What is the normal lung capacity of a child?

The health of every child is the most worrying issue for parents. In life, every child has different living habits and physical conditions. Many children always encounter some health problems during physical examinations. Among them, vital capacity is the simplest and most effective way to detect the development of children's lungs. However, since we know little about medical knowledge, we don't know what is a normal lung capacity for children. Let's take a look at what is a normal lung capacity for children.

What is the normal lung capacity of a child?

The normal value of vital capacity for 12-year-old children is 2200 ml for boys and 2076 ml for girls. Vital capacity refers to the total amount of gas exhaled after taking a deep breath.

Vital capacity = tidal volume + inspiratory reserve volume + expiratory reserve volume. Tidal volume refers to the amount of gas inhaled or exhaled during each breath. Inspiratory reserve volume is also called inspiratory reserve volume, which refers to the amount of gas that can be inhaled after a quiet inhalation and then a strong inhalation. Expiratory reserve volume is also called expiratory reserve volume, which refers to the amount of gas that can be exhaled after a quiet exhalation and then a strong exhalation. Vital capacity is the maximum ventilation volume of one breath, which can reflect the potential capacity of respiratory function in a certain sense.

The lung capacity of adult men is about 3500 ml, and that of women is about 2500 ml. The lung capacity of middle-aged people is the largest, while that of young and elderly people is smaller. The healthier the person, the greater the lung capacity. Lung tissue damage such as tuberculosis, pulmonary fibrosis, atelectasis or lobectomy to a certain extent may reduce the lung capacity; kyphosis, pleural thickening, exudative pleurisy or pneumothorax may also limit lung expansion and reduce lung capacity. Therefore, a significant reduction in lung capacity is a manifestation of restrictive ventilation disorder.

Since the method of measuring vital capacity is simple and has good repeatability, it is a commonly used indicator for health checks. Since the vital capacity is measured without limiting the speed of exhalation, it cannot detect diseases of poor respiratory ventilation. Therefore, the timed vital capacity measurement method is more ideal as a dynamic indicator of lung function. Timed vital capacity is the fastest exhalation after maximum inhalation until the exhalation is complete. At the same time, the amount of air exhaled at the end of the 1st, 2nd, and 3rd seconds is recorded separately. A normal person should exhale 83%, 96%, and 99% of his vital capacity respectively. People with obstructive pulmonary disease often need 5 to 6 seconds or more to exhale all their vital capacity; in many pathological conditions where respiratory movement is limited, the timed vital capacity in the first second increases, and the entire vital capacity can be exhaled in advance. Therefore, timed vital capacity can be used as a reference for distinguishing obstructive or restrictive ventilation disorders.

The above is an introduction to the normal lung capacity of children. After understanding it, we know that children's lung capacity is generally weaker than that of adults, but as long as it is within the normal range, we should not worry too much. In addition, children must be encouraged to develop the habit of exercising more, which can improve their body's immunity while also improving their lung capacity.