Page 618 - Clinical Application of Mechanical Ventilation

584 Chapter 18

TABLE 18-1 Diseases That May Benefit from Home Mechanical Ventilation

Pulmonary Problem Clinical Course

COPD Airflow obstruction
Excessively high compliance
Air trapping
Acute exacerbation (pneumonia)
Restrictive lung disease Reduction of lung volumes and capacities
Deadspace ventilation
Muscle fatigue
Ventilatory muscle dysfunction Inefficient ventilatory muscle
Atelectasis and pneumonia

Central hypoventilation syndrome Apnea
Chronic hypoventilation
Atelectasis and pneumonia
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and severe oxygen arterial desaturation not responding to low to moderate levels of
F O or PEEP. Other contraindications may include unwillingness of the patient to
I
2
receive HMV, and lack of financial and human resources (AARC CPG, 2007).
COPD. COPD is a group of lung impairments that includes chronic asthma, chronic
bronchitis, emphysema, and bronchiectasis. Airflow obstruction is the primary
clinical feature of these patients. Typically, stable COPD patients require only min-
imal care such as bronchodilators, flu vaccines, and bronchopulmonary hygiene.
Only on rare occasions do they require ventilatory assistance.
COPD patients who require mechanical ventilation are those who develop ven-
Patient with COPD may tilatory failure, oxygenation failure, or both. On occasion, these patients may dete-
deteriorate and progress to
ventilatory failure as a result riorate and progress to ventilatory failure as a result of an acute medical condition
of an acute medical condition (e.g., pneumonia) or complications from a major surgical procedure (e.g., abdomi-
(e.g., pneumonia) or compli-
cations from a major surgical nal surgery). When this occurs, blood gases usually reveal acute ventilatory failure
procedure (e.g., abdominal (acute respiratory acidosis) superimposed on chronic ventilatory failure (compen-
surgery).
sated respiratory acidosis). This condition of acute hypercapnia in COPD is also
called acute exacerbation of COPD (Malley, 1990). Table 18-2 shows the changes
in blood gas results when a stable patient with COPD goes into ventilatory failure
and requires mechanical ventilation.
Once placed on a ventilator, COPD patients may be difficult to wean off
mechanical ventilation because of inefficient ventilation and sub-optimal gas
exchange. This problem is primarily due to airflow obstruction, loss of elastic
recoil, and air trapping. In addition, COPD patients usually have coexisting
medical problems that are related to the primary lung disease. Some examples of
these related medical problems are ventilation/perfusion mismatch, pulmonary
hypertension, and cor pulmonale.

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