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Biomedical subjects

M W Elliott

Publications and source records attributed to M W Elliott.

At least 19 recordsLinked to original sources
PubMed2003

Cost effectiveness of ward based non-invasive ventilation for acute exacerbations of chronic obstructive pulmonary disease: economic analysis of randomised controlled trial.

OBJECTIVE: To evaluate the cost effectiveness of standard treatment with and without the addition of ward based non-invasive ventilation in patients admitted to hospital with an acute exacerbation of chronic obstructive pulmonary disease. DESIGN: Incremental cost effectiveness analysis of a randomised controlled trial. SETTING: Medical wards in 14 hospitals in the United Kingdom. PARTICIPANTS: The trial comprised 236 patients admitted to hospital with an acute exacerbation of chronic obstructive pulmonary disease and mild to moderate acidosis (pH 7.25-7.35) secondary to respiratory failure. The economic analysis compared the costs of treatment that these patients received after randomisation. MAIN OUTCOME MEASURE: Incremental cost per in-hospital death. RESULTS: 24/118 died in the group receiving standard treatment and 12/118 in the group receiving non-invasive ventilation (P=0.05). Allocation to the group receiving non-invasive ventilation was associated with a reduction in costs of 49362 pounds sterling (78741 dollars; 73109 euros), mainly through reduced use of intensive care units. The incremental cost effectiveness ratio was -645 pounds sterling per death avoided (95% confidence interval -2310 pounds sterling to 386 pounds sterling), indicating a dominant (more effective and less costly) strategy. Modelling of these data indicates that a typical UK hospital providing a non-invasive ventilation service will avoid six deaths and three to nine admissions to intensive care units per year, with an associated cost reduction of 12000-53000 pounds sterling per year. CONCLUSIONS: Non-invasive ventilation is a highly cost effective treatment that both reduced total costs and improved mortality in hospital.

Acute Disease↗
PubMed2003

Effects of incremental levels of continuous positive airway pressure on cerebral blood flow velocity in healthy adult humans.

Sleep disordered breathing is common in patients with cerebrovascular disease, and could exacerbate the cerebral damage in acute stroke. Data about the effects of continuous positive airway pressure (CPAP) upon cerebral perfusion are conflicting. We investigated whether increasing levels of CPAP may affect cerebral haemodynamics, assessed by transcranial Doppler (TCD) in normal humans. A group of 25 healthy young volunteers were evaluated before (CPAP0-pre), during (CPAP5, CPAP10 and CPAP15, denoting CPAP at 5, 10 and 15 cmH(2)O respectively) and after (CPAP0-post) application of incremental levels of CPAP delivered through a mouthpiece. The mean cerebral blood flow velocity (CBFV) and the pulsatility index (PI; an indirect measure of cerebrovascular resistance) in the middle cerebral artery were measured with TCD. Respiratory rate, heart rate, end-tidal carbon dioxide pressure (PETCO(2)), transcutaneous haemoglobin oxygen saturation (SpO(2)), mean arterial blood pressure and anxiety score were also recorded. Compared with CPAP0-pre, CBFV was significantly decreased as higher levels of CPAP were applied (P <0.0001). CPAP15 increased PI (P <0.05), ETCO(2) was reduced by CPAP10 and CPAP15 (P <0.0001), and anxiety score and SpO(2) increased at all levels of CPAP (P <0.05). Heart rate, respiratory rate and mean arterial pressure did not change. The decrease in CBFV was correlated with the fall in P ETCO(2) (CPAP15) and the increase in PI (CPAP10, CPAP15) (P <0.05). In conclusion, even low levels of CPAP delivered through a mouthpiece in awake, young volunteers led to a decrease in CBFV, measured by TCD. This fall in CBFV was associated with hypocapnia and with an increase in both cerebrovascular resistance and anxiety due to breathing against positive pressure. As the negative consequences of a fall in CBFV may outweigh the therapeutic effects of CPAP in the post-stroke setting, further studies of the cerebrovascular effects of CPAP with different interfaces in elderly patients with and without stroke are needed before intervention trials can be performed safely.

Adolescent↗
PubMed2002

Central sleep apnoea syndrome in patients with chronic heart disease: a critical review of the current literature.

The prevalence, prognosis, clinical presentation, pathophysiology, diagnosis, and treatment of the central sleep apnoea syndrome (CSAS) are reviewed and its relationship with congestive heart failure (CHF) is discussed. Adequately powered trials are needed with survival and health status as end points to establish whether correction of sleep related breathing abnormalities improves the outcome in patients with CHF.

Heart Failure↗
PubMed2002

Prevalence and predictors of upper airway obstruction in the first 24 hours after acute stroke.

BACKGROUND AND PURPOSE: The prevalence of sleep-disordered breathing after stroke has been reported to be between 32% and 71%. However, the first 24-hour period, when upper airway obstruction may have a critical effect on the cerebral circulation because of hemodynamic fluctuations and repetitive hypoxia, has not been studied. Furthermore, data on prediction of upper airway obstruction after stroke are limited. This study sought to assess the prevalence of upper airway obstruction in the first 24 hours of stroke and to ascertain whether its occurrence could be predicted. METHODS: One hundred twenty patients with acute stroke underwent a respiratory variable-only sleep study, started within 24 hours of onset of neurological symptoms. Sleep history and stroke characteristics were recorded on admission. RESULTS: We found that 79%, 61%, and 45% of the patients had a respiratory disturbance index greater than 5, 10, and 15 events per hour, respectively. Patients had a significantly higher respiratory disturbance index when nursed in the supine (29 events per hour), supine left (29 events per hour), and supine right (24 events per hour) positions than in any other position (P<0.0001). On logistic regression analysis, BMI (P=0.025), neck circumference (P=0.026), and limb weakness (P=0.025) independently predicted the occurrence of upper airway obstruction in the first 24 hours after acute stroke. CONCLUSIONS: Upper airway obstruction is common in the first 24 hours after stroke, especially if patients are nursed in the supine position, and typical obstructive sleep apnea risk factors (body mass index and neck circumference) appear to be the best predictors of its occurrence. Stroke characteristics (severity, clinical subtype, and clinically assessed pharyngeal function) are not independently associated with upper airway obstruction after stroke.

Acute Disease↗
PubMed2002

Assisted ventilation for heart failure patients with Cheyne-Stokes respiration.

Patients with chronic congestive cardiac failure (CCF) frequently suffer from central sleep apnoea syndrome (CSAS). Continuous positive airway pressure (CPAP) has been suggested as a treatment. The authors hypothesised that bilevel ventilation might be easier to initiate and superior to CPAP at correcting the sleep-related abnormality of breathing in patients with CCF. After excluding those with a history suggestive of obstructive sleep apnoea, 35 patients with CCF (left ventricular ejection fraction <35%) were screened with overnight oximetry and the diagnosis of CSAS was established with polysomnography in 18. Two 14-day cycles of CPAP (0.85 kPa (8.5 mbar)) or bilevel ventilation (0.85/0.3 kPa (8.5/3 mbar)) in random order, were compared in a crossover study. Sixteen patients (13 males), mean age 62.0+/-7.4 yrs completed the study. The pretreatment apnoea/hypopnoea index of 26.7+/-10.7 was significantly reduced by CPAP and bilevel ventilation to 7.7+/-5.6 and 6.5+/-6.6, respectively. The arousal index fell from 31.1+/-10.0 per hour of sleep to 15.7+/-5.4 and 16.4+/-6.9, respectively. Significant and equal improvements with CPAP and bilevel ventilation were found for sleep quality, daytime fatigue, circulation time and New York Heart Association class. The authors conclude that continuous positive airway pressure and bilevel ventilation equally and effectively improve Cheyne-Stokes respiration in patients with congestive cardiac failure.

Adolescent↗
PubMed2002

Noninvasive ventilation for acute respiratory failure.

Noninvasive ventilation (NIV) has emerged as a significant advance in the management of respiratory failure. There is now a wide body of prospective randomized-controlled trial data to support its use, particularly in the management of patients with acute or respiratory failure due to exacerbations of chronic obstructive pulmonary disease (COPD). Its successful application results in a more rapid resolution of the physiological derangements, reduces the need for intubation and, in larger studies, improves survival. A reduction in the number of infectious complications is a particular advantage. In patients with acute exacerbations of COPD there is evidence of benefit when NIV is introduced earlier in the course of the illness than would be the case for invasive ventilation and it should now be considered even with mild acidosis (pH<7.35) and tachypnoea (respiratory rate >23 breaths x min(-1)) after initial medical therapy. There is less clinical-trial data in patients with hypoxaemic respiratory failure, but again as with COPD those with less severe physiological disturbance are more likely to benefit. By contrast noninvasive continuous positive airways pressure, while being widely used has not been shown to reduce the need for intubation or to improve survival in patients with hypoxaemic respiratory failure, with the exception of acute cardiogenic pulmonary oedema. Noninvasive ventilation has been a real advance in the treatment of the critically ill. Most of the studies published to date, have excluded patients needing immediate intubation and it should be viewed as a complimentary technique rather than an alternative to invasive ventilation. It is best viewed as a means of preventing the need for endotracheal intubation and as a result should be introduced earlier than would be the case for invasive ventilation.

Acute Disease↗
PubMed2002

Where to perform noninvasive ventilation?

Noninvasive positive-pressure ventilation (NPPV) has been shown to be a means of reducing the need for endotracheal intubation, which when effective reduces the complication rate and improves outcome. Because paralysis and sedation are not needed and because the patient is not necessarily dependent upon a machine for respiration, ventilation outside the intensive care unit (ICU) is an option. A number of studies have shown that NPPV for acute exacerbations of chronic obstructive pulmonary disease (COPD) can be effective in the non-ICU environment, though usually in patients with less severe exacerbations. However, there have been no direct comparisons of the application of NPPV in different locations. The likelihood of success of the technique is an important factor in deciding there NPPV should be performed. Ready access to invasive ventilation is important when NPPV is not indicated from the outset or fails after an initial trial. In acute exacerbations of COPD, NPPV is less likely to be successful the more severe the exacerbation, as measured by the severity of acidosis. Good tolerance of NPPV, which translates into an improvement in pH and a fall in respiratory rate, predicts a successful outcome and is a useful way of monitoring progress. NPPV has been shown to be cost effective both in the ICU and when performed on general wards. A dedicated intermediate care unit with particular expertise in noninvasive modes of ventilation may provide the best environment, both in terms of outcome, but also cost effectiveness. The ideal location for noninvasive positive-pressure ventilation will vary from country to country and indeed from hospital to hospital, depending upon local factors. However, the most important factor is that staff be adequately trained in the technique and be available throughout the 24-h period.

Emergency Medical Services↗
PubMed2001

Non-invasive ventilation in the treatment of ventilatory failure following corrective spinal surgery.

Non-invasive positive pressure ventilation has previously been used successfully to treat both acute and chronic ventilatory failure secondary to a number of conditions, including scoliosis. We report two patients in whom it was used, on three separate occasions, to treat acute ventilatory failure following corrective spinal surgery. Non-invasive positive pressure ventilation may be useful postoperatively in high-risk patients undergoing major spinal surgery in an attempt to prevent intubation and its attendant complications.

Adolescent↗
PubMed2001

[Heart failure and central respiratory dysregulation. Cheyne-Stokes respiration during sleep in advanced left heart failure].

Central sleep apnoea, especially Cheyne-Stokes respiration, is found in 45 to 66% of patients with congestive heart failure (CHF) in functional classes NYHA II to IV. Cheyne-Stokes breathing cycles are characterised by central apnoeas, followed by a crescendo--like increase of tidal volume into hyperventilation and a subsequent decline of tidal volume, ending in another central apnoea. Cheyne-Stokes respiration has been shown to be a poor prognostic factor for patients with CHF. Apnoeas and hypopnoeas cause marked oxygen desaturation and rises of carbon dioxide concentrations in the blood. The resumption of breathing is frequently associated with arousals, which might cause daytime symptoms like fatigue and sleepiness as well as persistent activation of the sympathetic nervous system. Elevated concentrations of catecholamines increase cardiac work, adversely affecting cardiac function. Serum catecholamines are known to augment the chemoreceptor susceptibility for carbon dioxide. This might be one reason for the permanent mild hyperventilation found in these patients during wakefulness. Increased chemoreceptor responsiveness destabilises the feedback control of breathing, and hyperventilation below the apnoeic threshold grows more likely. Other contributing factors for the development of Cheyne-Stokes respiration include alterations in the control of breathing during sleep and the increased circulation time between the lung and chemoreceptors in CHF patients. The feedback regulation of breathing might be less dampened since carbon dioxide levels are reduced in these patients. Treatment includes nCPAP, but in many cases this is poorly tolerated in patients with central sleep apnoea. Future approaches to Cheyne-Stokes respiration might focus on improving ventilatory pattern and pharmacological manipulation of carbon dioxide receptor susceptibility.

Arousal↗
PubMed2001

Relationship between obstructive sleep apnoea, driving simulator performance, and risk of road traffic accidents.

BACKGROUND: Obstructive sleep apnoea (OSA) has been shown to be associated with an increased risk of road traffic accidents (RTAs). Predicting the driving ability and risk of RTAs in an individual with OSA is difficult. On-road testing is the gold standard, but this is time consuming, expensive, and potentially dangerous. Simple computer based driving simulators have been developed to help determine driving ability. Although patients with OSA have been shown to perform poorly compared with matched controls, it is not known whether these simulators can predict those at most risk of accidents. In this study we evaluated whether data derived from a simple driving simulator provided information over and above that obtained from the history and a sleep study that might be useful for advising patients about driving. METHODS: We examined 150 patients admitted for routine sleep studies for investigation of OSA and snoring. Each patient performed a 20 minute driving simulation and completed a questionnaire regarding their driving history and experience. RESULTS: Logistic regression analysis was used to investigate factors associated with patients' performance on the simulator. It was found that patient characteristics, older age (OR 1.05, 95% CI 1.01 to 1.09, p<0.01), female sex (OR 9.32, 95% CI 1.09 to 79.4, p<0.04), and self-reported alcohol consumption (OR 1.04, 95% CI 1.01 to 1.07, p<0.01) had the greatest influence; however, the number of self-reported near miss accidents was independently associated with a poor performance (OR 2.62, 95% CI 1.00 to 6.88, p<0.05). A further logistic regression was used to investigate whether clinical history, sleep study results, and data from the driving simulator were useful in classifying patients with OSA as having had an RTA. The number of off-road events per hour on the simulator was independently associated with a history of previous RTA (OR 1.004, 95% CI 1.0004 to 1.008, p<0.03). The Epworth score was independently associated with episodes of falling asleep at the wheel (OR 1.21, 95% CI 1.12 to 1.31, p<0.00001) and near miss accidents (OR 1.15, 95% CI 1.07 to 1.23, p<0.0001). Using this model, 100% of patients who did not have an accident could be identified, but only 10% of those who did. CONCLUSIONS: Although factors not directly related to OSA influence performance on a driving simulator, there is an independent relationship between driving ability in patients with OSA and performance on a simple computer based simulator. When combined with clinical history, it is those not reporting hypersomnolence and not having off-road events on the simulator who appear to be at least risk of adverse driving events. Poor performance on the simulator, however, relates poorly to accident history. These data require confirmation in future studies before simple computer simulators can be used in clinical practice to advise whether an individual is safe to drive.

Accidents, Traffic↗
PubMed2001

Non-invasive ventilation in acute exacerbations of chronic obstructive pulmonary disease: long term survival and predictors of in-hospital outcome.

BACKGROUND: Non-invasive ventilation (NIV) reduces the need for intubation and the mortality associated with an exacerbation of chronic obstructive pulmonary disease (COPD). This study aimed to identify factors that could be used to stratify patients according to their risk of requiring invasive mechanical ventilation. The second aim was to determine the long term survival of patients treated with and without NIV. METHODS: In this prospective multicentre randomised controlled trial 118 patients were allocated to standard treatment and 118 to NIV between November 1996 and September 1998. Arterial blood gas tensions and respiratory rate were recorded at enrolment and after 1 and 4 hours. Prognostic factors were identified using logistic regression analysis. All patients were followed until death or 1 January 1999. RESULTS: At enrolment the H(+) concentration (OR 1.22 per nmol/l, 95% CI 1.09 to 1.37, p<0.01) and PaCO2 (OR 1.14 per kPa, 95% CI 1.14 to 1.81, p<0.01) were associated with treatment failure. Allocation to NIV was protective (OR 0.39, 95% CI 0.19 to 0.80). After 4 hours of treatment improvement in acidosis (OR 0.89 per nmol/l, 95% CI 0.82 to 0.97, p<0.01) and fall in respiratory rate (OR 0.92 per breaths/min, 95% CI 0.84 to 0.99, p=0.04) were associated with success. Median length of survival was 16.8 months in those treated with NIV and 13.4 months in those receiving standard treatment (p=0.12). The trend in improved survival was attributable to prevention of death during the index admission. CONCLUSION: Initial pH and hypercapnia can be used to stratify groups of patients according to their risk of needing intubation. NIV reduces this risk and progress should be monitored using change in respiratory rate and pH. The long term survival after NIV is sufficiently good to render treatment appropriate.

Aged↗