0071643192.pdf

THORACIC AND RESPIRATORY

DISORDERS

DIAGNOSIS

Both ALI and ARDS are clinically defined by rapidity of symptom onset, oxy-
genation, hemodynamic criteria, and CXR findings (see Table 10.15). Addi-
tional findings are as follows:

■ CT chest: May demonstrate alveolar filling and consolidation in depen-
dent lung zones with sparing of other areas
■ Bronchoalveolar lavage (BAL): May help differentiate the etiology (eg,
Pneumocystisin the immunocompromised patient)

TREATMENT

■ Search for and treat the underlying cause of acute respiratory failure (ARF).
■ Most patients with ARDS require mechanical ventilation during the
course of the disease.
■ Use of tidal volumes ≤6 mL/kg of predicted body weight has been
shown to ↓mortality.
■ Add positive end-expiratory pressure (PEEP) as needed to maintain
FiO 2 <60%.
■ Inverse ratio ventilation with permissive hypercarbia allows for more
inspiratory time and may improve oxygenation.
■ Plateau pressure must be kept at <30 cm H 2 O to prevent barotrauma
(see the discussion of ventilator management).
■ A conservative fluid management strategy (ie, one involving less volume)
is preferred over a liberal fluid strategy. In a recent randomized trial com-
paring such strategies, both techniques yielded similar 60-day mortality
rates, but conservative management was found to be associated with
shorter mechanical ventilation and ICU times.
■ Corticosteroids have been given in the proliferative phase of ARDS, but
their use in this context is still considered experimental.
■ The use of inhaled vasodilators, exogenous surfactant, high-frequency ven-
tilation, liquid ventilation, and antioxidant therapy has been studied with
no proven benefit.
■ Approximately 25% of survivors have no pulmonary impairment at 1 year,
50% have mild impairment, 25% moderate impairment, and a small frac-
tion severe impairment.

PLEURAL EFFUSION

Defined as the abnormal accumulation of fluid in the pleural space, in the
United States, the most common causes are CHF, pneumonia, and cancer.
It is classified as transudativeorexudative.

To improve mortality in

patients with ARDS, target a

tidal volume of 6 mL/kg

predicted body weight.

TABLE 10.15. Diagnosis of Acute Lung Injury and ARDS

ONSET OF

SYMPTOMS OXYGENATION HEMODYNAMICS CXR

ALI Acute PaO 2 /FiO 2 ≤ 300 Low or normal Bilateral infiltrates

left atrial pressure

ARDS Acute PaO 2 /FiO 2 ≤ 200 Low or normal left Bilateral infiltrates

atrial pressure