Emergency lectures - Vietnam respiratory failure_and_dyspnea[1]

Acute Respiratory Failure:Approach to the patient with dyspnea

Nancy Warner, MDLoma Linda University Emergency Medicine

Definition of Dyspnea

Subjective experience of breathing discomfort

Derives from interactions among multiple physiological, psychological, social and environmental factors

Epidemiology

Shortness of breath is the chief complaint for approx 3.5% of ER visits

Dyspnea-related complaints result in 7.6% of ER visits (cough, chest discomfort)

Most Common Diagnoses presenting with dyspnea

Asthma Chronic Obstructive Pulmonary

Disease Interstitial lung disease Myocardial dysfunction

Pathophysiology

Dyspnea results when ventilatory demand exceeds respiratory function

Alterations in gas exchange, pulmonary circulation, cardiovascular function, respiratory mechanics, or oxygen carrying capacity

Categories of dyspnea

Airway causes Respiratory system dyspnea Cardiovascular system dyspnea

Airway causes

Foreign objects Angioedema Anaphylaxis Infections Airway trauma

Respiratory dysfunction

Controller Ventilatory Pump Gas Exchanger

Controller

Determines the rate and depth of breathing via signals sent to the ventilatory muscles

Related to hypoxia or hypercapnia due to ventilation/ perfusion mismatch

Stimulated by “air hunger” or “urge or need to breath”

Ventilatory Pump Ventilatory muscles and peripheral nerves

which transmit signals to the controller Derangements in the ventilatory pump result

in a sense of increased “work of breathing” Neuromuscular weakness can result in max

effort to achieve required air movement Reduced compliance of the chest wall results

in increase effort for air movement

Gas Exchanger

Consists of alveoli and pulmonary capillaries

Diffusion of oxygen and carbon dioxide

Dyspnea results from destruction of the membrane of the imposition of fluid or inflammatory material

Life- threatening respiratory causes

Pulmonary embolism COPD Asthma Pneumothorax or pneumomediatinum Pulmonary infection Pulmonary edema Pulmonary injury

Cardiovascular Dysfunction

Heart Failure Anemia Deconditioning

Heart Failure

Structural or functional cardiac disorder which impairs the ability of the ventricle to eject blood – reduction in cardiac output

Also occurs from increased pulmonary or systemic venous pressure

Leads to dyspnea by producing hypoxemia or by stimulating pulmonary vascular receptors

Anemia

Can impair oxygen delivery because most oxygen in the blood is hemoglobin bound

Mechanism by which this produces dyspnea is not completely clear but related to cells inability to continue aerobic metabolism

Deconditioning

Ability of the heart to increase maximal cardiac output

Ability of the peripheral muscles to utilize oxygen efficiently for aerobic metabolism

Sedentary existence reduces fitness and can lead to dyspnea with even minimal tasks

Life-threatening cardiac causes Acute coronary syndrome Acute decompensated heart failure Flash pulmonary edema High output heart failure Cardiomyopathy Cardiac arrhythmia Valvular dysfunction Cardiac tamponade

Other causes

Neurologic Stroke Neuromuscular disease

Toxic and metabolic Poisoning (salicylate, carbon monoxide) DKA Sepsis Acute chest syndrome (sickle cell)

More causes

Lung cancer Pleural effusion Intraabdominal process Ascites Pregnancy Massive obesity Hyperventilation and anxiety

Evaluation of Dyspnea

History and Physical Lab and Radiographic testing

History and Physical

General historical features Events leading up to episode Triggers Recent trauma or surgery

Past history New or recurring

Prior intubation Time course

More History Time course Severity Chest pain Trauma Fever Hemoptysis Cough and sputum Medications Tobacco and drugs Psychiatric conditions

Physical Exam

Clinic Danger signs: Depressed mental status Inability to maintain respiratory effort cyanosis

Physical Exam (cont)

Signs suggestive of severe respiratory distress Retractions or accessory muscle use Brief, fragmented speech Inablity to lie supine Profound diaphoresis, dusky skin Agitation or other altered mental

status

Labs and X-rays Oximetry Hemoglobin/ Hematocrit Chest x-ray – lung and heart appearance,

shows fluid and inflammation EKG Cardiac enzymes D-dimer BNP ABG

Approach to Treatment

General appearance of the patient is key to determining immediate need

Always start with ABC (airway/ breathing/ circulation)

Initial Intervention

Provide O2 supplement Place pulse oximetry to determine

hypoxemia and monitor therapy Determine need for breathing

assistance

Breathing Assistance

Positive airway pressure (BiPAP or CPAP)

Assist ventilation with bag-valve-mask or intubation

Treat Specific Cause

Med nebs and steroids (asthma/ COPD)

Antibiotics (pneumonia) Diuretics (CHF)

Disposition

Patients requiring supplemental O2 or those in respiratory distress require admission

Depends on underlying etiology and response to therapy

May be affected by clinical situation or comorbidities

Keep in Mind Normal appearance to breathing dose not

rule out serious underlying etiology Always consider ACS or PE (even if chest pain

is not present) Dyspnea in pregnancy is common but always

consider PE if out of proportion Psychogenic dyspnea is a diagnosis of

exclusion Ambulation is a functional “test” which

provides info on a patients respiratory status