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respiratory physiology > Upper & Lower airways > Flashcards

Upper & Lower airways Flashcards

1
Q

Name the components of the upper respiratory tract.

A

◉ It refers to the structures that are located above the larynx, outside of the thorax, and it consists of:
* Nose, nasal cavity and paranasal sinuses (seio paranasal).
* Mouth
* Pharynx

➜ Pharynx consists of:
* Nasopharynx
* Oropharynx
* Laryngopharynx

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2
Q

Explain how the upper airway remains patent during breathing.

Awake breathing

A

◉ Patency of the upper airway, is maintained by the following muscles:
* Genioglossus: the main dilator muscle of the pharynx (causes the tongue to protrude forward away from the pharyngeal wall);
* Palatal muscles: controls the position of the palate, tongue and pharynx;
* Geniohyoid: it controls the position of the hyoid.

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3
Q

What is the importance of the muscles in maintaining the upper airway patent?

A

◉ During normal breathing, the contraction of the diaphragm increases intrathoracic volume resulting in negative airway pressures.

  • In the large airways, collapse is preventable by the presence of cartilaginous support.
    ➜ The pharyngx is largely unsupported, thus susceptible to collapse during inspiration.

Thus the importance of the muscles keeping the upper airway patent.

When conscious, the airway will remain patent, even in the presence of intrathoracic pressures as low as –60 cmH2O.

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4
Q

Describe what happens to the upper airway patency during sleep.

A
  • ⬇︎ tone of the pharyngeal dilator muscles ⟶ ⬇︎ pharyngeal diameter.

In the majority of the population patency is still maintained in spite of the above.

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5
Q

Describe what happens to susceptible individuals when upper airway patency is lost during sleep.

A

Partial obstruction of the pharynx
* Turbulent airflow
* Snoring

Complete obstruction
* Obstructive sleep apnea

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6
Q

Name the components of the lower respiratory tract.

A
  • Larynx
  • Tracheobronchial tree
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7
Q

Name the components of the larynx.

A
  1. Eppiglottis
  2. Supraglottis
  3. Vocal cords
  4. Glottis
  5. Subglottis
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8
Q

Explain the conduction of air through the larynx and its clinical relevance.

A

➜ During inspiration, the vocal cords are abducted in order to decrease resistance to the inward gas flow.

➜ During expiration, the cords adduct slightly ↑ resistance to gas flow.

➜ This results to a physiological PEEP of 3 - 4 cmH₂O.

◘ Physio PEEP importance:
* Maintains FRC and prevents alveolar collapse by maintaining positive pressure in the small airways & alveoli during expiration.
* Vocalisation;
* Coughing.

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9
Q

Describe the clinical relevance of PEEP on an intubated patient.

A

➜ Upon intubation, the vocal cords cannot adduct during expiration.
➜ This leads to a loss of physiological PEEP resulting in:
* Atelectasias
* V/Q mismatch

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10
Q

What can be done to prevent the loss of physio PEEP on an intubated patient?

A
  • Apply extrensic PEEP (3-5 cmH₂O).

► It prevents atelectasia and maintains FRC.

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11
Q

What are the adverse effects of extrinsic PEEP?

A
  • ⬆︎ intrathoracic pressure ⟶
  • ⬆︎ extravascular pressure of veins ⟶
  • venous collapse ⟶
  • ⬇︎ venous return.
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12
Q

Describe the situations on which NOT applying extrinsic PEEP is advantageous.

A

◉ ⬆︎ intracranial pressure
* Increased intrathoracic pressure inhibits venous drainage from the cerebral venous sinuses ⟶ an ↑ in ICP.

◉ Tonsillectomy
* ↑ venous pressure may ↑ bleeding at the tonsillary bed, obstructing the surgeon’s view intraoperatively.

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13
Q

Describe the clinical significance of lack of humidification on a intubated patient.

A
  • The ETT bypasses the upper airway skipping warming and humidification of inspired air.
  • The inhalation of cold and dry gases causes ⬆︎ mucus viscosity ⟶ impairment of mucus removal causing:

➜ Accumulation of mucus in lower airways
➜ ⬆︎ risk of pulmonary infection
➜ Microatelectasis

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14
Q

Describe the composition and division of the tracheobronchial tree.

Lower resp. tract

A

► The tracheobronchial tree is composed of 23 divisions / generations, that become progressively narrower (with each division) from the trachea to the alveoli (and ⬆︎ its cross-sectional area as it progresses).

➔ The tracheobronchial tree can further be subdivided into:
* Conducting zone
* Respiratory zone

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15
Q

Name the structures that compose the conducting zone of the tracheobronchial tree.

Lower respiractory tract

A

◉ Airways generations 0-16
➜ 0: Trachea
➜ 1: Main bronchi
➜ 2: Lobar bronchi
➜ 3-4: Segmental bronchi
➜ 5-11: Subsegmental bronchi
➜ 12-15: Bronchioles
➜ 16: Terminal bronchioles

◉ Cartilaginous airways: 0-11
◉ Non-cartilaginous: 12-16

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16
Q

Name the structures that compose the respiratory zone of the tracheobronchial tree.

Lower resp. tract

A

◉ Airways generations 17-23
➜ 17-19: Respiratory bronchioles
➜ 20-22: Alveolar ducts
➜ 23: Alveolar sacs

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17
Q

What are the functions of the conducting and respiratory zones of the lower resp. tract?

Lower resp. tract

A 
Conducting airways:
  • Is responsible for conducting air from the larynx to the respiratory zone.
Respiratory airways:
  • Is responsible for gas exchange.
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18
Q

In a 70 Kg man

What is the volume of the conducting airways (anatomical dead space)?

Lower resp. tract

A

150 mL.

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19
Q

In a 70 Kg man

What is the volume of the respiratory airways (at rest)?

Lower resp. tract

A

3000 mL.

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20
Q

Describe the lining of the conducting zone.

Lower resp. tract

A

► Are lined with:
* Cilia
* Pseudostratified column epithelium
* Goblet cells (scattered)

Goblet cells secretes mucus that covers the epithelium, trapping inhaled foreign bodies and microorganisms.

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21
Q

Describe the function of the mucociliary escalator of the conducting airways.

Lower resp. tract

A

◉ The cilia beat in time, propelling mucus towards the oropharynx where it is either swallowed or expectorated:

  • It protects the lungs from microorganisms and foreign bodies.
  • Prevents mucus accumulation in the lower airways.
22
Q

Describe the anatomy of the trachea.

Lower resp. tract

A

(➔ The tracheobronchial tree starts right below the larynx.)

Trachea generation 0:
* Starts at the lower border of the cricoid cartilage (C6 vertebral level).
* It bifurcates at the carina (T4/T5 level).
* The anterior and lateral walls are reinforced with C-shaped cartilaginous rings.
* The posterior gap of the rings are bridged/joined by trachealis muscle.

The cartilaginous rings prevent tracheal collapse.

23
Q

Describe the anatomy of the main bronchi.

A

Main bronchi generation 1:
* The trachea divides into the right and left main bronchi.
* The right bronchus is shorter, wider and more vertical.

ETT’s and foreign bodies often enter the right bronchus due to its anatomy.

24
Q

Describe the anatomy of the lobar bronchi.

Lower respiratory tract.

A

Pulmonary lobes:
* Right lung: 3 lobes (upper, middle, lower);
* Left lung: 2 lobes (upper and lower).

► Lobar bronchi generation 2:
* Right lung: 10 lobar bronchi (3 upper, 2 middle, 5 lower);
* Left lung: 9 lobar bronchi (5 upper, 4 lower).

25
Q

Describe the anatomy of the segmental and subsegmental bronchi.

Lower resp. tract

A

Segmentalgeneration 3-4 and subsegmental generation 5-11:
* The epithelium is surrounded by a layer of smooth muscle.
* Irregularly shaped cartilaginous plates prevent airway collapse.

26
Q

Describe the anatomy of the bronchioles.

A

Bronchioles airway generation 12-15:
* 1st generation without cartilage;
* It has a layer of smooth muscle that modulates gas flow by contracting (bronchoconstriction) and relaxing (bronchodilatation);

27
Q

Describe how bronchoconstriction and bronchodilatation is achieved on the conducting airways.

A

On the bronchioles (generation 12-15)

Bronchodilatation:
* results from sympathetic nervous system activity (ex. exercise);
* ⬇︎ resistance to gas flow
* allowing greater ventilation during periods of O₂ demand.

Bronchoconstriction is caused by:
* parasympathetic nervous system
* histamine
* cold air
* noxious chemicals
➜ At rest, the reduction in gas flow velocity causes particulate material to settle in the mucus, which is then transported away from the respiratory zone by the cilia.

Drugs that induce bronchodilatation include β₂-agonists and anticholinergics.

28
Q

Terminal bronchioles?

A

The terminal bronchioles are the last (16th) airway generation of the conducting zone.

29
Q

What is the function of the respiratory bronchioles?

A

Generation 17-19:
* Are mainly “conducting” with interspersed alveoli that participate in gas exchange.

30
Q

Describe the anatomy of the alveoli.

A
  • Form the final airway generation of the tracheobronchial tree;
  • There are around 300 million alveoli
  • Each alveolus is surrounded by a capillary network.
31
Q

What cells type can be found in the alveolus?

A

The alveolus have a thin wall compromised of 3 cell types:

  • Type I pneumocytes
  • Type II pneumocytes
  • Alveolar macrophages
32
Q

Describe the Type I pneumocytes cells.

Alveolar cell types

A
  • Account for 90% of the alveolar surface area.
  • Extremely thin specialised epithelial cells.
  • They allow for efficient gas exchange.
33
Q

Describe the type II pneumocytes cells

Alveolar cell types

A
  • Cover the remaining 10% of the alveolar surface.
  • Specialised secretory cells.
  • Cover the alveolus surface with pulmonary surfactant.
34
Q

Describe the alveolar macrophages cells.

Alveolar cell types

A
  • Are found within the alveolar septa and the lung interstitium.
  • They phagocytose any particles that escape the conducting zone mucociliary escalator.
35
Q

Which are the 3 layers of the alveolar-capillary barrier.

A

The barrier is a very thin thus facilitating efficient gas exchange. The layers are:

  • Type I pneumocytes of the alveolar wall.
  • Extracellular matrix.
  • Pulmonary capillary endothelium.
36
Q

Describe the physical properties of the alveolar-capillary barrier.

A

◆ Extremely thin.
◆ Very strong due to type IV collagen within the extracellular matrix (despite being thin).
◆ Permeable to small gas molecules (O₂, CO₂, volatile anaesthetics, CO, N₂O).

37
Q

Describe the functions of the alveolar-capillary barrier.

A

◆ To allow for efficient gas exchange.
◆ To prevent gas bubbles from entering the circulation.
◆ To prevent blood from entering the alveolus.
◆ To limit the transudation of water.

38
Q

What are the main muscles involved in inspiration?

A

1. Eupnoea (normal quiet breathing):
◆ Diaphragm (innervated by the phrenic nerve).

2. Deep inspiration:
◆ External intercostal muscles.

39
Q

What are the main muscles involved in expiration?

A

1. Eupnoea (normal quiet breathing):
◆ Elastic recoil of the lungs produces passive expiration.

2. Forced expiration:
◆ Internal intercostal muscles.

40
Q

What are the acessory muscles involved in additional inspiration effort?

A

◆Sternocleidomastoid
◆ Scalene

41
Q

What are the acessory muscles involved in additional expiratory effort?

A

◆ Abdominal muscles
1. Rectus abdominis
2. Internal and external obliques
3. Transversalis

42
Q

What are the forces that act on the lungs?

A

◆ Intrapleural pressure
◆ Inward elastic recoil
◆ Transpulmonary pressure

43
Q

Describe what is the intrapleural pressure.

Forces that act on the lungs

A

➜ There are 2 pleuras.
◆ Visceral pleura: covers the lungs.
◆ Parietal pleura: it’s attached to the chest wall.

➜ There is a space created by the 2 pleurae.
◆ Intrapleural space: cointains pleural fluid to minimise friction between the pleurae.

➜ There is a pressure in the intrapleural space.
◆ Intrapleural pressure: It is negative at rest (-5 cmH₂O) due to the chest wall’s tendecy of expanding outwards.

44
Q

Describe what is the inward elastic recoil.

Forces that act on the lungs

A

◉ The tendency of the lung is to collapse (to contract) inwards due to stretched elastic fibres of the lung parenchyma

45
Q

Describe what is the transpulmonary pressure.

Forces that act on the lungs

A

It is the difference between the alveolar and intrapleural pressures.

46
Q

Describe the equilibrium between the lungs and thorax (chest wall)

A

◉ The elastic forces of the lungs and chest wall are in equilibrium:
➜ The tendency of the lung is to collapse.
➜ The tendency of the chest wall is to expand.
➜ This results in a negative intrapleural pressure.

47
Q

Describe the forces that act on the lung at REST.

A

During rest the lungs ar at FRC:

➜ The intrapleural pressure (-5 cmH₂O) & the inward elastic recoil pressure (+5 cmH₂O) ⟶ are equal but opposite.

➜ The alveolar pressure = the atmospheric pressure (0 cmH₂O) ⟶ airflow ceases.

48
Q

Describe the forces that act on the lung during INSPIRATION.

A

1. Early inspiration
◉ Diaphragmatic contraction:
◆ Descends 1 cm during quiet breathing;
◆ May descend up to 10 cm during maximimal inspiration.
◆ ⬆︎ the vertical dimension of the lungs.

◉ External intercostal contraction:
◆ ⬆︎ anterior-posterior diameter of thoracic cage;

◉ Bulk action of inspiratory muscles
◆ Inspiratory muscles contraction ⟶ ⬆︎ thoracic cavity volume ⟶ ⬇︎ intrapleural pressure from -5 cmH₂O to -8 cmH₂0.

◆ The intrapleural pressures > than the (inward) elastic recoil pressure of the lungs ⟶ lungs expand.

◆ Alveolar pressures ⬇︎ < atmospheric pressure ⟶ air flows into the lung ⟶ ⬆︎ alveolar volume.

2. End inspiration
◆ The elastic recoil pressure ⬆︎ (+ 8 cmH₂O) ⟶ matches the intrapleural pressure (opposite).
◆ (again) Alveolar pressure = atmospheric pressure ➔ air flow ceases.
◆ Lung volume ⬆︎ by about 500 mL (tidal volume).

49
Q

Describe the forces that act on the lung during EXPIRATION.

A

◆ Inspiratory muscles relax;
◆ The diaphragm and thoracic cage passively return to their resting state as the volume inside ⬇︎.
◆ Intrapleural pressure ⬆︎ -5 cmH₂O.
◆ Strectched elastic fibers return lung volume to FRC.
◆ ⬇︎ lung volume ⟶ ⬆︎ alveolar pressure
◆ Alveolar pressure > atmospheric pressure ⟶ air is expelled.
◆ Alveolar pressure = atmospheric pressure ⟶ airflow ceases at end expiration.

50
Q

Describe what happens when a pneumothorax occurs.

A

◆ A communication is made between the intrapleural space and the atmosphere (penetrating trauma, ruptuted bulla);
◆ The negative intrapleural pressure draws in air ⟶ pneumothorax.
◆ Intrapleural pressure = atmospheric pressure ⟶ lung succumbs to its elastic recoil and collapses.

respiratory physiology (2 decks)

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