Day-to-day variability of forced oscillatory mechanics for early detection of acute exacerbations in COPD.

BACKGROUND: Telemonitoring trials for early detection of acute exacerbations of chronic obstructive pulmonary disease (AECOPD) have provided mixed results. Day-to-day variations in lung function measured by the forced oscillation technique (FOT) may yield greater insight. We evaluated the clinical utility of home telemonitoring of variability in FOT measures in terms of 1) the relationship with symptoms and quality of life (QoL); and 2) the timing of variability of FOT measures and symptom changes prior to AECOPD. METHODS: Daily FOT parameters at 5 Hz (resistance (R) and reactance (X); Resmon Pro Diary, Restech Srl, Milan, Italy), daily symptoms (COPD Assessment Test (CAT)) and 4-weekly QoL data (St George's Respiratory Questionnaire (SGRQ)) were recorded over 8-9 months from chronic obstructive pulmonary disease (COPD) patients. Variability of R and X was calculated as the standard deviation (sd) over 7-day running windows and we also examined the effect of varying window size. The relationship of FOT versus CAT and SGRQ was assessed using linear mixed modelling, daily changes in FOT variability and CAT prior to AECOPD using one-way repeated measures ANOVA. RESULTS: Fifteen participants with a mean±sd age of 69±10 years and a % predicted forced expiratory volume in 1 s (FEV1) of 39±10% had a median (interquartile range (IQR)) adherence of 95.4% (79.0-98.8%). Variability of the inspiratory component of X (indicated by the standard deviation of inspiratory reactance (SDXinsp)) related to CAT and weakly to SGRQ (fixed effect estimates 1.57, 95% CI 0.65-2.49 (p=0.001) and 4.41, 95% CI -0.06 to 8.89 (p=0.05), respectively). SDXinsp changed significantly on the same day as CAT (1 day before AECOPD, both p=0.02) and earlier when using shorter running windows (3 days before AECOPD, p=0.01; accuracy=0.72 for 5-day windows). CONCLUSIONS: SDXinsp from FOT telemonitoring reflects COPD symptoms and may be a sensitive biomarker for early detection of AECOPD.

Ventilation heterogeneity and oscillometry predict asthma control improvement following step-up inhaled therapy in uncontrolled asthma.

BACKGROUND AND OBJECTIVE: Abnormal peripheral airway function is an important feature of asthma and relates to asthma symptoms and poor asthma control. We aimed to determine whether peripheral airway function, as measured by forced oscillatory impedance and multiple-breath nitrogen washout (MBNW), relates to symptom improvement in asthmatic participants with uncontrolled asthma, after stepping up to high-dose ICS/LABA treatment. METHODS: A total of 19 subjects (14 females, mean age: 29.9 ± 13.6 years) with uncontrolled asthma, as defined by an ACQ5 > 1.5, taking 500 µg/day fluticasone equivalent or less, underwent spirometry, plethysmography, fractional exhaled FeNO, forced oscillatory resistance (Rrs5Hz ) and reactance (Xrs5Hz ), and indices of MBNW ventilation heterogeneity (lung clearance index (LCI), diffusion-convection-dependent (Sacin) and convection-dependent (Scond)). Measurements were made before and after 8 weeks of treatment with fluticasone/formoterol combination inhaler 250/10 µg, 2 puffs twice daily. RESULTS: Treatment improved ACQ5 (P = 0.0002), FEV1 (P = 0.02), FVC (P = 0.04), FeNO (P = 0.0008), Xrs5Hz (P = 0.01), LCI (P = 0.0002), Sacin (P = 0.006) and Scond (P = 0.01). At baseline, ACQ5 correlated with Xrs5Hz (rs = 0.52, P = 0.03) and Rrs5Hz (rs = 0.55, P = 0.02). The improvement in ACQ5 was predicted by more abnormal baseline LCI (P = 0.03), Scond (P = 0.02) and Rrs5Hz (P = 0.006). Baseline Scond was the best predictor of a clinically meaningful improvement in asthma control (ΔACQ > 0.5, ROC-AUC = 0.91, P = 0.007). CONCLUSION: Step-up to high-dose combination treatment in uncontrolled asthma is associated with improved peripheral airway function as measured by Xrs5Hz and MBNW. Baseline MBNW and FOT parameters correlated with the improvement in symptoms and may predict a positive response to up-titration in uncontrolled asthmatic patients.

Discrepancy between in vivo and in vitro comparisons of forced oscillation devices.

The forced oscillation technique (FOT) is an emerging clinical lung function test, with commercial devices becoming increasingly available. However comparability across existing devices has not been established. We evaluated in vivo and in vitro measurements made using three commercial devices against a custom-built device (WIMR): Resmon Pro Diary (Restech srl, Italy), tremoFlo C-100 (Thorasys Medical Systems, Canada), Jaeger Masterscope CT IOS (CareFusion, Hoechberg, Germany). Respiratory system resistance Rrs and reactance Xrs at 5 Hz were examined in twelve healthy subjects (mean age 33 ± 11 years, 7 males), and in two test standards of known resistance and reactance. Subjects performed three measurements during tidal breathing on the four devices in random order. Total, inspiratory and expiratory Rrs and Xrs were calculated and compared using one-way repeated measures ANOVA and Bonferroni post-hoc tests. Rrs did not differ between devices, with <10% deviation from predicted, except for the IOS device. With Xrs, similar values were seen between the WIMR and Resmon devices and between the tremoFlo and IOS devices. No differences were observed using test standards; deviation from theoretical value was <2% for resistance and <5% for reactance. The WIMR, tremoFlo and Resmon Pro but not IOS devices measure similar Rrs, whereas there was more disparity across devices in the estimation of Xrs parameters. The discrepancy between in vivo and in vitro measurements suggest that FOT validation procedures need to take into account the breathing pattern, either using biological controls or a breathing model.

Measurement duration impacts variability but not impedance measured by the forced oscillation technique in healthy, asthma and COPD subjects.

The forced oscillation technique (FOT) is gaining clinical acceptance, facilitated by more commercial devices and clinical data. However, the effects of variations in testing protocols used in FOT data acquisition are unknown. We describe the effect of duration of data acquisition on FOT results in subjects with asthma, chronic obstructive pulmonary disease (COPD) and healthy controls. FOT data were acquired from 20 healthy, 22 asthmatic and 18 COPD subjects for 60 s in triplicate. The first 16, 30 and 60 s of each measurement were analysed to obtain total, inspiratory and expiratory resistance of respiratory system (Rrs) and respiratory system reactance (Xrs) at 5 and 19 Hz. With increasing duration, there was a decrease in total and expiratory Rrs for healthy controls, total and inspiratory Rrs for asthmatic subjects and magnitude of total and inspiratory Xrs for COPD subjects at 5 Hz. These decreases were small compared to the differences between clinical groups. Measuring for 16, 30 and 60 s provided ≥3 acceptable breaths in at least 90, 95 and 100% of subjects, respectively. The coefficient of variation for total Rrs and Xrs also decreased with duration. Similar results were found for Rrs and Xrs at 19 Hz. FOT results are statistically, but likely minimally, impacted by acquisition duration in healthy, asthmatic or COPD subjects.

Characteristics of teams, staff and patients: associations with outcomes of patients in assertive outreach.

BACKGROUND: Little is known about what characteristics of teams, staff and patients are associated with a favourable outcome of severe mental illness managed by assertive outreach. AIMS: To identify predictors of voluntary and compulsory admissions in routine assertive outreach services in the UK. METHOD: Nine features of team organisation and policy, five variables assessing staff satisfaction and burn-out and eleven patient characteristics taken from the baseline data of the Pan-London Assertive Outreach Study were tested as predictors of voluntary and compulsory admissions within a 9-month follow-up period. RESULTS: Weekend working, staff burn-out and lack of contact of the patient with out and lack of contact of the patient with other services were associated independently with a higher probability of both voluntary and compulsory admission. In addition, admissions in the past predicted further voluntary and compulsory admissions, and teams not working extended hours predicted compulsory admissions in the follow-up period. CONCLUSIONS: Characteristics of team working practice, staff burn-out and patients' history are associated independently with outcome. Patient contact with other services is a positive prognostic factor.

Assertive outreach teams in London: models of operation. Pan-London Assertive Outreach Study, part 1.

BACKGROUND: Assertive outreach teams have been introduced in the UK, based on the assertive community treatment (ACT) model. It is unclear how models of community care translate from one culture to another or the degree of adaptation that may result. AIMS: To characterise London assertive outreach teams and determine whether there are distinct groups within them. METHOD: Semi-structured interviews with team managers plus one month's prospective process of care data collection were used to test for 'model fidelity' to ACT and, by cluster analysis, to identify groupings. RESULTS: Fidelity varied widely, with four teams (out of 24 studied) rated 'high fidelity' and three teams rated 'low fidelity' by US standards and 17 rated 'ACT-like'. Three clusters were identified, with voluntary sector teams being the most distinct group. CONCLUSIONS: There is wide variation in the practice of assertive outreach in London. The role of the voluntary sector requires increased attention. Heterogeneity in practice is a clinical challenge but a research opportunity in distinguishing effective from redundant components of the approach.

Assertive outreach teams in London: staff experiences and perceptions. Pan-London Assertive Outreach Study, part 2.

BACKGROUND: The job satisfaction, burn-out and work experiences of assertive outreach team staff are likely to be important to the model's sustainability. AIMS: To describe self-reported views and work experiences of staff in London's 24 assertive outreach teams and to compare these with staff in community mental health teams (CMHTs) and between different types of assertive outreach team. METHOD: Confidential staff questionnaires in London's assertive outreach teams (n=187, response rate=89%) and nine randomly selected CMHTs (n=114, response rate=75%). RESULTS: Staff in assertive outreach teams and CMHTs were moderately satisfied with their jobs, with similar sources of satisfaction and stress. Mean scores were low or average for all sub-scales of the Maslach Burnout Inventory for the assertive outreach team and the CMHT staff, with some differences suggesting less burn-out in the assertive outreach teams. Nine of the 24 assertive outreach teams had team means in the high range for emotional exhaustion and there were significant differences between types of assertive outreach team in some components of burn-out and satisfaction. CONCLUSIONS: These findings are encouraging, but repeated investigation is needed when assertive outreach teams have been established for longer.

Assertive outreach teams in London: patient characteristics and outcomes. Pan-London Assertive Outreach Study, part 3.

BACKGROUND: Although the model of assertive outreach has been widely adopted, it is unclear who receives assertive outreach in practice and what outcomes can be expected under routine conditions. AIMS: To assess patient characteristics and outcome in routine assertive outreach services in the UK. METHOD: Patients (n=580) were sampled from 24 assertive outreach teams in London. Outcomes--days spent in hospital and compulsory hospitalisation--were assessed over a 9-month follow-up. RESULTS: The 6-month prevalence rate of substance misuse was 29%, and 35% of patients had been physically violent in the past 2 years. During follow-up, 39% were hospitalised and 25% compulsorily admitted. Outcome varied significantly between team types. These differences did not hold true when baseline differences in patient characteristics were controlled for. CONCLUSIONS: Routine assertive outreach serves a wide range of patients with significant rates of substance misuse and violent behaviour. Over a 9-month period an average of 25% of assertive outreach patients can be expected to be hospitalised compulsorily. Differences in outcome between team types can be explained by differences in patient characteristics.