Long-Term Follow-up of Nocturnal Ventilatory Assistance in Patients with Respiratory Failure Due: METHODS
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.
Not all patients tried all ventilators, but six of the eight tried both negative and positive pressure devices. Initial settings on the ventilator were selected to augment expired minute ventilation approximately 25 percent over baseline, and fine adjustments were made to optimize patient comfort. The ventilator for long-term use was selected by the patient as long as it was capable of augmenting minute ventilation by at least 25 percent, and patients remained in the hospital for two to three additional nights to familiarize themselves with nocturnal use of the ventilator. To optimize patient acceptance, ventilator use was initiated during the evening for several hours and was gradually extended through the night. Following discharge, a home respiratory care provider checked on the patient frequently until he developed a stabilized routine for ventilator use. canadian pharmacy
Following discharge, two additional studies were performed. To determine whether alterations in arterial blood gas tensions or respiratory muscle fatigue occurred during the daytime period of spontaneous ventilation, four patients were studied at home within one-half hour of finishing night-time ventilator use, and again on the same day one-half hour before resuming ventilator use. Studies consisted of measurement of spontaneous breathing rate, minute ventilation, vital capacity and maximal voluntary ventilation for 12 s using an Eagle 2 spirometer (Warren E. Collins, Inc., Braintree, MA), and maximal inspiratory and expiratory pressures from FRC using a hand-held manometer (Boehringer Laboratories, Wynne- wood, PA). Arterial blood gas values were determined while the patient sat at home breathing room air. Samples were transported on ice to the hospital where gas tensions were measured within 1 h of obtaining them.
To determine whether nocturnal desaturations were occurring in our patients, as has been reported in other patients with neuromuscular disease using negative pressure ventilators, we monitored blood oxygen saturation overnight in three patients using a portable finger oximeter (Ohmeda Biox IVA, Englewood, CO).
For statistical comparisons, we used paired f-tests for comparisons of paired means, and analysis of variance for repeated measures for serial samples. For significant F ratios, we used the Student- Newman-Keuls test for comparisons of individual means. Data are mean ± SE. Differences were considered significant when p<0.05.
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