Session 2: Case Studies Flashcards
Name structures a knife would have to go through to enter the pleural cavity.
It all depends on where it entered and the angle.
Let’s assume it’s in level with thoracic cavity and horizontal (in order to make it easier).
Skin
Subcutaneous layer
Fascia
Muscles (intercostal - external, internal, innermost), maybe pec major, pec minor, serratus anterior etc..
Neurovascular bundle (arteries, veins and nerves)
Parietal pleura
Visceral pleura
Why would air flow into the pleural cavity upon a stab wound to the thorax?
Because the intrapleural pressure is lower than atmospheric pressure which makes air enter the pleural space.
This makes the pleural seal to be disturbed and the visceral pleura will not stick to the chest wall any more. This means that there will be no outwards pull of the chest recoil.
Lung will collapse towards its hilum due to the only force being inwards (elastic recoil)
A tube is placed in the pleural space to drain the air. How could damage to the intercostal vessels and nerve be avoided during this procedure?
Go directly above the rib. Directly inferior to each rib you will find the intercostal vessels and nerve.
Could any intra-abdominal structures be damaged due to a stab wound? If so, give examples.
Yes, it all has to do with where the knife enter and the angle of it.
Liver, spleen, diaphragm, colon, intestines, stomach, pancreas etc… A lot of structures may be damaged.
A baby is delivered prematurely at 29 weeks gestational age. Following delivery, the baby is noted to have difficulty in breathing with grunting and intercostal and subcostal recessions. Respiratory distress syndrome in the new born due to lack of surfactant is suspected.
Explain why lack of surfactant caused difficulty in breathing.
Surfactant reduce surface tension.
An absence of surfactant causes an increase in surface tension which makes the lungs more stiff. This reduces compliance and makes it harder to breathe.
Also the surfactant works most efficiently in a small alveoli (which would have higher pressure if not for surfactant). This evens out the pressure of large and small alveoli by the Law of Laplace. If there is no surfactant small alveoli will empty into bigger ones and this will happen until bullae form. This greatly reduces surface area for gas exchange and impairs it.
Why do babies with RDS get intercostal recession?
Diaphragm and intercostal muscles still try to contract and expand but insufficient amounts of air is going into the lungs.
This means that the muscles try to increase a volume which is not ‘being allowed to increase’.
Think of it as pulling on a balloon which is closed. The balloon will only elongate and not get bigger. The radius of the balloon will shrink and this would happen to the thoracic cavity if not for the ribs. This means that skin will be ‘sucked in instead.
Briefly explain how inhaled particles and dust are removed from the respiratory tract.
Particles are trapped by mucous. The mucous with the particles are then expelled from the airways by the cilia. This is known as the mucociliary escalator.
Is the elastic recoil of the lung in emphysema the same, increased or decreased?
Decreased
Is the chest wall recoil in emphysema the same, increased or decreased?
Same
What will the effects on elastic recoil and chest wall in a patient with emphysema cause to the volume of air in lungs at the end of quiet expiration.
It will be increased. I.e. a patient with emphysema will have an elevated functional residual capacity.
This is because the net forces are not balanced anymore and not as much air will be expired.
What causes a barrel chest in emphysema?
Barrel chest is a distended chest. This is due to the increase in functional residual capacity. FRC is increased due to the decrease in elastic recoil.
Diaphragm will be lowered and contracted and the lungs become hyperinflated.
Why are bronchioles narrowed in emphysema?
Air spaces distal to the terminal bronchioles will increase.
The loss of elastic fibres which are supposed to exert an outwards pull (radial traction) on the small bronchioles causes narrowing.
