We're unable to sign you in at this time. Please try again in a few minutes.
We were able to sign you in, but your subscription(s) could not be found. Please try again in a few minutes.
There may be a problem with your account. Please contact the AMA Service Center to resolve this issue.
Contact the AMA Service Center:
Telephone: 1 (800) 262-2350 or 1 (312) 670-7827  *   Email: subscriptions@jamanetwork.com
Error Message ......

Venous Return and Mechanical Ventilators

Theodore C. Smith, MD
JAMA. 1986;256(1):38. doi:10.1001/jama.1986.03380010042016.
Text Size: A A A
Published online

To the Editor.—  The ex cathedra reply of Cane and Shapiro in the LETTERS section1 that true-negative pressure ventilators do not diminish venous return should not go unchallenged, despite decline in the use of such machines. The truth lies somewhere between Johnson's view that both negative- and positive-pressure ventilators are identical and Cane and Shapiro's view that they are different.Venous return, and hence cardiac output, is very nearly an Ohm's law relationship. The electrical law E = IR translates hydrodynamically to driving pressure = venous return × resistance. Driving pressure for venous return is the difference between venular pressure in tissues and right atrial pressure. Venular pressure in turn is partly dependent on tissue ambient pressure. Right atrial pressure is similarly dependent on alveolar pressure and lung compliance. In a full tank respirator, lowering the tank pressure to create a breath will lower driving pressure quite like an equivalentsized breath


Sign in

Purchase Options

• Buy this article
• Subscribe to the journal
• Rent this article ?




Also Meets CME requirements for:
Browse CME for all U.S. States
Accreditation Information
The American Medical Association is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The AMA designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditTM per course. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Physicians who complete the CME course and score at least 80% correct on the quiz are eligible for AMA PRA Category 1 CreditTM.
Note: You must get at least of the answers correct to pass this quiz.
Please click the checkbox indicating that you have read the full article in order to submit your answers.
Your answers have been saved for later.
You have not filled in all the answers to complete this quiz
The following questions were not answered:
Sorry, you have unsuccessfully completed this CME quiz with a score of
The following questions were not answered correctly:
Commitment to Change (optional):
Indicate what change(s) you will implement in your practice, if any, based on this CME course.
Your quiz results:
The filled radio buttons indicate your responses. The preferred responses are highlighted
For CME Course: A Proposed Model for Initial Assessment and Management of Acute Heart Failure Syndromes
Indicate what changes(s) you will implement in your practice, if any, based on this CME course.


Some tools below are only available to our subscribers or users with an online account.

0 Citations

Sign in

Purchase Options

• Buy this article
• Subscribe to the journal
• Rent this article ?

Related Content

Customize your page view by dragging & repositioning the boxes below.