The physician must be cautious to avoid complications related to mechanical ventilation during ventilatory support. The current evidence supports the use of noninvasive positive-pressure ventilation for these patients (especially in COPD), but invasive ventilation also is required frequently in patients who have more severe disease.
The main goal of mechanical ventilation in these kinds of patients is to improve pulmonary gas exchange and to allow for sufficient rest of compromised respiratory muscles to recover from the fatigued state. If ventilatory demand exceeds work output of the respiratory muscles, acute respiratory failure follows. From the pathophysiological standpoint, they have increased airway resistance, pulmonary hyperinflation, and high pulmonary dead space, leading to increased work of breathing. Ventilation may exceed perfusion in parts of the lung resulting in increased physiological dead air space.COPD and asthmatic patients use a substantial proportion of mechanical ventilation in the ICU, and their overall mortality with ventilatory support can be significant. Air may reach the periphery of the lungs but fail to make contact with the capillary blood. The alveoli become permanently damaged (see video above).This is why breathlessness and fatigue are common symptoms of COPD. This extra effort can make the patient feel very tired. However, this does not mean that your oxygen levels are low because the breathing muscles around the chest are working harder to compensate. The respiratory muscles then have to work harder to get air in and out of your lungs.As the lungs become hyper-inflated they elongate and flatten, which means the diaphragm does not work as well as it should. As a result, air gets trapped in the lungs and the lungs get bigger (hyper-inflated). These changes cause the air sacs (alveoli) to close before you have fully exhaled. In emphysema, exposure to an irritant over many years causes an inflammation in the lungs which causes the following changes: Please note there is no audio for this animation
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