Lungs, breathing and Lung function tests.

What are the divisions of the bronchial tree?

• 17 divisions before alveoli, total 23 divisions

What is the nomenclature of surfactant ?

• Anti-Surface

  = Surf-actin

What cells is the alveoli epithelium lined by?

• Alveolar type I- Gas exchange

• Alveolar type II- Pneumocytes, aka stem cells, surfactant production

What tension is type 2 cells responsible to resolve?

• Surface tension.

• Force between molecules of water casing collapse of alveoli

How do type 2 pneumocytes appear and where in them is surfactant secreted?

• Cubical secretory granules

• Contain lamellar bodies that produce surfactant.

What is surfactant?

• Made of oil and protein

• Phosphotydlcholine (lecithin)

• Phosphatydylglycerol

At what gestational age does surfactant production start?

• 28/40

Why is premature birth a risk in terms of surfactant?

• Prem babies have decreased surfactant resulting in lung collapse, less surface tension, resulting increased risk of collapse.

What is collapsing pressure?

• Surface tension over radius (aka leplace law)

What stimulates surfactant production?

• Cortisol

• Thyroxin

• Prolactin

What inhibits surfactant production?

Insulin

Define lung compliance.

• The ability of the lung to collapse

• Change in volume over (divide by) change in pressure.

What causes recoil?

• Surface tension- 2/3

• Elasticity ( elsatin and collagen)- 1/3

Name 3 types of spirometers?

• Water seal spirometer

• Dry rolling-seal spirometer

• Bellows/ Wedge spirometer

In spirometry, what is the difference between a volume and a capacity?

• A volume is one entity

• A capacity is 2 or more entities.

What muscles are involved in

• Normal inhalation

• Forced expiration

• Forced inspiration?

• Normal- Diaphragm and internal intercostal

• Forced expiration-Abdominal muscles and intercostal muscles

• Forced insp

  • Diaphragm

  • Ext intercostals

  • Sternocleidomastoids

  • Serratus anterior

  • Scalenes

Which volume cannot be meaured ( plus capacities)

• Residual volume

• FRC and TLC (Both need RV to calculate)

Define tidal volume

• All the air breathed in and out during normal respiratory cycle (tidal, like tides in sea)

• +- 500ml

Define inspiratory reserve volume and expiratory reserve volume.

• IRV- Max # of air inspired above TV

  • +- 300ml

• ERV- Max # air expired

Define Inspiratory Capacity, Residual Volume , Functional Residual Capacity ,Vital Capacity and Total Lung Capacity.

• IC= IRV +TV

• RV= Air remaining after max expiration

• FRC= RV + ERV

• VC= Max amount that can be inspired and expired

• TLC= IRV+TV+ERV+RV

What is the residual volume utilized for?

After stabbing, RV escapes, what is the remaining air called?

• Maintains aeration of blood

• E.g HR is 72bpm and RR is 12bpm, RV utilized while waiting for next cycle of resp.

• Remaining air after stabbing aka Minimal air

What is the difference between FRV and FVC?

• FVC= Maximally inhale then maximally exhale forcefully and quickly

• FRC= ERV +RV

Discuss FEV1/FVC

• FEV1= # air quickly and forcibly exhaled in 1 sec after max inhalation in 1 second

• FVC= # air quickly and forcibly exhaled after max inhalation- timed.

• Normal ratio= 80%

What are the features of obstructive lung disease?

• Air trapping

• Destroyed elastin resulting in decreased elastic recoil

• Increased compliance

• PFT features

  • RV , FRV, TLC increased

  • FEV1/FVC decreased

What are features of Restrictive lung disease?

• Decreased compliance

• Normal recoil

• Types

  • Intrinsic- Lung

  • Extrinsic- Thoracic wall

• PFT

  • RV, FRC, TLC, FVC decreased

  • FEV 1 /FVC= Normal or high

Define the flow volume loops.

• Characteristic triangular shape

• Peak triangle = Peak expiratory flow rate (PEFR)

• Positive deflection is expiration

• Negative deflection is inspiratory flow

Discuss flow volume loop with obstructive lung disease.

• Air cannot come out

• PEFR decreased

• Coving of expiratory curve

• Inspiration relatively normal

Discuss flow volume loops in regards to restrictive lung disease.

• Air can’t come in

• Decreased volumes and capacities

• Decreased PEFR

• No coving- Normal expiration

Discussed Flow volume loops in fixed upper airway obstruction.

• Air can’t get in or out e.g upper airway obstruction- trachea, goitre

• Flattening of both insp and exp limbs

Name the lung protective strategies.

• Lower tidal volume of 4-8 ml/lg of IBW

• Lower plateau pressures": <30 cm of H2O

• Higher peep

• Spontaneous breathing trials

• Conservative fluid

• Prone positioning

• NIV

• Paralysis

• Permissive hypercarbia- to achieve lower plateu pressures and TV except in metabolic acidosis and high ICP

Why is prone positioning utelised in ARDS?

• Most infiltrates are seen in dependent areas

• Prone positioning redistributes blood flow and ventilationto least affected areas of lung

• Promote secretion clearance

• Shifts mediastinal contents anteriorly to assist recruitment of atelectatic regions

What are the downside of proning

• Improvements if PF ratio seen with proning are transient , does not improve clinical outcomes, time on ventialtion or time in ICU