Spyridon Fortis

The Difference Between Slow and Forced Vital Capacity Increases With Increasing Body Mass Index: A Paradoxical Difference in Low and Normal Body Mass Indices

BACKGROUND: Obesity reduces FVC, the most commonly used measurement of vital capacity (VC) and slow VC (SVC). It is unknown whether the difference between SVC and FVC is constant in different body mass indices (BMIs). We hypothesized that the difference between SVC and FVC increases as a function of BMI. METHODS: We retrospectively reviewed pulmonary function tests (PFTs) that included spirometry and plethysmography and were performed in adults from January 2013 to August 2013. A total of 1,805 PFTs were enrolled. The non-parametric Wilcoxon signed-rank test was used to compare FVC with SVC, and to compare FEV1/FVC with FEV1/SVC ratio. Spearman correlation analysis was used to determine whether BMI has an effect on the discordance between FVC and SVC. Finally, we used the McNemar test for paired binary data to compare the prevalence rate of obstruction when using different measurements of VC. RESULTS: In individuals with BMI < 25 kg/m2 and no evidence of obstruction in the PFTs, FVC was larger than SVC (P = .03), whereas in overweight and obese individuals, SVC was significantly larger than FVC. The difference between SVC and FVC was positively correlated with BMI (P < .001). One hundred thirty-one patients had a normal FEV1/FVC but low FEV1/SVC ratio. Fifty of these 131 individuals also had a normal FVC; the majority of them (46 of 50) had the PFTs for investigation of respiratory symptoms and had BMI > 25 kg/m2 (42 of 50). CONCLUSIONS: Our results indicate that FVC is larger than SVC in patients with low and normal BMI and no evidence of obstruction in the PFTs, whereas FVC is smaller than SVC in overweight and obese individual. Our findings add to the existing literature that use of FEV1/FVC may lead to underdiagnosis of obstructive airway disease in overweight and obese individuals.

Does normal spirometry rule out an obstructive or restrictive ventilatory defect

Spirometry is often the first step in respiratory symptom investigation, as it does not require special equipment and is inexpensive. A reduced FEV1/FVC ratio with respiratory symptoms can confirm the diagnosis of obstructive lung disease (OLD) [1]. Abnormal inconclusive results such as reduced FEV1 or FVC with a normal ratio may trigger further investigation. Lung volume measurement can be useful to document air trapping (AT) or hyperinflation, which can be present in OLDs [1], and is also the test of choice to diagnose a restrictive ventilatory defect (RVD), which can be present in interstitial lung diseases (ILDs), scoliosis, obesity, etc, according to the American Thoracic Society-European Respiratory Society (ATS-ERS) guidelines [1]. Normal spirometry might discourage providers from pursuing further testing to diagnose a respiratory cause of a patients symptoms. However, is a normal spirometry enough to rule out an OLD or an RVD and restrictive respiratory disease? Recent

Does Size Matter in ICU Telemedicine

In a recent issue of CHEST (August 2016), Hawkins et al showed that direct intervention of ICU telemedicine is associated with reduced ICU and hospital lengths of stay. This is another “positive study” in a large academic center. While one would expect ICU telemedicine, known also as tele-ICU, to improve outcomes in small rural hospitals with no intensivist, urban large-volume hospitals seem to benefit the most.

Metabolomics in COPD Acute Respiratory Failure Requiring Noninvasive Positive Pressure Ventilation

We aimed to investigate whether metabolomic analysis can discriminate acute respiratory failure due to COPD exacerbation from respiratory failure due to heart failure and pneumonia. Since COPD exacerbation is often overdiagnosed, we focused on those COPD exacerbations that were severe enough to require noninvasive mechanical ventilation. We enrolled stable COPD subjects and patients with acute respiratory failure requiring noninvasive mechanical ventilation due to COPD, heart failure, and pneumonia. We excluded subjects with history of both COPD and heart failure and patients with obstructive sleep apnea and obstructive lung disease other than COPD. We performed metabolomics analysis using NMR. We constructed partial least squares discriminant analysis (PLS-DA) models to distinguish metabolic profiles. Serum (p=0.001, R2 = 0.397, Q2 = 0.058) and urine metabolic profiles (p < 0.001, R2 = 0.419, Q2 = 0.142) were significantly different between the four diagnosis groups by PLS-DA. After excluding stable COPD patients, the metabolomes of the various respiratory failure groups did not cluster separately in serum (p=0.2, R2 = 0.631, Q2 = 0.246) or urine (p=0.065, R2 = 0.602, Q2 = −0.134). However, several metabolites in the serum were reduced in patients with COPD exacerbation and pneumonia. We did not find a metabolic profile unique to COPD exacerbation, but we were able to clearly and reliably distinguish stable COPD patients from patients with respiratory failure in both serum and urine.

Lost in interpretation: should the highest VC value be used to calculate the FEV 1 /VC ratio?

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Obstructive Sleep Apnea: A Risk Factor for Surgical Site Infection following Colectomy

BACKGROUND Obstructive sleep apnea (OSA) is associated with increased systemic oxidative stress, endothelial dysfunction, and activation of pro-inflammatory cascades, which increase host susceptibility to infection. OSA has not been evaluated as a risk factor for surgical site infection (SSI) following colectomy. We hypothesized that OSA increases the risk for SSI after colectomy. METHODS We performed a retrospective review of 507 colectomies that took place between August 2011 and September 2013. Forty-two patients carried the diagnosis of OSA prior to surgery. These 42 patients were matched to 68 patients with no OSA for age, body mass index (BMI), diabetes mellitus (DM), reason for surgery and surgical approach. RESULTS The rate of SSI was 28.6% (12 of 42) in the patients with and 10.3% (7 of 68) in the patients without OSA (p=0.03). Using logistic regression, the predictors of SSI following colectomy were found to be OSA (odds ratio [OR] of 3.98, 95% confidence interval [CI]=1.29-12.27), and DM (OR of 7.16, 95% CI=2.36-21.96). The average hospital stay after colectomy for patients with OSA complicated with SSI was 16.7 d whereas patients with OSA without SSI stayed 7.4 d (p<0.001). The rate of organ space infections was 9.5% (4 of 42) in the patients with OSA compared with 0 (p=0.02) in patients without OSA. CONCLUSIONS OSA is an independent risk factor for SSI following colectomy. Patients with OSA have substantially greater rates of organ space SSI and longer hospital stay.

ICU Admissions From the Emergency Department on Holidays and Weekends

Emergency hospital admissions for respiratory diseases are sharply reduced by 18% on Christmas Day compared with the admissions on previous days, according to a single report based on data from the Office of National Statistics in England. Respiratory admissions and respiratory deaths increase above the trend on the next and subsequent days. We hypothesized that intensive care unit (ICU) admissions from the emergency department (ED) decrease during holidays and increase immediately after. We retrospectively reviewed the electronic medical records of ICU admissions from the ED during, before, and after major holidays at the University of Minnesota Medical Center (UMMC) and Fairview Health System. In Fairview Health System, the average number of ED ICU admissions per day was 3.6±2 (SD) and was not different between the various periods (analysis of variance, P=0.77). In UMMC, the average number of ICU admissions per day directly from the ED was 0.7±0.8 (SD) and was also not different between the various periods (analysis of variance, P=0.82). Similarly, in Fairview Health System the average number of ED ICU admissions per day during office hours (regular weekdays) was not different compared with the average number of admissions during off-hours (weekends and holidays) (t test, P=0.88). In UMMC, the number of ED ICU admissions per day did not vary between office hours (regular weekdays) and weekends-holidays (t test, P=0.99). ICU workload variation between office hours and off-hours is solely related to referrals and transfers from other facilities and other hospital units except the ED.

Higher BMI is associated with higher expiratory airflow normalised for lung volume (FEF25–75/FVC) in COPD

Introduction The obesity paradox in chronic obstructive pulmonary disease (COPD), whereby patients with higher body mass index (BMI) fare better, is poorly understood. Higher BMIs are associated with lower lung volumes and greater lung elastic recoil, a key determinant of expiratory airflow. The forced expiratory flow (25–75) (FEF25–75)/forced vital capacity (FVC) ratio reflects effort-independent expiratory airflow in the context of lung volume and could be modulated by BMI. Methods We analysed data from the COPDGene study, an observational study of 10 192 subjects, with at least a 10 pack-year smoking history. Data were limited to subjects with BMI 20–40 kg/m2 (n=9222). Subjects were stratified according to forced expiratory volume in 1 s (FEV1) (%predicted)-quintiles. In regression analyses and Cox proportional hazard models, we analysed the association between BMI, the FEF25–75/FVC ratio, the imaging phenotype, COPD exacerbations, hospitalisations and death. Results There was no correlation between BMI and FEV1(%predicted). However, a higher BMI is correlated with a higher FEF25–75/FVC ratio. In CT scans, a higher BMI was associated with less emphysema and less air trapping. In risk-adjusted models, the quintile with the highest FEF25–75/FVC ratio was associated with a 46% lower risk of COPD exacerbations (OR 0.54, p<0.001) and a 40% lower risk of death (HR 0.60, p=0.02), compared with the lowest quintile. BMI was not independently associated with these outcomes. Conclusions A higher BMI is associated with lower lung volumes and higher expiratory airflows when normalised for lung volume, as quantified by the FEF25–75/FVC ratio. A higher FEF25–75/FVC ratio is associated with a lower risk of COPD exacerbations and death and might quantify functional aspects of the paradoxical effect of higher BMIs on COPD.

Persistent Empiric COPD Diagnosis and Treatment After Pulmonary Function Test Showed No Obstruction

BACKGROUND: Health-care providers often diagnose and empirically treat COPD without a confirmative pulmonary function test (PFT) or even despite a PFT that is not diagnostic of obstructive lung disease. We hypothesized that a portion of patients continue to carry a persistent empiric COPD diagnosis and receive treatment with bronchodilators and inhaled steroids after a PFT shows no obstruction. METHODS: We retrospectively reviewed single PFT sessions with both spirometry and plethysmography in 1,805 subjects. We included subjects who had a normal PFT or a restrictive ventilatory defect. Persistent empiric COPD diagnosis and treatment were defined when subjects with normal PFTs or a restrictive ventilatory defect continued to carry a health-care provider COPD diagnosis or receive treatment with bronchodilators and/or inhaled glucocorticoids, respectively, after a PFT showed no obstruction. RESULTS: One quarter of subjects with FEV1/FVC ≥ lower limit of the normal range had nonspecific PFT abnormalities. We included 473 subjects with normal PFTs and 382 with a restrictive ventilatory defect (n = 855). Persistent empiric COPD diagnosis (60 of 855, 7% prevalence) was associated with current (odds ratio [OR] = 44.7, P < .001) and former smoking (OR = 17.3, P < .001) and older age (OR = 1.03/y, P = .005). Persistent empiric treatment (208 of 855, 24%) was associated with empiric COPD diagnosis (OR = 24.6, P < .001), female sex (OR = 1.75, P = .002), current (OR = 2.04, P = 0.040) and former smoking (OR = 1.53, P = 0.029), interstitial lung disease (OR = 2.09, P = .001), other respiratory diagnosis (OR = 3.17, P < .001), and obstructive sleep apnea (OR = 1.79, P = .006). CONCLUSIONS: Persistent empiric COPD diagnosis was 7%, but persistent empiric treatment was common.