Neurophysiological mechanisms of exertional dyspnea in post-pulmonary embolism syndrome.

Following pulmonary embolism (PE), a third of patients develop persistent dyspnea, which is commonly termed the post-PE syndrome. The neurophysiological underpinnings of exertional dyspnea in patients with post-PE syndrome without pulmonary hypertension (PH) are unclear. Thus, the current study determined if abnormally high inspiratory neural drive (IND) due, in part, to residual pulmonary gas-exchange abnormalities, was linked to heightened exertional dyspnea and exercise limitation, in such patients. Fourteen participants with post-PE syndrome (without resting PH) and 14 age-, sex-, and body mass index-matched healthy controls undertook pulmonary function testing and a symptom-limited cycle cardiopulmonary exercise test with measurements of IND (diaphragmatic electromyography), ventilatory requirements for CO2 (V̇e/V̇co2), and perceived dyspnea intensity (modified Borg 0-10 scale). Post-PE (vs. control) had a reduced resting transfer coefficient for carbon monoxide (KCO: 84 ± 15 vs. 104 ± 14%pred, P < 0.001) and peak oxygen uptake (V̇o2peak) (76 ± 14 vs. 124 ± 28%pred, P < 0.001). IND and V̇e/V̇co2 were higher in post-PE than controls at standardized submaximal work rates (P < 0.05). Dyspnea increased similarly in both groups as a function of increasing IND but was higher in post-PE at standardized submaximal work rates (P < 0.05). High IND was associated with low KCO (r = -0.484, P < 0.001), high V̇e/V̇co2 nadir (r = 0.453, P < 0.001), and low V̇o2peak (r = -0.523, P < 0.001). In patients with post-PE syndrome, exercise IND was higher than controls and was associated with greater dyspnea intensity. The heightened IND and dyspnea in post-PE, in turn, were strongly associated with low resting KCO and high exercise V̇e/V̇co2, which suggest important pulmonary gas-exchange abnormalities in this patient population.NEW & NOTEWORTHY This study is the first to show that increased exertional dyspnea in patients with post-pulmonary embolism (PE) syndrome, without overt pulmonary hypertension, was strongly associated with elevated inspiratory neural drive (IND) to the diaphragm during exercise, compared with healthy controls. The greater IND was associated with impairments in pulmonary gas exchange and significant deconditioning. Our results help to explain why many patients with post-PE syndrome report significant dyspnea at relatively low levels of physical activity.

The Role of Myositis-Specific Autoantibodies and the Management of Interstitial Lung Disease in Idiopathic Inflammatory Myopathies: A Systematic Review.

OBJECTIVE: To evaluate the role of myositis-specific autoantibodies (MSAs) in interstitial lung disease (ILD), management of idiopathic inflammatory myopathies (IIM) associated ILD, and if there is a role for MSA specific management of ILD. METHODS: A systematic review was performed examining how MSAs relate to ILD manifestations in IIM patients and comparing treatment outcomes with varying immunosuppressive regimens. RESULTS: 112 papers were included in this analysis. Patients with anti-aminoacyl tRNA synthetase (anti-ARS) and anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibodies had consistently higher rates of ILD than other MSA groups. Anti-ARS positive patients had higher rates of chronic ILD whereas anti-MDA5 positive patients had higher rates of rapidly progressive ILD (RP-ILD). The most common high-resolution computed tomography (HRCT) patterns for ILD in anti-ARS and anti-MDA5 positive patients were nonspecific interstitial pneumonia (NSIP) and unclassifiable respectively. Anti-transcription intermediary factor 1-gamma (anti-TIF1-γ), anti-Mi-2, anti-nuclear matrix protein 2 (anti-NXP-2), and anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (anti-HMGCR) antibodies were associated with a decreased risk of ILD. Small sample sizes, a lack of head-to-head trials, and non-randomized designs prevented drawing meaningful conclusions with respect to immunosuppressive management. CONCLUSION: Clear relationships exist with regards to the ILD manifestations of certain MSAs. Standard therapy for IIM associated ILD (IIM-ILD) is glucocorticoids with the addition of others immunosuppressives in patients with or at risk of RP-ILD as well as in refractory cases. Immunosuppressives should be preferentially used in MSA populations in which they have been studied and shown to be efficacious.

Kidney function and the use of nitrofurantoin to treat urinary tract infections in older women.

BACKGROUND: The antibiotic nitrofurantoin is commonly used to treat uncomplicated urinary tract infections. However, when this drug is used by patients with reduced kidney function, its urine concentration may be subtherapeutic. METHODS: We conducted a population-based study of older women (mean age 79 years) in Ontario, Canada, whose estimated glomerular filtration rate was relatively low (median 38 mL/min per 1.73 m(2)) and for whom 1 of 4 antibiotics had been prescribed for urinary tract infection: nitrofurantoin, ciprofloxacin, norfloxacin or trimethoprim-sulfamethoxazole. We assessed 2 measures of treatment failure in the subsequent 14 days: receipt of a second antibiotic indicated for urinary tract infection and hospital encounter (emergency department visit or hospital admission) with a urinary tract infection. We repeated the analysis for older women with relatively high estimated glomerular filtration rate (median 69 mL/min per 1.73 m(2)). RESULTS: The baseline characteristics of the 4 antibiotic groups were similar. Relative to nitrofurantoin, the other antibiotics (including ciprofloxacin) were associated with a lower rate of treatment failure among women with relatively low estimated glomerular filtration rate (for ciprofloxacin v. nitrofurantoin: second antibiotic prescription, 130/1989 [6.5%] v. 516/3739 [13.8%], odds ratio [OR] 0.44, 95% confidence interval [CI] 0.36-0.53; hospital encounter, 21/1989 [1.1%] v. 95/3739 [2.5%], OR 0.41, 95% CI 0.25-0.66). However, a similar risk of treatment failure with nitrofurantoin was also observed among women with relatively high estimated glomerular filtration rate. The results were consistent in multiple additional analyses. INTERPRETATION: In this study, the presence of mild or moderate reductions in estimated glomerular filtration rate did not justify avoidance of nitrofurantoin.