Suhail Raoof

Severe Hypoxemic Respiratory Failure: Part 2—Nonventilatory Strategies

ARDS is characterized by hypoxemic respiratory failure, which can be refractory and life-threatening. Modifications to traditional mechanical ventilation and nontraditional modes of ventilation are discussed in Part 1 of this two-part series. In this second article, we examine nonventilatory strategies that can influence oxygenation, with particular emphasis on their role in rescue from severe hypoxemia. A literature search was conducted and a narrative review written to summarize the use of adjunctive, nonventilatory interventions intended to improve oxygenation in ARDS. Several adjunctive interventions have been demonstrated to rapidly ameliorate severe hypoxemia in many patients with severe ARDS and therefore may be suitable as rescue therapy for hypoxemia that is refractory to prior optimization of mechanical ventilation. These include neuromuscular blockade, inhaled vasoactive agents, prone positioning, and extracorporeal life support. Although these interventions have been linked to physiologic improvement, including relief from severe hypoxemia, and some are associated with outcome benefits, such as shorter duration of mechanical ventilation, demonstration of survival benefit has been rare in clinical trials. Furthermore, some of these nonventilatory interventions carry additional risks and/or high cost; thus, when used as rescue therapy for hypoxemia, it is important that they be demonstrated to yield clinically significant improvement in gas exchange, which should be periodically reassessed. Additionally, various management strategies can produce a more gradual improvement in oxygenation in ARDS, such as conservative fluid management, intravenous corticosteroids, and nutritional modification. Although improvement in oxygenation has been reported with such strategies, demonstration of additional beneficial outcomes, such as reduced duration of mechanical ventilation or ICU length of stay, or improved survival in randomized controlled trials, as well as consideration of potential adverse effects should guide decisions on their use. Various nonventilatory interventions can positively impact oxygenation as well as outcomes of ARDS. These interventions may be considered for use, particularly for cases of refractory severe hypoxemia, with proper appreciation of potential costs and adverse effects.

Severe Hypoxemic Respiratory Failure

Approximately 16% of deaths in patients with ARDS results from refractory hypoxemia, which is the inability to achieve adequate arterial oxygenation despite high levels of inspired oxygen or the development of barotrauma. A number of ventilator-focused rescue therapies that can be used when conventional mechanical ventilation does not achieve a specific target level of oxygenation are discussed. A literature search was conducted and narrative review written to summarize the use of high levels of positive end-expiratory pressure, recruitment maneuvers, airway pressure-release ventilation, and high-frequency ventilation. Each therapy reviewed has been reported to improve oxygenation in patients with ARDS. However, none of them have been shown to improve survival when studied in heterogeneous populations of patients with ARDS. Moreover, none of the therapies has been reported to be superior to another for the goal of improving oxygenation. The goal of improving oxygenation must always be balanced against the risk of further lung injury. The optimal time to initiate rescue therapies, if needed, is within 96 h of the onset of ARDS, a time when alveolar recruitment potential is the greatest. A variety of ventilatory approaches are available to improve oxygenation in the setting of refractory hypoxemia and ARDS. Which, if any, of these approaches should be used is often determined by the availability of equipment and clinician bias.

A Practical Algorithmic Approach to the Diagnosis and Management of Solitary Pulmonary Nodules: Part 1: Radiologic Characteristics and Imaging Modalities

The solitary pulmonary nodule (SPN) is frequently encountered on chest imaging and poses an important diagnostic challenge to clinicians. The differential diagnosis is broad, ranging from benign granulomata and infectious processes to malignancy. Important concepts in the evaluation of SPNs include the definition, morphologic characteristics via appropriate imaging modalities, and the calculation of pretest probability of malignancy. Morphologic differentiation of SPN into solid or subsolid types is important in the choice of follow-up and further management. In this first part of a two-part series, we describe the morphologic characteristics and various imaging modalities available to further characterize SPN. In Part 2, we will describe the determination of pretest probability of malignancy and an algorithmic approach to the diagnosis of SPN.

Transthyretin as a marker to predict outcome in critically ill patients.

BACKGROUND A determination of serum Transthyretin (TTR, Prealbumin) level is an objective method of assessing protein catabolic loss of severely ill patients and numerous studies have shown that TTR levels correlate with patient outcomes of non-critically ill patients. We evaluated whether TTR level correlates with the prevalence of PEM in the ICU and evaluated serum TTR level as an indicator of the effectiveness of nutrition support and the prognosis in critically ill patients. METHODS We studied PEM prevalence in 118 patients admitted to a community hospitals medical intensive care unit and the association between TTR, low albumin (ALB) concentration and high-risk disease (HRD), i.e., sepsis, inability to take in oral nutrients, etc. Serum TTR was measured on the day of admission, day 3 and day 7 of their ICU stay. APACHE II and SOFA score was assessed on the day of admission and the nutritional status and nutritional requirement was assessed for their entire ICU stay. Patients were divided into three groups based on initial TTR level and the outcome analysis was performed for APACHE II score, SOFA score, ICU length of stay, hospital length of stay, and mortality. RESULTS TTR showed excellent concordance with patients classified with PEM or at high malnutrition risk, and followed for 7 days, it is a measure of the metabolic burden. TTR levels decline from day 1 to day 7 in spite of providing nutritional support. Patients were classified in 3 categories with respect to the level of TTR: more than 170 mg/L, twenty-five patients (group 3); 100-170 mg/L, forty-eight patients (group 2); less than 100 mg/L, forty-five patients (group 1). TTR level correlated with ICU length of stay, hospital length of stay, and APACHE II score, and predicts mortality. CONCLUSIONS TTR identified patients at highest risk for metabolic losses associated with stress hypermetabolism as serum TTR levels did not respond early to nutrition support because of the delayed return to anabolic status. It is particularly helpful in removing interpretation bias, and it is an excellent measure of the systemic inflammatory response concurrent with a preexisting state of chronic inanition.

A Practical Algorithmic Approach to the Diagnosis and Management of Solitary Pulmonary Nodules: Part 2: Pretest Probability and Algorithm

In this second part of a two-part series, we describe an algorithmic approach to the diagnosis of the solitary pulmonary nodule (SPN). An essential aspect of the evaluation of SPN is determining the pretest probability of malignancy, taking into account the significant medical history and social habits of the individual patient, as well as morphologic characteristics of the nodule. Because pretest probability plays an important role in determining the next step in the evaluation, we describe various methods the physician may use to make this determination. Subsequently, we outline a simple yet comprehensive algorithm for diagnosing a SPN, with distinct pathways for the solid and subsolid SPN.

Bronchiolar disorders: a clinical-radiological diagnostic algorithm.

Bronchiolar disorders are generally difficult to diagnose because most patients present with nonspecific respiratory symptoms of variable duration and severity. A detailed clinical history may point toward a specific diagnosis. Pertinent clinical questions include history of smoking, collagen vascular disease, inhalational injury, medication usage, and organ transplant. It is important also to evaluate possible systemic and pulmonary signs of infection, evidence of air trapping, and high-pitched expiratory wheezing, which may suggest small airways involvement. In this context, pulmonary function tests and plain chest radiographs may demonstrate abnormalities; however, they rarely prove sufficiently specific to obviate bronchoscopic or surgical biopsy. Given these limitations, in our experience, high-resolution CT (HRCT) scanning of the chest often proves to be the most important diagnostic tool to guide diagnosis in these difficult cases, because different subtypes of bronchiolar disorders may present with characteristic image findings. Three distinct HRCT patterns in particular are of value in assisting differential diagnosis. A tree-in-bud pattern of well-defined nodules is seen primarily as a result of infectious processes. Ill-defined centrilobular ground-glass nodules point toward respiratory bronchiolitis when localized in upper lobes in smokers or subacute hypersensitivity pneumonitis when more diffuse. Finally, a pattern of mosaic attenuation, especially when seen on expiratory images, is consistent with air-trapping characteristic of bronchiolitis obliterans or constrictive bronchiolitis. Based on an appreciation of the critical role played by HRCT scanning, this article provides clinicians with a practical algorithmic approach to the diagnosis of bronchiolar disorders.

Diagnostic criteria for idiopathic pulmonary fibrosis: a Fleischner Society White Paper.

This Review provides an updated approach to the diagnosis of idiopathic pulmonary fibrosis (IPF), based on a systematic search of the medical literature and the expert opinion of members of the Fleischner Society. A checklist is provided for the clinical evaluation of patients with suspected usual interstitial pneumonia (UIP). The role of CT is expanded to permit diagnosis of IPF without surgical lung biopsy in select cases when CT shows a probable UIP pattern. Additional investigations, including surgical lung biopsy, should be considered in patients with either clinical or CT findings that are indeterminate for IPF. A multidisciplinary approach is particularly important when deciding to perform additional diagnostic assessments, integrating biopsy results with clinical and CT features, and establishing a working diagnosis of IPF if lung tissue is not available. A working diagnosis of IPF should be reviewed at regular intervals since the diagnosis might change. Criteria are presented to establish confident and working diagnoses of IPF.

Official ERS/ATS clinical practice guidelines: Noninvasive ventilation for acute respiratory failure

Noninvasive mechanical ventilation (NIV) is widely used in the acute care setting for acute respiratory failure (ARF) across a variety of aetiologies. This document provides European Respiratory Society/American Thoracic Society recommendations for the clinical application of NIV based on the most current literature. The guideline committee was composed of clinicians, methodologists and experts in the field of NIV. The committee developed recommendations based on the GRADE (Grading, Recommendation, Assessment, Development and Evaluation) methodology for each actionable question. The GRADE Evidence to Decision framework in the guideline development tool was used to generate recommendations. A number of topics were addressed using technical summaries without recommendations and these are discussed in the supplementary material. This guideline committee developed recommendations for 11 actionable questions in a PICO (population–intervention–comparison–outcome) format, all addressing the use of NIV for various aetiologies of ARF. The specific conditions where recommendations were made include exacerbation of chronic obstructive pulmonary disease, cardiogenic pulmonary oedema, de novo hypoxaemic respiratory failure, immunocompromised patients, chest trauma, palliation, post-operative care, weaning and post-extubation. This document summarises the current state of knowledge regarding the role of NIV in ARF. Evidence-based recommendations provide guidance to relevant stakeholders. ERS/ATS evidence-based recommendations for the use of noninvasive ventilation in acute respiratory failure http://ow.ly/NrqB30dAYSQ

Interpretation of Plain Chest Roentgenogram

Plain chest roentgenogram remains the most commonly ordered screening test for pulmonary disorders. Its lower sensitivity demands greater accuracy in interpretation. This greater accuracy can be achieved by adhering to an optimal and organized approach to interpretation. It is important for clinicians not to misread an abnormal chest radiograph (CXR) as normal. Clinicians can only acquire the confidence in making this determination if they read hundreds of normal CXRs. An individual should follow the same systematic approach to reading CXRs each time. All clinicians must make a concerted effort to read plain CXRs themselves first without reading the radiologist report and then discuss the findings with their radiology colleagues. Looking at the lateral CXR may shed light on 15% of the lung that is hidden from view on the posteroanterior film. Comparing prior films with the recent films is mandatory, when available, to confirm and/or extend differential diagnosis. This article outlines one of the many systematic approaches to interpreting CXRs and highlights the lesions that are commonly missed. A brief description of the limitations of CXR is also included.

The role of chest radiography and computed tomography in the diagnosis and management of asthma

Purpose of review The management of asthma is guided by clinical symptoms, physiological measurements, and response to therapy. Recent advances in computed tomography imaging promise to add a new dimension to our diagnostic armamentarium. Accurate representation of airway pathology, visualized by high-resolution chest computed tomography scan, helps to improve the understanding of the pathophysiology of asthma. In addition, findings on computed tomography may help to guide therapies for asthma. As radiologists provide us with sophisticated modalities that may also have a bearing on treatment, clinicians should stay abreast of this evolving noninvasive technology. Recent findings This review focuses on the findings seen on computed tomography imaging as related to asthma. Airway wall thickness is discussed and how it relates to disease progression and pulmonary function test. In addition, indirect findings such as bronchial dilatation and mosaic attenuation, both consequences of air-trapping, are discussed. Other investigational tools, such as endobronchial ultrasound and positron emission tomography, are described. Summary New modalities in radiology hold promise to aid in the understanding and treatment of small-airway disease. Although still considered investigational modalities, research evidence is fast accumulating. It behooves the clinician to have a heightened awareness regarding further advancements in this field.