Conducting Airways & Deadspace Flashcards
What are the 3 airway levels
- upper conducting
- lower conducting
- gas exchange
What are the division generations of the airway levels?
Upper and Lower Conducting are 1 - 16 generations
Gas exchange is 17 - 23 generations
What structures in the upper conducting airway
- nose
- nasopharynx
- oral cavity
- oropharynx
- hypopharynx
- glottis
what are the structures in the lower conducting airways?
- glottis
- trachea
- mainstem bronchi
- lobar bronchi
- terminal respiratory bronchioles
what are the structures in the gas exchange level?
- terminal bronchioles
- alveolar ducts
- alveolar sacs
- alveoli
What is true of the trachea
- Fibroelastic tube
- horse shoe shape rigns
- Extends from the larynx at C6 in the lower neck to its bifurcation at the cranial border of T6 in the upper thorax
- Approximately 11 cm X 2 x 2.5 cm
- Conducts inspired and expired gases
- Part of the air conditioning system
what muscle makes up the posterior wall of the trachea
Trachealis muscle
Cross sectional view of trachea
what are the components of the trachea
- Cartilage
- Hyaline
- Horseshoe shaped
- Fibrous elastic tissue
- Trachealis muscle
- Mucous membrane
- Ciliated epithelium
- Lymphoid tissue
- Submucosa
- Connective tissue
- Blood vessels
- Nerves
- Mucous glands
what nerve innervates the trachea
- Sensory = CN X (vagus) –> Recurrent laryngeal nerves
- Motor = CN X
What are the landmarks associated with the major carina
- Dorsal side – T5 - T6 - T7
- Ventral side – sternal angle
NOTE: when finding the carina on X-ray AP or PA view, look for the inferior border of a mainstem bronchi and trace it up to the bifurcation of the trachea
What structure of the trachea should always be visualized during a FFOB intubation?
Major carina
What is ture of the Mainstem bronchi?
- Right Mainstem Bronchus
- 20 o in adult
- 300 in infant
- RUL bronchus takes off within 2 cm of mainstem origin
- Left Mainstem Bronchus
- 400 in adult
- 47o in infant
- Left mainstem bronchus is 5 cm
What is common complication associated with intubation of the Right main stem bronchi?
Atelectasis of the right upper lobe
cause: Right mainstem is only 2 cm long before approaching 2nd division of bronchus that supplies the upper lobe. The ETT tube can pass by the 2nd division.
how many gas exchange units are there?
approx. 23,000,000
How is the trachea divided up in regards to intrathoracic v/s extrathoracic?
50/50
Where are the heart and major vessels located?
mediastinum
where should the tip of the ETT cuff and bevel be on x-ray in regards to the vertebra level?
Cuff - T2-T3 (mid trachea)
Bevel - T3-T4
Identify structures 13, 16, 17, 37, 38
13 - innominate artery
16 - trachea
17- esophagus
37 - right upper lobe
38 - left upper lobe
what is dead space?
is the volume of air which is inhaled that does not take part in the gas exchange, either because it (1) remains in the conducting airways, or (2) reaches alveoli that are not perfused or poorly perfused. In other words, not all the air in each breath is available for the exchange of oxygen and carbon dioxide
What are the 2 forms of dead space
- anatomic ( upper and lower conducting airways)
- alveolar
anatomic + alveolar = total dead space (a.k.a. physiological dead space)
What is normal anatomic deadspace?
VD Anat = 2.2 ml x kg wt.
or 1 ml x lb. wt
what decreases VD ANAT ? increases?
decreased by: endotracheal intubation, tracheostomy, laryngectomy
Intrathoracic anatomic dead space is eliminated by what?
intubation
so take 1/2 of the anatomic dead space
VD ANAT x 0.5
What is physical dead space?
occurs with bi-directional airflow (i.e. ETT)
V D PHYSICAL = πr2h
r = 1/2 of ID of ETT
h = length of ETT - common adult tube is 30 cm (300 mm)
How is net change in deadspace calculated
VD ANAT + VD PHYSICAL
what % of tidal volume is dead space?
roughly 30 %
