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Published in Calver Pang, Ibraz Hussain, John Mayberry, Pre-Clinical Medicine, 2017
Calver Pang, Ibraz Hussain, John Mayberry
The functional residual capacity is the volume of air in the lungs at the end of expiration. This volume cannot be expired entirely hence cannot be measured by spirometry. However, this can be measured by the helium dilution technique.
Chapter Paper 3 Questions
Published in James Day, Amy Thomson, Tamsin McAllister, Nawal Bahal, Get Through, 2014
James Day, Amy Thomson, Tamsin McAllister, Nawal Bahal
When measuring lung volumes:The helium dilution method measures the total volume of gas in the lungA spirometer measures all lung volumes and capacities except residual volumeIn the helium dilution technique the patient is connected to the spirometer after a maximal expirationHelium is used due to its low solubility in bloodThe body plethysmograph uses the principle of Boyle’s law
Mechanical Properties of the Lungs
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Many of the lung volumes described can be measured by observing ventilation through a simple water volumetric spirometer. The residual volume (RV) (and therefore FRC and total lung capacity) cannot be measured in this way, requiring the use of gas dilution techniques. The volumes given in the following list are average values for adults (Figure 16.5): Functional residual capacity (FRC). This is the 2500 mL of air in the lungs at the end of a normal expiration (when the subject is standing). The FRC is the volume of the lungs at which the elastic outward force of chest wall expansion is balanced by the inward recoil of the lungs; muscular tone in the diaphragm is also involved (when this is lost, FRC falls by 400 mL).Tidal volume. This is a normal resting breath, usually about 500 mL. Tidal volume is measured by spirometry as the volume difference between resting inspiratory volume to the FRC.Inspiratory reserve volume. This is the volume of air that can be inspired over and above the resting tidal volume, and it is normally about 3000 mL.Inspiratory capacity. This is the total volume (3500 mL) that can be inspired from the resting expiratory state from the FRC.Vital capacity. This is the maximal volume (4500–5000 mL) expired after a maximal inspiration.Total lung capacity. This is the total volume (6000 mL) of air in the lungs after a maximal inspiration (this cannot be measured by simple spirometry).Expiratory reserve volume. This is the additional volume (1500 mL) that can be expired at the end of a normal expiration (from the FRC).Residual volume (RV). This is the volume of air (1000–1200 mL) remaining in the lungs after a maximal expiration. RV and FRC cannot be measured by simple spirometry because the lungs cannot be emptied completely after a forced expiration. They can be measured indirectly using a dilution technique involving 10% helium. The helium dilution technique is an excellent technique for the measurement of FRC and RV in normal individuals. In patients with diseased lungs, the helium dilution technique gives a falsely low FRC value because of trapped gas in the lungs. This problem can be overcome by using the body plethysmography technique where the lung volume is determined by applying Boyle's law.
Lung function in relation to six-minute walk test in pulmonary hypertension
Published in European Clinical Respiratory Journal, 2020
Amir Farkhooy, Michaela Bellocchia, Hans Hedenström, Daniela Libertucci, Caterina Bucca, Christer Janson, Paolo Solidoro, Andrei Malinovschi
Twenty-two patients (44%) presented exertional desaturation following the 6MWT. Lower levels of DLCO/VA, resting SpO2, FEV1/VC and PaO2 were significantly associated with exercise-induced oxygen desaturation (Table 4). None of the lung volumes obtained through the helium dilution technique showed a significant correlation with exertional desaturation. Lower DLCO/VA (OR 0.02, CI 0.001–0.4, p = 0.01), FEV1/VC-ratios (OR 0.92, CI 0.84–0.997, p = 0.04) and resting PaO2-values (OR 0.95, CI 0.89–0.999, p = 0.04) remained significantly correlated with desaturation also in a logistic regression model adjusted for age, sex, BMI, and smoking habits. After exclusion of COPD patients from above analyses, lower DLCO/VA (OR 0.01, CI 0.0004–0.33, p = 0.009), FEV1/VC-ratios (OR 0.90, CI 0.81–0.99, p = 0.04) and resting SpO2-values (OR 0.67, CI 0.46–0.98, p = 0.04) remained significantly correlated with desaturation in the adjusted logistic regression model.
Accuracy of optoelectronic plethysmography in childhood exercise-induced asthma
Published in Journal of Asthma, 2019
Larissa Andrade de Sá Feitosa, Murilo Carlos Amorim de Britto, Andrea Aliverti, Jéssica Brito Noronha, Armèle Dornelas de Andrade
Dellacà et al. (31) studied sedated and anaesthetized patients with respiratory failure on mechanical ventilation and demonstrated that OEP is reproducible in evaluating EEVcw variations resulting from changes in end-expiratory pressure of the ventilator. The author also found a strong positive correlation between EEVcw of OEP and end-expiratory lung volume recorded by the helium dilution technique. The EEVcw tends to decline during exercise to contribute to the increase in tidal volume among healthy individuals (32,33). However, in those with COPD, EEVcw tends to rise during exercise, primarily due to the limited expiratory flow in these patients (18,34). In an investigation of children with asthma, Kosmas et al. (35) reported that most of the asthmatics studied exhibited limited expiratory flow and dynamic hyperinflation when exercising, including those without EIA. According to Calverley & Koulouris (34), when expiratory flow is already limited at rest, any increase in ventilation during exercise can cause dynamic hyperinflation. The present study recorded a rise in EEVcw in the EIA group and a consequent increase in hyperinflation of the chest wall following exercise. However, those without EIA exhibited a decrease in EEVcw after exercise similar to that observed by Alivert et al. and Vogiatzis et al. (32,33) in healthy individuals.