Breath volume is the volume of air that is normally inhaled and exhaled, usually unconsciously, per breath. At rest, the volume of breath is about 500 milliliters, but it can increase to about 2.5 liters when muscles are required to work hard. Breath volume can be significantly increased by voluntary activation of the inspiratory and expiratory reserve volumes.
What is respiratory volume?
Breath volume is the volume of air that is normally inhaled and exhaled, usually unconsciously, per breath. Breath volume (BV) is the volume of air that is normally inhaled and exhaled per breath. It is mostly the unconscious breathing. The volume of air in a breath is about 0.5 liters at rest, but can increase to 2.5 liters with greater demand for effort. This value can be increased again by the inspiratory and expiratory reserve volumes by voluntary breathing. The inspiratory reserve volume can be used by voluntary deep inhalation involving diaphragmatic breathing, and the expiratory reserve volume can be activated by voluntary deep exhalation. When both reserve volumes are fully utilized, the respiratory volume is then identical to the vital capacity, the maximum usable volume of air for respiration. Accordingly, the AZV can be controlled vegetatively not only due to variable performance requirements, but also by consciously influencing respiration. The vital capacity in untrained persons is 4.5 l on average. In trained endurance athletes it can exceed 7 l. The size of the AZV does not say much about the performance of the respiratory system. For this purpose, the respiratory rate is also needed, which, multiplied by the AZV, gives the respiratory minute volume. Also referred to as respiratory time volume, respiratory minute volume gives an indication of the amount of air per unit time that passes through the lungs during respiration.
Function and task
The respiratory volume affects the air flow rate of the lungs and is normally adjusted by the autonomic nervous system in strength (volume) and respiratory rate to meet requirements. It is also possible to change both parameters volitionally to consciously adjust airflow even when there is a conflict with autonomic control or to consciously cause an oversupply or undersupply of oxygen. In situations where only a relatively low AZV is required, there are always volume reserves on both the expiratory and inspiratory sides, with inspiratory reserves being significantly higher than expiratory reserves. The bilateral volume reserves have the advantage that, in the event of a sudden demand for power, the reserves are available at all times, regardless of whether the moment of demand occurs during inhalation or during exhalation. It is often thought that lung volume can be increased by endurance training even in adult humans. This is not entirely true, because the size of the lungs is genetically determined and cannot change after the end of the growth phase. What can be changed by training, however, is the vital capacity, i.e. the respiratory volume plus the two reserve volumes. The training effect is based on the trained and strengthened chest and rib muscles, which can lift the chest better and give the lungs the opportunity to inflate further. When elite athletes in endurance sports have “high lung volume,” they are not referring to absolute lung volume, but rather maximum respiratory volume or vital capacity. Even with a trained high vital capacity and deep exhalation, a residual volume of air, the residual volume, remains in the lungs. It amounts to about 1.3 liters in healthy normal adults. With each deep breath, the air remaining in the lungs is also exchanged to the greatest possible extent, so that gas exchange still takes place even during the breathing pause before inhalation. In addition, the remaining air saves the alveoli from total collapse and sticking together.
Diseases and ailments
Dysfunctions or diseases that affect the maximum respiratory volume are usually associated with ventilatory disorders of breathing. In principle, ventilatory disorders can be divided into restrictive and obstructive disorders.Restrictive ventilation disorder is manifested, among other things, by a reduction in the maximum respiratory volume, i.e., a reduction in vital capacity. Symptoms may be caused, for example, by impairment of the chest or rib muscles after an accident or surgery, or by impairment of the muscles involved in active breathing due to disease or toxins. Causes may include neurotoxins (snake venom, cube jellyfish, sea wasp, etc.) or neuromuscular disease. Pneumonia or pulmonary edema also cause symptomatic functional limitations of the alveoli (air sacs) and are classified as restrictive ventilation disorders. For an obstructive ventilation disorder, increased airway resistance is usually symptomatic. The increased resistance is caused by increased accumulation of secretions, foreign substances such as dust, or airway narrowing due to inflammation. Usually, exhalation is more affected than inhalation. The most common diseases that also lead to reduced respiratory volume via obstructive ventilation disorder are bronchial asthma and chronic bronchitis, as well as a group of diseases and conditions collectively known as COPD (chronic obstructive pulmonary disease). This includes the so-called smoker’s lung. Until the 1960s, miners in coal mining centers were frequently diagnosed with pneumoconiosis, which, as a recognized occupational disease, could lead to considerable restrictions in maximum respiratory volume due to obstruction of the bronchi. Other disease complexes that, in advanced stages, also impair maximum respiratory volume via impairment of lung function include various types of carcinoma of the lungs and airways.
