What term is used to describe the volume of air that can be expired forcefully after a normal expiration?
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Definition of expiratory reserve volume Show
Ask a medical professional for a definition of expiratory reserve volume (ERV) and they’ll offer something along the lines of: “The extra volume of air that can be expired from the lungs with determined effort following a normal tidal volume expiration.” Let’s make that easier to understand. Picture yourself sitting normally and breathing as you do when you are not exerting yourself orexercising. The amount of air you breathe in is your tidal volume. After you breathe out, try to exhale more until you are unable to breathe out any more air. The amount of air you can force out after a normal breath (think about blowing up a balloon) is your expiratory reserve volume. You can tap into this reserve volume when you exercise and your tidal volume increases. To sum up: Your expiratory reserve volume is the amount of extra air — above anormal breath — exhaled during a forceful breath out. The average ERV volume is about 1100 mL in males and 800 mL in females. Respiratory volumes are the amount of air inhaled, exhaled, and stored in your lungs. Along with expiratory reserve volume, some terms that are often part of a ventilatory pulmonary function test and can be helpful to know include:
The amount of lung capacity varies from person to person based on their physical makeup and their environment. You are likely to have a larger volume if you:
You are likely to have a smaller volume if you:
Your expiratory reserve volume is the amount of extra air — above-normal volume — exhaled during a forceful breath out. Measured with spirometry, your ERV is part of the data gathered in pulmonary function tests used to diagnose restrictive pulmonary diseases and obstructive lung diseases. The following terms describe the various lung (respiratory) volumes: Summing specific lung volumes produces the following lung capacities: Some of the air in the lungs does not participate in gas exchange. Such air is located in the anatomical dead space within bronchi and bronchioles—that is, outside the alveoli. Definitions
Anatomical (serial) dead space is the volume of air that never reaches alveoli and so never participates in respiration. It includes volume in upper and lower respiratory tract up to and including the terminal bronchioles Alveolar (distributive) dead space is the volume of air that reaches alveoli but never participates in respiration. This can reflect alveoli that are ventilated but not perfused, for example secondary to a pulmonary embolus. By OpenStax College [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons Fig 1 – Diagram showing various lung volumes. Measuring Volumes and CapacitiesSimple SpirometrySimple spirometry can measure tidal volume, inspiratory reserve volume and expiratory reserve volume. However, it cannot measure residual volume. Measured values are standardised for height, age and sex, although height is the factor with the greatest influence upon capacities. Process British Lung Foundation Fig 2 – Simple spirometry Helium dilutionHelium dilution is used to measure total lung capacity. However, it is only accurate if the lungs are not obstructed. If there is a point of obstruction, helium may not reach all areas of the lung during a ventilation, producing an underestimate as only ventilated lung volumes are measured. Process After quiet expiration, the subject breathes in a gas with a known concentration of helium (an inert gas). They hold their breath for 10 seconds, allowing helium to mix with air in the lungs, diluting the concentration of helium. The concentration of helium is then measured after expiration. The volume of air which is ventilated is then calculated according to the degree of dilution of the helium. Nitrogen washoutA method for calculating serial/anatomical dead space in the conducting airways up to and including the terminal bronchioles (usually 150mL). Process The subject takes a breath of pure oxygen and then exhales through a valve which measures nitrogen levels. At first, pure oxygen is exhaled, representing the dead space volume as the air exhaled never reached the alveoli and underwent gaseous exchange. Then, a mixture of dead space air and alveolar air is expired, meaning the detected concentration of nitrogen increases as nitrogen rich air from the dead space reaches the valve. After a few breaths, the lungs are washed out of pure oxygen, meaning that purely alveolar air is expired, with the nitrogen levels reflecting that of alveolar air. The levels of nitrogen measured over time can be used to calculate the anatomical dead space volume of the lungs. Visualising lung volumesVitalographA vitalograph creates plots of volume against time, using data collected from spirometry tests. Two important spirometry volumes that can be measured from a Vitalograph are:
The proportion of air that can be exhaled in the first second compared to the total volume of air that can be exhaled is important in assessing for possible airway obstruction. This proportion is known as the FEV1/FVC ratio. This ratio is important in clinically for diagnosis of respiratory conditions. By National Heart Lung and Blood Insitute (NIH) (National Heart Lung and Blood Insitute (NIH)) [Public domain], via Wikimedia Commons  Fig 3 – Image showing the process of spirometry using a spirometer. Flow volume loopThis plots flow over volume (showing expiratory flow and inspiratory flow as positive and negative values respectively). Important factors to consider when assessing flow-volume curves are as follows:
By Evgenios Metaxas MD MSc, Pulmonologist Ευγένιος Μεταξάς MD MSc, Πνευμονολόγος [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons Fig 4 – A flow-volume loop Nitrogen washout graphThis plots the percentage concentration of nitrogen in exhaled air (%N) against the total volume of air expired. The anatomical dead space is determined by the volume of exhaled air at which the volume below the washout curve (A1) is equal to the volume above the washout curve (A2). Boston University School of Medicine Figure 5 – A nitrogen washout curve Clinical relevance – Obstructive and Restrictive Deficits
In obstructive disease, the FEV1 is reduced due to increased resistance during expiration. Air trapping can also occur where more air is inspired than is expired, which can cause the residual volume to increase. In asthma, the obstruction is reversible which can aid in diagnosis. This means that FEV1/FVC will recover on re-test after the application of a bronchodilator such as salbutamol. The so-called ‘spooning‘ of a flow-volume curve in obstructive disease arises when the affected small airways begin to collapse. As air exits the thorax in expiration, the pressure within the small airways reduces and thus the small airways are no longer propped open. This increases resistance to expiration and therefore reduces flow. Examples of obstructive diseases are asthma, COPD (chronic bronchitis, emphysema), tracheal stenosis and large airway tumours. By User:Evgenios Metaxas MD MSc, Pulmonologist Ευγένιος Μεταξάς MD MSc, Πνευμονολόγος [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons Fig 6 – Spirometry of a patient with asthma, an obstructive disorder. In restrictive disease, the FVC is reduced due to poor lung expansion. This can be neurological, due to weak inspiratory muscles or due to an anatomical deformity. This causes the inspiratory reserve volume to be reduced as the lungs can’t inflate as much during maximum inspiration. Residual volume can also be reduced as expiration is more effective than inspiration. Examples of restrictive diseases are interstitial pulmonary fibrosis, muscle weakness, kyphoscoliosis, obesity, tense ascites. What is the term for the volume of expired air at forced expiration?Forced expiratory volume (FEV) measures how much air a person can exhale during a forced breath. The amount of air exhaled may be measured during the first (FEV1), second (FEV2), and/or third seconds (FEV3) of the forced breath. Forced vital capacity (FVC) is the total amount of air exhaled during the FEV test.
What is the term that describes the amount of air a person can inhale forcefully after normal tidal volume inspiration?The inspiratory reserve volume is the amount of air a person can inhale forcefully after normal tidal volume inspiration; the expiratory reserve volume is the amount of air a person can exhale forcefully after a normal exhalation.
What is the name of the total volume of air that can be forcibly expired after a complete and full inspiration?Total Lung Capacity
The vital capacity (VC) is the maximal volume of gas exhaled during a forced exhalation after a forced inhalation. Thus VC is the sum of the VT, IRV, and ERV. The VC is approximately 4.5 L in a healthy 70-kg adult.
Which of these terms is used to describe the volume of air inspired or expired during the process of normal respiration?The volume of air inspired or expired during normal respiration is called tidal volume. The average human has a tidal volume of approximately 500cm3.
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