Update and perspectives on noninvasive respiratory muscle aids. Part 1: The inspiratory aids

Central alveolar hypoventilation in neurosarcoidosis

Although the lung is almost always involved in sarcoidosis and respiratory failure is not uncommonly caused by intrinsic lung disease, chronic alveolar hypoventilation on the basis of neurosarcoidosis has not been previously described. This report describes the case of a 42-year-old woman with sarcoidosis and documented involvement of the lungs, muscle, peripheral nerves, and skin. She presented with ventilatory failure and a vital capacity of 700mL and required hospitalization for intubation and mechanical ventilation. After failing ventilator weaning attempts and requiring continuous ventilatory assistance, she was extubated to continuous use of noninvasive intermittent positive pressure ventilation (IPPV). She eventually weaned to nocturnal-only use of noninvasive IPPV. However, her PaCO2 remained elevated during daytime hours despite the fact that her vital capacity had returned to 3,600mL. She was not obese, and her oxyhemoglobin saturation (SaO2) was normal on room air. Subsequent attempts to discontinue nocturnal nasal IPPV resulted in marked nocturnal decreases in SaO2 and return of symptoms. This case illustrates successful noninvasive management of an apparently unique occurrence of central alveolar hypoventilation caused by neurosarcoidosis.

Neuromuscular ventilatory insufficiency: effect of home mechanical ventilator use v oxygen therapy on pneumonia and hospitalization rates

The purpose of this study was to determine rates of pneumonia and hospitalization for patients receiving oxygen therapy, patients having indwelling tracheostomy tubes, and those using tracheostomy or noninvasive methods of home mechanical ventilation. Six hundred eighty-four users of assisted ventilation for 13,751 patient-years or 19.8 years per patient were surveyed by mail and twice by telephone over a span of four years. Pneumonia and hospitalization rates were significantly higher for ventilator users with chronic obstructive pulmonary disease or with neuromuscular ventilatory insufficiency and gastrostomy tubes than for ventilator users with neuromuscular ventilatory insufficiency without gastrostomy tubes. Of the latter group, more than 90% of the pneumonias and hospitalizations were triggered by otherwise benign intercurrent upper respiratory tract infections. Oxygen therapy was associated with a significantly (P < 0.001) higher rate of pneumonias and hospitalizations than that seen for untreated patients after initial episodes of respiratory distress or during the use of either tracheostomy intermittent positive pressure ventilation or noninvasive ventilatory assistance methods. The lowest pneumonia and hospitalization rates (P < 0.001) were by full-time, noninvasive intermittent positive pressure ventilation users. We conclude that oxygen therapy is not an effective substitute for assisted ventilation for patients with primarily ventilatory insufficiency. Noninvasive ventilatory aids can be used effectively for up to full-time ventilatory support for patients with neuromuscular conditions whose bulbar muscle function is adequate to avert the need for gastrostomy tube placement.

Amyotrophic lateral sclerosis. Successful treatment of mucous plugging by mechanical insufflation-exsufflation

Bronchial mucous plugging is the main precipitating factor of acute respiratory failure for patients with neuromuscular disease. Manually assisted coughing and mechanical insufflation-exsufflation can effectively eliminate airway secretions without resorting to tracheal intubation provided that bulbar muscle function is sufficient to permit assisted peak cough flows of 160 l/min or greater. We now report successful use of mechanical insufflation-exsufflation to prevent acute respiratory failure for a patient with amyotrophic lateral sclerosis with no measurable peak cough flow.

Clinical implications of maximal respiratory pressure determinations for individuals with Duchenne muscular dystrophy

OBJECTIVE

To analyze the relationship between disease progression, pulmonary volumes, respiratory muscle strength (maximum inspiratory [MIP] and expiratory [MEP] pressure), and arterial blood gases for patients with Duchenne muscular dystrophy (DMD).

DESIGN

An inception cohort study of pulmonary volumes, MIPs, and MEPs, correlated with age and PaCO2 levels and with each other using linear and nonlinear regression analyses.

SETTING

Outpatient clinic.

PATIENTS

Fifty-two consecutive DMD patients who presented for regular evaluations at a regional DMD center.

RESULTS

Maximum expiratory pressures were 47.7% +/- 10.9% of normal in the 167- to 14-year-old patients and decreased linearly thereafter (MEP% = -2.7 x age +73.8; p < .001). Declines in MEP also correlated linearly with expiratory reserve volume (p < .001) and inversely with residual volume (p < .001). By contrast, MIP was 66.3% +/- 19.0% in the 357- to 14-year-old patients and then declined to 30.2% +/- 19.5% after age 14. No linear relationships were found with age but declines did correlate linearly with inspiratory reserve volume (p < .001) and total lung capacity (p < .001). PaCO2 elevations correlated best with decreases in MIP (p < .0001) and appeared when MIP was below 30cmH2O.

CONCLUSIONS

Lung volume changes in DMD patients correlate with respiratory muscle weakness, and although inspiratory muscle dysfunction plays a key role in the development of chronic ventilatory insufficiency, reductions in expiratory muscle strength are the first signs of dysfunction and lead to the first episodes of respiratory failure.

Noninvasive long-term ventilatory support for individuals with spinal muscular atrophy and functional bulbar musculature

Ten individuals with spinal muscular atrophy (SMA) and chronic ventilatory insufficiency were trained in the use of assisted coughing techniques and received intermittent positive pressure ventilation (IPPV) via oral and/or nasal interfaces for a mean of 5.3 (range = 1 to 17) years. During this time they had significantly fewer respiratory complications than before introduction of noninvasive respiratory muscle aids despite the fact that 6 of the 10 went on to require more than 20 hours per day of ventilator use with less than 2 hours of ventilator-free breathing time (VFBT). All except two noninvasive IPPV users had vital capacities (VCs) less than 13% of predicted normal. They could, however, communicate verbally and take nutrition by mouth. All of the patients remained in the community. Five patients were gainfully employed and four were in school. We conclude that noninvasive respiratory muscle aids including noninvasive IPPV and assisted coughing techniques are effective and practical alternatives to tracheostomy for SMA patients with ventilatory failure but functional bulbar musculature.