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Lung volumes
Published in Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod, The Primary FRCA Structured Oral Examination Study Guide 1, 2017
Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod
Describe how nitrogen washout may be used to measure RV and FRC. The fractional lung nitrogen concentration (FLN2) is constant at 79% (i.e. 790 mL per 1000 mL air). The subject rebreathes several times from a bag of known volume containing a nitrogen-free gas. Thus, the nitrogen from the patient’s lungs equilibrates with gas in the bag and so the nitrogen concentration will decrease as the volume of distribution has increased.In order to measure RV, the rebreathing process is started from the end of a maximal expiration (i.e. from RV).In order to measure FRC, the rebreathing process is started from the end of a normal tidal breath (i.e. from FRC).The principle behind the nitrogen washout method is that the amount of nitrogen at the start of the determination (nitrogen in the patient’s lungs only) is the same amount that ultimately is distributed between the lung and the bag. As the volume of the bag and the fractional concentration of nitrogen in the lungs are known, the fractional concentration of nitrogen In the bag at equilibration is measured, allowing calculation of either RV or FRC.
Questions and answers
Published in Swati Gupta, Alexandra Marsh, David Dunleavy, Kevin Channer, Cardiology and the Cardiovascular System on the move, 2015
Swati Gupta, Alexandra Marsh, David Dunleavy, Kevin Channer
A neonate presents shortly after birth with signs of circulatory collapse. On a nitrogen washout test his oxygen saturations do not increase. The only pulse palpable is in the right arm. It is noticed that he also has a cleft palate and dysmorphic appearance.
Pleural disease induced by drugs
Published in Philippe Camus, Edward C Rosenow, Drug-induced and Iatrogenic Respiratory Disease, 2010
Recreational drug-related spontaneous pneumomediastinum is typically self-limited. These individuals can usually be managed as outpatients with supportive care and analgesia. Clinical and radiological resolution may be hastened by oxygen therapy that enhances the nitrogen washout effect from mediastinal air-pockets.
A teenaged patient with spontaneous pneumopericardium after hookah smoking
Published in Clinical Toxicology, 2022
An initial evaluation to determine the etiology for a teenaged patient with undifferentiated CP included: normal EKG [normal sinus rhythm, with no evidence of arrhythmia, ventricular hypertrophy, or ischemia]; chest radiographic imaging (Figures 1 and 2) revealed a spontaneous pneumopericardium [SPP] [arrows]. Serum troponin was <0.010. A serum carboxyhemoglobin level was not measured. The patient was admitted to the intensive care unit, and treated with supplemental oxygen to effect a “nitrogen washout”. There was complete radiographic resolution of the SPP after 24 h of oxygen therapy. It was only after multiple interviews by the medical team that he admitted to hookah smoking of cannabis for the past year, several times per week; and that he had smoked a hookah approximately 2 h prior to CP onset.
A multimodal approach to detect and monitor early lung disease in cystic fibrosis
Published in Expert Review of Respiratory Medicine, 2021
Pedro Mondéjar-López, Alexander Horsley, Felix Ratjen, Silvia Bertolo, Helene de Vicente, Òscar Asensio de la Cruz
Measuring LCI in infants can be especially difficult. At the rapid respiratory rates encountered in infants and young children, correct alignment of air flow and tracer gas signals becomes increasingly challenging to perform. Overall accuracy of the measurement is affected by small degrees of signal misalignment as well as by response times of the analyzers [65]. Choice of tracer gas is also important. Use of 100% oxygen during nitrogen washout is known to affect infant respiratory patterns and lung volumes, having demonstrated association with a temporary decline in tidal volume and lower functional residual capacity in infants [66,67]. Although the technique is generally considered acceptable in older preschool children, the age at which breathing 100% oxygen ceases to adversely affect washout physiology is unknown [68]. Alternatively, SF6 can be measured directly using a mass spectrometer [31,69] or indirectly using an ultrasonic flowmeter to derive SF6 concentration from expired viscosity [31,69,70]. Both methods require 4% SF6 which, at this concentration, may affect infant respiratory patterns due to increased density of the inspirate [71]. A recently reported alternative method that uses 0.2% SF6 may overcome many of these issues [72,73]. In all cases, measurement in an unsedated infant is challenging and, as such, it is usual to attempt the technique using light sedation [69,73].
Anti-IL-5 monoclonal antibodies for the treatment of asthma: an update
Published in Expert Opinion on Biological Therapy, 2020
Two meta-analysis of randomized placebo-controlled trials in patients with severe eosinophilic asthma found that mepolizumab treatment reduced exacerbation rates and improved the quality of life [29] or halved exacerbations that required hospitalization and/or emergency interventions [30]. A systematic literature review and indirect treatment comparison [31] found that mepolizumab to be at least as effective as the IgE inhibitor omalizumab in improving lung function in patients with severe asthma with similar tolerability profiles. These clinically relevant reductions in exacerbations were associated with eosinophil blood counts greater than 150 cells per microliter [32], thereby demonstrating the utility of blood eosinophil levels as a simple biomarker associated with positive clinical responses to mepolizumab treatment. To date, most clinical trials with mepolizumab reported primary outcomes at six months or later after initiation of treatment, although apparent improvements were noted within one month of commencing mepolizumab. In this regard, Farah and colleagues [33] have recently reported significant effects on lung function and quality-of-life in a prospective cohort of 20 subjects with severe eosinophilic asthma at 4-weeks following commencement of sub-cutaneous mepolizumab treatment. The use of the multiple breath nitrogen washout test to measure small airway function [34], demonstrated improvement in ventilation inhomogeneity that was evident in the absence of any change to other asthma medication in the first month, an outcome that was sustained for six months.