USMLE World Ventilator Question! - USMLE Forums
 USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
 Home USMLE Articles USMLE News USMLE Polls USMLE Books USMLE Apps
 USMLE Forums USMLE World Ventilator Question!
 Register FAQs Members List Search Today's Posts Mark Forums Read

 USMLE Step 2 CK Forum USMLE Step 2 CK Discussion Forum: Let's talk about anything related to USMLE Step 2 CK exam

#1
07-10-2012
 USMLE Forums Master Steps History: --- Posts: 1,365 Threads: 648 Thanked 591 Times in 355 Posts Reputation: 601
USMLE World Ventilator Question!

Quote:
 Several values related to pulmonary mechanics can be calculated in mechanically ventilated patients. Lung compliance is calculated by performing the end-inspiratory hold maneuver. Airway resistance is calculated by examining the peak airway pressures. Positive end-expiratory pressure (PEEP) is calculated with the end- expiratory hold maneuver.
please any one who understands this...please explain...it all sounds gibberish to me
 The above post was thanked by: mayursn39 (07-11-2012)

#2
07-10-2012
 USMLE Forums Master Steps History: --- Posts: 1,365 Threads: 648 Thanked 591 Times in 355 Posts Reputation: 601

question in regard to the above fact from uworld...

A 32-year-old man is intubated and mechanically ventilated after an opioid drug overdose. The ventilator
triggers 12 breaths per minute, each delivering 500 ml of tidal volume at a flow rate of 60 Umin. You perform
an inspiratory hold for 2 seconds following delivery of the tidal volume, and the airway pressure is measured
to be 30 em H20.
The measured pressure reflects which of the following?
A. Upper airway resistance
B. Total airway resistance
C. Pulmonary compliance
D. Expiratory muscle strength
E. End-expiratory pressure
#3
07-10-2012
 USMLE Forums Scout Steps History: Not yet Posts: 61 Threads: 7 Thanked 82 Times in 32 Posts Reputation: 92

okay I got this answer right on UWorld and my logic (although not good enough) is as follows:
When the patient is asked to perform an inspiratory hold it is essentially similar to Positive Pressure Ventilation. The air is trapped in the alveoli and the alveoli is prevented from collapsing. (Thats why we use PPV in atelectasis). Now the only parameter thats related to alveoli not collapsing is 'compliance'. It is the ability of the lung/alveoli to expand (and not collapse..collapse is 'recoil of the lung').
Its crude but thats the best I could come up with :/
 The above post was thanked by: mayursn39 (07-11-2012)

#4
07-11-2012
 USMLE Forums Master Steps History: --- Posts: 1,365 Threads: 648 Thanked 591 Times in 355 Posts Reputation: 601

can we get more explanation.this seems to be high yeild topic .

lets discuss it more...
 The above post was thanked by: legendkiller (09-01-2015)
#5
07-11-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,867 Threads: 149 Thanked 2,107 Times in 1,049 Posts Reputation: 2127

Think of the lung as a balloon.
Inspiration is an active phenomenon and compliance is the capacity of the lung,
Expiration is passive and depends on recoil of the lung.

Now, in a mechanically ventilated lung the ventilator is practically substituting for diaphragm.
To test for compliance you have to measure once the lung is inflated with the tidal volume and the pressure at the end of the delivery of TV is a reflection of the compliance of the lung.

To test for PEEP, you have to know how PEEP works. It provides resistance at the end of expiration to prevent alveoli from collapsing. So, it makes sense to check it at the end of expiration when no pressure is being exerted by the air in the alveoli delivered as TV.
 The above post was thanked by: excellence (03-04-2015), K06100 (10-05-2012), pkul85 (07-06-2013), Remee (08-02-2013), shaan.medico (06-03-2013), Thrax_usmle (08-03-2014), tyagee (07-12-2012), usmledr (07-12-2012), vikyeergreen (02-05-2014)
#6
06-29-2014
 USMLE Forums Scout Steps History: Not yet Posts: 10 Threads: 1 Thanked 0 Times in 0 Posts Reputation: 10

In ICUs they do it to measure a Static Compliance

 Tags Pulmonology-, Step-2-Questions

Message:
Options

## Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
User Name:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
 AMG IMG ---
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

 Not yet Step 1 Only CK Only CS Only 1 + CK 1 + CS 1+CK+CS CK+CS 1+CK+CS+3 ---
Favorite USMLE Books
 What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
 Where you live. Leave blank if you don't want to tell.

## Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.