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* From the Departments of Internal Medicine (Dr. Yasuma) and Neurology (Drs. Kato, Matsuoka, and Konagaya), Suzuka National Hospital, Suzuka, Japan.
Correspondence to: Fumihiko Yasuma, MD, FCCP, Physician-in-Chief, Department of Internal Medicine, Suzuka National Hospital, 3-2-1 Kasado, Suzuka, 513-8501 Japan; e-mail: f-yasuma{at}mtb.biglobe.ne.jp
| Abstract |
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Objectives: To support the hypothesis that RBP is an abnormal pattern of respiration to compensate for the atrophied respiratory muscles in advanced DMD.
Patients and methods: Age, degree of ventilator dependency, and blood gas and spirometry values of 12 patients with spontaneous RBP were compared to those of 8 patients without RBP. All patients were men, and all exhibited a comparable level of motor function (unable to ambulate). Spirometry was undertaken with an ambulatory pneumotachograph in six patients with RBP in two conditions: sitting with RBP and sitting without RBP. In the latter condition, because a patients shoulders, neck, and head were manually restricted, RBP was prevented.
Results: We found that the patients with RBP were older (mean, 25.98 years vs 19.84 years), more dependent on mechanical ventilation (13.96 h/d vs 4.31 h/d), and had lower FVC and percentage of FVC (511.3 mL vs 762.5 mL and 13.37% vs 20.11%, respectively) than those without RBP. We also found that the frequency of RBP was identical with tidal breathing, and FVC was increased by 50.8% by simply allowing RBP.
Conclusion: We conclude that RBP is a respiratory movement to compensate for the atrophied respiratory muscles in advanced DMD.
Key Words: Duchenne muscular dystrophy mechanical ventilation respiratory failure "row-a-boat" phenomenon
| Introduction |
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| Materials and Methods |
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Spirometry with an ambulatory pneumotachograph (Microspiro HI-510; Chest Medical Instruments; Tokyo, Japan) was measured under three different conditions in six patients with RBP who understood and agreed to the study protocol. All of the subjects started RBP immediately after being transferred to a wheelchair. First, the patient breathed spontaneously when lying supine; consequently, RBP could not occur. Second, the patient sat in the wheelchair while the examiners manually restricted any movement of his shoulders, neck, and head. Hence, RBP was prevented. Third, the patient was allowed to breathe spontaneously with RBP.
On a separate day, the examiners calculated the frequency of tidal breathing and that of RBP separately in the six patients for 1 min in each condition. Pulse oximetry (Pulsox 7; Minolta; Osaka, Japan) and ECG were continuously monitored.
Values were expressed as means ± SE, and a p value < 0.05 was considered statistically significant. An unpaired t test was used to compare the variables between the patients with and without RBP, and repeated-measures analysis of variance was used in the multiple comparisons for the six subjects.
| Results |
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FVC and heart rate in six of the patients with RBP in three different conditions are demonstrated in Figure 2 . FVC in the patients sitting with spontaneous RBP was increased by 50.8% compared to sitting without RBP (restricted; p < 0.05). FVC was also increased by 87.1% compared with that while lying supine (p < 0.05). Heart rate while sitting without RBP (restricted) tended to increase by 15.3 beats/min compared with that while sitting with RBP (p < 0.10). It also showed a significant increase by 19.8 beats/min compared with that while lying supine (p < 0.01). Oxygen saturation was maintained > 94% throughout these measurements; however, the patients sitting without RBP (restricted) soon expressed feelings of discomfort/dyspnea.
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| Discussion |
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Since the use of intermittent positive-pressure ventilation for DMD was established, life expectancy has been prolonged by at least several years according to our previous report.4 As a result, most DMD patients can survive until the latter half of the third or fourth decade of life. Hence, we have more opportunities to observe unusual methods of compensation for the atrophied respiratory muscles in advanced DMD.
Kawamura et al1 first recognized RBP in a 25-year-old man with DMD. They pointed out that RBP occurred when the PaCO2 under spontaneous room-air breathing was increased to 59.2 ± 3.1 mm Hg in five patients with RBP, suggesting that RBP could be a sign of respiratory failure in advanced DMD. In our study, PaCO2 in 12 subjects with RBP was 55.37 ± 3.00 mm Hg, which was 3.8 mm Hg lower than that from the above report. This discrepancy could be partly explained by the fact that RBP is not only a spontaneous but also a volitional movement. RBP mostly occurred spontaneously in a patient sitting in a wheelchair, although the patient did not himself notice the occurrence of RBP. Therefore, the patient possibly utilizes RBP to relieve discomfort, presumably secondary to hypoventilation.
The supplemental FVC with RBP in six patients with RBP was 50.8%; in other words, the respiratory contribution of RBP to FVC was 33.7%. When RBP was manually prevented, the patients expressed discomfort/dyspnea, and heart rate was elevated most among the three different conditions. These findings might imply the substantial contribution of RBP to respiration in advanced DMD.
The intersubject difference in the pattern of RBP might be attributed to the differential mechanisms generating the supplemental VT with RBP. Four possible mechanisms might exist.
The first is the gravitational effects of the abdominal viscera on the diaphragm, the mechanism that was utilized initially with a rocking bed by Eve5 in 1932. Eve5 reported rocking a patient with respiratory paralysis due to poliomyelitis up and down rhythmically on a stretcher that was pivoted about the middle on a trestle so that the weight of the viscera pushed the flaccid diaphragm alternately up and down.
The second is an activation of the accessory muscles of the neck and superior trunk, which serves to lift the ribs, sternum, clavicles, and scapulae. A similar rostral elevation of the thoracic cage was reported6 in a patient with a transected cervical cord. A tetraplegic patient has complete paralysis of the diaphragm and the respiratory muscles of the rib cage, and, yet, the functions in the sternocleidomastoid and trapezia are well preserved. Therefore, the patient volitionally contracts these muscles to lift the sternum and clavicles, which increases the volume of the rib cage and encourages inspiration.
The third is glossopharyngeal breathing, known as frog breathing.7 This abnormal pattern of breathing is found in a patient with severely atrophied respiratory muscles or cervical transection, whose facial and upper-airway muscle functions are preserved. Using the muscles of the tongue, cheek, pharynx, and larynx, the patient can swallow air down to the airway but not into the esophagus. In this study, glossopharyngeal breathing was found in only one of the six subjects sitting in a wheelchair in association with RBP. However, it is occasionally noted in patients with DMD when lying supine.
The fourth is an active compression of the thorax and abdomen during expiration with a wide and tightly woven cotton belt that is tied around a patient in a wheelchair to help maintain him in the upright position (Fig 1) . The preferable belt position around the trunk in the upright patients differed among the subjects, which explains the specific mechanism(s) to augment VT. When the belt was tied at the level of the lower rib cage and abdomen, the gravitational effects of the viscera or the compression of the lower thorax and abdomen could be more efficiently utilized. When the belt was tied at the upper rib cage level, the muscles of the face, head, neck, and shoulders were activated to achieve the rostral elevation of the rib cage or to generate the glossopharyngeal breathing. Therefore, the material, width, and position of the belt should be considered, not only to secure the patient to the wheelchair but also to allow a comfortable body movement for respiratory compensation for each patient.
These mechanisms to generate supplemental VT with RBP in the patients with DMD indicate that the various skeletal muscles can compensate for the atrophied respiratory muscles. Hence, medical staff can instruct patients with advanced DMD to utilize RBP for a temporary backup of tidal breathing. Nevertheless, we should note that the muscles used in RBP are more susceptible to muscle fatigue than the diaphragm, and volitional RBP can occur only in the sitting position during wakefulness.
| Conclusion |
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| Acknowledgements |
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| Footnotes |
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Received for publication August 5, 1999. Accepted for publication November 28, 2000.
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This article has been cited by other articles:
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F. Yasuma, T. Kato, and M. Naya Adequate Tidal Volume With Row-a-Boat Phenomenon in Advanced Duchenne Muscular Dystrophy Chest, May 1, 2002; 121(5): 1726 - 1726. [Full Text] [PDF] |
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