Treatment of ARDS; Ventilators; PEEP; Tidal Volume; O2
Sat Level?
No specific therapies currently exist for ARDS patients. ARDS
has no magical cure. No so-called wonder drug exists. Treatment primarily involves
supportive care in an intensive care unit (ICU), including use of a mechanical ventilator
and supplemental oxygen to help patients breathe. The goal of mechanical ventilation
is to support the patient's breathing during the time needed for the patient's lungs to
heal. ARDS patients are usually deeply sedated into a drug-induced coma and
intentionally paralyzed to prevent them from fighting the ventilator and to ensure all
available oxygen is made available for the functioning of critical organs. Patients may be
placed on a special bed, such as an "air bed" or a rotating bed to position them
properly to help prevent complications such a bed sores and pneumonia.
There are no currently established medication treatments for
combating ARDS itself. Use of steroids, whether through inhalation therapy or
otherwise, has been advocated and studied. Certain studies have ruled out various
other medication treatments as being ineffective. Some studies are underway to
determine the efficacy of other medication therapies. Most medication treatments are
oriented toward the underlying medical problems which the patient is battling, such as
sepsis and trauma. In addition, other common medications which may be employed
during the battle with ARDS include sedating drugs, paralyzing drugs, anti-anxiety
medication, and antibiotics to combat or stave off infections. These medications do
not directly battle ARDS in a medical sense, rather they are supportive in the battle
against ARDS to allow the lungs to heal in hopefully the best medical and physical
situation possible considering the underlying medical problems and the severity of the
ARDS.
Mechanical ventilators deliver breaths of oxygen-enriched air to the
body and remove breaths of carbon-dioxide produced by the body, to maintain enough oxygen
in the bloodstream while patients recover from ARDS and their other injuries or illness.
A ventilator can breathe completely for a patient or assist a patient's own
breathing. Ventilators deliver their oxygen-enriched breaths through an artificial
airway or endotracheal tube. The tube is connected to the ventilator. While in
place, the tube temporarily interferes with the patient's ability to speak since it passes
between the vocal cords. Positive end-expiratory pressure (PEEP), is a special
setting on the ventilator that keeps the lungs expanded to help get oxygen from the lungs
into the bloodstream.
Most often and common, the tube is inserted through the mouth or
nose. Sometimes, however, depending on the severity of the ARDS and the patient's ability
to tolerate ventilation through the mouth (that is, fighting the ventilator), a
tracheostomy is performed where an opening is cut through the neck into the trachea and
the ventilation tube is inserted through this opening for a safe airway. "Fighting
the vent" does not necessarily mean a conscious fighting in the sense most people
would understand that phrase. The body and lungs themselves may exhibit a
"fighting of the vent" which is not readily visible to family and friends
visiting the patient. A medical decision to proceed with a tracheostomy IS NOT an
indication of a worsening of the patient's condition. Instead, it is usually an
indication that the mechanical ventilation is not being optimized through the tube
inserted through the mouth. A tracheostomy might afford the patient a better pattern
of breathing and hence a better possibility of surviving ARDS. A tracheostomy might
also make for an easier, somewhat more comfortable course of treatment, in patients who
are prone to "fighting the vent".
There are a number of controls or settings on the ventilator that
are ordered by the doctor. The amount of oxygen that the patient receives can be
adjusted. The air we normally breathe contains 21% oxygen. It is possible to
give a patient as much as 100% oxygen through a ventilator but this, too, can cause damage
to the lung so an effort is made to give the lowest amount of oxygen necessary. PEEP
is one way to avoid giving the patient high levels of oxygen. While early data did
not establish whether high or low pressure was the better course of treatment in assisting
patients to recover from ARDS, on March 15, 1999, the National Institutes of Health issued
a press release concerning the early termination of the ventilator study being done by the
ARDS Clinical Network (ARDSNet) in the United States because the results showed that lower
pressure is the overwhelming favored treatment course, not entirely surprisingly because
high pressue ventilation itself may cause lung damage sometimes irreversible which may
significantly effect a patient's ability to recover from ARDS or have life long medical
implications.
PEEP, which is positive end expiratory pressure, is adjusted through
the ventilator. It keeps some pressure in the lungs at the end alveoli, the tiny air
sacs where oxygen passes into the bloodstream, from collapsing. The pressure is
measured and carefully adjusted because there can be complications with high levels of
PEEP. The amount of PEEP is often increased and decreased gradually but occasionally
it is important to change the level of PEEP more quickly.
Other adjustments on the ventilator include the size of each breath
(Tidal Volume) the patient receives and the number of breaths (respiratory rate) the
patient receives each minute. The ventilator can be adjusted so that it does all of
the breathing or so that the patient breathes partially on his or her own. These
settings are adjusted depending on the amount of oxygen and carbon dioxide in the blood as
well as other tests of lung function. Study data has shown that the use of lower
Tidal Volume is associated with less lung damage and improved chance of survival (lower
mortality rate).
The ventilator can sense when the patient takes a breath of his or
her own, timing the set number of breaths to the patient's own rhythm. Often the
amount of breathing needed by the body is much more than the patient is able to do on his
or her own. The patient may require sedatives or relaxing drugs to help them breathe
with the ventilator. PEEP is an odd sensation because it feels like the lungs do not
empty at the end of each breath. However, the patient may also feel better because
it can make breathing easier and gets more oxygen into the bloodstream.
The ventilator and these settings, which sometimes may be adjusted
numerous times and quite often by the doctors, are designed to assist the patient's body
in performing the critical pulmonary function of getting oxygen into the blood and CO2
removed from the body. The primary measure of this is the O2 Sat
level. With normal pulmonary functioning O2 Sat level should be in the
high nineties in percentage (96-99% range). If pulmonary function is compromised as
it is with ARDS (and many lung disorders and diseases), the O2 Sat level can
drop often precipitiously, rapid, and dangerously. The lower the O2 Sat
level, the more damage to vital organs and body processes may begin to manifest. If
the O2 Sat level is not brought up and maintained at adequate levels, this will
lead to significant damage often irreversible including severe brain damage and death.
This is why it is important to know what is going with the entire body, the vital organs
and body processes, because while ARDS is a pulmonary condition involving the lungs the
effects of ARDS strikes throughout the body. |
