Flock worker's lung disease: natural history of cases and exposed workers in Kingston, Ontario.

BACKGROUND: The natural history of flock worker's lung (FWL) and longitudinal lung function changes in nylon flock-exposed workers have not been well characterized. METHODS: Symptoms, pulmonary function testing, and chest radiographs from five index cases, subsequent case referrals, and screened employees of a flocking plant in Kingston, Ontario, Canada, were compared and analyzed for changes over time (variable follow-up intervals between 1991 and 2011). RESULTS: Nine cases and 30 flock-exposed workers without FWL were identified. Four cases had persistent interstitial lung disease despite three having left the workplace. Two developed hypoxemic respiratory failure and secondary pulmonary hypertension and died of complications 18 and 20 years after diagnosis, respectively. Five cases resolved after leaving the workplace. Compared with resolved cases, persistent cases had lower diffusing capacity of the lung for carbon monoxide at presentation (P < .05) and follow-up (P < .05). Among exposed workers employed for 14.5 ± 4.7 years, five had abnormal chest radiographs vs none at baseline (P = .001) over 14.8 ± 4.6 years of follow-up. The prevalence of wheeze increased (P = .001), and FEV1/FVC decreased (P < .001). FEV1% predicted was significantly lower at follow-up (P = .05). Average FEV1 decline was 46 mL/year (range, -27 to 151 mL/y). Seventy-seven percent of exposed workers were current or former smokers. CONCLUSIONS: The natural history of FWL includes the following patterns: complete resolution of symptoms; radiographic and pulmonary function abnormalities; permanent, but stable symptoms and restrictive pulmonary function deficits; and progressive decline in pulmonary function, causing death from respiratory failure and secondary pulmonary hypertension. A low baseline diffusing capacity of the lung for carbon monoxide is associated with the persistence and progression of FWL.

Perfil autonómico de los pacientes derivados a una clínica de trastornosdel sueño: impacto de la CPAPen el sistema nervioso autónomo / Autonomic profile of patients referred to a sleep disorder clinic: impact of CPAP on the autonomic nervous system

Introducción: la apnea obstructiva del sueño (AOS) severa ha sido asociada con disfunción autonómica. La presión positiva continua en la vía aérea (CPAP) es el tratamiento estándar para la AOS, aun cuando su impacto sobre la disfunción autonómica no haya sido plenamente investigado. La variabilidad de la frecuencia cardíaca (VFC) es una técnica cuantitativa no invasiva para la evaluación de la actividad autonómica. Nuestro objetivo fue determinar si los pacientes con AOS severa presentan niveles mayores de disfunción autonómica que los pacientes con un índice de apnea-hipopnea (IAH) normal, y si la CPAP mejora los parámetros de VFC a la vez que mejora el IAH.Métodos: todos los pacientes fueron sometidos a una polisomnografía (PSG) completa en una clínica de trastornos del sueño. Se definió como severa a una AOS que tuviera un IAH ³ 30 (eventos por hora), y se definió al grupo control como aquellos que tuvieran un IAH < 5. Se calculó la VFC antes y después de la CPAP, analizando trazados electrocardiogáficos de 10 minutos, conforme las pautas de normalización. Los pacientes con AOS severa fueron tratados con CPAP durante un período de 4-6 semanas (titulados durante la polisomnografía), y los pacientes control no recibieron ninguna intervención entre sus dos registros de electrocardiograma (ECG).Resultados: el estudio incluyó a un total de 20 pacientes con AOS severa y 10 controles. En los pacientes con AOS severa, el IAH se redujo al utilizar CPAP de 38,0 ± 11,0 a 23,0 ± 11,0 (p<0,01). Aparte de una diferencia significativa en el índice de masa corporl (IMC) entre los paciente con AOS y los controles (35,3±4,7 versus 26,6±4,6 kg/m2, p<0,01), los grupos fueron comparables en cuanto a edad, condición de hipertensión y género. No hubo ninguna diferencia significativa (p<0,05) en ningún parámetro de VFC entre los pacientes con AOS severa y los controles, ni entre los pacientes con AOS antes y después de CPAP (tabla 2).

Introduction: severe obstructive sleep apnea (OSA) has been associated with autonomic dysfunction. Continuous positive airway pressure (CPAP) is standard treatment for OSA, although its impact on autonomic dysfunction was not fully investigated. Heart rate variability (HRV) is a non-invasive quantitative technique for assessment of autonomic activity. We aimed to determine if patients with severe OSA exhibit greater levels of autonomic dysfunction than patients with normal apnea-hypopnea index (AHI), and if CPAP improves heart rate variability (HRV) parameters while improving AHI.Methods: all patients underwent full polysomnography (PSG) at a Sleep Disorder Clinic. Severe OSA was defined as AHI ³ 30 (events per hour), and control was defined as AHI < 5. HRV was calculated pre and post-CPAP from a 10-minute electrocardiogram (ECG) recording in accordance with guidelines for standardization. Patients with severe OSA were treated with CPAP for a period of 4-6 weeks (titrated during PSG), and control patients underwent no intervention between their two ECG recordings.Results: a total of 20 patients with severe OSA and 10 controls were included (Table 1). In patients with severe OSA, AHI was reduced by CPAP from 38.0 ± 11.0 to 23.0 ± 11.0 (P<0.01). Aside from a significant difference in BMI between OSA patients and controls (35.3±4.7 vs. 26.6±4.6 kg/m2, P<0.01), groups were comparable in age, hypertension, and gender. There was no significant difference (P<0.05) in any HRV parameters between patients with severe OSA and controls, and between OSA patients pre- and post-CPAP (table 2).

Validation of the MediByte® type 3 portable monitor compared with polysomnography for screening of obstructive sleep apnea.

BACKGROUND: Portable monitors are increasingly being used as a diagnostic screening tool for obstructive sleep apnea (OSA), and in-laboratory validation of these devices with polysomnography (PSG) is required. OBJECTIVE: To assess the reliability of the MediByte (Braebon Medical Corporation, Canada) type 3 screening device compared with overnight PSG. METHODS: To cover a range of OSA severity, a consecutive series of patients wore the screening device while simultaneously undergoing PSG. Data acquired from the screener and PSG were blinded and scored separately. The number of apneas and hypopneas per hour were calculated using recording time (respiratory disturbance index [RDI]) for the MediByte device, and sleep time (apnea-hypopnea index [AHI]) for PSG. RESULTS: Data from 73 patients with a mean age of 53 years and body mass index of 32.2 kg/m2 showed high measurement association between the RDI and AHI, with a Pearson correlation of 0.92, accounting for 85% of the variance. Based on Bland-Altman measurement agreement, the mean difference between the RDI and AHI (-5.9±11.2 events/h) indicated screener under-reporting. For an AHI of greater than 15 events/h, the sensitivity and specificity of the screener was 80% and 97%, respectively; for an AHI of greater than 30 events/h, the positive predictive value was 100%, while the negative predictive value was 88%. CONCLUSION: The MediByte device accurately identified patients without OSA and had a high sensitivity for moderate-to-severe OSA.

The acute impact of continuous positive airway pressure on nasal resistance: a randomized controlled comparison.

Subjective nasal obstruction is common among users of continuous positive airway pressure (CPAP). The aim of this study was to measure the acute effect of CPAP on nasal resistance and nasal symptoms in awake normal subjects. Twenty-four healthy CPAP-naive adults [8 men, 16 women; mean age 30 yr (SD 14)] underwent a randomized controlled crossover study comparing nasal CPAP (8 cmH(2)O) for 6 h on one occasion and the control condition (nasal mask without CPAP) on the other. Nasal resistance measurements (posterior active rhinometry) before and after the test exposure were similar on both test days. Nasal resistance during CPAP exposure [2.04 cmH(2)O.l(-1).s (SD 0.72)] was significantly lower than that of the control [2.67 cmH(2)O.l(-1).s (SD 1.07)]: mean difference 0.66 cmH(2)O.l(-1).s, 95% confidence interval 0.19-1.13 cmH(2)O.l(-1).s. The gradient in pressure from CPAP mask to posterior naris during CPAP exposure varied from 1.6 to 2 cmH(2)O but was not significantly different between time points. Subjective nasal symptom scores and peak nasal inspiratory flow rates did not change significantly on either test day. We conclude that in awake CPAP-naive normal subjects, acute CPAP exposure is associated with a reduction in nasal resistance compared with the control condition, but it is not associated with an immediate post-CPAP change in subjective or objective nasal resistance.

Can patients with obstructive sleep apnea titrate their own continuous positive airway pressure?

Manual continuous positive airway pressure (CPAP) titration in a sleep laboratory is costly and limits access for diagnostic studies. Many factors affect CPAP compliance, but education and support, rather than in-laboratory CPAP titration, appear to be pivotal. Self-adjustment of CPAP at home will provide equal or superior efficacy in the treatment of obstructive sleep apnea (OSA) as compared with in-laboratory titration. A randomized, single-blind, two-period crossover trial of CPAP treatment at the in-laboratory-determined optimal pressure versus at-home self-adjustment of CPAP (starting pressure based on prediction equation). Eighteen CPAP-naive patients (16 males, 50 +/- 15 years old, apnea hypopnea index 40 +/- 20) with a new diagnosis of OSA were tested. Testing was performed before and after CPAP treatment in each of two 5-week study limbs. CPAP, compliance with CPAP treatment, the Sleep Apnea Quality of Life Index, the Functional Outcomes of Sleep Questionnaire score, the Epworth sleepiness scale score, sleep architecture, sleep apnea severity, and maintenance of wakefulness tests were performed. Both modes of CPAP treatment significantly improved objective and subjective measures of OSA, but they did not differ in efficacy. Home self-titration of CPAP is as effective as in-laboratory manual titration in the management of patients with OSA.