Respiratory System Characteristics in Children

Respiratory System Characteristics in Children

The respiratory system of children has distinct characteristics compared to adults, which influence respiratory function and make them more vulnerable.

1. Airways:

• Nose:

• Nostrils and nasal passages are narrow, prone to nasal congestion, especially in infants under 6 months.

• Nasal mucosa is thin, with weak protective function, easily leading to rhinitis.

• Sinuses are not fully developed, maxillary sinuses only begin to develop after 2 years of age, making young children less susceptible to sinusitis.

• Throat – Pharynx:

• Throat is narrow, short, funnel-shaped, and oriented vertically.

• Throat size in males and females is comparable under 3 years old, but after 3 years, males tend to have larger throats.

• Develops most rapidly during the first year of life and puberty.

• Mucosa is lined with ciliated columnar epithelium, with abundant lymphoid tissue under the pharyngeal mucosa.

• Waldeyer’s Lymphoid Ring:

• Infants under 1 year old only have the pharyngeal tonsil developed.

• Palatine tonsils begin to develop from 2 years of age.

• Rapidly develops from 4-6 years old until puberty.

• Tonsils are prone to inflammation and hypertrophy in children aged 3-8, leading to airway obstruction, difficulty in placing nasogastric or endotracheal tubes.

• Larynx – Trachea – Bronchi:

• Narrow lumen, less elastic tissue, soft cartilage rings, mucosa rich in blood vessels.

• When inflamed, the mucosa easily becomes edematous, secretes fluids, and deforms.

• Trachea is generation 0, main bronchi are generation 1.

• Cricoid cartilage is the narrowest point, hence the lack of cuffed endotracheal tubes for young children.

• Terminal bronchioles are generation 16.

• Respiratory bronchioles are generation 17-19.

• Gas exchange function starts from generation 17.

• Alveolar ducts are generation 20-22.

2. Lungs:

• Weight:

• Newborn: 50-60g

• 6 months old: 3 times that of a newborn

• 12 years old: 10 times that of a newborn

• Adult: 20 times that of a newborn

• Lung Volume:

• Newborn: 65-67ml

• 12 years old: 10 times that of a newborn

• Number of Alveoli:

• Newborn: 30 million

• 8 years old: 10 times that of a newborn

• Adult: 300-600 million

• Children’s lungs:

• Rich in blood vessels, lymphatics, and smooth muscle fibers, enabling strong contractility and rapid reabsorption of fluid in the alveoli.

• Less elastic tissue, resulting in less mobile chest wall, prone to atelectasis and emphysema.

• Kohn’s pores (inter-alveolar communication) and Lambert’s canals (communication between bronchioles and alveoli) are not present before 3-4 years old, making young children prone to atelectasis and air trapping.

• Pleura:

• Very thin, easily stretched during deep inhalation, prone to effusion.

• Parietal pleura is not firmly attached to the chest wall.

3. Chest Wall:

• Newborns and infants:

• Short, cylindrical, with equal transverse and anteroposterior diameters.

• Ribs are horizontal and perpendicular to the spine.

• Diaphragm is high, horizontal, and intercostal muscles are underdeveloped.

• Therefore, the chest wall changes little during breathing, limiting chest breathing.

• Older children and toddlers:

• Ribs slant downwards.

• Transverse diameter increases rapidly, twice the anteroposterior diameter.

• Chest breathing develops.

4. Factors Influencing Airways:

• Airway size.

• Pressure between the lungs and mouth.

• Support from respiratory muscles.

5. Respiratory Capacity:

• Tidal volume in newborns: 18-20ml

• Tidal volume in 5-year-olds: 100ml

• Inspiratory volume:

• Newborn: 25ml

• 1-year-old: 70ml

• 4-year-old: 120ml

6. Respiratory Rate:

• Newborn: 40-60 breaths/minute, >60 breaths/minute: fast

• 3 months old: 40-45 breaths/minute, >50 breaths/minute: fast

• 6 months old: 35-40 breaths/minute, >50 breaths/minute: fast

• 1-year-old: 30-35 breaths/minute, >40 breaths/minute: fast

• 2-5 years old: 25-30 breaths/minute, >40 breaths/minute: fast

7. Breathing Pattern:

• Newborns and infants: abdominal breathing

• 2 years old: mixed chest-abdominal breathing

• 10 years old: males abdominal breathing, females chest breathing

8. Gas Exchange:

• Oxygen in the alveoli of children is higher than that of adults, while CO2 is lower.

• Oxygen uptake:

• Breastfed infants: 10ml/kg/minute

• Older children: 4ml/kg/minute

• Children have a higher oxygen demand than adults.

Note: This information is for reference only. To understand your child’s health status better, consult a specialist doctor.