Respiratory - Lung Anatomy and Function Flashcards
Why do we apply PEEP when a patient is intubated?
During exhalation, vocal cords slightly adducted –> physiological PEEP ± 3-4 cmH2).
When a tube splints the vocal cords open this effect is lost. extrinsic PEEP at physiological levels of ± 5 cmH20 maintains FRC and prevents atalectasis following intubation.
What is the effect of PEEP on cardiac output and intracranial pressure
PEEP increases intrathoracic pressure –> increases venous pressure –> reduces venous return –> potential to decrease CO.
Increased intrathoracic pressure may hinder venous drainage from the cerebral venous sinuses –> increased ICP.
Describe the airway generations
CONDUCTING ZONE 0 Trachea 1 Main bronchi 2 Lobar bronchi 3 - 4 Segmental bronchi 5 - 11 Subsegmental bronchi 12 - 15 Bronchioles 16 Terminal bronchioles
RESPIRATORY ZONE (exponential increase in cross sectional area –> graph)
17 - 19 Respiratory bronchioles
20 - 22 Alveolar ducts
23 Alveolar sacs
How would increasing PEEP affect a tonsillectomy
Increased PEEP with increased venous pressure may increase bleeding at the tonsillar bed, obstructing the surgeons view of the operative field.
Under what circumstances are the filtration, warming and humidification functions of the upper airways bypassed. What does this caused and how does the anaesthetist get around this problem
Endotracheal intubation.
Absence of filters/humidification and warming leads to:
- Accumulation of mucus in the lower airways (dried)
- Increased risk of infection
- Increased heat loss
- Microatalectasis
HME used - artificial humidification and warming.
Where does the trachea start
C6 (Cricoid) - T5 (Carina)
Where is the trachealis muscle
In the posterior gap of the anterolateral cartilaginous rings of the trachea.
What is the function of the cartilaginous rings of the trachea
To prevent tracheal collapse during extreme inspiratory effort with associated high negative pressure.
Describe the lung lobes
Right has three lobes: Upper middle and lower
Left has two lobes and a lingula (latin ‘little tongue’) lobe.
Describe the bronchopulmonary segments
Right - there are 10
3 upper, 2 middle and 5 lower
Left - there are 9
5 upper, 4 lower
Describe the bifurcation of the main bronchi and the clinical relevance of this
Right main bronchus bifurcates 2 cm distal to the carina whilst the left main bronchus bifurcates 5 cm distal to the carina –> keep this in mind during the insertion of double lumen endotracheal tubes: DLETTs.
Left sided double lumen tubes are preferred to right sided double lumen tubes as right sided tubes risk the occlusion of the right upper lobe bronchus by the ETT cuff.
Describe the walls of the segmental and subsegmental bronchi compared to the bronchioles
Segmental and subsegmental have respiratory epithelium surrounded by smooth muscle containing plates of irregular shaped cartilage to prevent airway collapse
Bronchiloes contain only smooth muscle subject to bronchodilatation and bronchoconstriction
What proportion of gas exchange occurs in the respiratory bronchioles + alveolar ducts vs alveoli
Resp. bronchioles + Ducts 10%
Alveoli 90%
How many alveoli do we have and what is the surface area of this
300 million alveoli
surface area 70 meters squared
What are the cell types found in the alveolus and what are their attributes and functions
Type 1 pneumocytes
Thin, cover 90% alveolar surface area –> allow for efficient gas exchange
Type 2 pneumocytes
Make alveolar surfactant
Alveolar macrophages
Found within alveolar septa and the lung interstitium.
