pRRAPID

B

Breathing

PAEDIATRIC ANATOMY AND PHYSIOLOGY

In infants and children the physiology of breathing differs from adults due to the following important factors:

  1. Smaller resting lung volumes leading to low oxygen reserve.
  2. Higher rate of oxygen consumption.
  3. The respiratory muscles are relatively less efficient then in adults therefore increased work in breathing can lead to easy fatigue and apnoea rapidly. In infancy, the diaphragm is the key respiratory muscle with very little contribution from intercostal and accessory muscles.
  4. Smaller upper and lower airways.

A combination of these makes infants and children more vulnerable to respiratory compromise. 
As the child ages the ribs will become more ossified and therefore act as a more secure “anchor” for the intercostal muscles.  Therefore significant recession in children over 5 years of age is a more ominous sign.

Physiological parameters in children

The physiological parameters in children vary to those in adults. As children get older their respiratory physiology changes leading to variation in respiratory rate. As you can see in the below table newborn infants are naturally “tachynpoeic”. Over time the normal respiratory rate comes in line with that of an adult.

Table: Normal vital signs in children

 

Infant

1-2 years

2-5 years

5-12 years

Adolescent

Pulse rate (bpm)

 110-160 100-150 95-140 80-120 60-90

Respiratory rate (rpm)

 30-40 25-35 25-30 20-25 14-18

Blood pressure Systolic mmHg

80-90 85-95 85-100 90-100 100-140

Temperature (define if oral etc)

 35-37oC 36-37.5 oC

Saturations

 94-98%

CO2 clearance versus Oxygenation

The lungs provide two major functions, oxygenation and CO2 clearance.  These are separate processes. 

Every minute a volume of gas is moved in and then out of our lungs.  This is known as the Minute Volume (MV).  This is dependent on the number of breaths we take (RR) and the volume of each breath (Tidal volume, TV)

MV = RR x TV