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Doesent matter S.Pneumonia or Klebsiella or what ..
The answer for any Pneumonia will be INADEQUATE VENTILATION =2

+ cocci can be what from a microbiology stand point that come in pairs ???
Strep.Pneumonia is lanc-shaped G + cocci or what??
Staph aureus is like agrap clusters ....
But if w ego from the most common cause of Pneumonia in his age is definetelly S.Pneumonia =CAP
Th equestion dosent ask us what type of Pneumonia ,BUT the pathogensis of the pneumonia

great work. yes this q is asking for pathogensis of the pneumonia induced hypoximia/apenea.

Decrease V/Q contributes to the problem but the main problem is due to inflmatory exudation in alveolar, thus impairs the diffusion capacity.

Answer is 5.

This is such common and such important a topic, please be clear of every aspect of the disease to be better prepared for the step1 test

quansar can u explain a little bit more?
i am really confused with diff explanations.

reta thinking ,BUT wron answer fro me..welll..it is PNEUMONIA , BUT NOT ASPIRATION pneumonia...so we have a V/Q mismatch
so

An abnormal A-a gradient is always associated with hypoxemia and indicates a primary problem in the lungs and/or in the heart..
In the lungs, it may be abnormality involving :
ventilation,
perfusion
diffusion
combinations of disorders.

Now
Hypoxemia is a low partial pressure of arterial oxygen dissolved in plasma
The partial pressure of Alveolar oxygen ( PAO2) rarely matches the partial pressure of arterial oxygen (PaO2) owing to the small ventilation /perfusion (V/Q) mismatches throughout the lungs

A-A Gradient
The difference between the PAO2 and Pao2 IS CALLED Alveolar-arterial gradient (A-a gradient; normally 5-15 mm Hg)
A medically significant A-a gradient is 30 mm Hg
The PAO2 is the difference between the amount of oxygen inspired, or PiO2 ( % O2 x 713 mm Hg ), from the amount that is exchanged in the lungs with CO2 ( PaCO2/0.8 ) hence, the PAO2=PiO2 “PaCO2/0.8

A patient breathing room air ( 21 % oxygen ) who has a normal PaCO2 ( 40 mm Hg ), and a PaO2 of 90 has an A-A gradient of 10 mm Hg
PAO2 = 0.21 (713) “ 40/0.8 = 100 MM Hg “ 90 mm Hg =10 mmHg

lung blood barrier got stucked with mucus, dead neutriphil, debrils ... thus increaseing the depth of the barrier, harder for O2 goes from alvelar side to blood now....

2222

Let's try again :
The pt has a Dyspnea , rigth ??
Rigth..
Now Dyspnea refers to difficulty with breathing and can be due to :
1.Airway obstruction
2.Atelectasis ( collapse of the lung tissue )
3.Lung consolidations like pneumonia
4.Interstitial lung disease ( edema, pneumoconiosis, etc .)
5.Pleural effusions
6.Any cause of hypoxemia
7.Anemia
8.Chest dysfunction

Now our 65 y/o pt base don the symptoms and based on the encapsulated bacteria probably has PNEUMONIA ...(we don't care which one now )..
So what is the pathogenesis of Pneumonia now ????
First by definition and Pathogenesis Pneumonia is An infection of the bronchoalveolar unit with an inflammatory exudate.
- Bacterial Infection --------Consolidation
-Viral, PCP ,Atypical Pneumonia------diffuse interstitial disease
-Nocardia, Mycobacterium, Aspergillus, Cryptococcus----Nodular or cavitary disease

Now do you think that si EXUDATE nad HOW will affect the V/Q Mismatch ???
We know that An abnormal A-a gradient is always associated with hypoxemia and indicates a primary problem in the lungs and/or in the heart..
In the lungs, it may be abnormality involving :
ventilation,
perfusion
diffusion
combinations of disorders..
So which on eof this can be affceted in Pneumonia ?????

so what is the A-a gradient ????
The difference between the PAO2 and Pao2 IS CALLED Alveolar-arterial gradient (A-a gradient; normally 5-15 mm Hg)
A medically significant A-a gradient is 30 mm Hg


and then what is the PAO2
The PAO2 is the difference between the amount of oxygen inspired, or PiO2 ( % O2 x 713 mm Hg ), from the amount that is exchanged in the lungs with CO2 ( PaCO2/0.8 ) hence, the PAO2=PiO2 “PaCO2/0.8

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