Respiratory Flashcards
What are the 2 types of pneumocytes? Which one precedes the other? Which is cuboidal? Which is squamous? Which responds to injury? Which secretes surfactant?
Type 1 Pneumocytes: Squamous, 97% of alveolar surfaces, gas diffusion.
Type 2 Pneumocytes: Cuboidal, Secrete surfactant, proliferate in response to injury, precursors to Type 1 cells.
What is the response to prolonged high altitude exposure?
Hypoxemia (respiratory alkalosis) with a compensating metabolic acidosis (decreased bicarbonate). The metabolic acidosis process takes 24-48 hours.
A patient comes in with respiratory acidosis (pH=7.2), with no respiratory alkalosis compensation. Why is this more likely to be heroin overdose than some sort of chronic obstructive process?
In an acute setting, you would see significant pH drop along with significant increase in PCO2, and there wouldn’t be enough time for any sort of metabolic compensation to occur. In a chronic process, you would see pH drop and PCO2 increase, but you would also see HCO3 compensation.
A patient was just stabbed above the clavicle and it pierced the apex of the lung. You suspect he has tension pneumothorax. What would you expect to see on Xray, and what are some clinical signs?
You would expect to see the lungs and mediastinum deviating to the opposite side of the chest. The increased pressure means less blood returns to the heart, leading to decreased cardiac output. There would be absent breath sounds with hyper-resonance to percussion on the side of the injury.
How do you differentiate between Cheyne-Stokes breathing secondary to CHF and Obstructive Sleep Apnea?
Cheyne-Stokes breathing=apnea followed by gradually increasing and then decreasing tidal volumes until next apneic period.
OSA=Periods of apnea, but the periods of breathing are generally consistently the same tidal volume.
What is Kussmaul breathing?
It’s the typical breathing that is seen in patients with DKA. It’s a deep and labored breathing pattern.
What are risk factors for PE, and what would you expect the respiratory status to be in acute PE situation?
Risk factors: Stasis, obesity, smoking, travel, post surgery, etc.
Respiratory status: Hypoxemia, hyperventilation, respiratory alkalosis with no metabolic compensation (acute)
What are the histological and clinical hallmarks of alpha-1 antitrypsin deficiency?
Effects both liver and lungs, causes shortness of breath. Proteolytic enzymes get into the liver and also destroy alveolar septa.
Histo: Reddish-pink periodic acid-schiff-positive granules of unsecreted, polymerized AAT in periportal hepatocytes.
What is the cause (ie what is released to cause) of centriacinar emphysema?
Proteinases, especially elastase, which is released by neutrophils and alveolar macrophages that infiltrate.
A patient comes in feeling short of breath. Her alveolar oxygen almost matches her tracheal oxygen, and her alveolar PCO2 is really low. What is probably happening?
Is ventilation usually perfusion-limited or diffusion-limited?
She probably has poor perfusion (ie embolus or blockage), so there are parts of the lung that simply can’t exchange. Thus, she can’t get O2 in.
Ventilation is usually perfusion-limited. If there is good perfusion, the ventilation usually is finished about 1/3 of the length of the capillary.
Ventilation becomes diffusion-limited in certain states such as emphysema, pulmonary fibrosis, or during exercise (when blood moves faster so there’s less time to diffuse).
What is the most sensitive test to exclude asthma as a diagnosis?
A negative methacholine challenge.
You are looking for bronchial hypersensitivity that causes a 20% decrease in FEV/FVC ratio.
The presence of eosinophils/IgE are not enough to make/exclude a diagnosis.
In relation to surfactant, what would you expect the levels of phosphatidylcholine (lecithin) and sphingomyelin (S) to be in amniotic fluid throughout pregnancy?
Lecithin levels are low and then peak during the 3rd trimester.
Sphingomyelin levels are constant throughout all 3 trimesters.
The L/S ratio should be greater than 2.0 to indicate adequate surfactant production.
What is the treatment of choice for anaphylactic shock?
Epinephrine. It reverses all of the effects of anaphylaxis.
Alpha-1=vasoconstriction
Beta1=increased heart rate/contractility
Beta 2=bronchodilation
How does the drive for increased/decreased respiration differ between healthy people and people with COPD?
In healthy people: Response is primarily to PaCO2 (in the central chemoreceptors).
In COPD: Response to PaCO2 is decreased, so the changes are detected by hypoxemia in the carotid bodies (peripheral chemoreceptors).
At which point is the pulmonary vascular resistance the lowest?
At the functional reserve capacity. The pressure then increases at increased volumes due to stretching the alveoli, and at lower volumes when there is decreased radial traction.
