Prolonged mechanical ventilation (PMV) is defined by the Centers
for Medicare and Medical Services in the United States as greater
than 21days of mechanical ventilation for at least six hours per
day.
Provision of mechanical ventilation is indicated to improve
pulmonary gas exchange and/or to reduce the work of breathing in
respiratory failure.
Major contributing
factors for
prolonged mechanical
ventilation
The duration of mechanical ventilation can be prolonged by
several factors such as
- Primary diagnosis for which the patient was transferred to
ICU
- Severity of illness and
- Development of complications during the ICU stay
- Admission diagnosis and acute physiology score(APS)on ICU day 1
calculated by the APACHE III scoring system,were most strongly
related to the duration of mechanical ventilation
- Among Admission diagnosis Pneumonia,ARDS,neuromuscular
disease,postoperative head trauma,and postoperative intracranial
hemorrhage were significantly related to the duration of mechanical
ventilation.
- Systemic factors
- Chronic comorbid conditions
(e.g.hypothroidism,malignancy,COPD,immunosuppression)
- Overall severity of illness
- Non-pulmonary organ failure
- Poor nutritional status
Mechanical factors
- Increased work of breathing
- Reduced respiratory muscle capacity
- Critical illness polyneuropathy,Steroid myopathy,Disuse
myopathy,Isolated phrenic nerve or diaphragmatic injury (e.g. after
surgery)
- Imbalance between increased work of breathing &respiratory
muscle capacity
- Upper airway obstructions (e.g. tracheal stenosis)preventing
decannulation
Latrogenic factors
- Failure to recognize withdrawal potential
- Inappropriate ventilator settings leading to excessive
loads/discomfort
- Imposed work of breathing from tracheostomy tubes
- Medical errors
Complications of long term hospital care
- Recurrent aspiration
- Infection(e.g. pneumonia,sepsis)
- Stress ulcer
- Deep vein thrombosis
Psychological factors
- Delirium
- Depression
- Anxiety
- Sleep deprivation
- Sedation
Process of care factors like a absence of weaning
protocols,inadequate nursing staffing,insufficient physician
experience.