Talk:Cardiac output

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Untitled[edit]

Please fix the equation.—Preceding unsigned comment added by 210.54.84.118 (talkcontribs) 01:32, 4 September 2007

Cardiac Output (CO) considered as Q is a close literal and mathematical description of Ejection Fraction (EF) and Systole. Q is well reasoned as a mathematical model of global cardiac performance. Q as a mathematical proxy of systole readily applies to terms first defined by Adolph Fick. Q as an overall index of myocardial performance deserves further reconsideration in phase/terms of systole and diastole. Systole/Ejection Fraction/Cardiac Output has another half deserving of mathematical and echocardiographic definition defined as Diastole/Injection Fraction/Cardiac Input. Clinical evidence of Q as Ejection Fraction is a reliable indicator of burden of systolic heart failure. Given inexpensive echocardiographic rendering, EF is readily equal to the difference between End Systolic Volume and End Diastolic Volume (EF=ESV/EDV). Burden of diastolic heart failure may be readily appreciated in simple inversion of terms (with no technology or licensing issues) as Injection Fraction. IF = EDV/ESV. Diastolic heart failure (decline of injection fraction) is perhaps better described as negative Windkessel physiology.--Lbeben (talk) 03:14, 11 February 2008 (UTC)

Darcy's Law?[edit]

In the Cardiac Output and Vascular Resistance section, how is Darcy's Law used? Temporaluser (talk) 06:42, 19 March 2008 (UTC)

Measuring O2 uptake[edit]

The statement of oxygen consumptions being difficult to measure accurately is vague and not true. First, what is meant by "difficult" and "accurate"?? These are weasel words if there ever were any. Further, oxygen uptake is routinely measured by automated systems in research/clinical laboratories, with the "accuracy" of most systems having been validated by the individual companies (info typically available on their websites) or research investigators (reports in the literature). —Preceding unsigned comment added by 138.88.163.79 (talk) 21:21, 19 March 2008 (UTC)

Symbol for cardiac output[edit]

Why? Please elaborate.

I always use  \dot Q_{c} as a symbol for cardiac output but it isn't mentioned in the text.

British English[edit]

During my copyediting drive in May 2015, I came across inconsistent use of -ise and -ize verb forms. Based on the repeated use of the metric system and the initial verb being of the -ise variety, I chose British English for standardization. I have updated the article and tagged it (as well as this page) with the appropriate templates. ← scribbleink ᗧHᗣT 23:09, 31 May 2015 (UTC)

Examples: catheterise, optimise, generalise, haemoglobin, paediatrics, etc. ← scribbleink ᗧHᗣT 00:10, 1 June 2015 (UTC)

May 2015 copyediting[edit]

@Tom (LT): Regarding your request at WP:WikiProject Guild of Copy Editors/Requests#Cardiac output: I made a first pass, including section rearranging, rewrites, image additions and WP:C/E. It is by no means complete, but it seems like a good time to ask you for your thoughts on the outcome. Thanks! ← scribbleink ᗧHᗣT 07:28, 1 June 2015 (UTC)

Woohoo, like Christmas!! Thanks Scribbleink, you made this article a lot more readable. I think it looks at least 100% improved, if it is OK I will make some changes too. You've really improved the page, I think it's gone from an article no reader would want to read to one at least 8/10 users will take a stab at (I think the other 2/10 will realise the article was too technical anyway...). --Tom (LT) (talk) 14:08, 1 June 2015 (UTC)
OK I've moved some things around to group things together. @Scribbleink, what's your opinion about:
  • moving some of the 'measurement' section into a 'history' section?
  • removing some of the unnecessary formulas (eg in 'ultrasound')
  • removing some information about the measurement techniques (especially eg ultrasound) that could be covered in the parent articles.
I can't state how much your edits have improved the article. I hope that you are pleased with my edits too, please feel free to change them also. --Tom (LT) (talk) 02:35, 2 June 2015 (UTC)
@Tom (LT): You're welcome. I like your idea of moving some of the year-marked statements into a history section. That should make the measurement techniques section easier to read. Go for it. Regarding the equations in the measurement section, I think they are fine as they are because they do translate directly to Q, e.g., via SV for Doppler ultrasound. If you can find the parent article for this, feel free to remove it form here and drop in a pointer. ← scribbleink ᗧHᗣT 05:15, 2 June 2015 (UTC)

Source[edit]

"Cardiac Output Monitoring: Is There a Gold Standard and How Do the Newer Technologies Compare?" [1] For future reference of future editors (myself included) --Tom (LT) (talk) 07:57, 6 June 2015 (UTC)

Removed text[edit]

Per WP:OR; unreferenced text can be nuked at will.

Noninvasive[edit]

A sphygmomanometer used to measure pulse pressure (PP) non-invasively
A sphygmomanometer used to measure pulse pressure (PP) non-invasively

The sphygmomanometer or cuff blood pressure device was introduced to clinical practice in 1903, allowing non-invasive measurements of blood pressure and providing the common PP waveform values of peak systolic and diastolic pressure, which can be used to calculate mean arterial pressure (MAP) and pulse pressure (PP). The pressure in the arteries, measured by sphygmomanometry, is often used as an indicator of the function of the heart. The pressure pulses in the heart are conducted to the arteries, and the arterial pressure is assumed to reflect the function of the heart or the Q. However, no account is made of the elasticity of the arterial bed, or its impact on the pressure signal.

  • The pressure in the heart rises as blood is forced into the aorta
  • The more stretched the aorta, the greater the pulse pressure (PP)
  • In healthy young subjects, each additional 2 ml of blood results in a 1 mmHg rise in pressure
  • Therefore:
SV = 2 ml × Pulse Pressure
Cardiac output = 2 ml × Pulse Pressure × HR
By resting a more sophisticated pressure sensing device, a tonometer, against the skin surface and sensing the pulsatile artery, continuous PP wave forms can be acquired non-invasively, and an analysis made of these pressure signals. However, as the heart and vessels function independently, and sometimes paradoxically, the changes in PP both reflect and mask changes in Q. So these measures represent combined cardiac and vascular function. A similar system that relies on arterial pulse is the pressure recording analytical method (PRAM).

Vascular resistance[edit]

The vascular beds are a dynamic and connected part of the circulatory system against which the heart must pump to transport the blood. Q is influenced by the resistance of the vascular bed against which the heart is pumping. For the right heart this is the pulmonary vascular bed, creating Pulmonary Vascular Resistance (PVR), while for the systemic circulation this is the systemic vascular bed, creating Systemic Vascular Resistance (SVR). The vessels actively change diameter under the influence of physiology or therapy, vasoconstrictors decrease vessel diameter and increase resistance, while vasodilators increase vessel diameter and decrease resistance. Put simply, increasing resistance decreases Q; conversely, decreased resistance increases Q.

This can be explained mathematically:

By simplifying Darcy's Law, we get the equation that

Flow = Pressure/Resistance

When applied to the circulatory system, we get:

Q = (MAP – RAP)/TPR

Where MAP is the Mean Aortic (or Arterial) Blood Pressure in mmHg, RAP is the Mean Right Atrial Pressure in mmHg, and TPR is the Total Peripheral Resistance in dynes·sec/cm5.

However, as MAP>>RAP, and RAP is approximately 0, this can be simplified to:

Q ≈ MAP/TPR

For the right heart Q ≈ MAP/PVR, while for the left heart Q ≈ MAP/SVR.

Physiologists will often re-arrange this equation, making MAP the subject, to study the body's responses.

As has already been stated, Q is also the product of the heart rate (HR) and the stroke volume (SV), which allows us to say:

Q ≈ (HR × SV) ≈ MAP / TPR

===Dilution methods===

The cardiac output of the heart is the ratio of the quantity of injected indicator dye to the average concentration in the arterial blood after a single circulation through the heart. This method was initially described using an indicator dye; it assumes the rate at which the indicator is diluted reflects the Q value. It measures the concentration of the dye at certain points in the circulation. The dye is usually injected intravenously; this is then measured at a downstream sampling site, usually in a systemic artery. Once the concentrations are measured, Q is the ratio of the quantity of injected dye to the area under the dilution curve measured downstream. This is referred to as the Stewart-Hamilton equation, whih was named after George N. Stewart (1897) and William F. Hamilton (1932).

\mathrm{Cardiac\ output} = \frac{\mathrm{Quantity\ of\ Indicator}}{\int_0^\infty \mathrm{Concentration\ of\ Indicator}\cdot {dt}}

When numerical methods are used to calculate this value computationally, the trapezoid rule is often used as an approximation of this integral.

References

Baffle gab1978 (talk) 01:10, 10 June 2015 (UTC))

Thanks, The second section in addition to being unsourced is covered in too much detail on this article anyway.--Tom (LT) (talk) 02:59, 9 June 2015 (UTC)

External links modified[edit]

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