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.

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.

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.

Hypoxic challenge flight assessments in patients with severe chest wall deformity or neuromuscular disease at risk for nocturnal hypoventilation.

BACKGROUND: The British Thoracic Society (BTS) recommendations for patients with respiratory disease planning air travel suggest that an oxygen saturation (SaO(2)) >95% precludes the need for any further assessment of the need for supplemental oxygen during flight. A hypoxic challenge test (HCT) is recommended for patients with a resting SaO(2) between 92% and 95% with an additional risk factor, including kyphoscoliosis (KS) or neuromuscular disease (NMD). However, this recommendation was based on very few data. PATIENTS AND METHODS: HCTs were performed on 19 adult patients with KS and/or NMD (age 22-73 years, forced expiratory volume in 1 s (FEV(1)) 0.76, forced vital capacity (FVC) 0.92, SaO(2) 95%, partial pressure of arterial CO(2) (PaCO(2)) 5.7 kPa) who were at risk for nocturnal hypoventilation. 15 were home ventilator users. Arterial blood gas measurements were made before and at the end of the hypoxic challenge. RESULTS: The results of HCTs show that the majority (15 of 19) of this cohort of patients met the criteria suggested by the BTS Standards of Care Committee for in-flight oxygen regardless of baseline SaO(2). CONCLUSIONS: This finding suggests that all patients with severe extrapulmonary restrictive lung disease should undergo assessment with HCT prior to air travel. The study confirms that even patients with a resting saturation of >95% can desaturate significantly during hypoxic challenge. This study does not address the question of whether desaturation at altitude has any adverse consequences for patients. A decision as to whether it is safe for a patient to fly should be made by an experienced clinician and based on a number of factors, which should include previous travel experience, the patient's overall condition and the results of an HCT.

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.

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.

Inspiratory muscle relaxation rate after voluntary maximal isocapnic ventilation in humans.

We have investigated whether the capacity of the inspiratory muscles to generate pressure and flow during a ventilatory load is related to changes in inspiratory muscle relaxation rate. Five highly motivated normal subjects performed voluntary maximal isocapnic ventilation (MIV) for 2 min. Minute ventilation and esophageal, gastric, and transdiaphragmatic pressures were measured breath by breath. We observed that ventilation, peak inspiratory and expiratory pressures, and inspiratory flow rate declined from the start of the run to reach a plateau at 60 s that was sustained for the remainder of the exercise. In a subsequent series of studies, MIV was performed for variable durations between 15 and 120 s. The normalized maximum relaxation rate of unoccluded inspiratory sniffs (sniff MRR, %pressure loss/10 ms) was determined immediately on stopping MIV. Sniff MRR slowed as the duration of MIV increased and paralleled the decline in inspiratory pressure and ventilation observed during the 2-min exercise. No further slowing in MRR occurred when ventilation became sustainable. We conclude that, during MIV, the progressive loss of ventilation and capacity to generate pressure is associated with the early onset and progression of a peripheral fatiguing process within the inspiratory muscles.

Randomised controlled comparison of continuous positive airways pressure, bilevel non-invasive ventilation, and standard treatment in emergency department patients with acute cardiogenic pulmonary oedema.

BACKGROUND: Continuous positive airways pressure (CPAP) and bilevel non-invasive ventilation may have beneficial effects in the treatment of patients with acute cardiogenic pulmonary oedema. The efficacy of both treatments was assessed in the UK emergency department setting, in a randomised comparison with standard oxygen therapy. METHODS: Sixty patients presenting with acidotic (pH<7.35) acute, cardiogenic pulmonary oedema, were randomly assigned conventional oxygen therapy, CPAP (10 cm H(2)O), or bilevel ventilation (IPAP 15 cm H(2)O, EPAP 5 cm H(2)O) provided by a standard ventilator through a face mask. The main end points were treatment success at two hours and in-hospital mortality. Analyses were by intention to treat. RESULTS: Treatment success (defined as all of respiratory rate<23 bpm, oxygen saturation of>90%, and arterial blood pH>7.35 (that is, reversal of acidosis), at the end of the two hour study period) occurred in three (15%) patients in the control group, seven (35%) in the CPAP group, and nine (45%) in the bilevel group (p = 0.116). Fourteen (70%) of the control group patients survived to hospital discharge, compared with 20 (100%) in the CPAP group and 15 (75%) in the bilevel group (p = 0.029; Fisher's test). CONCLUSIONS: In this study, patients presenting with acute cardiogenic pulmonary oedema and acidosis, were more likely to survive to hospital discharge if treated with CPAP, rather than with bilevel ventilation or with conventional oxygen therapy. There was no relation between in hospital survival and early physiological changes. Survival rates were similar to other studies despite a low rate of endotracheal intubation.

Pitfalls of bone mineral density evaluation by dual-photon absorptiometry.

Material absorbing photons aligned with the lumbar vertebrae can create falsely elevated measurements of bone mineral density during dual-photon absorptiometry. Three cases illustrating this phenomenon are presented. Although bone mineral density was overestimated in each case, calculated fracture risk was normal in two cases and greatly increased in the third. Photon-absorbing material can create overestimates of bone mineral density during dual-photon absorptiometry, even when a greatly increased fracture risk is computed.

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.

Non-invasive mechanical ventilation for acute respiratory failure.

The value of mechanical ventilation using intermittent positive pressure ventilation delivered non-invasively by nasal mask was assessed in six patients with life threatening exacerbations of chronic respiratory disease. Median (range) arterial oxygen and carbon dioxide tensions were 4.4 (3.5-7.2) kPa and 8.7 (5.5-10.9) kPa respectively, with four patients breathing air and two controlled concentrations of oxygen. The arterial oxygen tension increased with mechanical ventilation to a median (range) of 8.7 (8.0-12.6) kPa and the carbon dioxide tension fell to 8.2 (6.5-9.2) kPa. Four patients discharged after a median of 10 (8-17) days in hospital were well five to 22 months later. One died at four days of worsening sputum retention and another after five weeks using the ventilator for 12-16 hours each day while awaiting heart-lung transplantation. This technique of mechanical ventilation avoids endotracheal intubation and can be used intermittently. Hypercapnic respiratory failure can be relieved in patients with either restrictive or obstructive lung disease in whom controlled oxygen treatment results in unacceptable hypercapnia. Respiratory assistance can be tailored to individual need and undertaken without conventional intensive care facilities.

Non-invasive ventilation--mechanisms of benefit.

Over the last few years there has been growing interest in the use of non-invasive ventilation (NIV) in the management of ventilatory failure in acute on chronic ventilatory failure and in stable hypercapnic patients. To understand why assisted ventilation should be effective in improving gas exchange even during spontaneous breathing a basic understanding of the pathophysiology of ventilatory failure is required and this is discussed. The etiology of ventilatory failure is likely to be multifactorial with different factors assuming greater or lesser degrees of importance even in patients with the same condition. Indeed in an individual patient there may be differences at various stages of the illness. The same is true for the mechanism of benefit from NIV. With the current state of knowledge during NIV the aim should be to rest the respiratory muscles, control nocturnal hypoventilation and improve sleep quality. In some individuals severe symptoms, as a consequence of disturbed sleep, may occur and be symptomatically improved by non-invasive ventilation during sleep.