Physiology of Respiratory Signs ✅ Flashcards
What is normal tidal volume proportional to?
Weight
Why is the respiratory rate in higher in young children?
Because energy requirements and therefore oxygen demand and carbon dioxide production are relatively higher in younger children
What modulates the breathing pattern in an awake child?
Various baseline physical activities
Under what control is breathing pattern in an awake child?
Conscious control
What happens to breathing pattern during sleep?
Physiological changes occur that vary with sleep state
What are the changes that occur to breathing pattern during sleep influenced by?
Maturational changes in respiratory mechanics and control of breathing
What can happen to the breathing pattern during sleep in infants?
Pauses and gaps in breathing of up to 15 seconds during sleep are common
When might the pauses and gaps in breathing in infants be exaggerated?
In illness
Describe the response to hypoxia in infants
Biphasic, with an initial increase in respiratory rate followed by a decrease, often in association with apnoea
What happens to minute ventilation during sleep in well children?
It falls by 15% during sleep
What happens to breathing during REM sleep?
There is an automatic decrease in accessory muscle activity, accompanied by an increase in upper airway resistance
Why is there an increase in upper airway resistance in REM sleep?
As the muscles supporting the upper airway relax
How much do newborn infants sleep?
Approx 2/3 of the time
What % of new-born infants sleep is REM?
60%
How much do children sleep by 6 months of age?
11-14 hours per day
What proportion of a 6 month old child’s sleep is REM?
1/3
How much does the typical adult sleep?
8 hours a day
What % of an adults sleep is REM?
20%
Why do the airways and lungs not collapse completely during expiration?
It would be inefficient
Why would it be inefficient for the airways and lungs to collapse completely during expiration?
As re-inflation requires much more energy than widening/expanding a partially closed airway
What opposes airway closure under normal circumstances?
Maintenance of functional residual capacity (FRC) at a level above the point at which the airways collapse
What increases airway collapse?
- Surfactant deficiency
- Bronchiolitis
- Pneumonia
When does FRC reduce?
- When lying supine
- Anaesthesia
- Sleep
What factors affect FRC?
- Elastic recoil of the lungs
- Time allowed for expiration
- Expiratory flow rate
What happens to the elastic recoil of the lungs with age?
It increases
What is the result of the elastic recoil of the lungs increasing with age?
Older children are less susceptible to complete airway closure
How do younger children oppose airway collapse?
By having higher respiratory rates, thus reducing the time allowed for expiration
What happens if having a higher respiratory rate is insufficient to maintain FRC in infants?
They will attempt to reduce expiratory flow rates using partial closure of the glottis and upper airway
What does partial closure of the glottis and upper airway result in?
Grunting
When is grunting seen?
In neonates with respiratory distress
How does grunting prevent airway collapse?
It maintains a positive expiratory pressure but reduces expiratory flow
What does reflex or voluntary coughing require?
Co-ordination of a complex series of events
How does coughing begin?
With opening the glottis and a short inspiration to increase lung volume
Why is recruitment of lung volume essential in coughing?
To maximise expulsion