Examples of answered SEQs on respiration by Dr Khaled A Abulfadle

Admin عدد المساهمات : 9493 تاريخ التسجيل : 06/08/2009

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Dr Khaled A Abulfadle

Admin عدد المساهمات : 9493 تاريخ التسجيل : 06/08/2009

Q: Outline
1-Baroreceptor mechanism in regulation of blood pressure
2-Chemoreceptor mechanism in regulation of respiration
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A:

homeostatic system is formed of stimulus, receptor, center and response, thus:

1-Baroreceptor mechanism in regulation of blood pressure:
Stimulus: increased arterial blood pressure.
Receptor: baroreceptors ( receptors in carotid sinus and aortic arch respond to change in arterial blood pressure).
Center: cardiovascular centers in brainstem.
Response: decreased heart rate and vasodilatation to decrease arterial blood pressure towards normal.

2-Chemoreceptor mechanism in regulation of respiration:
Stimulus: decreased arterial O2 and increased arterial CO2.
Receptor: chemoreceptors ( receptors in carotid and aortic bodies respond to change in arterial O2 and CO2 concentrations).
Center: respiratory centers in brainstem.
Response: increased respiratory rate to increase O2 and decrease CO2 towards normal.

Admin عدد المساهمات : 9493 تاريخ التسجيل : 06/08/2009

Questions

what are the differences between total and specific compliance ?

how in emphysema the total compliance increase and the specific decrease?
if the 200 ml/cm H2O is a value of normal total compliance so whats is the normal value of specific compliance ?

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Answer

Compliance is the measure of how easy it is to inflate something. If it is easy to inflate something, then compliance is high. If it is hard to inflate something, then compliance is low.

Total Compliance in the lungs is defined as a change in volume divided by a change in transpulmonary pressure (CL = ΔV / ΔPL). A typical value of compliance is 200 ml/cm H20.

Specific compliance is defined as the total lung compliance divided by the initial volume of the lung (FRC in ml). Specific compliance is a property of the lung tissue itself and is not dependent on the body size. (Compliance depends on how much tissue is being considered).

In emphysema, the elastic fibers in the lungs are decreased. Thus, total lung compliance is increased (inverse relation) but, the initial volume of the lung is increased. thus, specific lung compliance is decreased.

The normal value of specific lung compliance: 0.05/cmH2O.

For more information, refer to my lecture here:

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Admin عدد المساهمات : 9493 تاريخ التسجيل : 06/08/2009

Question:

How come the compliance decrease in fibrosis , edema and congestion while in these conditions there decrease in the elasticity ?
what are the differences between the elastic recoil and elsticity of the lung ?

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Answer:

Again, compliance is the measure of how easy it is to inflate something. If it is easy to inflate something, then compliance is high. If it is hard to inflate something, then compliance is low.

Although, elasticity is decreased in these conditions, yet still compliance is decreased as ability of lung inflation is decreased by these conditions. This means that, there are other factors affecting lung compliance other than elasticity e.g. lung disease, surfactant, chest wall,..etc (refer to my lecture)

Lastly, elastic recoil occurs in a structure having elastic element.

Refer to the record of my lecture:

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Refer to the video of my lecture:

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Admin عدد المساهمات : 9493 تاريخ التسجيل : 06/08/2009

Question

If the patient had obstructive lung disease, what would you expect for FEV1/FVC ratio to be? Explain

Answer

In obstructive lung diseases, FEV1/FVC will be less than 0.8 as there is more decrease in FEV1 than FVC. (refer to my lecture)

VIDEOS

Part-I

Part-II

Part-III

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Lab file

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Admin عدد المساهمات : 9493 تاريخ التسجيل : 06/08/2009

Question

Discuss FEV1/FVC ratio

Answer

FVC (Forced Vital Capacity): is the total volume of air expired after a full inspiration. Patients with obstructive lung disease usually have a normal or only slightly decreased vital capacity. Patients with restrictive lung disease have a decreased vital capacity.

FEV1 (Forced Expiratory Volume in 1 Second): is the volume of air expired in the first second during maximal expiratory effort. The FEV1 is reduced in both obstructive and restrictive lung disease. The FEV1 is MARKEDLY reduced in obstructive lung disease because of increased airway resistance. It is reduced in restrictive lung disease because of the low vital capacity.

FEV1/FVC: is the percentage of the vital capacity which is expired in the first second of maximal expiration. In healthy patients the FEV1/FVC is usually around 80% i.e. 0.8. In patients with obstructive lung disease (e.g. asthma) FEV1/FVC decreases and can be as low as 20-30% in severe obstructive airway disease (as FEV1 is markedly decreased while FVC is slightly decreased) . Restrictive disorders have a near normal FEV1/FVC (as FVC and FEV1 are decreased by same ratio).

Simply,

Normally, FEV1= 4L, FVC = 5L. Thus, FEV1/FVC= 4/5= 0.8

In obstructive lung disease (e.g. asthma), FEV1= 1.8 L (markedly decreased), FVC= 3.2 L (slightly decreased). Thus, FEV1/FVC= 1.8/3.2= 0.56 i.e. decreased

In restrictive lung disease (e.g. pulmonary fibrosis), FEV1= 1.9 L (markedly decreased), FVC= 2 L (markedly decreased also). Thus, FEV1/FVC= 1.9/2= 0.95 i.e. increased i.e. > 0.8 i.e. in restrictive lung diseases the ratio is normal or even increased

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Also, see this video

Admin عدد المساهمات : 9493 تاريخ التسجيل : 06/08/2009

QUESTION:
What is the difference between reduced Hb, oxidized Hb and oxygenated Hb?
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ANSWER:
* Reduced Hb: it is a Hb that is not carrying oxygen if its amount is less than 2 gm/dl in superficial capillaries is normal but if it exceeds 5 gm/dl (threshold for cyanosis) in superficial capillaries it causes cyanosis.
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** Oxidized Hb (Met-Hb): it is formed when oxygen reacts with ferrous of heme part of Hb changing it into ferric form (by oxidation). It is normally present in minute amount but, if increased it will be abnormal.
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*** Oxygenated Hb (Oxy-Hb): it is formed when oxygen binds to the ferrous part of Hb (oxygenation). it is the normal reaction between Hb and oxygen and by which Hb is carrying oxygen. normally, one Hb molecule can carry four Oxygen molecules and this occurs in steps and it is the cause of S shaped oxygen Hb dissociation curve.
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» Examples of SEQs on respiration physiology with their answers by Dr Khaled A Abulfadle
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