CASE 9
A 64-year-old man, presented to his physician complaining of dyspnea. The patient, a smoker (2 packs a day for 45 years), stated that several months ago he noticed that his breathing was labored when he walked up the stairs of his home and that it has progressively worsened. The physical exam results were: height = 70 inches, weight = 150 lb, blood pressure = 135/85, and respiratory rate = 28. Additionally, peripheral cyanosis was noted, breath sounds were markedly diminished, lungs were hyperresonant upon percussion, expirations were prolonged and the patient exhaled through pursed lips, had a barrel chest (anterior-posterior chest dimension was increased), and accessory muscles of respiration were being used for breathing. Lab results for arterial blood gases were: PO2 = 70 (normal: 75-100), PCO2 = 52 (normal: 35–45), and pH = 7.30 (normal: 7.35–7.45). Pulmonary function tests indicated the following: increased residual volume, increased total lung capacity, decreased forced expiratory volume, and decreased vital capacity. The patient was diagnosed with emphysema.
WHAT ARE THE ACCESSORY MUSCLES OF RESPIRATION?
There are several accessory muscles of respiration. The muscles for inspiration and expiration are listed in Table 2-3.
TABLE 2-3 Accessory Muscle of Respiration
| Inspiration | Expiration |
|---|---|
| Pectoralis major | Quadratus lumborum |
| Pectoralis minor | Serratus posterior inferior |
| Serratus anterior | External abdominal oblique |
| Sternocleidomastoid | Internal abdominal oblique |
| Scalenus anterior | Transversus abdominis |
| Scalenus medius | Rectus abdominis |
| Scalenus posterior | |
| Serratus posterior superior | |
| Levatores costarum (longi and breves) |
DECREASED ARTERIAL OXYGEN SATURATION STIMULATES RESPIRATORY DRIVE. WHERE ARE THE PERIPHERAL CHEMORECEPTORS FOR ARTERIAL OXYGEN LOCATED AND HOW IS THIS SENSORY INFORMATION TRANSMITTED TO THE CENTRAL NERVOUS SYSTEM?
WHAT ARE THE HISTOLOGIC CHARACTERISTICS OF THE PERIPHERAL CHEMORECEPTORS?
Sustentacular cells have a role similar to that of glial cells. The long processes of the sustentacular cells wrap almost completely around the glomus cells and the sustentacular cells support nerve cell processes that lost their Schwann cells when they penetrated the substance of the body
