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(Chest. 2005;128:184-189.)
© 2005 American College of Chest Physicians

Effects of Partial Isothermic Immersion on the Spirometry Parameters of Tetraplegic Patients*

Sérgio Thomaz, PT, MSc; Paulo Beraldo, MD, PhD; Sergio Mateus, PT, MSc; Thomas Horan, MD, FCCP and Josevan Cerqueira Leal, PT

* From the SARAH Network of Hospitals for the Locomotor System (Drs. Beraldo and Horan), Master’s Degree Program in Rehabilitation Sciences (Mr. Thomaz, Mr. Mateus, and Mr. Leal), Brasília, Federal District, Brazil.

Correspondence to: Thomas A. Horan, MD, FCCP, Hospital SARAH, SMHS, Quadra 501, Conjunto "A", Brasília-DF, 70 000-150, Brazil; e-mail: thoran{at}bsb.sarah.br


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Study objectives: Our objective was to compare under controlled conditions the effect of immersion on spirometry parameters of patients with tetraplegia vs those of normal individuals.

Design and patients: Twenty-three otherwise well tetraplegic subjects were compared to a control group of 11 similar healthy subjects before and during 5 to 15 min of isothermal immersion in water to shoulder level.

Results: Measured at baseline, tetraplegic subjects exhibited significant pulmonary restriction, characterized by a mean FVC of 54.9 ± 14.6% of the predicted value (range, 23.2 to 80.4%), whereas all controls subjects had > 80% of predicted values. Immersion increased the FVC of tetraplegic patients an average of 18.4 ± 18.7% above basal measurements, while that of the control group worsened ({Delta}FVC, – 8.8 ± 4.4%). Among the tetraplegic patients, the lower the preimmersion vital capacity, the greater the percentage of improvement following immersion (r = 0.79; 95% confidence interval, – 0.91 to – 0.56; p < 0.0001). No relationship was found between the time elapsed since cervical cord injury or its level and the degree of improvement.

Conclusions: Water activities play an important role in the rehabilitation of patients with spinal cord injury. Immersion in isothermal water at shoulder level, under strictly controlled experimental conditions, reduces the vital capacity of normal individuals, while it improves in a group of patients with tetraplegia. The observed phenomenon seems to be mediated by an improvement in breathing mechanics, impaired by cervical cord injury.

Key Words: hydrotherapy • immersion • lung function tests • respiratory mechanics • spinal cord injuries • tetraplegia


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Pulmonary dysfunction is one of the chief clinical challenges facing patients with high spine cord lesions.12 Hydrotherapy frequently plays a role in the rehabilitation of these patients.3456 Immersion reduces the vital capacity of normal individuals.789 The two available studies1011 of partial immersion reported in patients with tetraplegia showed an improvement in pulmonary function. However, the suggested benefit is difficult to interpret since description of important clinical variables and methodologic information, such as water temperature, time, and depth of immersion, were unreported. One study10 was limited to examining only residual volume. Thus, our objective was to describe the effect on spirometry of patients with tetraplegia immersed in water under controlled test conditions, correlating changes with clinical variables, including the level of and time since the occurrence of traumatic cervical cord lesion.


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
The study protocol was subjected to an institutional ethics review. Prior signed informed consent was obtained from each participant. From April 2000 to September 2001, 23 male tetraplegic patients with complete motor interruption (American Spinal Injury Association A or B)12 of the cervical spinal cord (C4 to C8) were studied. For this group, the median age was 25 years, and the median time since injury was 9 months (range, 2 to 89 months). No patients with prior tracheostomy, active pulmonary complications, or the presence of other clinical instability were included in the study. During the same period, 11 healthy male volunteers, median age 27 years, were studied under identical conditions.

All tests were performed in the afternoon. The individuals underwent spirometry (MasterScope; Erich Jaeger GmbH; Hoechberg, Germany), adhering to the recommendations of the American Thoracic Society.13 The spirometer was calibrated every day before the tests. Volume was electronically obtained from integrates of flow. Measures were obtained immediately before and 5 to 15 min following immersion to shoulder level in water temperatures between 33.5°C and 34.5°C, and again 5 to 10 min after withdrawal from the water. All subjects were studied in upright, seated posture, in and out of the water.14

The Shapiro-Wilks test demonstrated all variables to be with in a normal distribution. The spirometry results obtained before and after immersion were subjected to the paired Student t test. The percentage change in spirometry findings before and during immersion were compared to the results in healthy volunteers by Student t test. We performed analysis of variance for repeated measurements of the spirometry results between the healthy and tetraplegic groups, before and during immersion. Correlation was sought for the percentage change in slow vital capacity (SVC) during immersion with the basal percentage of predicted SVC, with the neurologic level, and with the time since trauma. Relationships between percentage change in SVC with immersion and injury level were assessed by assigning a corresponding numeric value between 1 and 8 for neurologic levels C1 through C8. Pearson coefficient and 95% confidence limits were calculated for this purpose. All statistical analysis was conducted using software (StatView for Windows, Version 5.0.1; SAS Institute; Cary, NC).


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Measured at baseline, the tetraplegic subjects exhibited significant pulmonary restriction, characterized by a mean FVC of 54.9 ± 14.6% of predicted (range, 23.2 to 80.4% predicted), while all the values of the control group were > 80% of predicted (Table 1 ). We found no difference in the values obtained immediately prior and within 5 to 10 min following withdrawal from immersion in either the volunteer or tetraplegic study groups. Because of this, analysis was limited to the values obtained prior to and during immersion.


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  		Table 1. Forced Spirometric Parameters of Patients With Spinal Cord Injury and Control Group at Baseline and During Immersion

 
During immersion, tetraplegic subjects showed improvement of FVC by an average of 18.3 ± 18.4% (p < 0.001). In contrast, the average FVC of the control group fell during immersion by 8.8 ± 4.4% (p < 0.001). FEV1 showed a similar response to immersion, with improvement in the tetraplegic group (p < 0.05) and a modest decline in the control group (p < 0.05). In tetraplegic patients, the FEV1/FVC ratio lessened during immersion when compared to basal values by – 4.5% (p < 0.05), while the control group showed no change. Similarly, SVC in tetraplegics showed an average percentage change of + 24.7 ± 28.1%, whereas the control group averaged – 3.9 ± 5.6% (p < 0.001) [Fig 1 ]. Three tetraplegic patients exhibited a fall in SVC from 4 to 6% during immersion, but none had symptoms of dyspnea. These three patients had no other distinguishing features from the rest of their group. The analysis of variance shows the different effect (p < 0.0001) that immersion had on the FVC of the two groups. For illustration, the most marked flow-volume curves before and during immersion from a patient and a control subject are shown in Figure 2 .



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  		Figure 1. Change in SVC from baseline to immersion. Fine lines indicate individuals; thick lines indicate groups. The average percentage change for both groups ({Delta}%) ± SD is shown. *p < 0.001 (control vs tetraplegic).

 


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  		Figure 2. Illustrative flow-volume curves in tetraplegic patients (left) showing a 42% improvement in FVC; control subjects (right) had a 19% reduction in FVC. Continuous lines indicate before immersion; dotted lines indicate during immersion. vol = volume.

 
During immersion, there was an equivalent improvement of mean inspiratory capacity (IC) in the tetraplegic (40.7 ± 48.6%; p < 0.001) and control (26.7 ± 15.7%; p < 0.001) groups. The mean percentage change of expiratory reserve volume (ERV) in control subjects decreased significantly (– 62.7 ± 15.9%; p < 0.001), while there was no change in patients with tetraplegia (– 6.4 ± 58.4%; p = 0.30), who exhibited a remarkable dispersion. The fall of ERV in control subjects were greater than that observed in tetraplegic patients during immersion (p < 0.001).

Tetraplegic subjects showed a strong negative correlation between percentage change of SVC during immersion and the basal percentage of predicted SVC (r = – 0.79; 95% confidence interval [CI], – 0.91 to – 0.56; p < 0.001). The correlation between the level of the neurologic lesion and percentage change of SVC was weak (r = – 0.41; 95% CI, – 0.71 to – 0.0003; p < 0.05). There was no discernible correlation between time since injury and changes in SVC during immersion (Table 2 ).


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  		Table 2. Correlative Analysis Between Percentage Change of SVC During Immersion and Basal Percentage of Predicted SVC and Clinical Parameters (Level and Length of Injury)*

 

   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
In tetraplegic patients, immersion to shoulder level in isothermic water increased the SVC nearly 25% above basal measurements. However, a healthy control group showed the opposite pattern with an average reduction of 4%. Among the tetraplegic patients, the lower the preimmersion vital capacity, the greater was the percentage of improvement following immersion.

Only two prior investigations1011 have studied the effect of immersion on the pulmonary function of subjects with tetraplegia, and agree with and complement the results of present study. In 1982, Jaeger-Denavit et al11 evaluated 12 tetraplegic subjects immersed in water (29 to 31°C) with "head out" and showed an elevation of vital capacity, accompanied by a fall in residual volume. In 1991, this reduction in residual volume was confirmed by Bosch and Wells10 in eight tetraplegic subjects immersed to the "neck" in water at 34°C. Neither study mentions the time of immersion. In spite of these similar results, the studies were conducted in different experimental conditions without considering the potential effect of water temperature and time of immersion on the results.

In studies715161718 that refer to the effects of water immersion on the spirometry findings in normal individuals, a reduction in vital capacity ranging from 3 to 10% has been demonstrated. Two factors may be responsible for this reduction in healthy subjects: the intrathoracic shift of blood volume and the pulmonary restriction, both occasioned by hydrostatic water pressure.

A displacement of approximately 700 mL of blood by increased circulating plasma volume from the lower extremities and abdomen to the chest has been shown in able-bodied persons.719 This additional thoracic blood volume occupies space, diminishes pulmonary compliance, and increases closing volume,20 thus increasing respiratory work.21 The pulmonary restrictive effect of the hydrostatic water pressure decreases thoracic expansion, reduces chest circumference by an average of 10%, and shifts the diaphragm to a more cranial position.7 Of these potential explanations for the reduction in pulmonary function in healthy individuals, the transfer of peripheral blood to the chest has been deemed the most important.222324 The only existing report of the hemodynamic effects in tetraplegics subjects immersed in water has demonstrated an elevation in cardiac output of the same extent as observed in healthy control subjects.25 Therefore, it appears that vascular volume shifts are similar in both tetraplegics and control subjects. The improvement in vital capacity noted in 20 of the 23 tetraplegic patients seems to be mediated by an enhancement in breathing mechanics that is not seen in healthy individuals.

It is known that the principal cause of respiratory dysfunction in patients with spinal cord lesions below C5 is weakness of the expiratory musculature.26 The resultant flaccid abdominal musculature favors the descent of the diaphragm and in direct proportion causes lessening of the zone of apposition. This mechanism is believed to lead to mechanical inefficiency of the diaphragm.2 The present study has shown a significant negative correlation between the percentage of the predicted resting vital capacity and the improvement of this parameter following immersion. This suggests that the hydrostatic pressure adjusts the position of the diaphragm to a higher and mechanically more efficient level. The hydrostatic pressure similarly seems to assist the expiratory phase of respiration by providing an upward driving force through the flaccid abdomen whenever the diaphragm is relaxed. This same hydrostatic pressure helps the diaphragm function during its contraction by the appositional force of raising the abdominal pressure. The effect of the hydrostatic pressure on the abdominal wall by immersion seems similar to the effects described for abdominal compression belts,27 and the benefit of the supine position.2829 The elevation of the diaphragm and the resultant increase in the area of apposition provides the ideal conformation for diaphragmatic function.30 The present results suggest that the more caudal the apex of the diaphragm prior to immersion, the greater the benefit of the hydrostatic pressure in tetraplegic patients. In this context, however, we cannot discard a concurrent influence of buoyancy force from abdominal hollow viscera as a support to the diaphragm contraction.

We found an improvement of IC in both groups and a reduction of ERV only in control subjects. Spirometry does not provide all data necessary, mainly residual volume, for a complete explanation of these findings. However, based on other studies,31 we can speculate that the SVC fall in control subjects is the net result of the diaphragmatic elevation favoring improvement of IC and the greater effects of pulmonary restriction (intrathoracic shift of blood volume and pulmonary compression) resulting in the reduction of functional residual capacity. As immersion raises the diaphragm, its radius decreases and a more effective transdiaphragmatic pressure is generated resulting in the IC increases (LaPlace law).32 However, the increase of SVC observed among tetraplegic patients can be related to the predominant improvement in IC because of the higher position of the diaphragm. ERV in these patients is usually small, and it was not affected by the immersion. It is possible that the residual volume, which is usually elevated in these patients,26 decreases during the immersion,1011 thus contributing to the improvement of the vital capacity.

No discernible difference existed in spirometry measures before immersion and after withdrawal from the water in both tetraplegic and healthy subjects. This suggests that there was no potential confounding learning effect as a result of repeated measurements. The level of spinal cord injury bore no relationship to the benefit of immersion. This result can be explained by the narrow range of injury level involved in the present study (C4 to C8). Regardless, this fact may add support for the contention that the benefit of immersion observed in tetraplegics is related to reversal of the effects of abdominal flaccidity and low-lying diaphragm, which normally impede the expiratory phase of respiration.

Tetraplegic patients demonstrate deficient thermoregulatory capacity and core temperature varies with environmental temperature.33 Changing body temperature can induce cardiovascular alterations in able-bodied subjects.18 Moreover vital capacity does appear to fluctuate somewhat with temperature, decreasing with cooler water immersion (25°C) and increasing slightly in warm water immersion (40°C).34 Consequently, isothermic water temperature (34 ± 0.5°C) was rigorously maintained to minimize the potential for cardiovascular and pulmonary alteration as a function of differing or changing experimental environmental temperatures.1835 To further minimize the possibility of environmental temperature effects, as well as potential fatigue, no patient was submitted to immersion for > 15 min prior to completion of spirometry. This study shows a significant improvement in FEV1, FVC, and SVC in tetraplegic patients immersed in water at 34°C for a period limited to 15 min. Whether this improvement could be sustained for more lengthy times of immersion is unknown. The possible conditioning effect of programmed repetitive immersions on diaphragmatic strength needs study. Moreover only a clinical trial will be capable of confirming the potential benefit of a program of immersion to improve the pulmonary function and to reduce the respiratory complications in these patients.

Our study design does not permit conclusions regarding the relative importance of central blood volume shift vs the chest muscular support of water pressure in immersed tetraplegic patients. The effect of differing lengths of time, and variations in depth of immersion and water temperature appear to warrant future investigation. We recognize that our research has studied limited parameters, does not have a comparison between immersion to xyphisternum and shoulders, and ignores potential modified gas exchange. Similarly, we did not use legs cuffs to block the venous return to measure blood displacement effects during immersion. We also did not compare data on the effects of abdominal strapping and supine posture in air. Further study of these factors may help explain the exact mechanisms of the increase in vital capacity observed in tetraplegic patients. The present study was a first step on this road. In conclusion, the study demonstrates a significant respiratory function benefit for partial isothermic immersion, and no acute contraindication of aquatic activity affecting pulmonary function has been demonstrated for tetraplegic patients.


   Footnotes
 
Abbreviations: CI = confidence interval; ERV = expiratory reserve volume; IC = inspiratory capacity; SVC = slow vital capacity

Received for publication February 23, 2004. Accepted for publication December 15, 2004.


   References
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

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