ACUTE RESPIRATORY DISTRESS SYNDROME

(ARDS)

Shannon AdairSarah Conway

Melanie NilandDan Sandberg

ARDS

Definition: A fulminant form of respiratory failure characterized by acute lung inflammation and diffuse alveolocapillary injury

ARDS is a syndrome and not a specific pathophysiologic disease. Therefore, patients are diagnosed with ARDS when they meet specific diagnostic criteria.

Patho Text

ALI vs ARDS

Acute Lung Injury (ALI) is a less severe form of ARDS

All pts with ARDS have ALI, but not all pts with ALI have ARDS

The American-European Consensus Conference on ARDS 1994

Diagnostic Criteria

Etiology

The result of injury to the lung by numerous unrelated causes

New causes of ARDS are continually being reported

60 different causes have been identified already

Need for further research

Patho Text

Most Common EtiologiesPancreatitis

Drug Overdose

Smoke or noxious gas inhalation

Oxygen toxicity

Radiation therapy

Disseminated Intravascular Coagulation

Secondary MODS (Sepsis and trauma)

Pneumonia

Burns

Aspiration

Cardiopulmonary bypass surgery

Near drowning

Prevalence/Incidence

Always a Secondary issue to original ailment

190,000-220,000 Americans affected annually

Higher incidence in Elderly

4.3x10^-3% if under 30 as compared to 74x10^-3% if age 75 or over

Why Elderly?

Prevalence/Incidence

Precipitating factors

Pneumonia (56%)

Surgery (23%)

Sepsis (9%)

Trauma (3.8%)

Other (8.9%)

Signs and Symptoms

Diagnostic Criteria

Rapid Breathing

Low blood oxygen levels

Dyspnea

Inability to feel like you are obtaining sufficient air (shortness of breath)

Signs and Symptoms Continued

Cough and fever-(pneumonia)

Confusion

Extreme fatigue

Crackles heard in lungs through stethoscope

Bluish hue to skin color

A spirometer is used to measure

lung volumes.

Spirometer

Respiratory Volumes

Tidal volume is the amount of air moved into the lungs with a

breath.

Vital capacity is the maximum amount of air that can be moved

into and out of the lungs.

Residual volume is the volume of air that

cannot be exhaled from the lungs.

Tidal Volume and Minute Respiratory Volume (MRV)

Tidal volume is the amount of air moved into and out of the lung with a typical breath.

Minute respiratory volume (MRV)is the total amount of air moved into and out of the lungs each minute.

MRV = Tidal Volume x Respiratory Rate

Minute alveolar ventilation (MAV) is amount of air that reaches the alveoli each minute.

MAV= (Tidal Volume- Dead Space) x Respiratory Rate

Lung Function TestsFor normal breathing, assume tidal volume 500 ml/breath and respiratory rate 12 breaths/minute. Assume a dead space of 150ml/breath at all breathing rates.

MRVNormal = (500 ml/breath)(12 breaths/min) = 6000 ml/min

MAVNormal = (500 ml/breath – 150 ml/breath)(12 breaths/min) = 4200 ml/min

For shallow rapid breathing, assume a breathing rate of 40 breaths/min and a tidal volume of 150 ml.

MRVShallow = (150 ml/breath)(40 breaths/min) = 6000 ml

MAVShallow = (150 ml/breath-150 ml/breath) 40 breaths/min= 0 ml