T
Tim McNamara
Guest
In article <[email protected]>,
[email protected] wrote:
> On Jul 30, 2:53 pm, Tim McNamara <[email protected]> wrote:
> > In article <[email protected]>,
> >
> > [email protected] wrote:
> > > On Jun 7, 11:57 am, Andy Coggan <[email protected]> wrote:
> >
> > > > In fact, mild-to-moderate arterial desaturation tends to occur
> > > > during maximal exercise in a significant portion of the
> > > > population (at least discounting young, healthy, untrained
> > > > men!), indicating that, at least to some extent, aerobic
> > > > capacity (i.e., VO2max) is limited, in part, by pulmonary
> > > > function.
> >
> > > Phoeey. A small arterial desaturation is most likely explained by
> > > increased left to right shunting
> >
> > Left to right shunting from where to where through what? This term
> > is usually used to indicate left to right shunting through an
> > atrial septal defect or cases of tricuspid atresia. There should
> > be little or no left to right shunting through a patent foramen
> > ovale and should be no shunting at all in a normal heart. So I am
> > not clear to what you refer. Thanks.
>
> My bad, I should have said increased right to left shunting although
> this is not so much as a physiological shunt but as a ventilation
> perfusion defect behaving as a shunt.
That didn't really clarify. Ventilation defects are generally caused by
obstructions somewhere in the airway; perfusion defects are generally
caused by emboli in the pulmonary vasculature. What is the cause of the
"ventilation perfusion defect" you are pointing towards? Does this
occur in non-pathological individuals?
I trimmed the rest of your previous post in an over-zealous fit of good
netiquette, unfortunately. It would appear that Nielsen (2003) found
that arterial desaturation during exercise is multifactoral and that
large lung capacity does offer some protection from this. Perhaps this
link offers some light on the subject:
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids
=14617055&dopt=AbstractPlus
[email protected] wrote:
> On Jul 30, 2:53 pm, Tim McNamara <[email protected]> wrote:
> > In article <[email protected]>,
> >
> > [email protected] wrote:
> > > On Jun 7, 11:57 am, Andy Coggan <[email protected]> wrote:
> >
> > > > In fact, mild-to-moderate arterial desaturation tends to occur
> > > > during maximal exercise in a significant portion of the
> > > > population (at least discounting young, healthy, untrained
> > > > men!), indicating that, at least to some extent, aerobic
> > > > capacity (i.e., VO2max) is limited, in part, by pulmonary
> > > > function.
> >
> > > Phoeey. A small arterial desaturation is most likely explained by
> > > increased left to right shunting
> >
> > Left to right shunting from where to where through what? This term
> > is usually used to indicate left to right shunting through an
> > atrial septal defect or cases of tricuspid atresia. There should
> > be little or no left to right shunting through a patent foramen
> > ovale and should be no shunting at all in a normal heart. So I am
> > not clear to what you refer. Thanks.
>
> My bad, I should have said increased right to left shunting although
> this is not so much as a physiological shunt but as a ventilation
> perfusion defect behaving as a shunt.
That didn't really clarify. Ventilation defects are generally caused by
obstructions somewhere in the airway; perfusion defects are generally
caused by emboli in the pulmonary vasculature. What is the cause of the
"ventilation perfusion defect" you are pointing towards? Does this
occur in non-pathological individuals?
I trimmed the rest of your previous post in an over-zealous fit of good
netiquette, unfortunately. It would appear that Nielsen (2003) found
that arterial desaturation during exercise is multifactoral and that
large lung capacity does offer some protection from this. Perhaps this
link offers some light on the subject:
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids
=14617055&dopt=AbstractPlus