Bronchial Hyperresponsiveness After Cervical Spinal Cord Injury: Methods
Eight male outpatients with traumatic lesions of the cervical spinal cord (level of injury, C4-7) underwent bronchoprovocation testing with methacholine (Provocholine, Roche Laboratories, Nutley, NJ). Time elapsed since spinal cord injury ranged from 3 to 23 years. Mean age was 34.5 ±5.8 (SD) years (Table 1). None of the subjects had ever been cigarette smokers, nor had they had any history of pulmonary disease or respiratory symptoms prior to their injury. None of the patients required assisted ventilation. Subjects were without respiratory complaints or evidence of recent or active infection at the time of the study, though two subjects reported infrequent episodes of mild dyspnea in the past. None of the patients was receiving any medications expected to alter airway reactivity except for one study participant who ingested 5 mg daily of prazosin, a drug reported to have bronchodilator activity after oral administration.9 All subjects granted informed consent for the study, which was approved by the institutional review board of the Veterans Affairs Medical Center. canada health and care mall
Spirometry was performed with subjects seated in their own wheelchairs, using a SensorMedics 2100 Automated Pulmonary Function Laboratory (Yorba Linda, Cal). Baseline values were obtained for each patient in compliance with current American Thoracic Society criteria.10 Results were expressed as percent predicted based on the spirometric standards of Morris et al.
Subjects inhaled five breaths from functional residual capacity to total lung capacity of normal saline solution administered via a nebulizer (AsthmaKit, Diemolding Healthcare Division, Canastota, NY) driven with air at a flow rate of 8 L/min. Nebulization was achieved by the manual occlusion of a thumbport upon initiation of each breath; gas source pressure was 50 psi. The procedure was repeated with progressively increasing concentrations of methacholine (0.025,0.25,2.5,10, and 25 mg/ml). Spirometry was performed 5 min after the inhalation of saline solution and of each incremental concentration of methacholine, or sooner if the patient experienced chest tightness. The study was terminated when either the concentration of methacholine producing a fall in FEVi of 20 percent from baseline (PC20), or the maximal concentration (25 mg/ml) was reached. The criterion for a positive challenge was taken to be a value of PC20 less than 8 mg/ml. Subjects then underwent subsequent methacholine challenge testing within 20 days of the initial study. The repeat challenge was performed 15 min after the inhalation of 72 Mg (4 puffs) of ipratropium bromide (Atrovent, Boehringer Ingelheim, Ridgefield, Conn) administered via a metered-dose inhaler with an attached spacer device (InspirEase, Key Pharmaceuticals, Miami). The PC20 was then calculated in an identical manner, using a SensorMedics computer program which generated the value of PC20 by interpolation from a log dose-response curve.
Table 1—Patient and Baseline Pulmonary Function Data
|Patient||Age, yr||Duration of Injury, yr||Level of Injury||FEVb L||FVC, L||FEVi/FVC Ratio|
|1||31||5||C5-6||3.82 (86)||4.43 (77)||0.86|
|2||28||5||C6-7||3.88 (89)||4.40 (79)||0.88|
|3||28||9||C4-5||2.27 (48)||2.28 (37)||1.00|
|4||39||18||C5-6||2.48 (68)||2.91 (62)||0.85|
|5||44||23||C5-6||3.00 (72)||3.69 (66)||0.81|
|6||38||3||C6-7||3.47 (84)||3.77 (69)||0.92|
|7||37||6||C5-6||2.86 (64)||3.04 (51)||0.94|
|8||31||4||C6-7||2.68 (64)||3.13 (59)||0.86|