Table of Contents
Advertisement
Rapid Shallow Breathing RSB
The Rapid Shallow Breathing index (RSB)* is the quotient
of the spontaneous breathing frequency (spontaneously
breathed breaths per minute) and the tidal volume:
RSB [ 1 /(min x L)] =
f
spont
V
The lower the RSB index for a patient with spontaneous
breathing, the more probably he or she can be weaned
successfully. The significance of the RSB index is due to
the fact that patients who can be weaned successfully
tend to have a lower spontaneous breathing frequency
and a higher tidal volume than those who are not yet
ready to be weaned.
In their 1991 study*, Yang and Tobin showed that the
RSB index is an effective instrument for predicting the
success of an attempt to wean the patient. Patients with
an RSB index <100 1 /(min x L) were weaned with a
probability of 80 %, while 95 % of those with an
RSB index >100 were not yet ready to be weaned.
Evita 4 indicates the RSB index in CPAP/ASB and PPS
modes.
Negative Inspiratory Force NIF
The Negative Inspiratory Force index (NIF)** measures
the patient's maximum inhalation effort after exhaling. The
patient system is closed during measurement of the NIF.
This value is also known as the Maximum Inspiratory
Pressure (MIP). As a result of the inhalation effort during
manually extended expiration, the patient generates a
negative pressure in relation to PEEP. The probability that
the patient can be weaned successfully increases with
the magnitude of this negative pressure. Patients with a
NIF < –30 mbar can in all probability be weaned
successfully, while those with a NIF of up to –20 mbar
will most probably prove unsuccessful.
Evita 4 determines the NIF value during manually
extended expiration. The patient system closes following
expiration by the patient while the »Exp. hold« key is held
down and Evita 4 measures the maximum inhalation effort
made by the patient. The NIF is measured as a pressure
against PEEP. The measuring procedure is ended when
the »Exp. hold« key is released or after not more than
15 seconds. The last measured NIF value and the time of
measurement are shown in Table 2 on the screen.
––––––––––––––––
*
Bibliography (16), page 182
** Bibliography (17), (18), page 182
[1/min]
[L]
T
Description
Rapid Shallow Breathing RSB
Negative Inspiratory Force NIF
175
Advertisement
Table of Contents
