Justin K. Lui

Linking Ventilation Heterogeneity Quantified via Hyperpolarized 3He MRI to Dynamic Lung Mechanics and Airway Hyperresponsiveness

Advancements in hyperpolarized helium-3 MRI (HP 3He-MRI) have introduced the ability to render and quantify ventilation patterns throughout the anatomic regions of the lung. The goal of this study was to establish how ventilation heterogeneity relates to the dynamic changes in mechanical lung function and airway hyperresponsiveness in asthmatic subjects. In four healthy and nine mild-to-moderate asthmatic subjects, we measured dynamic lung resistance and lung elastance from 0.1 to 8 Hz via a broadband ventilation waveform technique. We quantified ventilation heterogeneity using a recently developed coefficient of variation method from HP 3He-MRI imaging. Dynamic lung mechanics and imaging were performed at baseline, post-challenge, and after a series of five deep inspirations. AHR was measured via the concentration of agonist that elicits a 20% decrease in the subject’s forced expiratory volume in one second compared to baseline (PC20) dose. The ventilation coefficient of variation was correlated to low-frequency lung resistance (R = 0.647, P < 0.0001), the difference between high and low frequency lung resistance (R = 0.668, P < 0.0001), and low-frequency lung elastance (R = 0.547, P = 0.0003). In asthmatic subjects with PC20 values <25 mg/mL, the coefficient of variation at baseline exhibited a strong negative trend (R = -0.798, P = 0.02) to PC20 dose. Our findings were consistent with the notion of peripheral rather than central involvement of ventilation heterogeneity. Also, the degree of AHR appears to be dependent on the degree to which baseline airway constriction creates baseline ventilation heterogeneity. HP 3He-MRI imaging may be a powerful predictor of the degree of AHR and in tracking the efficacy of therapy.

The role of heterogeneity in asthma: a structure-to-function perspective

A number of methods have evolved through the years in probing the dysfunction that impacts mechanics and ventilation in asthma. What has been consistently found is the notion of heterogeneity that is not only captured in the frequency dependence of lung mechanics measurements but also rendered on imaging as patchy diffuse areas of ventilation defects. The degree of heterogeneity has been linked to airway hyperresponsiveness, a hallmark feature of asthma. How these heterogeneous constriction patterns lead to functional impairment in asthma have only been recently explored using computational airway tree models. By synthesizing measurements of lung mechanics and advances in imaging, computational airway tree models serve as a powerful engine to accelerate our understanding of the physiologic changes that occur in asthma. This review will be focused on the current state of investigational work on the role of heterogeneity in asthma, specifically exploring the structural and functional relationships.

Acute inflammatory demyelinating polyradiculopathy in Legionella pneumonia

lomatous, non-eczematous eruptions (Fig. 1). The disposable concentric needle electrodes used in the EMG examination consisted of stainless-steel, platinum, and palladium. Patch testing was performed on the upper back with the German Contact Dermatitis Research Group (DKG) standard series and the DKG dental metal series. Positive reactions to palladium chloride (1.0% pet.) and ammonium tetrachloroplatinate (0.25% pet.) were observed at 72and 168-hour readings. No positive reactions were observed to any of the other 36 test substances. Sensitization may have occurred some years ago, when she wore a platinum piercing in the left eyebrow, which was removed due to persistent local inflammation. EMG and nerve conduction studies with needle electrodes may be associated with iatrogenic complications such as bleeding, infection, nerve injury, pneumothorax, urticaria, and complex regional pain syndrome. Although metal allergies are a well-known problem, they are probably rare after EMG. We could only find a single report of an EMG-associated allergic contact dermatitis, in which nickel could be identified as the allergen. In our patient, clinical signs of a delayed-type hypersensitivity reaction occurred at all needle electrode insertion points. They appeared as painful swelling and subsequent prominent granulomatous eruptions that persisted for several weeks. It is noteworthy that, unlike typical allergic contact dermatitis, the skin lesions were non-eczematous. Allergic reactions to 2 metals contained in the needle electrodes, platinum and palladium, were proven by patch testing. Delayed-type hypersensitivity reactions are T-cell driven and can include several metals due to crossreactivity, as in our patient. Because metal ions are haptens and are considered to be incomplete antigens, protein or peptide binding is needed for immunogenicity. Persistent local inflammation may have facilitated the generation of a metal-specific T-cell response in this patient. Treatment of contact dermatitis includes local steroid therapy and strict allergen avoidance. In conclusion, an allergic contact dermatitis to EMG needle electrodes should be considered in patients with previous sensitization and eczematous skin reactions or atypical granulomatous eruptions.

Diagnostic Bedside Ultrasonography for Acute Respiratory Failure and Severe Hypoxemia in the Medical Intensive Care Unit Basics and Comprehensive Approaches

Bedside goal-directed ultrasound is a powerful tool for rapid differential diagnosis and monitoring of cardiopulmonary disease in the critically ill patient population. The bedside intensivist is in a unique position to integrate ultrasound findings with the overall clinical situation. Medically critically ill patients who require urgent bedside diagnostic assessment fall into 2 categories: (1) acute respiratory failure and (2) hemodynamic derangements. The first portion of this review outlines the diagnostic role of bedside ultrasound in the medically critically ill patient population for the diagnosis and treatment of acute respiratory failure, acute respiratory distress, and severe hypoxemia. The second portion will focus on the diagnostic role of ultrasound for the evaluation and treatment of shock states, as well as describe protocolized approaches for evaluation of shock during cardiopulmonary resuscitation. Different respiratory system pathologies that result in acute respiratory failure (such as increased interstitial fluid, alveolar consolidation, pleural effusion) cause characteristic ultrasonographic findings; diaphragmatic assessment may also add information. Intracardiac shunting can cause severe hypoxemia. Protocolized approaches for the evaluation of patients with acute respiratory failure or distress are discussed.

Facial Drooping, Aphasia, and an Incidental Lung Mass in a Nonsmoker

Background: Atrial fibrillation and atrial flutter are atrial tachycardias associated with embolic strokes. To date, there have only been a few reports highlighting the incidence of these atrial tachycardias due to mechanical compression of myocardial structures and the pulmonary vasculature in certain mediastinal masses and cysts. Case: We present a case of a 75-year-old gentleman who is a nonsmoker with a history of hypertension who presents with an acute embolic stroke due to atrial flutter likely from mechanical compression from an underlying squamous cell carcinoma of the lung. Conclusion: This case represents, to the best of our knowledge, a rare case of squamous cell carcinoma of the lung in a nonsmoker likely leading to mechanical compression and a resultant atrial tachycardia with an embolic stroke.

Legionella pneumophila cases in a community hospital: A 12-month retrospective review

Background: Legionella pneumonia has long been recognized as an important cause of community-acquired pneumonia associated with significant morbidity and mortality; however, the description of the incidence of this disease is restricted to sporadic cases in the literature. With the advent of an inexpensive and rapid urine antigen test, routine testing has become more common. We report findings of a retrospective review of 266 patients who were admitted with a clinical diagnosis of community-acquired pneumonia over a 12-month period and were tested for Legionella pneumophila serogroup 1, reporting the prevalence and determinants of Legionella infection. Methods: Chart reviews of 266 patients admitted for community-acquired pneumonia and who underwent urine antigen testing for Legionella pneumophila during a 1-year time period were conducted, looking at demographic information as well as clinical and laboratory presentation, reporting on the prevalence and determinants of urine antigen positivity using multivariate logistic regression analysis. Results: Legionella pneumophila serogroup 1 was found in 2.3% of cases of community-acquired pneumonia. We also found that altered mental status, diarrhea, history of lung disease, and alcohol intake were significantly associated with pneumonia associated with Legionella. The presence of these four factors had a low sensitivity in predicting Legionella infection (33%); however, they had a positive predictive value of 98%, with a specificity of 100. All the Legionella-infected patients in our study required admission to the intensive care unit, and one of them developed Guillain–Barré syndrome, which to our knowledge represents the only reported case of this syndrome related to Legionella infection in an adult in the English scientific literature. Conclusion: Legionella pneumophila serogroup 1 is a common cause of sporadic cases of community-acquired pneumonia associated with a high morbidity and protean manifestations. Clinical features have a poor sensitivity in identifying cases, and routine urine antigen testing in patients with suggestive clinical symptoms appears to be a rational approach in the evaluation of community-acquired pneumonia.