Medical Inspection – Health Blog

Patients were referred for the management of hypercarbia from the Muscular Dystrophy Association Clinic at New England Medical Center. Patients had been diagnosed as having Duchenne or Duchenne-type muscular dystrophy using standard clinical criteria including male sex, elevation of creatine phosphokinase, and a compatible muscle biopsy and clinical picture. All patients were in functional class 9 and had severe quadraparesis.

All patients expressed a desire to try intermittent ventilatory assistance and were hospitalized for four to seven days to undergo an initial trial. Baseline studies included pulmonary (unction studies consisting of spirometry and measurement of lung volumes (P.K. Morgan, Inc.), and room air arterial blood gas values (Radiometer, Inc., Copenhagen) obtained while the patient was seated. The patients were then introduced to a variety of “body” ventilators including negative pressure devices (tank ventilators [iron lung and Portalung] Pneumowrap and chest shell), positive pressure-assisted ventilation administered via a face or nose mask or lip seal, or a Pneumobelt. Devices to be tested were selected based on patient preference and body habitus, as previously described.

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Duchenne and Duchenne-type muscular dystrophies are x-linked recessive hereditary disorders characterized by diffuse skeletal and cardiac muscle involvement. They lead inexorably to quadraparesis in the preteen years and death due to respiratory failure at an average age of 20 years or slightly older for the more slowly progressive Duchenne-type dys­trophies. Although the use of ventilatory support for the treatment of respiratory failure in these patients is controversial, noninvasive intermittent ventilatory assistance has been shown to effect sustained stabili­zation and even reversal of hypoventilation. Read More…

Nocturnal NIPPV can normalize Sa0₂ for many patients with САН without oxygen therapy. It can provide adequate ventilation for some patients with little or no free time or VC and can reverse signs and symptoms of САН. It can decrease the number of hospitalizations for respiratory insufficiency for pa­tients with САН. It can, thus, be an alternative to IPPV via intubation, tracheostomy or phrenic nerve pacing for some patients when:

Excessive oral leak rendering NIPPV entirely inef­fective was surprisingly uncommon. The greatest difficulties encountered were from the discomfort of CPAP mask pressure and leak into the eyes. Although this was largely corrected by the fabrication and use of a custom nasal interface, its use, too, was not without difficulty. The gasket material for the nasal seal needed to be repaired or replaced every two to six months and two patients were more comfortable with the CPAP mask.

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Table 2 lists the signs and symptoms alleviated by long-term nocturnal intermittent positive airway pres­sure assisted ventilation for the 45 symptomatic pa­tients. Of the 52 patients who underwent trials of nocturnal NIPPV 40 continued it on a long-term basis. The average length of use of NIPPV by the 42 patients who have used NIPPV for one month or more was 21 (three to 67) months. All 18 patients who were dependent on nocturnal assistance alone demon­strated significant improvement and in most cases normalization of daytime ABG off aid. Relief of the signs and/or symptoms of САН occurred in all 40 patients on long-term nocturnal NIPPV without added 0₂. Two patients had dramatic relief of right ventric­ular failure and edema (No. 6 and 13). The symptoms of the other five patients were relieved by long-term nocturnal MIPPV.

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The 52 patients had a mean sitting VC of 766 ± 639 ml (16.3 ± 12.5 percent predicted) and a mean supine VC of 407 ± 257 ml (9.9 ±2.3 percent). This included who could not remain off ventilatory assistance for 24 h without severe dyspnea, hypercapnia and hypoxia. The complaints of dyspnea and fatigue that necessi¬tated reinstitution of assisted ventilation and termi¬nated the trial of free time were generally accompa¬nied by a decrease in Sa02 of >5 percent and an elevation of Pco2 of >7 mm Hg from baseline levels. The free time that a patient had was related to his VC. None of the 20 patients with VC supine <12 percent of predicted had more than 15 min of free time supine except for three patients with Duchenne muscular dystrophy for whom significant free time was accompanied by severe hypoventilation. Nineteen patients with supine VC between 12 to 26 percent had varying amounts of free time, often at the expense of significant hypercapnia, and could not go overnight without ventilatory aid. In all, 35 patients had <6 h of free time supine with 23 having <15 min. Although up to 22 patients could sleep supine for varying periods of time unaided, any decrease in the customary aid schedule was accompanied by deterioration in ABG or overt respiratory failure in a matter of days.

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Twenty-nine of 52 patients were dependent on overnight venti­latory support and could not sleep unaided at the time of referral. The aids used included the iron lung by five patients for an average of 31.0 (13 to 39) years; rocking bed, six patients for an average of 17 (2 to 34) years; chest shell ventilator, eight patients for an average of 16 years (3 weeks to 35 years); MIPPV, 12 patients for an average of 6 (2 to 15) years; Pulmowrap ventilator, one patient for three years, two and four years. Three patients were extubated and placed directly on NIPPV.

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Fifty-two patients with the diagnoses and average VC values listed in Table 1 were referred because of symptomatic САН, poorly tolerated and/or ineffective assisted ventilation on body ventilators, or desire to remove or avoid tracheostomy. All were alert and cooperative with functional oropharyngeal muscles and no acute pulmonary disease. All had primarily paralytic/restrictive respira­tory insufficiency due to neuromuscular disorders or severe ky­phoscoliosis diagnosed by pulmonary function testing prior to referral. No patient had substance abuse problems.

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