Eric Gartman

Diaphragm ultrasound as a predictor of successful extubation from mechanical ventilation

Introduction The purpose of this study was to evaluate if ultrasound derived measures of diaphragm thickening, rather than diaphragm motion, can be used to predict extubation success or failure. Methods Sixty-three mechanically ventilated patients were prospectively recruited. Diaphragm thickness (tdi) was measured in the zone of apposition of the diaphragm to the rib cage using a 7–10 MHz ultrasound transducer. The percent change in tdi between end-expiration and end-inspiration (Δtdi%) was calculated during either spontaneous breathing (SB) or pressure support (PS) weaning trials. A successful extubation was defined as SB for >48 h following endotracheal tube removal. Results Of the 63 subjects studied, 27 patients were weaned with SB and 36 were weaned with PS. The combined sensitivity and specificity of Δtdi%≥30% for extubation success was 88% and 71%, respectively. The positive predictive value and negative predictive value were 91% and 63%, respectively. The area under the receiver operating characteristic curve was 0.79 for Δtdi%. Conclusions Ultrasound measures of diaphragm thickening in the zone of apposition may be useful to predict extubation success or failure during SB or PS trials.

Electromyographic analysis of repeated bouts of eccentric exercise

The repeated bout effect refers to the protective effect provided by a single bout of eccentric exercise against muscle damage from a similar subsequent bout. The aim of this study was to determine if the repeated bout was associated with an increase in motor unit activation relative to force production, an increased recruitment of slow-twitch motor units or increased motor unit synchronization. Surface electromyographic (EMG) signals were recorded from the hamstring muscles during two bouts of submaximal isokinetic (2.6 rad·s¹) eccentric (11 men, 9 women) or concentric (6 men, 4 women) contractions separated by 2 weeks. The EMG per unit torque and median frequency were analysed. The initial bout of eccentric exercise resulted in strength loss, pain and muscle tenderness, while the repeated eccentric bout resulted in a slight increase in strength, no pain and no muscle tenderness (bout x time effects, P < 0.05). Strength, pain and tenderness were unaffected by either bout of concentric exercise. The EMG per unit torque and median frequency were not different between the initial and repeated bouts of eccentric exercise. The EMG per unit torque and median frequency increased during both bouts of eccentric exercise (P < 0.01) but did not change during either concentric bout. In conclusion, there was no evidence that the repeated bout effect was due to a neural adaptation.

The relative stress on the Achilles tendon during ambulation in an ankle immobiliser: implications for rehabilitation after Achilles tendon repair

Background—After Achilles tendon repair, immediate weightbearing and immobilisation closer to neutral plantarflexion are thought to limit atrophy and stiffness, but may place deleterious stress on the repair. Objectives—To estimate the relative stress on the Achilles tendon during weightbearing with immobilisation in varying degrees of plantarflexion. Methods—Electromyographic (EMG) activity from the plantarflexors was recorded during walking in 10 subjects (six men, four women) without ankle pathology. Four walking conditions were examined: (a) normal walking; (b) immobilised (cam-walker) in neutral plantarflexion; (c) immobilised with a 0.5 inch heel lift; (d) immobilised with a 1 inch heel lift. EMG activity relative to plantarflexor torque was determined for each subject during isometric contractions at 25%, 50%, 75%, and 100% of maximal voluntary contraction (MVC). EMG activity during walking was calculated as a percentage of MVC based on the EMG-torque relation during graded isometric contractions. Results—During normal walking, the plantarflexor torque was estimated to be 30 (12)% (mean (SD)) of MVC, compared with 21 (15)% MVC for immobilisation in neutral (p<0.05), 17 (15)% MVC with the addition of a 0.5 inch heel lift (p<0.01), and 12 (12)% MVC with the addition of a 1 inch heel lift (p<0.01). The 1 inch heel lift resulted in less than 10° plantarflexion in all subjects. Conclusions—When the ankle is immobilised, stress on the Achilles tendon is determined by the degree of plantarflexion and the contractile activity of the plantarflexors. In the immobilised ankle, the addition of a 1 inch heel lift was sufficient to minimise plantarflexor activity during walking.

New developments in the assessment of COPD: early diagnosis is key

Chronic obstructive pulmonary disease (COPD) is the most common chronic lung disease in the world, and its associated health burdens and costs are mounting. Until recently, it was generally accepted that targeting the diagnosis of COPD early in its course was a relatively fruitless effort, since treatments other than already ubiquitous smoking-cessation efforts were unlikely to alter its course. However, there is strong evidence to suggest that the majority of patients with objective COPD are not aware of their condition, and this leads to a significant delay in diagnosis, more aggressive smoking-cessation intervention, and potential treatment. Novel methods of diagnostic testing, community health programs, and primary-care provider recommendations hold promise to expand the recognition of COPD in its incipient stages – where recent evidence suggests a rapid decline in lung function occurs and may be prevented if acted upon. This review explores the evidence to support the efforts to justify programs aimed at early diagnosis, alternative diagnostic strategies that may augment traditional spirometry, therapeutic modalities that could potentially be used in the future to alter early lung-function decline, and emphasizes the necessary cooperative role that physicians, patients, communities, and governments need to play to realize the significant health impact that stands to be gained.

Using serial severity scores to predict death in ICU patients: a validation study and review of the literature.

Purpose of reviewThe present study describes the use of serial severity scores to predict death in ICU patients and compares the results with previously published literature on this topic. Recent findingsPredicting mortality in critically ill patients has tremendous significance and methods to do so accurately have been studied for decades. The ability to accurately predict death impacts medical therapies, triaging, end-of-life care, and many other aspects of ICU care. There are many methods in existence to help physicians predict mortality, but most are not very accurate on an individual basis. The main tools available are severity scores, published outcomes data, and personal experience and all of them have significant limitations. One strategy that has been shown to be effective in accurately predicting death is to use serial severity scoring during the patients ICU admission. Recently, a retrospective study done on a large cohort of ICU patients at a single institution showed very high specificity in predicting death by using serial acute physiology, age, and chronic health evaluation (APACHE III) scores on days 1 and 3. The authors of this article sought to validate this study in a different institution using a slightly different model that was easier to use and might increase sensitivity. The results of this small study are presented with a review of the literature on the use of serial scores to predict death in ICU patients. SummaryOver the years multiple studies have shown that systems using serial severity scores can predict death in ICU patients with very high but not perfect accuracy. The clinical use of these systems remains low however and ultimately their main utility may be in research.

The use of thrombolytic therapy in pregnancy

The relative hypercoagulable state of pregnancy leads to an increased risk of thrombotic complications, of which some may be life-threatening or medically devastating. In the non-pregnant patient, the current guidelines suggest thrombolysis as the primary treatment in acute ischemic stroke, myocardial infarction when percutaneous intervention is unavailable, certain cases of mechanical valve thrombosis, and pulmonary embolism with hemodynamic compromise or shock. Given that clinical trial data regarding thrombolytic use in pregnant women are absent due to exclusion, the goal of this review is to summarize the available published data regarding the use of thrombolytic agents and subsequent outcomes and complications in pregnant women. Overall, the use of thrombolytic agents in pregnancy is associated with a relatively low reported complication rate, especially given the severe medical conditions for which they are indicated. The data would suggest that thrombolysis should be considered for appropriate indications similar to that of non-pregnant patients. However, caution should be exercised when drawing conclusions regarding maternal and fetal safety, given the lack of controlled clinical trials including pregnant women and the nature of the weak evidence level of the cumulative data presented in this review.

The role of natriuretic peptides in inflammation and immunity.

The natriuretic peptides (NPs) are a family of widely distributed, but evolutionarily conserved, polypeptide mediators that exert a range of effects throughout the body. There is growing realization that NP actions go far beyond volume and blood pressure homeostasis. Their pleiotropic effects include a significant role in regulating the immune system. Localization of NP receptors in various immune organs as well as in modulation of inflammation in vascular disease supports this hypothesis. Immune cells, including macrophages, dendritic cells, and T lymphocytes, express receptors for NPs. NPs are also involved in polarizing the immune response to allergens. NPs play an important role in shaping the early immune response to environmental antigens and appear to play a critical role in the interaction between cells of the innate and adaptive immune systems. The recent explosion of basic and clinical research has resulted in improved understanding of their molecular structure. This has facilitated development of chimeric forms of NPs as well as more convenient routes of administration. Thus, the NPs and their receptors could be exploited to develop therapeutics for the inflammatory and immune responses in wide range of diseases. Also discussed are several patents regarding NPs in the present review.

Physiology in Medicine: physiological basis of diaphragmatic dysfunction with abdominal hernias–implications for therapy

An incisional hernia is a common complication after abdominal surgery. Complaints of dyspnea in this population may be attributed to cardiopulmonary dysfunction or deconditioning. Large abdominal incisional hernias, however, may cause diaphragm dysfunction and result in dyspnea, which is more pronounced when standing (platypnea). The use of an abdominal binder may alleviate platypnea in this population. We discuss the link between diaphragm dysfunction and the lack of abdominal wall integrity and how abdominal wall support partially restores diaphragm function.

Methacholine-Induced Airway Hyper-Reactivity Phenotypes

Objective. The incorporation of airways conductance/resistance is a rare feature in clinical methacholine challenge test (MCT) protocols, and the majority of pulmonary laboratories rely solely on the spirometric parameters. The importance and interpretation of an MCT demonstrating a significant decline in specific airway conductance specific airway conductance (sGaw), but not forced expiratory volume in one second (FEV1), remains undefined. This study sought to elucidate the clinical and physiologic phenotypes of individuals with a ≥40% sGaw decline but <20% FEV1 change. Methods. All subjects completed the Asthma Quality of Life Questionnaire (AQLQ), followed by standard MCT, with measurements of sGaw and an additional independent measurement of resistance and reactance by impulse oscillation system (IOS) before and after MCT. Results. Of 201 subjects, 47(23.4%) were in Group 1 (FEV1 declined by ≥20%), 45(22.4%) were in Group 2 (non-significant FEV1 drop, sGaw declined ≥40%), and 109(54.2%) were in Group 3 (no significant decline in FEV1/sGaw). There was a nearly identical change in all oscillometric parameters and sGaw for Groups 1 and 2 versus Group 3. There were no differences between Groups 1 and 2 in any AQLQ category, and Groups 1 and 2 were statistically different from Group 3. Conclusions. Our prospective study suggests that patients with a significant sGaw decline alone during MCT are a clinically and physiologically important hyper-reactivity phenotype—whose hyper-reactivity independently was confirmed to be nearly identical to those with an FEV1 decline. By failing to assess airways conductance/resistance, asthma may be inappropriately “ruled out” in ∼20% of the patients referred for MCT. Based on this, standardized incorporation of body plethysmography and/or IOS to MCT protocols should be considered.

Pulmonary Function Testing in Neuromuscular and Chest Wall Disorders

Neuromuscular and chest wall disorders frequently compromise pulmonary function, and thorough respiratory evaluation often can assist in diagnosis, risk assessment, and prognosis. Because many of these disorders can be progressive, serial assessments are necessary to best define a trajectory of impairment (or improvement with therapy). This article covers the major respiratory testing modalities available in the evaluation of these patients, emphasizing both the benefits and shortcomings of each approach. Most parameters are available in a standard pulmonary laboratory (flows, volumes, static pressures), although referral to a specialized center may be necessary to conclusively evaluate a given patient.