOSE

We hypothesized that non-invasively determined work of breathing per minute (WOB(N)/min) (esophageal balloon not required) may be useful for predicting extubation outcome, i.e., appropriate work of breathing values may be associated with extubation success, while inappropriately increased values may be associated with failure.

METHODS

Adult candidates for extubation were divided into a training set (n = 38) to determine threshold values of indices for assessing extubation and a prospective validation set (n = 59) to determine the predictive power of the threshold values for patients successfully extubated and those who failed extubation. All were evaluated for extubation during a spontaneous breathing trial (5 cmH(2)O pressure support ventilation, 5 cmH(2)O positive end expiratory pressure) using routine clinical practice standards. WOB(N)/min data were blinded to attending physicians. Area under the receiver operating characteristic curves (AUC), sensitivity, specificity, and positive and negative predictive values of all extubation indices were determined.

RESULTS

AUC for WOB(N)/min was 0.96 and significantly greater (p < 0.05) than AUC for breathing frequency at 0.81, tidal volume at 0.61, breathing frequency-to-tidal volume ratio at 0.73, and other traditionally used indices. WOB(N)/min had a specificity of 0.83, the highest sensitivity at 0.96, positive predictive value at 0.84, and negative predictive value at 0.96 compared to all indices. For 95% of those successfully extubated, WOB(N)/min was ≤10 J/min.

CONCLUSIONS

WOB(N)/min had the greatest overall predictive accuracy for extubation compared to traditional indices. WOB(N)/min warrants consideration for use in a complementary manner with spontaneous breathing pattern data for predicting extubation outcome.

Spontaneous breathing trial needs to be prolonged in critically ill and older patients requiring mechanical ventilation

PURPOSE

To investigate a modified weaning procedure to predict extubation outcome in critically older and ventilated patients.

METHODS

We retrospectively analyzed extubation outcome in older (≥ 70 years) and ventilated patients. In period I (2007), patients passing a 2-hour spontaneous breathing trial (SBT) were extubated. In period II (2008), patients underwent an 8-hour SBT on day 1 and a 2-hour SBT, followed by extubation on day 2. Weaning parameters were recorded at baseline (T(0)) (periods I and II), 2 and 8 (T(8)) hours after SBT (period II).

RESULTS

The demographic data of patients in each period (n = 64 and 67, respectively) were similar. Patients in period II demonstrated a higher rate of SBT failure but a significantly lower rate of extubation failure and reintubation mortality. In period II, successfully extubated patients demonstrated a significantly lower value of rapid shallow breathing index (RSBI) at T(8). The ratio of RSBI at T(8) over T(0) (T(8)/T(0) ≤ 1.4) demonstrated good diagnostic value (sensitivity 89.5%, specificity 80.0%, accuracy 88.4%) in predicting successful extubation.

CONCLUSIONS

For critically older and ventilated patients, a prolonged SBT in conjunction with evolution of the RSBI ratio over baseline during SBT may serve as a useful procedure to predict extubation outcome.

Clinical Prediction of Weaning and Extubation in Australian and New Zealand Intensive Care Units

Our objective was to describe, in Australian and New Zealand adult intensive care units, the relative frequency in which various clinical criteria were used to predict weaning and extubation, and the weaning methods employed.

Participant intensivists at 55 intensive care units completed a self-administered questionnaire, using visual analogue scales (0=not at all predictive, 10=perfectly predictive, not used=null score) to record the perceived utility of 30 potential predictors.

Survey response rate was 71% (164/230). Those variables thought most predictive of weaning readiness were respiratory rate (median score 8.0, interquartile range 7.0 to 8.6) effective cough (7.3, 5.9 to 8.2) and pressure support setting (7.2, 6.0 to 8.0). The most highly rated predictors of extubation success were effective cough (8.0, 7.0 to 9.0), respiratory rate (8.0, 7.0 to 8.5) and Glasgow Coma Score (7.9, 6.1 to 8.3). Variables perceived least predictive of weaning and extubation success were P0.1, Acute Physiological and Chronic Health Evaluation score II, mean arterial pressure, electrolytes and maximum inspiratory pressure (individual median scores <5). Most popular clinical criteria were those perceived to have high predictive accuracy, both for weaning (respiratory rate 96%, pressure support setting 94% and Glasgow coma score 91%) and extubation readiness (respiratory rate 98%, effective cough 94% and Glasgow Coma Score 92%). Weaning mostly employed pressure support ventilation (55%), with less use of synchronised intermittent mandatory ventilation (32%) and spontaneous breathing trials (13%).

Classic ventilatory performance predictors including respiratory rate and effective cough were reported to be of greater clinical utility than other more recently proposed measures.

Providing perioperative care for patients with hip fractures

Providing perioperative care for patients with hip fractures can present major challenges for the anaesthesiologist. These patients often have multiple comorbidities, the deterioration of any one of which may have precipitated the fall. A careful balance has to be achieved between minimising the time before operation and spending time to optimise their medical status. This review will present insights into preoperative patient assessment and optimization in this group of patients from the anaesthesiologists' perspective. In particular, it will highlight important medical issues of concern that may alter anaesthetic risks and management. With a greater understanding of what these issues are, potentially a more prompt and integrated approach to managing these patients may be made. Hopefully, this would result in minimising last minute cancellations due to medical reasons for these patients.

Aplicação clínica do pico de fluxo da tosse: uma revisão de literatura

INTRODUÇÃO: A tosse é responsável pela manutenção da via aérea livre de secreção e corpos estranhos. O pico de fluxo da tosse (PFT) é o fluxo expirado máximo medido durante uma manobra de tosse por meio de um peak flow meter. A eficácia da tosse depende da magnitude do pico de fluxo. Técnicas de insuflação assistida e de assistência manual à tosse podem aumentar a sua eficácia. Um PFT mínimo de 160 L/min foi relatado por alguns autores como necessário para manutenção da clearance brônquica e desmame da ventilação mecânica. OBJETIVO:Realizar uma revisão de literatura sobre a utilização do pico de fluxo da tosse na avaliação da eficácia da tosse em diferentes situações clínicas. MÉTODOS: Foi utilizado o descritor peak cough flow, durante a pesquisa realizada nas bases de dados Medline, SciELO e LILACS. RESULTADOS:Foi encontrado um total de 36 artigos, sendo 31 selecionados para leitura. Foram selecionados os artigos em português, espanhol ou inglês. CONCLUSÃO:O PFT vem sendo cada vez mais utilizado na avaliação dos doentes neuromusculares e também em outras situações clínicas.

Peak flow rate during induced cough: a predictor of successful decannulation of a tracheotomy tube in neurosurgical patients

BACKGROUND

An accurate predictor of successful decannulation in neurosurgical patients that indicates the best time for tracheotomy decannulation would minimize the risks of continued cannulation and unsuccessful decannulation.

OBJECTIVE

To determine whether the peak flow rate during induced cough is an appropriate predictor of successful decannulation.

METHODS

A total of 32 neurosurgical patients with a tracheotomy were enrolled. The highest peak expiratory flow rate during 3 induced coughs, the total volume of tracheal secretions collected in 6 hours, and scores on the Glasgow Coma Scale were recorded. Logistic regression analysis was applied to determine the relationship between these variables and successful decannulation (reintubation not required within 72 hours).

RESULTS

Decannulation was attempted in 23 of 32 patients. The remaining 9 patients were considered clinically inappropriate for the procedure. Of the 23 patients decannulated, 2 required reinsertion of the tracheotomy tube. Analysis revealed that peak flow rate during induced cough (odds ratio, 1.12; 95% confidence interval, 1.02-1.23) was independently associated with successful decannulation (accuracy, 75%; sensitivity, 85.7%; specificity, 54.5%). The receiver operating characteristic curve indicated an optimal cutoff point of 29 L/min.

CONCLUSION

Measurement of peak flow rate during induced cough is a simple and reproducible intervention that improves predictability of successful decannulation in patients with tracheotomy.

Involuntary cough strength and extubation outcomes for patients in an ICU

BACKGROUND

Removing the artificial airway is the last step in the mechanical ventilation withdrawal process. In order to assess cough effectiveness, a critical component of this process, we evaluated the involuntary cough peak flow (CPFi) to predict the extubation outcome for patients weaned from mechanical ventilation in ICUs.

METHODS

One hundred fifty patients were weaned from ventilators, passed a spontaneous breathing trial (SBT), and were judged by their physician to be ready for extubation in the Tri-Service General Hospital ICUs from February 2003 to July 2003. CPFi was induced by 2 mL of normal saline solution at the end of inspiration and measured using a hand-held respiratory mechanics monitor. All patients were then extubated.

RESULTS

Of 150 enrolled patients for this study, 118 (78.7%) had successful extubation and 32 (21.3%) failed. In the univariate analysis, there were higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores (16.0 vs 18.5, P = .018), less negative maximum inspiratory pressure (-45.0 vs -39.0, P = .010), lower cough peak flows (CPFs) (74.0 vs 42.0 L/min, P < .001), longer postextubation hospital stays (15.0 vs 31.5 days, P < .001), and longer postextubation ICU stays (1.0 vs 9.5 days, P < .001) in the extubation failures compared with the extubation successes. In the multivariate analysis, we found that a higher APACHE II score and a lower CPF were related to increasing risk of extubation failure (odds ratio [OR] = 1.13; 95% CI, 1.03-1.25; and OR = 0.95; 95% CI, 0.93-0.98, respectively). The receiver operator characteristic curve cutoff point for CPF was 58.5 L/min, with a sensitivity of 78.8% and specificity of 78.1%.

CONCLUSIONS

CPFi as an indication of cough reflex has the potential to predict successful extubation in patients who pass an SBT.

Extubation of patients with neuromuscular weakness: a new management paradigm

BACKGROUND

Successful extubation conventionally necessitates the passing of spontaneous breathing trials (SBTs) and ventilator weaning parameters. We report successful extubation of patients with neuromuscular disease (NMD) and weakness who could not pass them.

METHODS

NMD-specific extubation criteria and a new extubation protocol were developed. Data were collected on 157 consecutive "unweanable" patients, including 83 transferred from other hospitals who refused tracheostomies. They could not pass the SBTs before or after extubation. Once the pulse oxyhemoglobin saturation (Spo(2)) was maintained at > or = 95% in ambient air, patients were extubated to full noninvasive mechanical ventilation (NIV) support and aggressive mechanically assisted coughing (MAC). Rather than oxygen, NIV and MAC were used to maintain or return the Spo(2) to > or = 95%. Extubation success was defined as not requiring reintubation during the hospitalization and was considered as a function of diagnosis, preintubation NIV experience, and vital capacity and assisted cough peak flows (CPF) at extubation.

RESULTS

Before hospitalization 96 (61%) patients had no experience with NIV, 41 (26%) used it < 24 h per day, and 20 (13%) were continuously NIV dependent. The first-attempt protocol extubation success rate was 95% (149 patients). All 98 extubation attempts on patients with assisted CPF > or = 160 L/m were successful. The dependence on continuous NIV and the duration of dependence prior to intubation correlated with extubation success (P < .005). Six of eight patients who initially failed extubation succeeded on subsequent attempts, so only two with no measurable assisted CPF underwent tracheotomy.

CONCLUSIONS

Continuous volume-cycled NIV via oral interfaces and masks and MAC with oximetry feedback in ambient air can permit safe extubation of unweanable patients with NMD.

A pilot study of a new test to predict extubation failure

Introduction

To determine whether subjecting patients to 100 ml of additional dead space after a 120-minute weaning trial could predict readiness for extubation.

Methods

This was a prospective, non-randomised pilot study in an intensive care unit at a university hospital with 14 beds. It included all non-tracheostomised patients with improvement of the underlying cause of acute respiratory failure, and those with no need for vasoactive or sedative drugs were eligible. Patients fulfilling the Consensus Conference on Weaning extubation criteria after 120 minutes spontaneous breathing (n = 152) were included. To the endotracheal tube, 100 cc dead space was added for 30 minutes. Patients tolerating the test were extubated; those not tolerating it received six hours of supplementary ventilation before extubation. The measurements taken and main results were: arterial pressure, heart rate, respiratory rate, oxygen saturation, end-tidal carbon dioxide and signs of respiratory insufficiency were recorded every five minutes; and arterial blood gases were measured at the beginning and end of the test. Extubation failure was defined as the need for mechanical and non-invasive ventilation within 48 hours of extubation.

Results

Twenty-two patients (14.5%) experienced extubation failure. Only intercostal retraction was independently associated with extubation failure. The sensitivity (40.9%) and specificity (97.7%) yield a probability of extubation failure of 75.1% for patients not tolerating the test versus 9.3% for those tolerating it.

Conclusions

Observing intercostal retraction after adding dead space may help detect susceptibility to extubation failure. The ideal amount of dead space remains to be determined.

Trial registration

Current Controlled Trials ISRCTN76206152.

A prospective trial of elective extubation in brain injured patients meeting extubation criteria for ventilatory support: a feasibility study

Introduction

To assess the safety and feasibility of recruiting mechanically ventilated patients with brain injury who are solely intubated for airway protection and randomising them into early or delayed extubation, and to obtain estimates to refine sample-size calculations for a larger study. The design is a single-blinded block randomised controlled trial. A single large academic medical centre is the setting.

Methods

Sixteen neurologically stable but severely brain injured patients with a Glasgow Coma Score (GCS) of 8 or less were randomised to early or delayed extubation until their neurological examination improved. Eligible patients met standard respiratory criteria for extubation and passed a modified Airway Care Score (ACS) to ensure adequate control of respiratory secretions. The primary outcome measured between groups was the functional status of the patient at hospital discharge as measured by a Modified Rankin Score (MRS) and Functional Independence Measure (FIM). Secondary measurements included the number of nosocomial pneumonias and re-intubations, and intensive care unit (ICU) and hospital length of stay. Standard statistical assessments were employed for analysis.

Results

Five female and eleven male patients ranging in age from 30 to 93 years were enrolled. Aetiologies responsible for the neurological injury included six head traumas, three brain tumours, two intracerebral haemorrhages, two subarachnoid haemorrhages and three ischaemic strokes. There were no demographic differences between the groups. There were no unexpected deaths and no significant differences in secondary measures. The difference in means between the MRS and FIM were small (0.25 and 5.62, respectively). These results suggest that between 64 and 110 patients are needed in each treatment arm to detect a treatment effect with 80% power.

Conclusions

Recruitment and randomisation of severely brain injured patients appears to be safe and feasible. A large multicentre trial will be needed to determine if stable, severely brain injured patients who meet respiratory and airway control criteria for extubation need to remain intubated.

Swallowing Disorders as a Predictor of Unsuccessful Extubation: A Clinical Evaluation

Background Unsuccessful extubation may be due to swallowing dysfunction that causes airway obstruction and impairs patients’ ability to cough and expectorate.

Objective To determine whether swallowing assessment before extubation is helpful in predicting unsuccessful extubation due to airway secretions.

Methods This prospective study included all patients intubated orotracheally for more than 6 days. Before extubation, 3 tests designed to assess (1) cervical, oral, labial, and lingual motility; (2) gag reflex; and (3) swallowing were used at the bedside. Causes of reintubation were identified, and their relationship to patients’ swallowing function before extubation was evaluated.

Results Sixty-two patients were enrolled. Data on 55 patients reintubated for swallowing dysfunction were analyzed. Nine patients were reintubated because of obstruction related to upper airway secretions. Evaluation before extubation enabled prediction of 7 of those 9 unsuccessful extubations. Among the 23 patients with central nervous system disease, 3 of 4 unsuccessful extubations were predicted. According to a multivariate logistic regression model, motility and swallowing were independent predictors of unsuccessful extubation (area under receiver-operating-characteristic curve, 80%). The gag reflex was the only significant predictor of the ability to cough (area under curve, 73%) and excessive pulmonary secretion (area under curve, 67%). Swallowing was an independent predictor of the need for suctioning (area under curve, 78%).

Conclusions Using simple bedside tests to evaluate swallowing before extubation is helpful when deciding whether to extubate patients who have been intubated for more than 6 days. Involvement of nurses in these decisions would improve patients’ management.

[Field 5. Safety practices procedures for mechanical ventilation. French-speaking Society of Intensive Care. French Society of Anesthesia and Resuscitation]

Invasive or endotracheal mechanical ventilation can lead to numerous complications likely to burden morbidity and mortality of patients in the intensive care unit. Various safety practices for mechanical ventilation may involve intubation, the mechanical ventilation period, weaning and extubation, the use of tracheostomy as well as non-invasive ventilation. The main objective of safety practices described in this chapter is to prevent or avoid the main risks due to invasive mechanical ventilation.

Liberation from mechanical ventilation: what monitoring matters?

Over the past 2 decades, the art of "weaning" from mechanical ventilation has been informed by increasing published basic science and outcomes studies. Although monitoring technologies can provide vast amounts of information before, during, and after liberation from mechanical ventilation, little data exists on how to maximally harness even routinely monitored, basic physiologic parameters. Overdependence on technology and derived variables, without data to demonstrate benefit, may even inhibit the patient's progress if it is used inappropriately. We review the scientific evidence for best using routinely available physiologic data and a few more sophisticated and invasive monitoring technologies during weaning. We also suggest future study designs that would better inform the process of liberation from the ventilator and endotracheal extubation.

Minute Ventilation Recovery Time Measured Using a New, Simplified Methodology Predicts Extubation Outcome

Extubation failure is associated with poor intensive care unit and hospital outcomes. Minute ventilation recovery time, an integrative measure of a patient's respiratory reserve, has been shown in a pilot study to predict extubation outcome; however, the methodology is subjective and impractical for routine use. The authors hypothesize that minute ventilation recovery time, measured using an objective and simpler method, would predict extubation outcome. A prospective cohort study was performed in adult medical and surgical intensive care unit patients intubated for >24 hours who were weaning from mechanical ventilation. Minute ventilation recovery time was measured using a new, simplified, and objective method following the final spontaneous breathing trial prior to extubation. The primary outcome was extubation failure, defined as reintubation within 7 days. The study cohort comprised 88 patients, of whom 22 (25%) failed extubation after a median of 3 days. Demographic data, weaning parameters, and the proportion of patients who passed an extubation screen were similar between groups ( P > .05). Minute ventilation recovery time was significantly longer in patients who failed extubation (15 [5-15] vs 2 [1-5] minutes, P < .001), consistent in both medical and surgical subgroups. Operating characteristics for a preliminary threshold (minute ventilation recovery time ≥5 minutes) for prediction of extubation failure were sensitivity = 0.78, specificity = 0.71, positive predictive value = 0.47, negative predictive value = 0.90, correctly classified = 0.72. Adjustment for significant covariates did not alter the relationship between minute ventilation recovery time ≥5 minutes and extubation failure (odds ratio = 4.9, 95% confidence interval 1.45-16.2, P < .02). C statistic was 0.79 ± 0.17. It was concluded that minute ventilation recovery time, measured using a feasible methodology, can predict extubation outcome in medical and surgical intensive care unit patients.

Extubation failure in intensive care unit: Predictors and management

Extubation failure-need for reintubation within 72 h of extubation, is common in intensive care unit (ICU). It can cause increased morbidity, higher costs, higher ICU and hospital length of stay (LOS) and mortality. Patients with advanced age, high severity of illness at ICU admission and extubation, preexisting chronic respiratory and cardiovascular disorders are at increased risk of extubation failure. Unresolved illness, development and progression of organ failure during the time from extubation to reintubation and reintubation itself have been proposed as reasons for increased morbidity and mortality. Parameters used to predict extubation failure can be categorized into parameters assessing respiratory mechanics, airway patency and protection and cardiovascular reserve. Adequate cough strength, minimal secretions and alertness are necessary for successful extubation. Evidence suggests that early institution of non-invasive ventilation and prophylactic administration of methylprednisolone may prevent reintubation in some patients. The intensivist needs to identify patients at high risk of extubation failure and be prepared to reinstitute ventilation early to prevent adverse outcomes.

Acute respiratory infections in persons with spinal cord injury

Respiratory disorders are the leading cause of death for persons with both acute and chronic spinal cord injury (SCI), and much of the morbidity and mortality associated with respiratory disorders is related to acute respiratory infections. Pneumonia is the best recognized respiratory infection associated with mortality in this population. Recent evidence supports some management strategies that differ from those recommended for the general population. Upper respiratory tract infections and acute bronchitis may be precipitating factors in the development of pneumonia or ventilatory failure in patients with chronic SCI. This review emphasizes management principles for treatment and prevention of respiratory infections in persons with SCI.

Risk Factors for Extubation Failure in Patients Following a Successful Spontaneous Breathing Trial

BACKGROUND

To assess the factors associated with reintubation in patients who had successfully passed a spontaneous breathing trial.

METHODS

We used logistic regression and recursive partitioning analyses of prospectively collected clinical data from adults admitted to ICUs of 37 hospitals in eight countries, who had undergone invasive mechanical ventilation for > 48 h and were deemed ready for extubation.

RESULTS

Extubation failure occurred in 121 of the 900 patients (13.4%). The logistic regression analysis identified the following associations with reintubation: rapid shallow breathing index (RSBI) [odds ratio (OR), 1.009 per unit; 95% confidence interval (CI), 1.003 to 1.015]; positive fluid balance (OR, 1.70; 95% CI, 1.15 to 2.53); and pneumonia as the reason for initiating mechanical ventilation (OR, 1.77; 95% CI, 1.10 to 2.84). The recursive partitioning analysis allowed the separation of patients into different risk groups for extubation failure: (1) RSBI of > 57 breaths/L/min and positive fluid balance (OR, 3.0; 95% CI, 1.8 to 4.8); (2) RSBI of < 57 breaths/L/min and pneumonia as reason for mechanical ventilation (OR, 2.0; 95% CI, 1.1 to 3.6); (3) RSBI of > 57 breaths/L/min and negative fluid balance (OR, 1.4; 95% CI, 0.8 to 2.5); and (4) RSBI of < 57 breaths/L/min (OR, 1 [reference value]).

CONCLUSIONS

Among routinely measured clinical variables, RSBI, positive fluid balance 24 h prior to extubation, and pneumonia at the initiation of ventilation were the best predictors of extubation failure. However, the combined predictive ability of these variables was weak.

Variable performance of weaning-predictor tests: role of Bayes' theorem and spectrum and test-referral bias

OBJECTIVE

We examined whether variation in reported reliability of the frequency-to-tidal volume ratio (f/V(T)) in predicting weaning success is explained by spectrum and test-referral bias, as reflected by variation in pretest probability of success.

DESIGN

Two authors extracted data from all studies on reliability of f/V(T) as a weaning predictor.

RESULTS

Prevalence of successful weaning in studies of f/V(T) revealed significant heterogeneity; mean success rate was 0.75. The heterogeneity and high success rate reflects occurrence of spectrum bias, suggested by the lower value of f/V(T) in subsequent studies than in the original report (77.4 vs. 89.1) and test-referral bias, suggested by lower specificity of f/V(T) in subsequent studies than in the original report (0.52 vs. 0.64). When data from studies in the ACCP Task Force's meta-analysis of studies on f/V(T) were entered into a Bayesian model with pretest probability (prevalence of success) as the operating point, observed posttest probabilities were closely correlated with values predicted by the original report on f/V(T): positive-predictive value r = 0.86 and negative-predictive value r = 0.82. Average sensitivity, the most precise measure of screening-test reliability, was 0.87 +/- 0.14 and average specificity 0.52 +/- 0.26.

CONCLUSIONS

Much of the heterogeneity in performance of f/V(T) can be explained by variation in pretest probability of successful outcome, which may be secondary to spectrum and test-referral bias. The average sensitivity of 0.87 indicates that f/V(T) is a reliable screening test for successful weaning.

Early noninvasive ventilation averts extubation failure in patients at risk: a randomized trial

RATIONALE

Respiratory failure after extubation and reintubation is associated with increased morbidity and mortality.

OBJECTIVES

To assess the efficacy of noninvasive ventilation in averting respiratory failure after extubation in patients at increased risk.

METHODS

A prospective randomized controlled trial was conducted in 162 mechanically ventilated patients who tolerated a spontaneous breathing trial after recovery from the acute episode but had increased risk for respiratory failure after extubation. Patients were randomly allocated after extubation to receive noninvasive ventilation for 24 h (n = 79), or conventional management with oxygen therapy (control group, n = 83).

MEASUREMENTS AND MAIN RESULTS

The primary end-point variable was the decrease in respiratory failure after extubation. In the noninvasive ventilation group, respiratory failure after extubation was less frequent (13, 16 vs. 27, 33%; p = 0.029) and the intensive care unit mortality was lower (2, 3 versus 12, 14%; p = 0.015). However, 90-d survival did not change significantly between groups. Separate analyses of patients without and with hypercapnia (arterial CO(2) tension greater than 45 mm Hg) during the spontaneous breathing trial showed that noninvasive ventilation improved intensive care unit mortality (0 vs. 4, 18%; p = 0.035) and 90-d survival (p = 0.006) in hypercapnic patients only; of them, 98% had chronic respiratory disorders.

CONCLUSIONS

The early use of noninvasive ventilation averted respiratory failure after extubation and decreased intensive care unit mortality among patients at increased risk. The beneficial effect of noninvasive ventilation in improving survival of hypercapnic patients with chronic respiratory disorders warrants a new prospective clinical trial.

Fluid balance and weaning outcomes

OBJECTIVE

To examine the relationship of fluid balance and weaning outcomes.

METHODS

We prospectively collected demographic, physiological, daily fluid balance (measured inputs minus outputs), and weaning data from 87 mechanically ventilated patients.

PATIENTS

We examined 87 patients, a median age of 66 years, APACHE II of 22, and performed 205 breathing trials (BT); 38 patients (44%) were successfully extubated after their first BT with minimal or no pressure support.

RESULTS

Positive fluid balance (inputs>outputs) in the 24, 48, and 72 h and cumulatively (from hospital admission) prior to weaning were significantly greater in weaning failures than successes. Both univariate and multivariate analyses, adjusted for duration of mechanical ventilation and presence of chronic obstructive pulmonary disease, showed negative cumulative fluid balance 24 h prior to BTs (OR=2.9) and cumulative fluid balance (OR=3.4) to be independently associated with first-day weaning success. Similar relationships were demonstrated when all weaning attempts were analyzed. Negative fluid balance was as predictive of weaning outcomes as f/V(t) (likelihood of success was 1.7 for patients with negative fluid balance 24 h prior to weaning and 1.2 for those with f/Vt<100 min-1 l-1). Although administration of diuretics was associated with more negative fluid balance, it was not independently associated with weaning outcomes.

CONCLUSIONS

These data suggest that fluid balance, a potentially modifiable factor, is associated with weaning outcomes. A randomized study is required to determine whether diuresis to treat positive fluid balance expedites liberation from mechanical ventilation.

Other approaches to open-lung ventilation: Airway pressure release ventilation

OBJECTIVE

To review the use of airway pressure release ventilation (APRV) in the treatment of acute lung injury/acute respiratory distress syndrome.

DATA SOURCE

Published animal studies, human studies, and review articles of APRV.

DATA SUMMARY

APRV has been successfully used in neonatal, pediatric, and adult forms of respiratory failure. Experimental and clinical use of APRV has been shown to facilitate spontaneous breathing and is associated with decreased peak airway pressures and improved oxygenation/ventilation when compared with conventional ventilation. Additionally, improvements in hemodynamic parameters, splanchnic perfusion, and reduced sedation/neuromuscular blocker requirements have been reported.

CONCLUSION

APRV may offer potential clinical advantages for ventilator management of acute lung injury/acute respiratory distress syndrome and may be considered as an alternative "open lung approach" to mechanical ventilation. Whether APRV reduces mortality or increases ventilator-free days compared with a conventional volume-cycled "lung protective" strategy will require future randomized, controlled trials.

Extubation failure: an outcome to be avoided

Extubation failure is an outcome of increasing importance but nearly all studies have been conducted in academic settings. The article by Seymour and colleagues demonstrates that extubation failure is an outcome to be avoided in the community hospital setting as well. Patients failing extubation experience longer lengths of stay, experience higher intensive care unit mortality, and incur greater hospital costs. Investigators have identified tools for predicting extubated patients at highest risk for reintubation. The predictors focus on detecting upper airway obstruction, inadequate cough, excess respiratory secretions, and abnormal mental status. Systematic application of these predictors has the potential to improve outcome.

Neurologic status, cough, secretions and extubation outcomes

OBJECTIVE

To determine the degree to which neurologic function, cough peak flows and quantity of endotracheal secretions affected the extubation outcomes of patients who had passed a trial of spontaneous breathing (SBT).

DESIGN

Prospective observational study.

SETTING

The medical intensive care unit of a 325-bed teaching hospital.

MEASUREMENTS AND MAIN RESULTS

Cough peak flow (CPF), endotracheal secretions and ability to complete four simple tasks were measured just before extubation in patients who had passed a SBT. Eighty-eight patients were studied; 14 failed their first trials of extubation. The CPF of patients who failed was lower than that of those who had a successful extubation (58.1+/-4.6 l/min vs 79.7+/-4.1 l/min, p=0.03) and those with CPF 60 l/min or less were nearly five times as likely to fail extubation compared to those with CPF higher than 60 l/min (risk ratio [RR]=4.8; 95% CI=1.4-16.2). Patients with secretions of more than 2.5 ml/h were three times as likely to fail (RR=3.0; 95% CI=1.0-8.8) as those with fewer secretions. Patients who were unable to complete four simple tasks (i.e. open eyes, follow with eyes, grasp hand, stick out tongue) were more than four times as likely to fail as those who completed the four commands (RR=4.3; 95% CI=1.8-10.4). There was synergistic interaction between these risk factors. The failure rate was 100% for patients with all three risk factors compared to 3% for those with no risk factors (RR=23.2; 95% CI=3.2-167.2). The presence of any two of the above risk factors had a sensitivity of 71 and specificity of 81% in predicting extubation failure. Patients who failed a trial of extubation were 3.8 times as likely to have any two risk factors compared to those who were successful.

CONCLUSIONS

These simple, reproducible methods may provide a clinically useful approach to guiding the extubation of patients who have passed a SBT.