Successful Virtual CPAP Set up in Obstructive Sleep Apnoea: A positive innovation during the pandemic

BACKGROUND

Traditionally continuous positive airways pressure (CPAP) trials for obstructive sleep apnoea (OSA) are through face to face (F2F) set up. During Covid-19 pandemic CPAP was classed as aerosol-generating hence Leeds sleep service moved to a virtual service. Patients received equipment by post followed by virtual reviews (VR). We evaluated the adherence and symptomatic benefit of postal compared to F2F method.

METHODS

Observational data were collected from databases monitoring CPAP loans. F2F patients met a sleep technician for hands on setup in 2019, and in 2020 postal patients received equipment, written guides, and links to custom made YouTube videos. All (F2F and postal) patients had a telephone and VR appointment to discuss symptoms, and CPAP machine (AirSense 10, ResMed Inc., San Diego, USA) data including data on usage and treatment apnoea-hypopnoea index (AHI). Data was analysed using unpaired T-tests, Mann-Whitney U tests, and chi-square tests to examine differences in means, medians, and proportions, respectively of the F2F and postal groups.

RESULTS

Both groups (n = 1,221, 656 F2F, 53.7%) were similar in all categories except length of CPAP trial (postal 33 vs F2F 84 days,p < 0.0001), change in AHI (postal 22.4/Hr vs F2F 25.1/Hr,p = 0.04), and trial average use (postal 4.9 vs F2F 5.2 h,p = 0.04). There was no significant difference in the proportion of patients continuing with CPAP (postal 64%, F2F 66%, p = 0.71), the improvement in Epworth Sleepiness Score (ESS) (postal 6.9/24, F2F 7.1/24, p = 0.31) or the patient's subjective rating on whether they felt much better, better, the same or worse on CPAP (p = 0.27). Logistic regression showed factors which affected odds ratios of continuing CPAP were diagnostic AHI, treatment AHI, treatment ESS and how they felt on CPAP. Trial type did not affect the odds ratios of continuing CPAP.

CONCLUSIONS

Postal CPAP trial patients had similar odds of continuing CPAP therapy compared to patients with F2F trials and achieved similar levels of ESS improvement and reporting feeling better on CPAP. This provides support for postal trials as a viable option post-pandemic.

The Noninvasive Ventilation Outcomes (NIVO) score: prediction of in-hospital mortality in exacerbations of COPD requiring assisted ventilation

Introduction

Acute exacerbations of COPD (AECOPD) complicated by acute (acidaemic) hypercapnic respiratory failure (AHRF) requiring ventilation are common. When applied appropriately, ventilation substantially reduces mortality. Despite this, there is evidence of poor practice and prognostic pessimism. A clinical prediction tool could improve decision making regarding ventilation, but none is routinely used.

Methods

Consecutive patients admitted with AECOPD and AHRF treated with assisted ventilation (principally noninvasive ventilation) were identified in two hospitals serving differing populations. Known and potential prognostic indices were identified a priori. A prediction tool for in-hospital death was derived using multivariable regression analysis. Prospective, external validation was performed in a temporally separate, geographically diverse 10-centre study. The trial methodology adhered to TRIPOD (Transparent Reporting of a Multivariable Prediction Model for Individual Prognosis or Diagnosis) recommendations.

Results

Derivation cohort: n=489, in-hospital mortality 25.4%; validation cohort: n=733, in-hospital mortality 20.1%. Using six simple categorised variables (extended Medical Research Council Dyspnoea score 1–4/5a/5b, time from admission to acidaemia >12 h, pH <7.25, presence of atrial fibrillation, Glasgow coma scale ≤14 and chest radiograph consolidation), a simple scoring system with strong prediction of in-hospital mortality is achieved. The resultant Noninvasive Ventilation Outcomes (NIVO) score had area under the receiver operating curve of 0.79 and offers good calibration and discrimination across stratified risk groups in its validation cohort.

Discussion

The NIVO score outperformed pre-specified comparator scores. It is validated in a generalisable cohort and works despite the heterogeneity inherent to both this patient group and this intervention. Potential applications include informing discussions with patients and their families, aiding treatment escalation decisions, challenging pessimism and comparing risk-adjusted outcomes across centres.

The NIVO score was created to predict in-hospital mortality in exacerbations of COPD requiring assisted ventilation. Prospective validation under real-world conditions in 10 UK hospitals shows it easily outperforms existing alternative scores.https://bit.ly/3oKMZdI

European Respiratory Society statement on sleep apnoea, sleepiness and driving risk

Obstructive sleep apnoea (OSA) is highly prevalent and is a recognised risk factor for motor vehicle accidents (MVA). Effective treatment with continuous positive airway pressure has been associated with a normalisation of this increased accident risk. Thus, many jurisdictions have introduced regulations restricting the ability of OSA patients from driving until effectively treated. However, uncertainty prevails regarding the relative importance of OSA severity determined by the apnoea–hypopnoea frequency per hour and the degree of sleepiness in determining accident risk. Furthermore, the identification of subjects at risk of OSA and/or accident risk remains elusive. The introduction of official European regulations regarding fitness to drive prompted the European Respiratory Society to establish a task force to address the topic of sleep apnoea, sleepiness and driving with a view to providing an overview to clinicians involved in treating patients with the disorder. The present report evaluates the epidemiology of MVA in patients with OSA; the mechanisms involved in this association; the role of screening questionnaires, driving simulators and other techniques to evaluate sleepiness and/or impaired vigilance; the impact of treatment on MVA risk in affected drivers; and highlights the evidence gaps regarding the identification of OSA patients at risk of MVA.

Assessment of Sleepiness in Drivers: Current Methodology and Future Possibilities

Many patients with obstructive sleep apnea syndrome (OSAS) drive a vehicle both for pleasure and as part of their employment. Some, but not all, patients with OSAS are at increased risk of being involved in road traffic accidents. Clinicians are often asked to make recommendations about an individual's fitness to drive, and these are likely to be inconsistent in the absence of objective criteria. This article discusses the current practice of the assessment of individuals' sleepiness with respect to driving, the limitations of available techniques, and future possibilities.

Acute non-invasive ventilation - getting it right on the acute medical take

Non-invasive ventilation (NIV) given to the right patient, in the right setting, in the right way and at the right time improves outcomes. However, national audits reveal poor practice in patient selection, clinical judgement, treatment initiation and availability of trained staff. NIV is indicated for persistent acute hypercapnic respiratory failure (AHRF) with acidosis after usual medical management in chronic obstructive pulmonary disease (COPD) exacerbation and even without acidosis in neuromuscular disorders or other restrictive conditions eg obesity hypoventilation or kyphoscoliosis. Having trained staff in a suitable environment with adequate equipment are keys to its success, along with close monitoring. A plan should be put in place at the time of initiating NIV about the ceiling of care, eg escalation to intubation or palliation, if the patient is not improving with NIV. Early NIV failure is most likely due to technical issues, such as inadequate pressures or mask leak, while late failure is usually the consequence of advanced disease. Any presentation with AHRF is a poor prognostic indicator and outpatient respiratory follow-up is indicated following discharge. For selected patients with COPD who remain hypercapnic 2 weeks after an exacerbation, domiciliary NIV can reduce admissions and improve survival. For patients with neuromuscular disorders or kyphoscoliosis a presentation with AHRF almost always indicates the need for domiciliary NIV.

Non-invasive ventilation: Essential requirements and clinical skills for successful practice

Audits and case reviews of the acute delivery of non-invasive ventilation (NIV) have shown that the results achieved in real life often fall short of those achieved in research trials. Factors include inappropriate selection of patients for NIV and failure to apply NIV correctly. This highlights the need for proper training of all involved individuals. This article addresses the different skills needed in a team to provide an effective NIV service. Some detail is given in each of the key areas but it is not comprehensive and should stimulate further learning (reading, attendance on courses, e-learning, etc.), determined by the needs of the individual.

A CD3-bispecific molecule targeting P-cadherin demonstrates T cell-mediated regression of established solid tumors in mice

Strong evidence exists supporting the important role T cells play in the immune response against tumors. Still, the ability to initiate tumor-specific immune responses remains a challenge. Recent clinical trials suggest that bispecific antibody-mediated retargeted T cells are a promising therapeutic approach to eliminate hematopoietic tumors. However, this approach has not been validated in solid tumors. PF-06671008 is a dual-affinity retargeting (DART®)-bispecific protein engineered with enhanced pharmacokinetic properties to extend in vivo half-life, and designed to engage and activate endogenous polyclonal T cell populations via the CD3 complex in the presence of solid tumors expressing P-cadherin. This bispecific molecule elicited potent P-cadherin expression-dependent cytotoxic T cell activity across a range of tumor indications in vitro, and in vivo in tumor-bearing mice. Regression of established tumors in vivo was observed in both cell line and patient-derived xenograft models engrafted with circulating human T lymphocytes. Measurement of in vivo pharmacodynamic markers demonstrates PF-06671008-mediated T cell activation, infiltration and killing as the mechanism of tumor inhibition.

Looking under the bonnet of patient-ventilator asynchrony during noninvasive ventilation: does it add value?

Noninvasive ventilation (NIV) has significant advantages over invasive ventilation in certain situations, such as hypercapnic respiratory failure due to an acute exacerbation of chronic obstructive pulmonary disease (COPD), acute cardiogenic pulmonary oedema, respiratory failure in immunocompromised patients and weaning from invasive ventilation in patients with COPD, in terms of reducing mortality, duration of hospital stay, the need for intubation and infectious complications [1–5].

During noninvasive ventilation it is reasonable to try to abolish clinically apparent patient-ventilator asynchronies but the use of more invasive tests to detect subtle asynchronies cannot be justifiedhttp://ow.ly/rXoA30gCm8O

Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure

Noninvasive mechanical ventilation (NIV) is widely used in the acute care setting for acute respiratory failure (ARF) across a variety of aetiologies. This document provides European Respiratory Society/American Thoracic Society recommendations for the clinical application of NIV based on the most current literature.The guideline committee was composed of clinicians, methodologists and experts in the field of NIV. The committee developed recommendations based on the GRADE (Grading, Recommendation, Assessment, Development and Evaluation) methodology for each actionable question. The GRADE Evidence to Decision framework in the guideline development tool was used to generate recommendations. A number of topics were addressed using technical summaries without recommendations and these are discussed in the supplementary material.This guideline committee developed recommendations for 11 actionable questions in a PICO (population-intervention-comparison-outcome) format, all addressing the use of NIV for various aetiologies of ARF. The specific conditions where recommendations were made include exacerbation of chronic obstructive pulmonary disease, cardiogenic pulmonary oedema, de novo hypoxaemic respiratory failure, immunocompromised patients, chest trauma, palliation, post-operative care, weaning and post-extubation.This document summarises the current state of knowledge regarding the role of NIV in ARF. Evidence-based recommendations provide guidance to relevant stakeholders.

Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure

Noninvasive mechanical ventilation (NIV) is widely used in the acute care setting for acute respiratory failure (ARF) across a variety of aetiologies. This document provides European Respiratory Society/American Thoracic Society recommendations for the clinical application of NIV based on the most current literature.The guideline committee was composed of clinicians, methodologists and experts in the field of NIV. The committee developed recommendations based on the GRADE (Grading, Recommendation, Assessment, Development and Evaluation) methodology for each actionable question. The GRADE Evidence to Decision framework in the guideline development tool was used to generate recommendations. A number of topics were addressed using technical summaries without recommendations and these are discussed in the supplementary material.This guideline committee developed recommendations for 11 actionable questions in a PICO (population-intervention-comparison-outcome) format, all addressing the use of NIV for various aetiologies of ARF. The specific conditions where recommendations were made include exacerbation of chronic obstructive pulmonary disease, cardiogenic pulmonary oedema, de novo hypoxaemic respiratory failure, immunocompromised patients, chest trauma, palliation, post-operative care, weaning and post-extubation.This document summarises the current state of knowledge regarding the role of NIV in ARF. Evidence-based recommendations provide guidance to relevant stakeholders.

Effect of Home Noninvasive Ventilation With Oxygen Therapy vs Oxygen Therapy Alone on Hospital Readmission or Death After an Acute COPD Exacerbation: A Randomized Clinical Trial

IMPORTANCE

Outcomes after exacerbations of chronic obstructive pulmonary disease (COPD) requiring acute noninvasive ventilation (NIV) are poor and there are few treatments to prevent hospital readmission and death.

OBJECTIVE

To investigate the effect of home NIV plus oxygen on time to readmission or death in patients with persistent hypercapnia after an acute COPD exacerbation.

DESIGN, SETTING, AND PARTICIPANTS

A randomized clinical trial of patients with persistent hypercapnia (Paco2 >53 mm Hg) 2 weeks to 4 weeks after resolution of respiratory acidemia, who were recruited from 13 UK centers between 2010 and 2015. Exclusion criteria included obesity (body mass index [BMI] >35), obstructive sleep apnea syndrome, or other causes of respiratory failure. Of 2021 patients screened, 124 were eligible.

INTERVENTIONS

There were 59 patients randomized to home oxygen alone (median oxygen flow rate, 1.0 L/min [interquartile range {IQR}, 0.5-2.0 L/min]) and 57 patients to home oxygen plus home NIV (median oxygen flow rate, 1.0 L/min [IQR, 0.5-1.5 L/min]). The median home ventilator settings were an inspiratory positive airway pressure of 24 (IQR, 22-26) cm H2O, an expiratory positive airway pressure of 4 (IQR, 4-5) cm H2O, and a backup rate of 14 (IQR, 14-16) breaths/minute.

MAIN OUTCOMES AND MEASURES

Time to readmission or death within 12 months adjusted for the number of previous COPD admissions, previous use of long-term oxygen, age, and BMI.

RESULTS

A total of 116 patients (mean [SD] age of 67 [10] years, 53% female, mean BMI of 21.6 [IQR, 18.2-26.1], mean [SD] forced expiratory volume in the first second of expiration of 0.6 L [0.2 L], and mean [SD] Paco2 while breathing room air of 59 [7] mm Hg) were randomized. Sixty-four patients (28 in home oxygen alone and 36 in home oxygen plus home NIV) completed the 12-month study period. The median time to readmission or death was 4.3 months (IQR, 1.3-13.8 months) in the home oxygen plus home NIV group vs 1.4 months (IQR, 0.5-3.9 months) in the home oxygen alone group, adjusted hazard ratio of 0.49 (95% CI, 0.31-0.77; P = .002). The 12-month risk of readmission or death was 63.4% in the home oxygen plus home NIV group vs 80.4% in the home oxygen alone group, absolute risk reduction of 17.0% (95% CI, 0.1%-34.0%). At 12 months, 16 patients had died in the home oxygen plus home NIV group vs 19 in the home oxygen alone group.

CONCLUSIONS AND RELEVANCE

Among patients with persistent hypercapnia following an acute exacerbation of COPD, adding home noninvasive ventilation to home oxygen therapy prolonged the time to readmission or death within 12 months.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00990132.

Factors that affect simulated driving in patients with obstructive sleep apnoea

Patients with obstructive sleep apnoea syndrome (OSAS) are at increased risk of involvement in road traffic accidents (RTAs) [1]. Clinicians diagnosing OSAS need to advise patients about driving but there are no validated tools and no robust objective data about which factors are important [2]. There are position statements, based solely on expert opinion, from various professional bodies [3–6]. In general, they conclude that a patient with significant daytime sleepiness and a recent RTA or near miss attributable to sleepiness, fatigue or inattention, should be considered a high-risk driver [3–6]. In a recent survey using clinical vignettes, we have shown that there is considerable variability in the advice that patients are likely to receive [7]. This indicates that clinicians require more robust guidance.

Objective data for advising sleep apnoea sufferers whether they are at increased risk of an accident when drivinghttp://ow.ly/TWPgm

Prevalence of and treatment outcomes for patients with obstructive sleep apnoea identified by preoperative screening compared with clinician referrals

Obstructive sleep apnoea (OSA) has implications perioperatively. We compared the prevalence of OSA and outcome with continuous positive airway pressure (CPAP) in patients diagnosed through preoperative screening and following referrals from other clinicians.Among 1412 patients (62% males) the prevalence of OSA, Epworth Sleepiness Score (ESS), the number referred for CPAP, and short and longer term use of CPAP were compared between the two groups.The prevalence of OSA was similar (62% versus 58%). There were differences in mean±sd age (61±16 versus 55±13 years; p<0.0001), ESS (11±6 versus 8±5; p<0.0001) and oxygen desaturation index (22±20 versus 19±17; p=0.039). Clinician-referred patients were more likely to be offered CPAP (p<0.0001; OR 2.84). Pre-assessment patients with mild OSA were less likely to continue CPAP long term (p=0.002; OR 6.8). No difference was seen between moderate and severe OSA patients.The prevalence of OSA was similar in both groups but pre-assessment patients were younger and less symptomatic. Preoperative screening of patients is worthwhile, independent of any effect of CPAP upon surgical outcomes; younger and less symptomatic patients are identified earlier. Pre-assessment patients with mild OSA were less likely to use CPAP; this should be considered when offering CPAP to these patients prior to surgery.

Diaphragm pacing and motor neurone disease: lessons for all?

Respiratory muscle involvement is inevitable in motor neurone disease (MND) and most patients will die a respiratory death. Noninvasive ventilation (NIV) has been shown to prolong life and improve quality of life [1]. It is therefore important to identify patients who should be offered NIV at an early stage, as a delay may result in presentation with catastrophic respiratory failure, requiring endotracheal intubation, which almost always results in an unplanned tracheostomy. It used to be considered that respiratory muscle involvement was only a feature of advanced disease, but this is not correct; if looked for there is evidence of respiratory muscle weakness in most patients by the time the diagnosis is made [2]. In a small number, the diagnosis is made when the patient presents with hypercapnic respiratory failure.

Respiratory physicians and neurologists should be cognisant of the respiratory complications of motor neurone diseasehttp://ow.ly/TIxe5

Medium-term cost-effectiveness of an automated non-invasive ventilation outpatient set-up versus a standard fixed level non-invasive ventilation inpatient set-up in obese patients with chronic respiratory failure: a protocol description

INTRODUCTION

Obesity is an escalating issue, with an accompanying increase in referrals of patients with obesity-related respiratory failure. Currently, these patients are electively admitted to hospital for initiation of non-invasive ventilation (NIV), but it is unknown whether outpatient initiation is as effective as inpatient set-up. We hypothesise that outpatient set-up using an autotitrating NIV device will be more cost-effective than a nurse-led inpatient titration and set-up.

METHODS AND ANALYSIS

We will undertake a multinational, multicentre randomised controlled trial. Participants will be randomised to receive the usual inpatient set-up, which will include nurse-led initiation of NIV or outpatient set-up with an automated NIV device. They will be stratified according to the trial site, gender and previous use of NIV or continuous positive airway pressure. Assuming a 10% dropout rate, a total sample of 82 patients will be required. Cost-effectiveness will be evaluated using standard treatment costs and health service utilisation as well as health-related quality of life measures (severe respiratory insufficiency (SRI) and EuroQol-5 dimensions (EQ-5D)). A change in the SRI questionnaire will be based on the analysis of covariance adjusting for the baseline measurements between the two arms of patients.

ETHICS AND DISSEMINATION

This study has been approved by the Westminster National Research Ethics Committee (11/LO/0414) and is the trial registered on the UKCRN portfolio. The trial is planned to start in January 2015 with publication of the trial results in 2017.

TRIAL REGISTRATION NUMBER

ISRCTN 51420481.

Variability in clinicians' opinions regarding fitness to drive in patients with obstructive sleep apnoea syndrome (OSAS)

We evaluated clinicians' current practice for giving advice to patients with obstructive sleep apnoea syndrome. Clinicians were invited to complete a web-based survey and indicate the advice they would give to patients in a number of scenarios about driving; they were also asked what they considered to be residual drowsiness and adequate compliance following CPAP treatment. In the least contentious scenario, 94% of clinicians would allow driving; in the most contentious a patient had a 50% chance of being allowed to drive. Following treatment with CPAP, clinicians' interpretation of what constituted residual drowsiness was inconsistent. In each vignette the same clinician was more likely to say 'yes' to 'excessive' than to 'irresistible' (71%±12% vs 42%±10%, p=0.0045). There was also a lack of consensus regarding 'adequate CPAP compliance'; 'yes' responses ranged from 13% to 64%. There is a need for clearer guidance; a recent update to the Driver and Vehicle Licensing Agency guidance, and a statement from the British Thoracic Society, making it clear that sleepiness while driving is the key issue, may help.

PET imaging to non-invasively study immune activation leading to antitumor responses with a 4-1BB agonistic antibody

Background

Molecular imaging with positron emission tomography (PET) may allow the non-invasive study of the pharmacodynamic effects of agonistic monoclonal antibodies (mAb) to 4-1BB (CD137). 4-1BB is a member of the tumor necrosis factor family expressed on activated T cells and other immune cells, and activating 4-1BB antibodies are being tested for the treatment of patients with advanced cancers.

Methods

We studied the antitumor activity of 4-1BB mAb therapy using [¹⁸ F]-labeled fluoro-2-deoxy-2-D-glucose ([¹⁸ F]FDG) microPET scanning in a mouse model of colon cancer. Results of microPET imaging were correlated with morphological changes in tumors, draining lymph nodes as well as cell subset uptake of the metabolic PET tracer in vitro.

Results

The administration of 4-1BB mAb to Balb/c mice induced reproducible CT26 tumor regressions and improved survival; complete tumor shrinkage was achieved in the majority of mice. There was markedly increased [¹⁸ F]FDG signal at the tumor site and draining lymph nodes. In a metabolic probe in vitro uptake assay, there was an 8-fold increase in uptake of [³H]DDG in leukocytes extracted from tumors and draining lymph nodes of mice treated with 4-1BB mAb compared to untreated mice, supporting the in vivo PET data.

Conclusion

Increased uptake of [¹⁸ F]FDG by PET scans visualizes 4-1BB agonistic antibody-induced antitumor immune responses and can be used as a pharmacodynamic readout to guide the development of this class of antibodies in the clinic.

Provision of home mechanical ventilation and sleep services for England survey

The Department of Health is promoting the generation of specialist networks to manage long term ventilatory weaning and domiciliary non-invasive ventilation patients. Currently the availability of these services in England is not known. We performed a short survey to establish the prevalence of sleep and ventilation diagnostic and treatment services. The survey focussed on diagnostic services and Home Mechanical Ventilation (HMV) provision, and was divided into (a) availability of diagnostics, (b) funding, and (c) patient groups. This survey has confirmed that the majority of Home Mechanical Ventilation set-ups are currently for Obesity Related Respiratory Failure and Chronic Obstructive Pulmonary Disease. We have found that there is variable provision of diagnostic services, with the majority of units offering overnight oximetry (95%) but only 55% of responders providing a home mechanical ventilation service. Even more interestingly, less than two thirds of units charged their primary care trust for this service. These data may assist in the development of regional networks and specialist home mechanical ventilation centres.

Abstract 2336: Assessment of mechanisms of action (MOAs) of the Fc-engineered integrin α5β1 targeting antibody PF-04605412 in human integrin α5 knock-in mice

Integrin α5β1 plays an important role in tumor angiogenesis, invasion, and metastasis. Overexpression of α5β1 has been associated with poor prognosis in various types of cancers, and also plays a critical role in the resistance of cancers to radiotherapy and chemotherapy. We have previously reported that PF-04605412 (PF-5412), a fully human Fc-engineered IgG1 mAb against human α5β1, displayed robust and dose-dependent antitumor efficacy in multiple preclinical tumor models. Assessment of PF-5412 mechanism of action (MOA) in standard mouse xenograft models has been limited, however, because this antibody does not cross-react with murine integrin α5. To further our understanding of PF-5412 MOAs, we generated human integrin α5 knock-in mice (ITGA5 KI) in which the entire murine coding sequence of integrin α5 was replaced with the corresponding human coding sequence. Mice that were homozygous for human integrin α5 were viable and no abnormal phenotype or behavior was observed. qPCR and FACS analyses showed that human integrin α5 was expressed in various types of tissues and peripheral blood in ITGA5 KI mice, whereas no mouse integrin α5 was detected. Murine integrin β1 expression in ITGA5 KI mice was comparable to wild type mice. Growth of MC38 murine CRC tumors engineered to express human α5 was inhibited by treatment with PF-5412 in a dose-dependent manner. Tumor regression was observed at high doses of PF-5412 but not at comparable dose levels of α5 antibodies lacking ADCC activity (IgG4). IHC analyses of CD31 positive vessels showed that PF-5412 significantly inhibited blood vessel density and induced greater macrophages infiltration into tumors than non-ADCC-inducing antibodies. Notably, parental MC38 tumors lacking endogenous human α5 expression were also controlled by PF-5412 treatment (60% TGI) in ITGA5 KI mice. PF-5412 efficacy in this model also exceeded that of non-ADCC-inducing antibodies. Immunohistochemistry (IHC) analyses showed that PF-5412 treatment significantly decreased blood vessel density in the parental MC38 tumors. These results demonstrate that PF-5412 benefit does not depend on integrin α5β1 expression by the tumor cell itself, and support the hypothesis that ADCC-mediated killing of tumor endothelium will confer clinical benefit. The results showed here indicate that ITGA5 KI mouse is a relevant model for evaluating anti-human integrin α5 antibody MOA.

Citation Format: Lianglin Zhang, Jeffrey L. Stock, Mark W. Elliott, Enhong Chen, Thao Nguyen, Anthony Wong, Craig B. Davis, James G. Christensen. Assessment of mechanisms of action (MOAs) of the Fc-engineered integrin α5β1 targeting antibody PF-04605412 in human integrin α5 knock-in mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2336. doi:10.1158/1538-7445.AM2013-2336

Continuous measures of driving performance on an advanced office-based driving simulator can be used to predict simulator task failure in patients with obstructive sleep apnoea syndrome

INTRODUCTION

Some patients with obstructive sleep apnoea syndrome are at higher risk of being involved in road traffic accidents. It has not been possible to identify this group from clinical and polysomnographic information or using simple simulators. We explore the possibility of identifying this group from variables generated in an advanced PC-based driving simulator.

METHODS

All patients performed a 90 km motorway driving simulation. Two events were programmed to trigger evasive actions, one subtle and an alert driver should not crash, while for the other, even a fully alert driver might crash. Simulator parameters including standard deviation of lane position (SDLP) and reaction times at the veer event (VeerRT) were recorded. There were three possible outcomes: 'fail', 'indeterminate' and 'pass'. An exploratory study identified the simulator parameters predicting a 'fail' by regression analysis and this was then validated prospectively.

RESULTS

72 patients were included in the exploratory phase and 133 patients in the validation phase. 65 (32%) patients completed the run without any incidents, 45 (22%) failed, 95 (46%) were indeterminate. Prediction models using SDLP and VeerRT could predict 'fails' with a sensitivity of 82% and specificity of 96%. The models were subsequently confirmed in the validation phase.

CONCLUSIONS

Using continuously measured variables it has been possible to identify, with a high degree of accuracy, a subset of patients with obstructive sleep apnoea syndrome who fail a simulated driving test. This has the potential to identify at-risk drivers and improve the reliability of a clinician's decision-making.

Non-invasive ventilation: established and expanding roles

Non-invasive ventilation (NIV) has become the standard of care for most patients with ventilatory failure due to an acute exacerbation of chronic obstructive pulmonary disease (COPD). In all but a small minority, even of the very sickest, there is little to be lost by at least a short trial of NIV. In patients with acute cardiogenic pulmonary oedema, NIV results in a more rapid physiological improvement and resolution of dyspnoea, but the benefits in terms of survival have been called into question by two recent randomised controlled trials. There are no randomised controlled trials of NIV in patients with acute ventilatory failure due to obesity but the outcome from invasive ventilation is poor and the results of NIV encouraging. Finally, NIV may have a role during the transition from active care, aimed to extend life, to palliative care.

Quantification of lung surface area using computed tomography

Objective

To refine the CT prediction of emphysema by comparing histology and CT for specific regions of lung. To incorporate both regional lung density measured by CT and cluster analysis of low attenuation areas for comparison with histological measurement of surface area per unit lung volume.

Methods

The histological surface area per unit lung volume was estimated for 140 samples taken from resected lung specimens of fourteen subjects. The region of the lung sampled for histology was located on the pre-operative CT scan; the regional CT median lung density and emphysematous lesion size were calculated using the X-ray attenuation values and a low attenuation cluster analysis. Linear mixed models were used to examine the relationships between histological surface area per unit lung volume and CT measures.

Results

The median CT lung density, low attenuation cluster analysis, and the combination of both were important predictors of surface area per unit lung volume measured by histology (p < 0.0001). Akaike's information criterion showed the model incorporating both parameters provided the most accurate prediction of emphysema.

Conclusion

Combining CT measures of lung density and emphysematous lesion size provides a more accurate estimate of lung surface area per unit lung volume than either measure alone.

Nitric oxide synthase isoenzyme expression and activity in peripheral lung tissue of patients with chronic obstructive pulmonary disease

RATIONALE

Nitric oxide (NO) is increased in the lung periphery of patients with chronic obstructive pulmonary disease (COPD). However, expression of the NO synthase(s) responsible for elevated NO has not been identified in the peripheral lung tissue of patients with COPD of varying severity.

OBJECTIVES

METHODS

Protein and mRNA expression of nitric oxide synthase type I (neuronal NOS [nNOS]), type II (inducible NOS [iNOS]), and type III (endothelial NOS [eNOS]) were quantified by Western blotting and reverse transcription-polymerase chain reaction, respectively, in specimens of surgically resected lung tissue from nonsmoker control subjects, patients with COPD of varying severity, and smokers without COPD, and in a lung epithelial cell line (A549). The effects of nitrative/oxidative stress on NOS expression and activity were also evaluated in vitro in A549 cells. nNOS nitration was quantified by immunoprecipitation and dimerization of nNOS was detected by low-temperature SDS-PAGE/Western blot in the presence of the peroxynitrite generator, 3-morpholinosydnonimine-N-ethylcarbamide (SIN1), in vitro and in vivo.

MEASUREMENTS AND MAIN RESULTS

Lung tissue from patients with severe and very severe COPD had graded increases in nNOS (mRNA and protein) compared with nonsmokers and normal smokers. Hydrogen peroxide (H(2)O(2)) and SIN1 as well as the cytokine mixture (IFN-gamma, IL-1beta, and tumor necrosis factor-alpha) increased mRNA expression and activity of nNOS in A549 cells in a concentration-dependent manner compared with nontreated cells. Tyrosine nitration resulted in an increase in nNOS activity in vitro, but did not affect its dimerization.

CONCLUSIONS

Patients with COPD have a significant increase in nNOS expression and activity that reflects the severity of the disease and may be secondary to oxidative stress.

Acceptance, effectiveness and safety of continuous positive airway pressure in acute stroke: a pilot study

OBJECTIVES

To evaluate the acceptance, effectiveness in preventing upper airways obstruction, and haemodynamic effects of continuous positive airway pressure (CPAP) in acute stroke.

METHODS

Twelve patients (4 M, and 8 F; mean (SD), 75.2 (5.5) years) within 48 h of acute stroke onset underwent: (1) sleep studies (1st night: auto-CPAP mode; 2nd night: diagnostic); (2) nocturnal non-invasive blood pressure studies (1st night during CPAP; 2nd night during spontaneous breathing (SB)); and (3) daytime cerebral blood flow velocity measurement in middle cerebral artery (FV) with transcranial Doppler during SB and with CPAP (5, 10, 15 cm H(2)O).

RESULTS

Ninety percent, 60% and 50% of stroke patients had a respiratory disturbance index (RDI) of >or=5, >or=10 and >or=15 events per hour, respectively (18.2 (11.3)). CPAP acceptance was 84%; 42% used CPAP more than 6h and 42% between 1-3h with a mean use of CPAP of 5.2h (4.0). Compared to SB, CPAP reduced, though not significantly, RDI, time with SaO(2)<90%, mean blood pressure and mean blood pressure dips (10 mm Hg)/h. Compared with SB, any level of CPAP progressively and significantly reduced systolic and mean FV; drop in diastolic FV was significant at CPAP10 and CPAP15. The partial pressure of end-tidal CO(2) was significantly lowered by all levels of CPAP.

CONCLUSIONS

According to this pilot study, CPAP is reasonably well tolerated by patients with acute stroke for at least one night. Despite its possible beneficial effect on obstructive sleep-disordered breathing and blood pressure variability, CPAP use in acute stroke should be still considered with caution due to possible harmful haemodynamic effects at higher pressures.

An unusual exacerbation of chronic obstructive pulmonary disease (COPD) with herpes simplex tracheitis: case report

Chronic obstructive pulmonary disease (COPD) is a common cause of morbidity in the UK and is increasingly seen in elderly patients, often requiring multiple courses of steroids. We present a case of a 72 year old lady with repeated exacerbations of COPD which did not respond to conventional treatment. Herpes simplex virus (HSV1) tracheobronchitis was diagnosed following a rigid bronchoscopy and her symptoms improved with intravenous acyclovir. This is the first published case of HSV tracheitis in a non immunosuppressed individual with chronic lung disease.

The effect of mouth leak and humidification during nasal non-invasive ventilation

BACKGROUND

Poor mask fit and mouth leak are associated with nasal symptoms and poor sleep quality in patients receiving domiciliary non-invasive ventilation (NIV) through a nasal mask. Normal subjects receiving continuous positive airways pressure demonstrate increased nasal resistance following periods of mouth leak. This study explores the effect of mouth leak during pressure-targeted nasal NIV, and whether this results in increased nasal resistance and consequently a reduction in effective ventilatory support.

METHODS

A randomised crossover study of 16 normal subjects was performed on separate days. Comparison was made of the effect of 5 min of mouth leak during daytime nasal NIV with and without heated humidification. Expired tidal volume (V(T)), nasal resistance (R(N)), and patient comfort were measured.

RESULTS

Mean change (Delta) in V(T) and R(N) were significantly less following mouth leak with heated humidification compared to the without (DeltaV(T) -36+/-65 ml vs. -88+/-50 ml, p<0.001; DeltaR(N) +0.9+/-0.4 vs. +2.0+/-0.7 cm H(2)O l s(-1), p<0.001). Baseline comfort was worse without humidification (5.3+/-0.4 vs. 6.2+/-0.4, p<0.01), and only deteriorated following mouth leak without humidification.

CONCLUSIONS

In normal subjects, heated humidification during nasal NIV attenuates the adverse effects of mouth leak on effective tidal volume, nasal resistance and improves overall comfort. Heated humidification should be considered as part of an approach to patients who are troubled with nasal symptoms, once leak has been minimised.

Daytime variability in carotid baroreflex function in healthy human subjects

Variability of blood pressure is limited by arterial baroreceptors, yet blood pressure still shows circadian changes. This study was undertaken to examine if the responses to the carotid baroreflex also change throughout the day. Responses of cardiac interval (RR), mean arterial pressure (MAP) and vascular resistance (VR) to carotid baroreflex stimulation and inhibition using pressures and suction applied to a neck chamber, were measured in 14 healthy, normotensive subjects. Studies were carried out at three hourly intervals between 09:00 and 21:00 hours. Stimulus-response curves were defined and the first differential of the curve was calculated to establish reflex sensitivity (maximal slope) and "operating" point (estimated carotid sinus pressure at point of maximum slope, OP). The principal findings are: (1) baroreflex sensitivity for the control of VR was at its highest at 09:00 (-3.4 +/- 0.6 units) compared to 12:00 (-1.9 +/- 0.4 units), 15:00 (-2.0 +/- 0.4 units) and 18:00 (-1.9 +/- 0.3 units) (all P < 0.05); (2) baroreflex OP for the control of MAP was at its lowest at 09:00 (P < 0.01); (3) baroreflex sensitivity for control of VR was significantly correlated with prevailing mean pressure (P < 0.05) and OP for the control of MAP (P < 0.02); (4) OP for control of RR, MAP and VR are all highly correlated to prevailing MAP (P < 0.0001). Our results suggest that baroreflex function varies throughout the day and this favors higher sensitivity and lower blood pressure in the mornings. We speculate that this may be of importance in long-term blood pressure regulation.

Daytime variability of baroreflex function in patients with obstructive sleep apnoea: implications for hypertension

Obstructive events during sleep in patients with obstructive sleep apnoea (OSA) cause large alterations in blood pressure, and this may lead to changes in baroreflex function with implications for long-term blood pressure control. This study examined the daytime variations in the responses to carotid baroreceptor stimulation in OSA patients. We determined the cardiac and vascular responses every 3 h between 09.00 and 21.00 h in 20 patients with OSA, using graded suctions and pressures applied to a neck collar. These responses were plotted against estimated carotid sinus pressures and, from these plots, baroreflex sensitivities and operating points were taken as the maximal slopes and the corresponding carotid sinus pressures, respectively. We found that at 09.00 h, sensitivity for the control of vascular resistance was at its lowest (--1.2 +/- 0.2% mmHg(-1), compared with --1.9 +/- 0.3% mmHg(-1) at 12.00 h, P < 0.02) and operating point for control of mean arterial pressure was at its highest (101.1 +/- 5.8 mmHg, compared with 94.1 +/- 5.8 mmHg at 12.00 h, P < 0.05). This is in contrast to previous data from normal subjects, in whom sensitivity was highest and operating point lowest at 09.00 h. We suggest that the higher baroreflex sensitivity and lower operating point seen in the mornings in normal subjects may provide a protective mechanism against hypertension and that this protection is absent in patients with OSA. It is possible that the reduced reflex sensitivity and increased operating point in the mornings may actually promote hypertension.

Titration of non-invasive positive pressure ventilation in chronic respiratory failure

Non-invasive ventilation (NIV) is widely used for acute and chronic respiratory failure. If arterial blood gas tensions do not improve, the level of support can be increased. However, there may be a limit above which increasing ventilatory support leads only to greater interface leak with no improvement in ventilation. The aim of this study was to establish whether there is such a limit. During a daytime study in 24 ventilated stable patients (10 with chronic obstructive pulmonary disease (COPD), 14 with chest wall deformity, CWD), inspiratory pressures up to 20 cm H(2)O and set tidal volumes up to 10 ml kg(-1) were associated with mask leak of <5 l min(-1). Although leak increased with higher levels of support, there was still an increase in minute ventilation. The mean (2 sd) tolerated pressure was 24 cm H(2)O (8-40) in both groups, and set tidal volume 12.7 ml kg(-1) (5.0-20.4) in CWD and 9.6 ml kg(-1) (3.9-14.8) in COPD. Measures of respiratory effort were significantly reduced at all levels with both forms of ventilatory support. There is debate about whether the therapeutic aim of NIV should be to reduce respiratory muscle effort, or to reverse nocturnal hypoventilation. We conclude that if the primary aim is to improve arterial blood gas tensions and this is not achieved, higher levels of ventilation can be obtained using greater pressure or volume, despite additional interface leak. If the aim is to abolish muscle effort completely, there is little to be gained by increasing the level of inspiratory pressure above 20 (CWD) or 25 (COPD) cm H(2)O.

Interaction of chemoreceptor and baroreceptor reflexes by hypoxia and hypercapnia - a mechanism for promoting hypertension in obstructive sleep apnoea

Asphyxia, which occurs during obstructive sleep apnoeic events, alters the baroreceptor reflex and this may lead to hypertension. We have recently reported that breathing an asphyxic gas resets the baroreceptor-vascular resistance reflex towards higher pressures. The present study was designed to determine whether this effect was caused by the reduced oxygen tension, which affects mainly peripheral chemoreceptors, or by the increased carbon dioxide, which acts mainly on central chemoreceptors. We studied 11 healthy volunteer subjects aged between 20 and 55 years old (6 male). The stimulus to the carotid baroreceptors was changed using graded pressures of -40 to +60 mmHg applied to a neck chamber. Responses of vascular resistance were assessed in the forearm from changes in blood pressure (Finapres) divided by brachial blood flow velocity (Doppler) and cardiac responses from the changes in RR interval and heart rate. Stimulus-response curves were defined during (i) air breathing, (ii) hypoxia (12% O(2) in N(2)), and (iii) hypercapnia (5% CO(2) in 95% O(2)). Responses during air breathing were assessed both prior to and after either hypoxia or hypercapnia. We applied a sigmoid function or third order polynomial to the curves and determined the maximal differential (equivalent to peak sensitivity) and the corresponding carotid sinus pressure (equivalent to 'set point'). Hypoxia resulted in an increase in heart rate but no significant change in mean blood pressure or vascular resistance. However, there was an increase in vascular resistance in the post-stimulus period. Hypoxia had no significant effect on baroreflex sensitivity or 'set point' for the control of RR interval, heart rate or mean arterial pressure. Peak sensitivity of the vascular resistance response to baroreceptor stimulation was significantly reduced from -2.5 +/- 0.4 units to -1.4 +/- 0.1 units (P < 0.05) and this was restored in the post-stimulus period to -2.6 +/- 0.5 units. There was no effect on 'set point'. Hypercapnia, on the other hand, resulted in a decrease in heart rate, which remained reduced in the post-stimulus period and significantly increased mean blood pressure. Baseline vascular resistance was significantly increased and then further increased in the post-control period. Like hypoxia, hypercapnia had no effect on baroreflex control of RR interval, heart rate or mean arterial pressure. There was, also no significant change in the sensitivity of the vascular resistance responses, however, 'set point' was significantly increased from 74.7 +/- 4 to 87.0 +/- 2 mmHg (P < 0.02). This was not completely restored to pre-stimulus control levels in the post-stimulus control period (82.2 +/- 3 mmHg). These results suggest that the hypoxic component of asphyxia reduces baroreceptor-vascular resistance reflex sensitivity, whilst the hypercapnic component is responsible for increasing blood pressure and reflex 'set point'. Hypercapnia appears to have a lasting effect after the removal of the stimulus. Thus the effect of both peripheral and central chemoreceptors on baroreflex function may contribute to promoting hypertension in patients with obstructive sleep apnoea.

Randomised crossover study of pressure and volume non-invasive ventilation in chest wall deformity

BACKGROUND

Non-invasive ventilation is an established treatment for chronic respiratory failure due to chest wall deformity. There are few data available to inform the choice between volume and pressure ventilators. The aim of this study was to compare pressure and volume targeted ventilation in terms of diurnal arterial blood gas tensions, lung volumes, hypercapnic ventilatory responses, sleep quality, and effect on daytime function and health status when ventilators were carefully set to provide the same minute ventilation.

METHODS

Thirteen patients with chest wall deformity underwent a 4 week single blind randomised crossover study using the Breas PV403 ventilator in either pressure or volume mode with assessments made at the end of each 4 week period.

RESULTS

Minute ventilation at night was less than that set during the day with greater leakage for both modes of ventilation. There was more leakage with pressure than volume ventilation (13.8 (1.9) v 5.9 (1.0) l/min, p = 0.01). There were no significant differences in sleep quality, daytime arterial blood gas tensions, lung mechanics, ventilatory drive, health status or daytime functioning.

CONCLUSIONS

These data suggest that pressure and volume ventilation are equivalent in terms of the effect on nocturnal and daytime physiology, and resulting daytime function and health status.

Sleep disordered breathing following stroke

In recent years there has been increasing interest in the relationship between obstructive sleep apnoea and stroke. It is clear that many patients who have had a stroke have marked obstructive sleep apnoea. This is seen during recovery but also during the acute phase when transient hypoxaemia and the blood pressure swings associated with upper airway obstruction, may worsen the ischaemic penumbra of the area of the brain which is compromised, leading to a worse outcome. There is some evidence to support this hypothesis. This article explores these issues.

Effect of upper airway obstruction on blood pressure variability after stroke

Approx. 60% of acute stroke patients have periods of significant UAO (upper airway obstruction) and this is associated with a worse outcome. UAO is associated with repeated fluctuation in BP (blood pressure) and increased BP variability is also associated with a poor outcome in patients with acute stroke. UAO-induced changes in BP, at a time when regional cerebral perfusion is pressure-dependent in areas of critically ischaemic brain, could explain the detrimental effect of UAO on outcome in these patients. The aim of the present study was to examine the relationship between UAO and BP variability in patients with acute stroke. Twelve acute stroke patients and 12 age-, sex- and BMI (body mass index)-matched controls underwent a sleep study with non-invasive continuous monitoring of BP to assess the impact of UAO on BP control after stroke. Stroke patients had significantly more 15 mmHg dips in BP/h than the controls (51 compared with 6.7 respectively; P<0.004). Stroke patients also demonstrated significantly higher BP variability than the controls (26.8 compared with 14.4 mmHg; P<0.001). There were significantly more 15 mmHg dips in BP/h in stroke patients who had significant UAO than those who did not (85.7 compared with 29.5 respectively; P<0.032). Furthermore, stroke patients without UAO (RDI <10, where RDI is respiratory disturbance index) had significantly more 15 mmHg dips in BP/h than the controls (29.5 compared with 6.7 respectively; P<0.037). There was a positive correlation between the severity of UAO (RDI) and 15 mmHg dips in BP/h (r=0.574, P<0.005) in stroke patients. Our results suggest that UAO alone does not explain BP variation post-stroke, but it does play an important role, particularly in determining the severity of the BP fluctuation.

Co-morbidity and acute decompensations of COPD requiring non-invasive positive-pressure ventilation

OBJECTIVE

To assess the prevalence and the impact of chronic and/or acute non-respiratory co-morbidity on short and longer-term outcome of non-invasive positive pressure ventilation (NIPPV) in acute decompensations of chronic obstructive pulmonary disease (COPD) with acute hypercapnic respiratory failure (AHRF).

DESIGN AND SETTING

An observational study in a three-bed respiratory monitoring unit in a respiratory ward of a non-university hospital.

PATIENTS

We grouped 120 consecutive COPD patients requiring NIPPV for AHRF (pH 7.28+/-0.05, PaO2/FIO2 ratio 192+/-63, PaCO2 78.3+/-12.3 mmHg) according to whether NIPPV succeeded (n=98) or failed (n=22) in avoiding the need for endotracheal intubation and whether alive (n=77) or dead (n=42) at 6 months.

MEASUREMENTS AND RESULTS

The prevalence of chronic and acute co-morbidity was, respectively, 20% and 41.7%; most of the cases were cardiovascular. In-hospital NIPPV failure was greater in patients with than in those without chronic (33.3% vs. 14.6%) or acute co-morbidity (32% vs. 8.6%). Six-month mortality was worse in patients with than in those without chronic (54.2% vs. 30.5%) or more than one acute co-morbidity (66.7% vs. 30.8%). Multiple regression analysis predicted in-hospital NIPPV failure by acute co-morbidity and forced expiratory volume in 1 s, while death at 6 months was predicted by having more than one acute co-morbidity, non-cardiovascular chronic co-morbidity and Activities of Daily Living score.

CONCLUSIONS

Chronic and acute co-morbidities are common in COPD patients with AHRF needing NIPPV and their presence influences short and longer-term outcome.

Effects of simulated obstructive sleep apnoea on the human carotid baroreceptor-vascular resistance reflex

Obstructive sleep apnoea (OSA), which is characterized by periodic inspiratory obstruction, is associated with hypertension and possibly with changes in the baroreceptor reflex. In this investigation we induced changes in inspiratory resistance and in inspiratory oxygen and carbon dioxide content, which simulate some of the changes in OSA, to determine whether this caused changes in the gain or setting of the carotid baroreflex. In eight healthy subjects (aged 21-62 years) we changed the stimulus to carotid baroreceptors, using neck chambers and graded pressures of -40 to +60 mmHg, and assessed vascular resistance responses in the brachial artery from changes in blood pressure (Finapres) divided by brachial artery blood flow velocity (Doppler ultrasound). Stimulus-response curves were defined during (a) sham (no additional stimulus), (b) addition of an inspiratory resistance (inspiratory pressure -10 mmHg), (c) breathing asphyxic gas (12% O(2), 5% CO(2)), and (d) combined resistance and asphyxia. Sigmoid or polynomial functions were applied to the curves and maximum differentials (equivalent to peak gain) and the corresponding carotid pressures (equivalent to 'set point') were determined. The sham test had no effect on either gain or 'set point'. Inspiratory resistance alone had no effect on blood pressure and did not displace the curve. However, it reduced gain from -3.0 +/- 0.6 to -2.1 +/- 0.4 units (P < 0.05). Asphyxia alone did increase blood pressure (+7.0 +/- 1.1 mmHg, P < 0.0005) and displaced the curve to higher pressures by +16.8 +/- 2.1 mmHg (P < 0.0005). However, it did not affect gain. The combination of resistance and asphyxia both reduced gain and displaced the curve to higher pressures. These results suggest that inspiratory resistance and asphyxia cause changes in the baroreceptor reflex which could lead to an increase in blood pressure. These changes, if sustained, could provide a mechanism linking hypertension to obstructive sleep apnoea.

Effect of upper airway obstruction in acute stroke on functional outcome at 6 months

BACKGROUND

The aim of this study was to determine whether upper airway obstruction occurring within the first 24 hours of stroke onset has an effect on outcome following stroke at 6 months. Traditional definitions used for obstructive sleep apnoea (OSA) are arbitrary and may not apply in the acute stroke setting, so a further aim of the study was to redefine respiratory events and to assess their impact on outcome.

METHODS

120 patients with acute stroke underwent a sleep study within 24 hours of onset to determine the severity of upper airway obstruction (respiratory disturbance index, RDI-total study). Stroke severity (Scandinavian Stroke Scale, SSS) and disability (Barthel score) were also recorded. Each patient was subsequently followed up at 6 months to determine morbidity and mortality.

RESULTS

Death was independently associated with SSS (OR (95% CI) 0.92 (0.88 to 0.95), p<0.00001) and RDI-total study (OR (95% CI) 1.07 (1.03 to 1.12), p<0.01). The Barthel index was independently predicted by SSS (p = 0.0001; r = 0.259; 95% CI 0.191 to 0.327) and minimum oxygen saturation during the night (p = 0.037; r = 0.16; 95% CI 0.006 to 0.184). The mean length of the respiratory event most significantly associated with death at 6 months was 15 seconds (sensitivity 0.625, specificity 0.525) using ROC curve analysis.

CONCLUSION

The severity of upper airway obstruction appears to be associated with a worse functional outcome following stroke, increasing the likelihood of death and dependency. Longer respiratory events appear to have a greater effect. These data suggest that long term outcome might be improved by reducing upper airway obstruction in acute stroke.