CHAPTER 34: Respiratory Failure and Anaphylaxis

INTRODUCTION

Respiratory failure is the inability of the lungs to perform the vital function of gas exchange, and may be caused by an inability to either obtain sufficient oxygen or eliminate carbon dioxide. Numerically, respiratory failure may be defined on arterial blood gas measurement as hypoxemia, with a PaO₂ <60 mmHg, or as hypercarbia, with a PaCO₂ >45 mm Hg.¹ Acute respiratory failure may be divided into four types. Type 1 respiratory failure is caused by acute hypoxia, and may be seen in patients with pulmonary edema, pneumonia, pulmonary hemorrhage, or acute respiratory distress syndrome. Type 2 respiratory failure may be seen with hypoventilation and an inability to rid the body of carbon dioxide. Examples of disease processes where this may be seen include central nervous system disorders where the respiratory drive is diminished, neuromuscular disorders where the muscles of respiration are not sufficiently able to produce ventilation, as well as in pulmonary conditions such as pneumothorax, airway obstruction, or pleural effusions. Significant atelectasis is the cause for Type 3 respiratory failure, and is most commonly seen after mechanical ventilation. Type 4 respiratory failure is seen in patients who have hypoperfusion of the muscles of respiration caused by another process, such as shock.² Identifying the incidence of acute respiratory failure in the United States is extremely difficult but has been estimated near 140 cases per 100,000 individuals over the age of 5. Of the patients with acute respiratory failure, approximately 36% will not survive to hospital discharge. There seems to be a correlation with increased mortality seen in patients with increase in age, presence of multisystem organ failure, cancer, underlying liver disease, and HIV infection.³

OBJECTIVES

1. Describe the causes of respiratory failure and anaphylaxis.

2. Describe interventions used in the prehospital environment to treat respiratory failure and anaphylaxis.

3. Delineate equipment useful in the prehospital management.

4. Outline some easy-to-use mnemonics for airway assessment in the field.

5. Describe unique challenges encountered in the prehospital environment.

6. Delineate medications that are appropriate for use in airway interventions in the prehospital environment.

CAUSES OF ACUTE RESPIRATORY FAILURE

There are many causes of acute respiratory failure, and oftentimes more than one in any given patient. Understanding the underlying disease process may better direct treatment and management of the patient in both the prehospital and hospital environments. Appropriate early interventions may have a significant effect on patient outcome and subsequent management.

NEUROMUSCULAR

Communication from the medullary respiratory center to the muscles of respiration is crucial in the mechanics of respiration. Disruption of neurotransmission may occur by several mechanisms. Severe intoxication or overdoses may decrease the intrinsic capability of the medullary respiratory center to function. Environmental clues may allow for the detection of organophosphate induced respiratory failure, which occurs within the first 4 days of exposure. It is believed that the central nervous action ...