Learning Outcomes
- Identify the basic principles of gas exchange
- Name and describe lung volumes and capacities
Basic Principles of Gas Exchange
Gas exchange during respiration occurs primarily through diffusion. Diffusion is a process in which transport is driven by a concentration gradient. Gas molecules move from a region of high concentration to a region of low concentration. Blood that is low in oxygen concentration and high in carbon dioxide concentration undergoes gas exchange with air in the lungs. The air in the lungs has a higher concentration of oxygen than that of oxygen-depleted blood and a lower concentration of carbon dioxide. This concentration gradient allows for gas exchange during respiration.
Partial pressure is a measure of the concentration of the individual components in a mixture of gases. The total pressure exerted by the mixture is the sum of the partial pressures of the components in the mixture. The rate of diffusion of a gas is proportional to its partial pressure within the total gas mixture. This concept is discussed further in detail below.
Lung Volumes and Capacities
Different animals have different lung capacities based on their activities. Cheetahs have evolved a much higher lung capacity than humans; it helps provide oxygen to all the muscles in the body and allows them to run very fast. Elephants also have a high lung capacity. In this case, it is not because they run fast but because they have a large body and must be able to take up oxygen in accordance with their body size.
Human lung size is determined by genetics, gender, and height. At maximal capacity, an average lung can hold almost six liters of air, but lungs do not usually operate at maximal capacity. Air in the lungs is measured in terms of lung volumes and lung capacities (seeFigure 1 and Table 1). Volume measures the amount of air for one function (such as inhalation or exhalation). Capacity is any two or more volumes (for example, how much can be inhaled from the end of a maximal exhalation).
Figure 1.Human lung volumes and capacities are shown. The total lung capacity of the adult male is six liters. Tidal volume is the volume of air inhaled in a single, normal breath. Inspiratory capacity is the amount of air taken in during a deep breath, and residual volume is the amount of air left in the lungs after forceful respiration.
| Table 1. Lung Volumes and Capacities (Avg Adult Male) | |||
|---|---|---|---|
| Volume/Capacity | Definition | Volume (liters) | Equations |
| Tidal volume (TV) | Amount of air inhaled during a normal breath | 0.5 | – |
| Expiratory reserve volume (ERV) | Amount of air that can be exhaled after a normal exhalation | 1.2 | – |
| Inspiratory reserve volume (IRV) | Amount of air that can be further inhaled after a normal inhalation | 3.1 | – |
| Residual volume (RV) | Air left in the lungs after a forced exhalation | 1.2 | – |
| Vital capacity (VC) | Maximum amount of air that can be moved in or out of the lungs in a single respiratory cycle | 4.8 | ERV+TV+IRV |
| Inspiratory capacity (IC) | Volume of air that can be inhaled in addition to a normal exhalation | 3.6 | TV+IRV |
| Functional residual capacity (FRC) | Volume of air remaining after a normal exhalation | 2.4 | ERV+RV |
| Total lung capacity (TLC) | Total volume of air in the lungs after a maximal inspiration | 6.0 | RV+ERV+TV+IRV |
| Forced expiratory volume (FEV1) | How much air can be forced out of the lungs over a specific time period, usually one second | ~4.1 to 5.5 | – |
The volume in the lung can be divided into four units: tidal volume, expiratory reserve volume, inspiratory reserve volume, and residual volume. Tidal volume (TV) measures the amount of air that is inspired and expired during a normal breath. On average, this volume is around one-half liter, which is a little less than the capacity of a 20-ounce drink bottle. The expiratory reserve volume (ERV) is the additional amount of air that can be exhaled after a normal exhalation. It is the reserve amount that can be exhaled beyond what is normal. Conversely, the inspiratory reserve volume (IRV) is the additional amount of air that can be inhaled after a normal inhalation. The residual volume (RV) is the amount of air that is left after expiratory reserve volume is exhaled. The lungs are never completely empty: There is always some air left in the lungs after a maximal exhalation. If this residual volume did not exist and the lungs emptied completely, the lung tissues would stick together and the energy necessary to re-inflate the lung could be too great to overcome. Therefore, there is always some air remaining in the lungs. Residual volume is also important for preventing large fluctuations in respiratory gases (O2 and CO2). The residual volume is the only lung volume that cannot be measured directly because it is impossible to completely empty the lung of air. This volume can only be calculated rather than measured.
Capacities are measurements of two or more volumes. The vital capacity (VC) measures the maximum amount of air that can be inhaled or exhaled during a respiratory cycle. It is the sum of the expiratory reserve volume, tidal volume, and inspiratory reserve volume. The inspiratory capacity (IC) is the amount of air that can be inhaled after the end of a normal expiration. It is, therefore, the sum of the tidal volume and inspiratory reserve volume. The functional residual capacity (FRC) includes the expiratory reserve volume and the residual volume. The FRC measures the amount of additional air that can be exhaled after a normal exhalation. Lastly, the total lung capacity (TLC) is a measurement of the total amount of air that the lung can hold. It is the sum of the residual volume, expiratory reserve volume, tidal volume, and inspiratory reserve volume.
Lung volumes are measured by a technique called spirometry. An important measurement taken during spirometry is the forced expiratory volume (FEV), which measures how much air can be forced out of the lung over a specific period, usually one second (FEV1). In addition, the forced vital capacity (FVC), which is the total amount of air that can be forcibly exhaled, is measured. The ratio of these values (FEV1/FVC ratio) is used to diagnose lung diseases including asthma, emphysema, and fibrosis. If the FEV1/FVC ratio is high, the lungs are not compliant (meaning they are stiff and unable to bend properly), and the patient most likely has lung fibrosis. Patients exhale most of the lung volume very quickly. Conversely, when the FEV1/FVC ratio is low, there is resistance in the lung that is characteristic of asthma. In this instance, it is hard for the patient to get the air out of their lungs, and it takes a long time to reach the maximal exhalation volume. In either case, breathing is difficult and complications arise.
Practice Questions
The inspiratory reserve volume measures the ________.
- amount of air remaining in the lung after a maximal exhalation
- amount of air that the lung holds
- amount of air the can be further exhaled after a normal breath
- amount of air that can be further inhaled after a normal breath
Show Answer
Of the following, which does not explain why the partial pressure of oxygen is lower in the lung than in the external air?
- Air in the lung is humidified; therefore, water vapor pressure alters the pressure.
- Carbon dioxide mixes with oxygen.
- Lungs exert a pressure on the air to reduce the oxygen pressure.
- Oxygen is moved into the blood and is headed to the tissues.
Show Answer
The total lung capacity is calculated using which of the following formulas?
- residual volume + expiratory reserve volume + tidal volume + inspiratory reserve volume
- residual volume + tidal volume + inspiratory reserve volume
- residual volume + expiratory reserve volume + inspiratory reserve volume
- expiratory reserve volume + tidal volume + inspiratory reserve volume
Show Answer
Careers in ScienCE
Respiratory Therapist
Respiratory therapists or respiratory practitioners evaluate and treat patients with lung and cardiovascular diseases. They work as part of a medical team to develop treatment plans for patients. Respiratory therapists may treat premature babies with underdeveloped lungs, patients with chronic conditions such as asthma, or older patients suffering from lung disease such as emphysema and chronic obstructive pulmonary disease (COPD). They may operate advanced equipment such as compressed gas delivery systems, ventilators, blood gas analyzers, and resuscitators. Specialized programs to become a respiratory therapist generally lead to a bachelor’s degree with a respiratory therapist specialty. Because of a growing aging population, career opportunities as a respiratory therapist are expected to remain strong.
Respiratory therapists use various tests to evaluate patients. For example, theytest lung capacity by having patients breathe into an instrument that measures the volume and flow of oxygen when they inhale and exhale. Respiratory therapists also may take blood samples and use a blood gas analyzer to test oxygen and carbon dioxide levels.
Respiratory therapists also perform chest physiotherapy on patients to remove mucus from their lungs and make it easier for them to breathe. Removing mucus is necessary for patients suffering from lung diseases, such as cystic fibrosis, and it involves the therapist vibrating the patient’s rib cage, often by tapping the patient’s chest and encouraging him or her to cough. Respiratory therapists may connect patients who cannot breathe on their own to ventilators that deliver oxygen to the lungs. Therapists insert a tube in the patient’s windpipe (trachea) and connect the tube to ventilator equipment. They set up and monitor the equipment to ensure that the patient is receiving the correct amount of oxygen at the correct rate.
Respiratory therapists who work in home care teach patients and their families to use ventilators and other life-support systems in their homes. During these visits, they may inspect and clean equipment, check the home for environmental hazards, and ensure that patients know how to use their medications. Therapists also make emergency home visits when necessary.
In some hospitals, respiratory therapists are involved in related areas, such as diagnosing breathing problems for people with sleep apnea and counseling people on how to stop smoking.
In Summary:Breathing Capacity
The lungs can hold a large volume of air, but they are not usually filled to maximal capacity. Lung volume measurements include tidal volume, expiratory reserve volume, inspiratory reserve volume, and residual volume. The sum of these equals the total lung capacity.
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FAQs
How do you calculate breathing capacity? ›
This relationship calculates as the total lung capacity equaling the sum of functional residual capacity and the inspiratory capacity or as the equation: TLC = FRC + IC.
What is the average score for lung capacity test? ›Peak expiratory flow (PEF) is measured in litres per minute. Normal adult peak flow scores range between around 400 and 700 litres per minute, although scores in older women can be lower and still be normal.
What is normal maximum breathing capacity? ›Did you know that the maximum amount of air your lungs can hold—your total lung capacity—is about 6 liters? That is about three large soda bottles.
What is respiratory capacity quizlet? ›It is the maximum volume of air that a person can expel from the respiratory tract after a maximum inspiration. Total Lung Capacity. The sum of the inspiratory and expiratory reserves and the tidal and residual volumes (about 5800mL). The total lung capacity is also equal to the vital capacity plus the residual volume.
What is the formula for breathing? ›Aerobic respiration takes place in the mitochondria and requires oxygen and glucose, and produces carbon dioxide, water, and energy. The chemical equation is C6H12O6 + 6O2 → 6CO2 + 6H2O (glucose + oxygen -> carbon dioxide + water).
What is considered poor lung capacity? ›Normal: FEV1 is greater or equal to 80% of predicted value. Mild obstruction: FEV1 is greater or equal to 70% and less than 80% of predicted value. Moderate obstruction: FEV1 is greater or equal to 60% and less than 100% of predicted value.
What is a good number on a spirometer? ›Normal values in healthy males aged 20-60 range from 4.5 to 3.5 liters, and normal values for females aged 20-60 range from 3.25 to 2.5 liters.
What is poor lung capacity? ›Restrictive lung disease, a decrease in the total volume of air that the lungs are able to hold, is often due to a decrease in the elasticity of the lungs themselves or caused by a problem related to the expansion of the chest wall during inhalation.
What is normal breathing level? ›When checking respiration, it is important to also note whether a person has any difficulty breathing. Normal respiration rates for an adult person at rest range from 12 to 16 breaths per minute.
How do I read my pulmonary function test results? ›If the FVC and the FEV1 are within 80% of the reference value, the results are considered normal. The normal value for the FEV1/FVC ratio is 70% (and 65% in persons older than age 65). When compared to the reference value, a lower measured value corresponds to a more severe lung abnormality.
What is normal breathing effort? ›
A normal breathing rate for an adult at rest is 8 to 16 breaths per minute. For an infant, a normal rate is up to 44 breaths per minute.
What is vital capacity Short answer? ›The vital capacity is called the sum total volume of air that can be expired after maximum inhalation or maximum air that a person can breathe in after forced expiration. It is very important to measure a person's respiratory health.
What is vital capacity answers? ›Vital capacity (VC) is the maximum amount of air a person can expel from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume.
What makes respiratory capacity? ›Lung Capacities
It is the sum of the expiratory reserve volume, tidal volume, and inspiratory reserve volume. The inspiratory capacity (IC) is the amount of air that can be inhaled after the end of a normal expiration. It is, therefore, the sum of the tidal volume and inspiratory reserve volume.
The diaphragm (a muscle under the lungs) moves down. This makes more space for the lungs which fill up with air from the mouth and nose. The air moves through tubes in the lungs to tiny air sacs called alveoli. Oxygen passes from these into the blood, which carries the oxygen to all the cells in the body.
What are the 3 stages of breathing? ›The breathing cycle can be divided into three basic stages including rest, inspiration, and expiration which are discussed separately below.
What are the 4 steps of breathing? ›- Ventilation.
- Pulmonary gas exchange.
- Gas transport.
- Peripheral gas exchange.
There's no such thing as failing a PFT. If it's abnormal, your provider will discuss additional work you may need to obtain a diagnosis and a treatment plan.
What causes you to fail a pulmonary test? ›Abnormal results usually mean that you may have chest or lung disease. Some lung diseases (such as emphysema, asthma, chronic bronchitis, and infections) can make the lungs contain too much air and take longer to empty. These lung diseases are called obstructive lung disorders.
How do you pass a pulmonary breathing test? ›- No bronchodilator medication for four hours.
- No smoking for four hours before the test.
- No heavy meals.
- Do not wear any tight clothing.
- The complete pulmonary function test takes around one and a half hours.
Can you improve lung capacity? ›
Yes, diaphragmatic breathing and other types of breathing exercises can potentially help maintain or increase lung capacity in those without underlying lung conditions. Increasing physical activity can also help maintain lung function.
What makes your lung capacity worse? ›Your lung capacity is the total amount of air that your lungs are able to hold. As we age, our lung capacity tends to decrease. However, our lung capacity can also decrease due to a chronic disease or extreme illness such as COPD, COVID-19, or cancer.
What is the best way to increase lung capacity? ›Exhale from your mouth, and then inhale again through your nose, feeling your stomach rise each time. If possible, hold your breath for 7 seconds, and breathe out for 8 seconds. You should contract your abdominal muscles to push all the air out of your lungs. Repeat 5 times.
What is normal lung capacity spirometer? ›Normal findings of spirometry are an FEV1/FVC ratio of greater than 0.70 and both FEV1 and FVC above 80% of the predicted value. If lung volumes are performed, TLC above 80% of the predictive value is normal. Diffusion capacity above 75% of the predicted value is also considered normal.
What value indicates a lung problem? ›The ratio of FVC and FEV1 can help doctors diagnose the specific type of lung disease a person has. To calculate this ratio, a doctor divides the FVC reading by the FEV1 result. When the value of FEV1 is less than 70% of an FVC in adults or below 85% in those aged 5–18 years, an obstruction may be present.
What is a normal reading for incentive spirometer? ›Incentive Spirometer Goal by Age
However, if you still want to know the incentive spirometer goals by age, there are general goals for both genders based on age. For males between the ages of 20 and 60, their normal values are from 4.75 – 5.5 Litres, and for females between the age of 20 and 60 are 3.25 – 3.75 Litres.
The lungs' large surface area exposes the organ to a continual risk of damage from pathogens, toxins or irritants; however, lung damage can be rapidly healed via regenerative processes that restore its structure and function.
How do you build weak lungs? ›- Diaphragmatic breathing. ...
- Simple deep breathing. ...
- 'Counting' your breaths. ...
- Watching your posture. ...
- Staying hydrated. ...
- Laughing. ...
- Staying active. ...
- Joining a breathing club.
o You need to understand that if lung function has fallen to less than 30% of normal then 50 in 100 patients will die within 2-3 years and 50 in 100 will be alive.
What percentage of lung capacity is asthma? ›If your lung function drops by at least 20%, you have asthma.
What is a good breathing pattern? ›
The correct way to breathe is called belly breathing, also known as diaphragmatic breathing or horizontal breathing. What you do is inhale using your belly. Your belly should come outward as you take in air, and you'll feel your lungs opening up. This draws oxygen all the way down into the bottom of your lungs.
What is total lung capacity formula? ›The total lung capacity (TLC) is the volume of gas in the lung at the end of a full inspiration. It is either calculated from: TLC = RV+IVC, or from: TLC = FRC+IC; the latter is the preferred method in body plethysmography. It can also be measured directly by the radiologic technique.
How do you use vital capacity? ›- You are seated in a chair and asked to breathe comfortably.
- A clip is placed over your nose.
- You are given a tube to breathe into.
- Sealing your lips tightly over the tube, you are asked to inhale as deeply as possible. You then exhale as forcefully as you can.
Measuring forced vital capacity (FVC) is part of a spirometry or pulmonary function test that is conducted to assess lung health, airflow, and help in disease diagnosis and effectiveness of medical treatment.
What is vital capacity and lung capacity? ›Background: Vital Capacity (VC) is defined as a change in volume of lung after maximal inspiration followed by maximal expiration is called Vital Capacity of lungs. It is the sum of tidal volume, inspiratory reserve volume . and expiratory reserve volume. Vital capacity of normal adults ranges between 3 to 5 litres.
What is vital capacity and total lung capacity? ›The total lung capacity (TLC) is the maximal volume of gas in the lungs after a maximal inhalation; thus it is the sum of the RV, ERV, VT, and IRV. TLC is approximately 6 L for a healthy 70-kg adult. The vital capacity (VC) is the maximal volume of gas exhaled during a forced exhalation after a forced inhalation.
What is vital capacity quizlet? ›Vital Capacity (VC) The vital capacity is the maximum amount of air that you can move into or out of your lungs in a single respiratory cycle. The vital capacity is the sum of the expiratory reserve volume.
What affects lung capacity? ›Physiological factors that influence lung volumes/capacities include age, gender, weight, height and ethnicity, physical activity, altitude and others, which should be considered while interpreting results of spirometry.
How are the four respiratory capacities calculated? ›It is calculated by summing tidal volume, inspiratory reserve volume, and expiratory reserve volume. VC = TV+IRV+ERV. It is the amount of air remaining in the lungs at the end of a normal exhalation.
What is normal vital capacity? ›Vital capacity (VC), the volume of exhaled air after maximal inspiration, normally is 60 to 70 mL/kg and in normal persons is determined primarily by the size of the thorax and lungs. Reduction of VC to 30 mL/kg is associated with weak cough, accumulation of oropharyngeal secretions, atelectasis, and hypoxemia.
What is the formula of total lung capacity? ›
*TLC is the volume of air in the lungs at maximal inspiration. (Also, TLC= VC+RV).
How do you calculate respiratory volume and capacities? ›- Residual Volume (RV) (see image below)– the amount of air remaining in the lungs after an ERV (= about 1,200 ml in men & women).
- Respiratory (lung) capacities (= two or more respiratory volumes added together):1. Inspiratory capacity = TV + IRV. Functional reserve capacity = ERV + RV.
Minute ventilation = tidal volume x respiratory rate (normal is 4-6 L/min)
What is total lung capacity quizlet? ›total lung capacity (TLC) volume of air in the lungs after a maximal inhalation.
How is lung volume capacity calculated quizlet? ›It is calculated by summing tidal volume, inspiratory reserve volume, and expiratory reserve volume. It is the amount of air remaining in the lungs at the end of a normal exhalation. it is calculated by adding together residual and expiratory reserve volumes. The normal value is about 1800-2200 mL.
What are the terms for lung capacity? ›Four standard lung volumes, namely, tidal (TV), inspiratory reserve (IRV), expiratory reserve (ERV), and residual volumes (RV) are described in the literature. Alternatively, the standard lung capacities are inspiratory (IC), functional residual (FRC), vital (VC) and total lung capacities (TLC).
How do you manually calculate breathing rate? ›It's best to take your respiratory rate while sitting up in a chair or in bed. Measure your breathing rate by counting the number of times your chest or abdomen rises over the course of one minute. Record this number.
What is a normal respiratory minute volume? ›Physiological significance of minute volume
A normal minute volume while resting is about 5–8 liters per minute in humans. Minute volume generally decreases when at rest, and increases with exercise. For example, during light activities minute volume may be around 12 litres.
Respiratory rate is a fundamental vital sign that is sensitive to different pathological conditions (e.g., adverse cardiac events, pneumonia, and clinical deterioration) and stressors, including emotional stress, cognitive load, heat, cold, physical effort, and exercise-induced fatigue.