When pulmonary physicians evaluate patients with progressive respiratory insufficiency, it is important to consider neuromuscular disease in the differential diag­nosis, as emphasized by the patient who is the subject of this report.

Case Report

A 64-year-old water pipe installer was diagnosed as having obesity- hypoventilation syndrome associated with recurrent cor pulmonale. Three months earlier, he had presented to another hospital with peripheral edema and weight gain. Values of a room air blood gas analysis were as follow: Pos, 61 mm Hg; Pco, 51 mm Hg; pH, 7.37; (Table 1) and the chest x-ray film showed a reduction in lung volumes interpreted as poor inspiratory eflort. No other abnormal­ities were noted. Spirometry showed FEVj of 2.20 (60 percent of predicted); FVC, 2.78 (54 percent); FEV./FVC, .78; FEF25-75, 2.39 (68 percent) with no change after bronchodilator therapy. He was treated with diuretics and discharged with diagnoses of hyper­tension, restrictive lung disease of unspecified etiology, and chronic hypoxia.

Over the next six weeks, he noted increasing lethargy, weakness, dyspnea on exertion, pedal edema, cyanosis, and weight gain. On examination, a right sided S3 gallop, crackles at both lung bases, and 3+ pedal edema were noted. An arterial blood gas analysis on room air showed worsening CO, retention and hypoxemia; spirom­etry was unchanged. In spite of treatment with diuretics and intravenous aminophylline, his dyspnea worsened, and he was transferred to the New England Deaconess Hospital. tadacip 20 mg

Table 1—Arterial Blood Gas Determination» and Pulmonary Function Test

Pco2

Deo,

Date

Po,

mm Hg

pH

FEV„ L

FVC, L

Ratio

FEF25-75, Us
TLC, L

L

ml/min/mm Hg

5/8/87

61

51

7.37

5/11/87

2.20 (.56)

2.78 (.54)

78

2.39 (.68)

6/2/87

2.35 (NA)*

2.83 (NA)

82

2.93 (NA) 3.92 (NA)

1.78 (NA)

14.79 (NA)

7/31/87

66 103

73

46 82 71

7.36 7.30 7.38

(on 3L/min OJ (on 1.5L/min OJ 2.35 (.61)

NA (.57)

8/6/87

91

56

7.32

(on 1.5L/min OJ

8/7/87

1.62 (.43)

1.98 (.42)

82

17.78 (.57)

8/8/87

45 51

103 89

7.28 7.33

(on l.OL/min Os) (on 24% Venturi mask)

12/2/87

3.03 (.80)

3.76 (.79)

81

3.19 (.85)

On admission, he reported loud snoring, five to six years of daytime hypersomnolence, fatigue, and nocturnal apneic spells. In addition, he complained of a lump in his throat, some difficulty swallowing, and several episodes of diplopia over the past two months. His medications were hydrochlorothiazide (Dyazide), dil- tiazem, captopril, colchicine, and probenecid. He denied alcohol and cigarette use. On examination, he was tachypneic, and had diminished breath sounds at the right lung base without crackles or wheezes, an irregular rhythm without murmur or gallop, and a liver span of 8 cm. Laboratory test results were significant for the fol­lowing: hematocrit, 50.6 percent; serum bicarbonate, 45 mEq/L; arterial blood gas on 1.5 L/min nasal cannula of POj, 91 mm Hg; pH, 7.32; Pco„ 56 mm Hg/7.32; and chest x-ray film showing borderline cardiomegaly, normal pulmonary vasculature, and ate­lectasis at both lung bases. Spirometry showed FEVl 1.62 (43 percent); FVC, 1.98 (42 percent); FEV/FVC, .82; FEFmax, 3.86 (43 percent); Deo, 17.78 (57 percent).

Table 2—Weaning Mechanics and Interventions

Date

Vt,
L

Vc, L

IF, cm H20

8/7/87

.200

1.00

-И . . ……..

8/13/87

.250

.800
V >

^

**”4
‘■ -8

.225

.600

-11

(on 0.25mg
neostigmine q4h)

8/15/87

.300

.800

-16

(neostigmine
continued)

8/17/87

.213

.550

-5

(neostigmine
discontinued
8/16/87)

8/18/87

.400

.800

-14

(neostigmine
restarted at

0.5
mg q4h
8/17/87)

Over the next 24 hours, the patient deteriorated, developing respiratory distress and paradoxical abdominal motion without muscle weakness elsewhere. An arterial blood gas analysis on 1.0 L/min was Po2, 45 mm Hg; Pco2,103 mm Hg; pH, 7.28. Pulmonary mechanics results disclosed: tidal volume of 200 ml, vital capacity of 1.0 L, and inspiratory force of —11 cm H20. A standard edrophonium (Tensilon) test was performed with no change in IF or VC. The patient was intubated and mechanical ventilation begun (Table 2).

Electrolytes, ESR, CT scan of the head, noninvasive venous studies of the lower extremities, repeat edrophonium test, electro- myogram including cranial nerves, and repetitive nerve stimulation of brachial plexus, median, ulnar, and spinal accessory nerves all were subsequendy normal. Studies for heavy metal exposure were negative. During this period, the patient complained of intermittent vertical diplopia, but dysconjugate gaze was not observed.
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Because of persistent clinical suspicion of myasthenia gravis, an empiric trial of neostigmine, 0.25 mg every four hours, was begun. While the patients baseline pulmonary mechanics (TV, 250 ml; VC, 800 ml; IF, —8 cm H20) were unchanged after four hours, his diplopia had resolved. Neostigmine was therefore continued and after 48 hours, respiratory mechanics had improved. When neostig­mine was discontinued, mechanics deteriorated significantly. Neo­stigmine was therefore reinstituted at an increased dose (0.5 mg q4h) with definite improvement in respiratory mechanics.

Myasthenia gravis was confirmed when an antistriated muscle antibody titer was reported at 1:80 and an acetylcholine receptor antibody titer was reported at greater than 1:30 (normal <1:0.8). Neostigmine was increased to 1.0 mg q4h and prednisone 60 mg po qd was added. However, only with the institution of plasma­pheresis was he successfully extubated.