Abstract
Background and objectiveLung mechanics measurements provide clinically useful information about disease progression and lung health. Currently, there are no commonly practiced methods to non-invasively measure both resistive and elastic lung mechanics during tidal breathing, preventing the important information provided by lung mechanics from being utilised. This study presents a novel method to easily assess lung mechanics of spontaneously breathing subjects using a dynamic elastance, single-compartment lung model.MethodsA spirometer with a built-in shutter was used to occlude expiration during tidal breathing, creating exponentially decaying flow when the shutter re-opened. The lung mechanics measured were respiratory system elastance and resistance, separated from the exponentially decaying flow, and interrupter resistance calculated at shutter closure. Progressively increasing resistance was added to the spirometer mouthpiece to simulate upper airway obstruction. The lung mechanics of 17 healthy subjects were successfully measured through spirometry.ResultsN = 17 (8 female, 9 male) healthy subjects were recruited. Measured decay rates ranged from 5 to 42/s, subjects with large variation of decay rates showed higher muscular breathing effort. Lung elastance measurements ranged from 3.9 to 21.2 cmH_2O/L, with no clear trend between change in elastance and added resistance. Resistance calculated from decay rate and elastance ranged from 0.15 to 1.95 cmH_2Os/L. These very small resistance values are due to the airflow measured originating from low-resistance areas in the centre of airways. Occlusion resistance measurements were as expected for healthy subjects, and increased as expected as resistance was added.ConclusionsThis test was able to identify reasonable dynamic lung elastance and occlusion resistance values, providing new insight into expiratory breathing effort. Clinically, this lung function test could impact current practice. It does not require high levels of cooperation from the subject, allowing a wider cohort of patients to be assessed more easily. Additionally, this test can be simply implemented in a small standalone device, or with standard lung function testing equipment.
Highlights
Background and objectiveLung mechanics measurements provide clinically useful information about disease progression and lung health
Underlying lung mechanics cannot be directly measured without further testing [4]
These mechanics are affected by lung disease, and monitoring how they change over time may provide a more accurate assessment of lung condition in response to therapy
Summary
Lung mechanics measurements provide clinically useful information about disease progression and lung health. This study presents a novel method to assess lung mechanics of spontaneously breathing subjects using a dynamic elastance, single-compartment lung model. Spirometry is the most frequently performed lung function test It is a simple and lowcost test which assesses lung health by analysing airflow and lung volume during specific breathing manoeuvres [1,2,3]. Underlying lung mechanics cannot be directly measured without further testing [4] These mechanics are affected by lung disease, and monitoring how they change over time may provide a more accurate assessment of lung condition in response to therapy. There is a need to link obtained spirometry data with clinically and physiologically relevant lung mechanics models
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