Under spontaneous ventilation and high PEEP, the benefits of a relatively higher compliance are i) a reduction of the work of breathing
and ii) low level of PS generating adequate Vt and minimizing 'ventilatory fatigue' (anxiety, nasal flaring, sternal notch retraction, use of accessory muscles and thoracoabdominal dys-coordination).
Hypercarbia ensues as the work of breathing
continues to increase.
The possible mechanical advantages of tracheostomy over ETT intubation are believed to be secondary to changes in respiratory dynamics, such as decreased dead space, airway resistance and, thus, a decrease in work of breathing
. However, there is no physiological basis for this observation.
Continuous positive airway pressure reduces work of breathing
and dyspnea during weaning from mechanical ventilation in severe chronic obstructive pulmonary disease.
Ventilator and patient must be in synchrony in this mode of ventilation otherwise work of breathing
may be significantly increased.
Work of breathing
: Two studies involving 31 participants with chronic respiratory disease reported the impact of breathing control on the work of breathing
measured in joules per litre (McKinley et al 1961, Vitacca et al 1998).
The principle behind each one is to allow patients to increase their own work of breathing
while reducing the contribution of the ventilator without unnecessary delay.
Although subjectively we did not find the work of breathing
required with the prototype mask to be different from that required with a standard N95 filtering facepiece, persons with respiratory compromise of any type should not use this mask.
Lungs: Inspiratory and expiratory wheezing bilaterally; diminished breath sounds throughout all lung fields; increased work of breathing
O'Kroy and the team of researchers found no significant differences between the placebo and the active nasal dilator regarding the total work of breathing
. After measuring metabolic variables at sub maximal and peak exercise levels, they concluded that nasal dilators did not result in any significant alteration to V[O.sub.2]max, maximal power output, ventilation or maximal heart rate.
To overcome chronic airway obstruction, patients with COPD must increase their work of breathing
. Additional work is created when hyperinflation is present because with a greater amount of air remaining in the lungs after exhalation, the diaphragm is pushed downward and is unable to move the chest cage effectively on inspiration (Manning & Schwartzstein, 1995).
The goal--and this is crucial--is to titrate to a dosage that will relieve the patient's subjective sense of the work of breathing
, not to reduce the respiratory rate.