Affiliations: Bronx, NY
Dr. Dantzker is Professor of Medicine, Albert Einstein College of Medicine.
Correspondence to: David R. Dantzker, MD, FCCP, 64 East 86th St, New York, NY 10028; e-mail: firstname.lastname@example.org
In 1997, I wrote an editorial for CHEST
regarding the search for a method to monitor the adequacy of tissue
oxygenation that could be used by clinicians to guide the treatment of
physiologically unstable patients.1 At that time, I
likened this to the quest for the Holy Grail. Here it is 4 years later
and, like the search for the grail, the goal appears to remain
tantalizingly out of reach. While elusiveness is a wonderfully romantic
part of the fascination with a quest, it is disappointing that more
progress has not been made. The article by Marik in this issue of
CHEST (see page 923) provides additional evidence
that monitoring changes in luminal Pco2,
reflecting the interstitial hydrogen ion concentration, signals a
change in overall homeostasis that correlates with a bad outcome. This
additional proof of principal is welcomed, but begs the question of
whether this variable can be put to use in a clinically useful and
Over the years, many indexes have been suggested as ways of monitoring
tissue oxygenation. Most of these, such as venous
Po2, lactate, and O2
consumption-O2 delivery relationships have fallen by the
way either because they could not stand up to rigorous clinical
appraisal or because they were successfully challenged by newer
theoretical understandings of the microcirculation and tissue
metabolism. Some techniques, such as direct magnetic resonance or near
infrared spectroscopic measurements of tissue metabolic state, would
probably be quite useful, but have not yet been developed to the point
of clinical applicability.
In 1964, Bergofsky showed that hollow organs such as the bladder
could be used as an in vivo tonometer to approximate tissue
gas tensions.2Fiddian-Green et al3in the
early 1980s used this approach to measure interstitial
Pco2 in the gut and offered this measurement as
an index of tissue hydrogen ion concentration (pHi) and by inference
the adequacy of tissue oxygenation. The principle is quite simple. As
the oxygen-deprived tissue depends increasingly on glycolysis for
adenosine triphosphate generation, buffering of the rising hydrogen ion
concentration leads to CO2 production, which diffuses into
the lumen of the gut and can be measured. Subsequent
studies4 in animals validated the concept, and human
studies5–6 showed that a fall in pHi correlated with a
poor outcome in a large number of clinical situations, such as
high-risk and cardiac surgery, as well as in the ICU.
Weil and his coworkers,7 allowing for the use of
sublingual measurements of Pco2 to replace
gastric or small-bowel sampling, accomplished subsequent modification
of the technique of monitoring pHi. Their data plus those presented in
the study by Marik suggest that an easier measure of tissue
anaerobiosis is now available. Are we now closer to a clinically useful
Physicians taking care of physiologically unstable patients have always
been fascinated with exotic means of monitoring bodily functions. In
the days of seemingly endless health-care resources, we could indulge
this intellectual curiosity and hope that sufficient information could
be extracted to alter outcome and justify the added cost in care time
and capital investment. Over time, many of these “black boxes” have
been relegated to the hospital storeroom as the initial enthusiasm
waned. Measurement of pHi, as originally described by Fiddian-Green et
al3 or in the form of sublingual capnography, has been
enticing us long enough. Before it meets a similar fate, it is time for
a coordinated effort to study its clinical usefulness. We already have
a number of ways of predicting outcome, including the clinical acumen
of seasoned clinicians. What we need is an objective tool to direct
The only attempt thus far to prospectively study pHi as a guide to
therapy was a heroic, but less than satisfying, effort by Gutierrez and
his colleagues.8 Despite some methodologic flaws, their
data did suggest that patients treated using pHi as a guide had a
better outcome than those treated using standard monitoring techniques.
What is called for now is a well-planned, multicenter, prospective
trial comparing outcome in a relatively well-defined category of
patients using pHi in the study group to guide clearly specified
One should not underestimate the difficulty of such a clinical trial.
Time, money, courage, and fortitude will be required. However, only
with such an effort, do we have any chance at turning a quest
into a real journey of discovery.
Become a CHEST member and receive a FREE subscription as a benefit of membership.
Individuals can purchase this article on ScienceDirect.
Individuals can purchase a subscription to the journal.
Individuals can purchase a subscription to the journal or buy individual articles.
Learn more about membership or Purchase a Full Subscription.
Institutional access is now available through ScienceDirect and can be purchased at myelsevier.com.
Some tools below are only available to our subscribers or users with an online account.
Download citation file:
Web of Science® Times Cited: 1
Customize your page view by dragging & repositioning the boxes below.
Enter your username and email address. We'll send you a reminder to the email address on record.
Athens and Shibboleth are access management services that provide single sign-on to protected resources. They replace the multiple user names and passwords necessary to access subscription-based content with a single user name and password that can be entered once per session. It operates independently of a user's location or IP address. If your institution uses Athens or Shibboleth authentication, please contact your site administrator to receive your user name and password.