Other Treatments for Acute Respiratory Distress Syndrome
Noninvasive Positive Pressure Ventilation (NIPPV)
Positive pressure ventilation is sometimes accomplished with a facemask that forms a tight seal around the mouth and nose or just the nose in patients who have ARDS. Since ventilation via an endotracheal tube is more efficient, NIPPV is usually used on a temporary basis and for milder cases.
Continous Positive Airway Pressure (CPAP)
CPAP may be used temporarily in patients who can maintain breathing but cannot oxygenate adequately. CPAP is applied through a mask, in this instance usually over both the nose and mouth, that forms a tight seal. Positive pressure is applied by a machine with inspiration and expiration, causing fluid to be pushed out of the alveolar space and opening alveoli or preventing them from collapsing.
Techniques for Patients Who Are Difficult to Oxygenate
Sometimes, putting a patient into the prone position (on their stomach) helps positive pressure get oxygen into the bloodstream easier. Lying on the stomach increases gas exchange in the alveoli.
Inverse Ratio Ventilation and Muscle-paralyzing Drugs
Inverse ratio ventilation is reserved for severe cases when it is impossible to oxygenate the patient adequately. Treatment involves increasing the amount of time that the ventilator is inspiring versus expiring.
Patients normally spend more time exhaling than inhaling, at a ratio of about 3:1. Increasing the amount of time spent inhaling re-expands more collapsed alveoli than positive pressure alone. This is an uncomfortable technique and usually requires sedation and a muscle-paralyzing drug that keeps the respiratory muscles from resisting the unnatural inverse ratio ventilation.
Complications of Mechanical Ventilation
Volutrauma, over expansion of the alveoli, can contribute to lung injury and is one of the most common complications of mechanical ventilation. Recent studies have shown that decreasing the amount of air pushed into the lungs can reduce the risk for volutrauma.
Pneumothorax, air in the pleural cavity (the normally empty space between the lungs and the ultra thin membranes that surround the lungs [pleura]), occurs when lung tissue ruptures. Weakened lungs, high pressures from the ventilator, and the high volume of air increase the risk for pneumothorax.
Medication to Treat ARDS
Most medications prescribed during an ARDS episode treat the underlying condition. Although corticosteroids have no proven benefit for early ARDS, they may be beneficial 7 to 10 days following mechanical ventilation. Sedating or muscle-paralyzing drugs are used during mechanical ventilation to prevent resistance to the forced movement of air.
Other techniques have been used to restore breathing in patients with ARDS (e.g., inhalation of nitric oxide), but they do not prolong survival or prevent further lung damage. For example, inhaled nitric oxide can significantly improve pulmonary hypertension, a complication of ARDS, but its toxic byproducts can be damaging. Initial studies of an aerosolized synthetic surfactant designed to keep the alveoli from collapsing have been disappointing.
ARDS Resources for Patients and Families
The ARDS Support Center, Inc. is an excellent source of information, support, and education resources for patients and families.