|Year : 2006 | Volume
| Issue : 1 | Page : 39-41
Ventilator dependence: Role of nutrition and airway clearance therapy
G Sindhwani, J Rawat
Department of Tuberculosis and Respiratory Diseases, Himalayan Institute of Medical Sciences, Dehradun., India
Department of Tuberculosis and Respiratory Diseases, Himalayan Institute of Medical Sciences, Dehradun.
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sindhwani G, Rawat J. Ventilator dependence: Role of nutrition and airway clearance therapy. Lung India 2006;23:39-41
| Introduction|| |
It is estimated that 1 to 5% of mechanically ventilated patients repeatedly fail attempts at weaning from mechanical ventilation and face a substantial risk of becoming chronic ventilator-dependent patients who cannot sustain spontaneous breathing for longer than a few hours  . Chronic ventilation is an extremely uncomfortable state for a patient, carrying important medical and social implications  . A better understanding of the mechanisms contributing to the development of ventilator dependence could help to improve the general management of such patients. Patients with advanced chronic obstructive pulmonary disease (COPD) and postoperative patients suffering from phrenic nerve lesion after cardiac surgery, patients with neuromuscular disease present special challenges. Studies show that patients who could not be liberated from the ventilator had some common pathophysiologic characteristics, which became apparent soon after disconnection from the ventilator like: (1) small tidal volume; (2) high neuromuscular drive; (3) abnormal lung mechanics; (4) reduced inspiratory muscle strength. As a result, both the load/ capacity balance and the effective inspiratory impedance were greater than in patients who continued to breathe spontaneously. Clearly, there were also some differences related to the underlying pathology.
But, this is of utmost importance to identify the patients at higher risk and act vigorously to prevent the deadly complication.
Identifying at risk population
Patients with certain diseases are at especially high risk for developing ventilator dependence.
COPD : Patients with advanced COPD have pulmonary hyperinflation caused by the loss of lung recoil and small airway closure early in expiration, aggravated by dynamic hyperinflation because of expiratory flow limitation.  Furthermore, because of pulmonary hyperinflation, patients with severe COPD breathe close to the upper portion of the volume/ pressure (V/P) curve, where a nonlinear relationship occurs.
Post-surgical patients: Upper abdominal/ thoracic surgery encourages a restrictive physiology and diminished vital capacity. Various factors are responsible including:
- inhibitory effects of inhaled anaesthetics on hypoxic pulmonary vasoconstriction;
- the diminution of the hypoxic and hypercapnic ventilatory drives because of intravenous (IV) narcotics used for induction; and
- alteration in the shape and motion of the diaphragm and chest wall may result in a 20% decrease in functional residual capacity (FRC) in cardiothoracic cases.
- post-operative pulmonary complications (PPC), like atelectasis and bronchopulmonary infections not only contribute to increased morbidity and mortality; they are a major factor in driving up total medical expenditures - especially in terms of intensive care unit utilization.
Patients with neuromuscular disease:
Myopathies associated with systemic conditions (such as cancer, cachexia /anorexia nervosa, and medication use).
The primary difficulty lies in achieving adequate airway clearance. Traditional chest physiotherapy may help mobilize secretions, but without an ability to expectorate the secretions, the patient must rely almost solely on the mucociliary escalator for clearance of the mobilized secretions.
Patient-related Risk Factors: Certain patients are at increased risk for developing ventilator dependence like patients with:
- significant systemic disease
- significant smoking history
- chronic lung disease
- advanced acquired immunodeficiency disease
- nutritional or metabolic deficiencies: hypokalaemia, hypomagnesaemia, hypocalcaemia, hypophosphataemia, hypothyroidism
- steroids use
- decreased protein synthesis and increased degradation
- decreased glycogen stores
- persistently increased work of breathing
- cardiovascular failure
- neuromuscular blockers
- critical illness polyneuropathy
Steps towards prevention: After identifying at risk population, following steps may be taken to prevent this deadly complication:
Airway Clearance Therapy
Some form of airway clearance therapy is prescribed routinely to treat post-surgical patients with evidence of ineffective secretion control. This is especially true for patients with pre-existing pulmonary disease. Chest physiotherapy (CPT) is the subject of the largest number of studies. CPT depends heavily upon precise execution of technique and patient positioning. All critically ill/post surgical patients cannot tolerate several daily CPT sessions requiring arduous physical manipulation. Transient hypoxaemia associated with postural drainage and inducement of gastro-oesophageal reflux pose additional risks.
High-frequency chest wall oscillation  (HFCWO): It works on the principle that rapid compression and relaxation (oscillation) of the chest wall generates increased airflow velocities, thus creating brief changes in lung airflow patterns similar to coughing. The percussive effects of chest wall oscillation also thin sticky secretions, making them easier to clear.
Continuous lateral rotational therapy (CLRT): With CLRT, patients are turned up to 200 times per day.CLRT has been used safely and effectively in critically ill patients including those with stroke or neurological injury, with stabilized trauma/spinal cord injury and in ventilated patients. The therapy is associated with prevention or improvement of atelectasis, reduced risk for nosocomial and ventilator associated pneumonia and reduction in acute care days.
HFCWO and CLRT are gaining rapid acceptance in the acute care setting. Because HFCWO and CLRT require minimal staff time and effort, they have the potential to optimize therapy.
Mechanical insufflator-exsufflator: Having a weak cough is the first symptom of respiratory difficulties in Duchenne muscular dystrophy and is a frightening aspect of every neuromuscular disease. Introduction of a mechanical insufflator-exsufflator, which aids coughing, must be considered in set-ups, which encounter such patients  .
The Role of Nutritional Support
Weight loss and malnutrition are common findings in patients with COPD  and also in other mechanically ventilated patients. Numerous studies have demonstrated that malnutrition causes an extensive loss of diaphragm muscle mass, accompanied by a decline in pulmonary function , . Malnutrition is also associated with a decline in immune function, poor wound healing, and increased mortality. For these reasons, the malnourished patient is at high risk for complications following illness, injury, or surgery.
A number of studies have demonstrated improved outcome in patients with pulmonary disease who were either well nourished or receiving some form of nutritional support. Another study showed that well-nourished patients who required mechanical ventilation had a lower mortality rate than malnourished ventilator-dependent patients  . A third study revealed that ventilator-dependent patients who received nutritional support, either enteral or parenteral, were significantly more likely to be weaned from the ventilator than those receiving no nutritional support  .
A study in ventilator-dependent patients has shown that excessive caloric intake, rather than a highcarbohydrate diet, is responsible for increased carbon dioxide production. In addition, carbohydrate is the primary energy source during vigorous muscle exercise, as required in ventilator weaning. Therefore, adequate carbohydrate intake is needed for replenishment of respiratory muscle glycogen. For these reasons, many nutrition experts are now recommending more moderate levels of fat (20% to 40%) and avoidance of overfeeding in patients with pulmonary disease. ,
Key Nutritional Needs
- Provide early enteral feeding to prevent loss of muscles that support lung function.
- Avoid overfeeding.
- Provide 15% to 20% of calories as protein (1 to 2 g/kg) body weight, 20% to 40% of calories as fat, 40% to 60% of calories as carbohydrate.
- Increase caloric density (1.5 cal/mL) if fluid restriction is required.
- Supplement with immune-enhancing nutrients (arginine, glutamine, dietary nucleotides, and fish oil), if the patient is critically ill, injured, or ventilator-dependent and at risk for pneumonia
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