Ability to generate adequate cough is important
to protect respiratory functions in SCI patients. Peak
Cough Flow is the maximum flow recorded
immediately following opening of the glottis. This
leads to the rapid expulsive phase of a cough,
resulting from the sudden release of high intrapleural
and thoraco-abdominal pressures. To achieve a
functional PCF (to expectorate secretions) requires
at least 50% of vital capacity and sufficient thoraco-
abdominal pressure (in excess of 100 cmH
2
O) to
produce at least a flow of 270 l/m. In order to move
any mucus within the airways, PCF must exceed at
least 160l/m. Combination with sufficient expiratory
muscle strength is required to generate the required
thoraco-abdominal pressures (Anderson, 2005).
Both patients had been through rehabilitation
program for six weeks. The results corresponding to
the PCF and PFR before and after rehabilitation
program are described in Table 1. In case I, patient
experienced an increase in PCF and PFR during
active rehabilitation following training to improve
cardiorespiratory endurance, this is in line with
research by Houtte et al and Moro et al which
confirmed that respiratory muscle training tended to
improve expiratory muscle strength, vital capacity,
residual volume, and also increasing ventilation
efficiency in subjects with SCI (Moro et al, 2005).
She continues to train her expiratory muscles using
PEP. In case II, after the prone position is applied,
the patient is still able to do strengthening exercises
on the upper limb in the form of push up and weight
training for as long as 30 minutes/day, 5 days a
week. Patient wasn’t given training using PEP
because he have good PCF and PFR baselines (more
than 270 l/m).
Pulmonary function in SCI is mainly limited by
the weakness of respiratory muscles, therefore,
training of the remaining respiratory muscles in SCI
and the use of compensatory respiratory mechanism,
such as m. pectorals function for expiration may
improve pulmonary function (Houtte et al, 2006).
Prone position can also give benefit to respiratory
function by improving lung parenchyma mechanics
and arterial oxygenation, attenuating lung inflation
gradient, eliminating lung compression by the heart,
and make regional alveolar ventilation become more
homogenous resulting in reduction of alveolar
atelectasis and hyperinflation. Decreased atelectasis
and more uniform inflation may result in more
homogenous and increased average alveolar septal
tension (Metzelopoulos et al, 2005). The
gravitational gradient of intrapleural pressure is
suggested to be less in prone posture than supine.
Thus the gravitational distribution of ventilation is
expected to be more uniform prone, potentially
affecting regional ventilation-perfusion ratio
(Henderson et al, 2014).
In the supine position, there is predominance of
ventilation in the ventral area of the lung and
perfusion in the dorsal area of the lung, resulting in a
heterogeneous ventilation-perfusion ratio in various
lung areas. This is due to the influence of gravity on
the solid mass of the lung, pulmonary
vascularization and the transpulmonary gradient
associated with alveolar size. In contrast to the
pronation position, the solid lung mass and blood
flow are distributed to the ventral by the influence of
gravity, resulting in a more homogeneous
ventilation-perfusion ratio in the ventral and dorsal
areas so as to improve gas exchange and increase
oxygenation (Glenny et al, 2011).
Patients with prone positioning experience a
more even distribution of tidal volume because the
vertical gradient of pleural pressure becomes more
negative in the dorsal portion of the lung. In the
pronation position, the pressure from the heart and
the abdominal cavity also decreases so that the lung
volume in the dorso-caudal region increases (Glenny
et al, 2011).
In the supine position, the size of the alveolar
will become more heterogeneous, where the size of
the alveolar from the non-dependent (ventral) to the
dependent (dorsal) area of the lung will become
smaller, thereby increasing the risk of atelectasis in
the lung-dependent area. In contrast to the pronation
position, alveolar size in the lung dependent area
will be greater due to the Slingky effect on lung
tissue, thus, alveolar size will become more
homogeneous while reducing the risk of atelectasis
(figure 1) (Hopkins et al, 2015).
Figure 1: Slinky effect.
5 CONCLUSIONS
Good exercise tolerance is required to maintain
activities level needed by SCI patients along with
good airway cleansing technique to prevent