BackgroundThe effect on PaCO 2 of high concentration oxygen therapy when administered to patients with severe exacerbations of asthma is uncertain. Methods 106 patients with severe exacerbations of asthma presenting to the Emergency Department were randomised to high concentration oxygen (8 l/min via medium concentration mask) or titrated oxygen (to achieve oxygen saturations between 93% and 95%) for 60 min. Patients with chronic obstructive pulmonary disease or disorders associated with hypercapnic respiratory failure were excluded. The transcutaneous partial pressure of carbon dioxide (PtCO 2 ) was measured at 0, 20, 40 and 60 min. The primary outcome variable was the proportion of patients with a rise in PtCO 2 $4 mm Hg at 60 min. Results The proportion of patients with a rise in PtCO 2 $4 mm Hg at 60 min was significantly higher in the high concentration oxygen group, 22/50 (44%) vs 10/53 (19%), RR 2.3 (95% CI 1.2 to 4.4, p<0.006). The high concentration group had a higher proportion of patients with a rise in PtCO 2 $8 mm Hg, 11/50 (22%) vs 3/53 (6%), RR 3.9 (95% CI 1.2 to 13

SummaryObjective To determine the risk of venous thromboembolism (VTE) associated with prolonged work-and computer-related seated immobility.Design Case-control study in which cases were patients aged 18-65 years attending outpatient VTE clinics, and controls were patients aged 18-65 years admitted to CCU with a condition other than VTE. Interviewer-administered questionnaires obtained detailed information on VTE risk factors and clinical details. Main outcome measureThe relative risk of VTE associated with prolonged work-and computer-related seated immobility, defined as being seated at work and on the computer at home, at least 10 hours in a 24-hour period and at least 2 hours at a time without getting up, during the four weeks prior to the onset of symptoms that led to VTE diagnosis or CCU admission.Results There were 197 cases and 197 controls. Prolonged work-and computer-related seated immobility was present in 33/197 (16.8%) and 19/197 (9.6%) cases and controls, respectively. In multivariate analyses, prolonged work-and computer-related seated immobility was associated with an increased risk of VTE, odds ratio 2.8 (95% CI 1.2-6.1, P=0.013). The maximum and average number of hours seated in a 24-hour period were associated with an increased risk of VTE, with odds ratios of 1.1 (95% CI 1.0-1.2, P=0.008) and 1.1 (95% CI 1.0-1.2, P=0.014) per additional hour seated. ConclusionProlonged work-and computer-related seated immobility increases the risk of VTE. We suggest that there needs to be both a greater awareness of the role of prolonged work-related seated immobility in the pathogenesis of VTE, and the development of occupational strategies to decrease the risk. DECLARATIONS Competing interests None declared FundingThe study was

In AECOPD high flow oxygen in the ambulance is associated with poor clinical outcomes. A number of easily identified markers of chronic disease severity indicate an increased risk of a poor clinical outcome.

We report an audit of 208 patients with a mean age of 39 years (16 to 65) attending the Orthopaedic Assessment Unit at the Wellington Hospital between January 2006 and December 2007 with an injury of the tendo Achillis requiring immobilisation in a cast. Information on assessment of venous thromboembolism (VTE) risk, prophylactic measures and VTE events for all patients was obtained from the medical records. A VTE risk factor was documented in the records of three (1%) patients. One of the 208 patients received aspirin prophylaxis; none received low molecular weight heparin. In all, 13 patients (6.3%, 95% confidence interval 3.4 to 10.5) developed symptomatic VTE during immobilisation in a cast, including six with a distal deep-vein thrombosis (DVT), four with a proximal DVT, and three with a confirmed pulmonary embolus. This incidence of symptomatic VTE is similar to that reported following elective hip replacement. We propose that consideration is given to VTE prophylaxis during prolonged immobilisation of the lower limbs in a cast, to ensure that the same level of protection is provided as for patients undergoing elective hip replacement.