A comparison of two breathing exercise programs for patients with quadriplegia.

Key Words: Breathing exercises; Pulmonary, breathing exercises; Quadriplegia; Spinal cord dysfunction, quadriplegia.

Respiratory complications are the most frequent cause of morbidity and mortality in patients after acute spinal cord injury that leads to quadriplegia.[1] Mortality has been documented to increase to 30% in patients with quadriplegia who develop atelectasis or pneumonia.[2] Paralysis and paresis of the inspiratory and expiratory muscles result in decreased inspiratory force,[3,4] decreased vital capacity,[5] secretion retention, and decreased coughing ability, all of which are risk factors for the development of pneumonia and atelectasis.

Several different techniques have been described that may strengthen and improve endurance of the diaphragm and accessory respiratory muscles. Inspiratory resistive muscle training (IMT) and abdominal weights (AbWts) training are two techniques that are easy to administer, can be applied to intubated patients, and require active exercise by the patient. Alternative techniques include a manually operated pump and valve system,[6] intermittent positive pressure breathing (IPPB),[7] glossopharyngeal breathing,[8,9] and incentive spirometry.[10] The manually operated pump and valve system[6] and IPPB are passive exercises, which only temporarily increase lung volume but do not provide an active maneuver toward maximal inspiration.[4] Both have the additional disadvantages of equipment malfunction, contamination, and induction of barotrauma (ie, injury resulting from changes in barometric pressure).[11] Glossopharyngeal breathing increases vital capacity from 60% to 81% in patients with quadriplegia who have no active disease but is not routinely used because it is difficult to learn and teach and cannot be performed in acutely ill patients with an inflated tracheostomy cuff.[8] Incentive spirometry, has not been studied in patients with quadriplegia, but was shown to be of no additional benefit to aggressive physical therapy in decreasing the incidence of atelectasis following upper abdominal surgery.[10]

Ventilatory muscle endurance has been defined and measured as the capacity for sustaining high levels of ventilation for relatively long periods.[12] In the absence of air flow limitation, maximal voluntary ventilation (MVV) is a good index of ventilatory and respiratory muscle endurance.[13] Respiratory muscle strength has been defined as the maximum or minimum pressures developed within the respiratory system at a specific lung volume.[14] Inspiratory muscle strength is defined as the maximum static pressures measurable at the mouth and attributable to muscle effort.[12]

Inspiratory muscle training causes both endurance and strength changes in patients with quadriplegia, Gross et al[15] determined that an IMT program for six patients with quadriplegia resulted in increased respiratory muscle strength (increased inspiratory mouth pressure [PImax]) and endurance (decreased diaphragmatic fatigue or increase in high to low electromyogram [EMG] amplitudes). Hornstein and Ledsome[1] documented improvements in inspiratory muscle strength and endurance and reported decreases in shortness of breath in two subjects with quadriplegia using a graded resistor. Inspiratory mouth pressure was used as an indicator of ventilatory muscle strength, and endurance was measured as a function of the duration a patient could breathe through a given resistance.[1]

Although AbWts training is commonly used in physical therapy practice as a method of strength training because it is based on successively increasing the resistance to the diaphragm, no studies have documented a strength training effect. In a retrospective sample, Lane[16] demonstrated statistically significant increases in forced vital capacity (FVC) comparing 16 patients with quadriplegia who received weight training three times a week for 6 weeks to 15 subjects who had routine physical therapy management. She also concluded that patients with C4 quadriplegia made slower, but more consistent, improvement in FVC values than did patients with C5 quadriplegia. Merrick and Axon,[17] studying healthy subjects, did not find isotonic diaphragmatic exercise to improve inspiratory capacity (IC), peak inspiratory flow rate, or peak inspiratory pressure, although the subjects' increased exercise capacity may suggest improved inspiratory muscle endurance.

The need for improving inspiratory versus expiratory muscle strength in patients with quadriplegia is evident as the expiratory muscles are denervated in complete injuries. Since 1982, standard practice at the Maryland Institute for Emergency Medical Services System (Baltimore, Md) has included the use of AbWts in conjunction with weaning from mechanical ventilation to improve pulmonary function for patients with quadriplegia in both acute care and rehabilitation settings. To date, no studies have compared the effects of IMT with those of AbWts training.

The purpose of this study was to evaluate the effects of two types of breathing exercise--IMT versus AbWts training--for patients with acute quadriplegia. The following pulmonary function measures were used to determine study outcomes: FVC, IC, MVV, peak expiratory flow rate (PEFR), and PImax.

Method

Subjects

Eleven patients with complete neurological deficit (C4-5 to C7 level), as defined by American Spinal Injury Association (ASIA) standards, were studied after spontaneous breathing for at least 24 hours and when free from active pulmonary disease. Chest radiographs were evaluated daily to rule out any acute changes in the patients' pulmonary status. Informed consent was granted by each subject. Of 40 patients meeting the admission criteria, 11 patients with traumatic quadriplegia completed the study. The clinical details of these 11 patients are presented in Table 1. Subjects were assigned by use of a random numbers table to either an IMT or AbWts treatment group. Complete data were available on 6 patients in the IMT group and 5 patients in the AbWts group, all of whom met the ASIA standards of complete injury. Secondary, to return of motor function (5), poor compliance (1), exacerbations of acute medical conditions (4), experimental error (1), or discharge to other facilities (18), as determined by the medical team, 29 subjects did not complete the study. [TABULAR DATA 1 OMITTED]

Instrumentation

Forced vital capacity, MVV, and PEFR were measured with a Collins volume displacement spirometer.(*) This device met the 1978 American Thoracic Society Standards for spirometry testing and the Snowbird Conference recommendations accepted by the National Institutes of Health.[18] The microprocessor/spirometer was calibrated prior to each patient test. Inspiratory capacity was measured with a Wright respirometer.([dagger]) Inspiratory mouth pressure was measured from functional residual capacity by mouthpiece and Boehringer manometer.([double dagger]) A slight leak was entered into the system to keep the subject's glottis open and reduce the influence of buccal pressures on the measurements.[19,20] A DHD Medical Products inspiratory muscle trainer([section]) was used with the IMT group subjects. Because of the effect of position change on respiratory function, all measurements were taken with subjects in the supine position and with the lateral chest straps open on any braces or vests worn by the subjects.

Procedure

Each subject in the IMT and AbWts groups received his or her respective treatment protocol for 7 weeks. Training sessions consisted of two 15-minute treatments each day, 5 days a week.

All subjects in the IMT group were positioned supine wearing a noseclip and initially trained with the least amount of resistance to inspiration (Fig. 1). The amount of inspiratory resistance was increased when the subject was able to complete three successive sessions of continuous breathing for 15 minutes. The subject was instructed to breathe continuously through the device during each session.

All subjects treated with the AbWts were positioned supine. Maximal inhalation volume without weights was recorded using an incentive spirometer. Standard dish weights (plates from a barbell) were then placed on the subject's upper abdomen in 0.23-kg (0.5-lb) increments (Fig. 2). The maximum weight that did not alter IC (the average weight used in training was 11.34 kg [25 lb]; range=3.4-20.4 kg [7.5-45 lb]) was placed on the abdomen while the subject performed 10 maximal inspirations, holding each breath for several seconds. This sequence was repeated three times for a total of 40 breaths per session.

Data Analysis

Weekly data for FVC, MVV, PEFR, PImax, and IC were analyzed by analysis of variance (ANOVA) for repeated measures with one grouping factor. Data were grouped according to treatment group (grouping factor). An ANOVA was also used to analyze the within-group significance on the five dependent variables.

A power analysis was conducted for the mean difference between the two treatment groups for continuous variables, using a beta level of .2 and an alpha level of .05 to determine the sample size needed to minimize Type II errors.[21] The power analysis revealed that the mean difference between the two treatment groups was detectable with a sample size of 5.0 for FVC and MVV, but larger sample sizes were needed to detect the mean differences for PEFR (N = 14.3), PImax (N=11.2), and IC (N=9.22).

Results

The ANOVA demonstrated no significant difference for FVC, MVV, PEFR, PImax, and IC between treatment groups. There were significant differences within groups, however, for all variables, except IC. Table 2 compares the results of pulmonary function tests performed at 1 and 7 weeks. The mean difference from week 1 to week 7 was greater on all pulmonary function tests for the IMT group than for the AbWts group, although there were no significant differences between groups on pulmonary function values at the beginning of the study. [TABULAR DATA 2 OMITTED]

Discussion

The results of this study suggest that both IMT and AbWts training appear to be equally effective for the respiratory training of patients with quadriplegia and that both protocols result in improvement in pulmonary function. One method of training was not shown to be more effective than the other. A larger gain in MVV with the IMT protocol was observed in our pilot study of 29 patients who received 3 weeks of breathing exercise treatment.[22] The increase in MVV for the IMT group may be indicative of endurance training with this protocol. Both IMT and AbWts training are routinely used in physical therapy practices for the respiratory muscle training of patients with quadriplegia. The relative benefits of IMT include an inexpensive training procedure that may be self-administered over the long term in comparison with training with AbWts, which requires more staff or family intervention. Weights, however, are available in all physical therapy departments.

Differences in the two groups of patients in this study were noted with respect to sex, level of injury, number and type of associated injuries, initial pulmonary function values, number of days postinjury prior to study admission, and compliance with the treatment regimen. The group that trained with AbWts had fewer men than did the IMT group. In regard to level of injury, there were more patients with low-level quadriplegia (C7) in the IMT group than in the AbWts group. Although the AbWts group had fewer associated injuries than did the IMT group, the number of chest injuries was equally prevalent in both samples. Based on the higher initial volumes at week 1 and earlier admission to the study, the participants in the IMT group were probably more medically stable than those in the AbWts group, which may have influenced our results. The percentage of missed treatment sessions was 28% for the IMT group and 50% for the AbWts group. Two subjects in the AbWts group complained of "abdominal discomfort" when using the weights. These subjects missed the greatest number of treatment sessions in both groups. The percentage difference may also he attributed to the ease of use of the resistor in clinical research.

Limitations to the study include the possibility of spontaneous motor recovery of the respiratory muscles following quadriplegia as the muscle flaccidity associated with spinal shock converts to associated hyperreflexia of paralyzed muscles. This increased muscle activity may enhance diaphragmatic contraction while affecting both abdominal and inspiratory muscle activity.[23] Ledsome and Sharp[5] documented rapid improvements in vital capacity within 5 weeks of injury in patients with complete transection of the spinal cord at the C4, C5, and C6 levels. Patients in their study with injury at the C4 level demonstrated an approximate doubling of vital capacity 3 months after injury. In our study, although there was a 32% gain in FVC from 72 hours after admission to 7 weeks postinjury, this gain is lower than documented improvement in patients who were not treated with breathing exercises.[5,23] Patients with motor return or abdominal muscle activity, however, were excluded from our study. There was therefore less probability of spontaneous recovery in the patients we studied, which may account for the lower pulmonary function values over time compared with those for nontreated patient groups. The patients who participated in our study also may not be comparable to those of the previous studies in view of the number who received mechanical ventilation and had associated injuries. Finally, larger sample sizes would improve the power of the study, especially for the variables PEFR, PImax, and IC.

Other limitations include use of the nonlinear breathing device and lack of an assessment of the degree of inspiratory muscle fatigue prior to and after training. With nonlinear resistive breathing, both the rate of air flow and the size of the inspiratory orifice determine the pressure load. The magnitude of the inspiratory pressure load will vary depending on the air flow rate. When using a pressure threshold training device, a spring-loaded valve opens when a predetermined inspiratory pressure is attained. The inspiratory pressure remains constant, regardless of the inspiratory flow rate. Larson et al[24] demonstrated that inspiratory pressure load is an important variable in IMT. These authors demonstrated that patients with chronic obstructive pulmonary disease trained at higher pressure loads with a pressure threshold resistor. The use of a threshold training device achieved improved inspiratory muscle strength, endurance, and general exercise tolerance when compared with the outcomes of patients who trained at lower pressure loads. This device was not commercially available when this study was initiated.

We evaluated the results of training by pulmonary function testing rather than using EMG biofeedback or transdiaphragmatic pressure measurements to determine the amount of muscle fatigue. These techniques require sophisticated equipment and insertion of an esophageal balloon, both of which are impractical in the acute care setting. Vilozni et al[25] found that EMG activity measured with surface electrodes placed on the sternocleidomastoid muscle correlated with the EMG activity of the diaphragm. In future studies, this technique may allow for more objective respiratory assessment of the hospitalized patient with quadriplegia to determine respiratory muscle fatigue associated with weaning from mechanical ventilation as well as determination of a specific training stimulus.

Assessment of interrater reliability was not conducted for the measurements used in this study. To minimize this source of error, however, each patient had a primary therapist. Training was conducted for each therapist involved in administering the pulmonary function tests. Use of the Collins volume displacement spirometer resulted in a hard-copy printout for three out of the five tests (ie, FVC, MVV, and PEFR). The consistency of measurements of the independent variable indicated that all patients followed uniform instructions and encouragement during the breathing exercises and weekly data collection sessions.

Future research should compare the effectiveness of the IMT and AbWts training protocols using the pressure threshold device for IMT and a control group to rule out the effects of spontaneous motor recovery. Although larger patient samples may be difficult to obtain in view of the decreasing number of complete quadriplegic injuries reported nationally,[26] enrolling larger numbers of patients in the study would allow statistical evaluation of differences according to level of motor injury.

Summary

This study compared the effectiveness of AbWts training with that of IMT for strengthening the inspiratory muscles of 11 patients with quadriplegia during 7 weeks of treatment. No significant difference was found between the treatment protocols (P>.05); the mean difference from week 1 to week 7 of treatment was greater on all pulmonary function tests for the IMT group. There were significant differences within groups on all five pulmonary function tests. Although the data did not support the effectiveness of one method of training over the other, measurements of selected pulmonary function tests did improve. Further studies are necessary with larger samples of patients and control subjects to determine conclusively the benefit of either treatment protocol.

Acknowledgments

We gratefully acknowledge Paul Anderson, PhD, for assisting with the initial study design; Mary Salmon, PT, and Kathy Corlew, PT, for assisting with the initial data collection; and Colin Mackenzie, MD, and Joan Stoklosa for reviewing the manuscript. ([dagger]) Fraser Harlake, 145 Midcountry Dr, Orchard Park, NY 14127. ([double dagger]) Boehringer, 4427 Parkview Dr, Wynnewood, PA 19096. ([section]) DSD Medical Products, Div of Diemolding Corp, Canastota, NY 13032.

References

[1] Hornstein S, Ledsome JR. Ventilatory muscle training in acute quadriplegia. Physiotherapy Canada. 1986;38:145-149. [2] Reines AO, Harris RC. Pulmonary complications in acute spinal cord injuries. Neurosurgery. 1987;21:193-196. [3] Loveridge BM, Dubo HI. Breathing pattern in chronic quadriplegia. Arch Phys Med Rehabil. 1990;71:495-499. [4] Mackenzie CF, Imle PC, Ciesla N. Chest Physiotherapy in the Intensive Care Unit. 2nd ed. Baltimore, Md: Williams & Wilkins; 1989:298. [5] Ledsome JR, Sharp JM. Pulmonary function in acute cervical cord injury. Am Rev Respir Dis. 1981;124:41-44. [6] Fugl-Meyer AR. A model for treatment of impaired ventilatory function in tetraplegic patients. Scand J Rehabil Med. 1971;3:168-177. [7] McCool FD, Mayewski RF, Shayne DS, et al. Intermittent positive pressure breathing in patients with respiratory muscle weakness. Chest. 1986;90:546-552. [8] Metcalf VA. Vital capacity and glossopharyngeal breathing in traumatic quadriplegia. Phys Ther. 1966;46:835-838. [9] Montero JC, Feldman DJ, Montero D. Effects of glossopharyngeal breathing on respiratory function after cervical cord transection. Arch Phys Med Rehabil. 1967;48:650-653. [10] O'Donohue WJ. National survey of the usage of lung expansion modalities for the prevention and treatment of postoperative atelectasis following abdominal and thoracic surgery. Chest. 1985;87:76-80. [11] Shapiro BA, Peterson J, Cane RD. Complications of mechanical aids to intermittent lung inflation. Respir Care. 1982;27:467-470. [12] Leith D, Bradley M. Ventilatory muscle strength and endurance training. J Appl Physiol. 1976;41:508-516. [13] Aldrich TK, Arora NS, Rochester DF. The influence of airway obstruction and respiratory muscle strength on maximal voluntary ventilation in lung disease. Am Rev Respir Dis. 1982; 126:195-199. [14] Irwin S, Tecklin J. Cardiopulmonary Physical Therapy. 2nd ed. Philadelphia, Pa: CV Mosby Co; 1990:515-516. [15] Gross D, Ladd HW, Riley EJ, et al. The effect of training on strength and endurance of the diaphragm in quadriplegia. Am J Med. 1980;68:27-35. [16] Lane CS. Inspiratory muscle weight training and its effect on the vital capacity of patients with quadriplegia. Cardiopulmonary Quarterly. 1982;5(10):13. [17] Merrick J, Axen K. Inspiratory muscle function following abdominal weight exercises in healthy subjects. Phys Ther. 1981;61:651-656. [18] Black KH, Petusevsky EM, Gaensler EA. A general microprocessor for spirometry. Chest 1980;78:605-612. [19] Gilbert R, Auchincloss JH, Bleb S. Measurement of maximum inspiratory pressure during routine spirometry. Lung. 1978;155:23-32. [20] Pardy RL, Rivington RN, Despas PJ, et al. The effects of inspiratory muscle training on exercise performance in chronic airflow limitation. Am Rev Respir Dis. 1981;123:426-433. [21] Rosner B. Fundamentals of Biostatistics 2nd ed. Boston, Mass: Duxbury Press; 1986: 264-265. [22] Ciesla N, Simpson N, Derrickson J, Salmon N. A comparison of two different breathing exercises for quadriplegic patients. Phys Ther. 1989;69:393. Abstract. [23] McMichan JC, Michel L, Westbrook PR. Pulmonary dysfunction following traumatic quadriplegia. JAMA. 1980;243:528-531. [24] Larson JL, Kim MJ, Sharp JT, et al. Inspiratory muscle training with a pressure threshold breathing device in patients with chronic obstructive disease. Am Rev Respir Dis. 1988; 138: 689-696. [25] Vilozni D, Bar Yishay E, Beardsmore C, et al. A non-invasive method for measuring inspiratory muscle fatigue during progressive isocapnic hyperventilation in man. Eur J Appl Physiol. 1987;56:433-439. [26] Duncan EG, Tator CH, Edmonds VE, et al. Treatment in a specialized unit improves three measures of outcome after acute spinal cord injury: statistical analysis of 552 cases. Surg Forum. 1987;38:501-503.

J Derrickson, EdD, PT, is Assistant Professor, Family Support/Early Intervention, New York Medical College, WIHD, Room 423, Cedarwood Hall, Valhalla, NY 10595. She was Research Coordinator, Department of Physical Therapy, Montebello Rehabilitation Hospital-Maryland Institute for Emergency Medical Services System, 22 S Greene St, Baltimore, MD 21201, when this study was conducted. Address all correspondence to Dr Derrickson at 24 Barnum Rd, Larchmont, NY 10538 (USA).

N Ciesla, PT, is Director, Department of Physical Therapy, Maryland Institute for Emergency Medica Services System, and Clinical Instructor, School of Physical Therapy, University of Maryland, Baltimore, MD 21201.

N Simpson, PT, is Staff Physical Therapist, Montebello Rehabilitation Hospital. She was Physical Therapy Supervisor, Spinal Cord Unit, Montebello Rehabilitation Hospital, when this study was conducted.

PC Imle, PT, is Clinical Instructor, School of Physical Therapy, University of Maryland. She was Senior Physical Therapist, Department of Physical Therapy, Maryland Institute for Emergency Medical Services, when this study was conducted.