Fig. 11.1
Soda pop can model of postural control. The diaphragm is the body’s major pressure regulator, completely separating the thoracic and abdominal chambers. Together with the superior valve (vocal folds) and inferior valve (pelvic floor), the diaphragm simultaneously controls trunk pressure for breathing and postural stability, which functionally links the top and the bottom of the can
When disease or trauma, such as a phrenic nerve injury, prevents or limits the diaphragm from significantly contributing to inspiration, there is a substantial risk of secondary problems with balance and spinal control [9, 10]. The altered motor control of the trunk can lead to musculoskeletal consequences including chronic pain (most often low back, neck, shoulder, or hip pain), shoulder range of motion restrictions, and/or pelvic floor dysfunction [8, 11]. The relationship of the diaphragm to upright postural control goes far beyond inspiration. The critical relationship of the diaphragm to respiratory and postural control function means that all patients with phrenic nerve paralysis should be screened for impairments of both functions.
Physical Therapy (PT) Preoperative Assessment
A physical therapist should assess the patient’s breathing and postural presentation with this broader understanding of the diaphragm’s multiple roles. Recommended assessments are listed in Table 11.1.
Table 11.1
Preoperative PT assessment should ideally address the following potential impairments
Respiration | Pulmonary function tests Compensatory breathing patterns, assessed in multiple postures and activities Chest wall excursion (CWE) Sleep-disordered breathing |
Endurance | Mobility tests (i.e., 6-min walk test) Perceived exertion during activities |
Postural alignment in upright, especially | Spine and neck Rib cage Shoulders Pelvis/hips Pediatric vs. adults |
Postural stability | Balance Gait deviations Pain Continence |
Respiration
Pulmonary Function Tests (PFT)
The combination of forced vital capacity (FVC) and the ratio of forced expiratory volume in one second to FVC (FEV1/FVC) are commonly used to clarify the severity of the lung restriction [12].
Compensatory Breathing Patterns
Analysis of the patient’s breathing pattern should be screened to identify which substitution patterns are used to achieve inspiratory lung volumes at rest (tidal volume) and with effort (vital capacity). Did the patient compensate in a functional manner or did the adaptive strategy add a burden to their pulmonary efficiency or postural control? PTs should assess the patient’s breathing strategy in multiple postures and activities presurgically for post-nerve regeneration comparison. Specific manual palpation exam of both hemidiaphragms during inhalation should be done to determine the contributing function of each hemidiaphragm for postsurgical comparison. Where available, a videofluoroscopy or an ultrasound test can confirm or refute the therapist’s manual palpation findings, which will be helpful for postoperative comparison [13, 14].
Chest Wall Excursion (CWE)
CWE measurements can quantify the chest movements and have been shown to have good inter-/intra-tester reliability after minimal training [15, 16]. Suggested measurement sites that capture the common variations of breathing patterns are (1) level of the third rib (axilla), (2) xiphoid process, and (3) half the distance from xiphoid to umbilicus [17] (Fig. 11.2). CWE should be tracked through rehabilitation, hopefully showing a shift downward (increased diaphragm excursion and decreased upper chest accessory muscle recruitment), and a more symmetrical response.
Fig. 11.2
Chest wall excursion (CWE) circumferential measurement sites: Top line: level of the third rib (axilla). Middle line: xiphoid process. Bottom line: half the distance between the xiphoid process and the umbilicus
Sleep
Breathing assessment should encompass the entire day, thus including sleep. Bilateral diaphragm paralysis will require nocturnal support such as CPAP (continuous positive airway pressure), BPAP (bi-level positive airway pressure), or mechanical ventilation, but mounting evidence suggests that unilateral diaphragm paralysis results in sleep-disordered breathing, cespecially during REM sleep, that often goes undetected [18–21]. Sleep studies should be a routine. PTs’ expertise in positioning may help patients and their physicians determine optimal sleep postures for oxygenation.
Endurance
Endurance tests must be individually chosen to ensure that the measure will be sensitive enough to capture a change postsurgically. A 6- or 12-min walk test is easy to administer clinically. The length of the test is determined by the patient’s level of impairment. A patient who is very weak may not be able to walk even 6 full minutes, whereas a patient with lesser impairment won’t show an endurance limitation until pushed a greater distance, like the full 12-min test [22]. There are many tests to choose from that are appropriate to the patient’s activity level [23].
Endurance could also be measured in terms of perceived exertion [24]. These subjective tests are particularly sensitive measures for patients who are very weak and may not show an increase in functional endurance such as walking further, but who may report less perceived effort for the same breathing and/or ADL skills recorded preoperatively.
Postural Alignment
Compensatory breathing patterns and the secondary impairments in balance may cause postural abnormalities [9]. This is particularly true for long-standing phrenic nerve paralysis where disuse has caused decreased chest wall and spinal mobility. Postural compensations may have developed slowly, and the patient may not even be aware of how much his posture has changed. Manual assessment of the entire rib cage and spine is necessary as restrictions are common in long-standing phrenic nerve paralysis. Shoulder range of motion (ROM) is often restricted secondary to diaphragm dysfunction. The weakness/paralysis disrupts the normal coupling effect between the shoulder and rib cage, especially when reaching above 90° of shoulder flexion [25, 26]. Limitations may also be noted at the hip/pelvis or neck due to compensatory breathing and/or postural control strategies. PTs should anticipate the need to mobilize noted musculoskeletal restrictions in order to regain maximal breathing and postural control function.
Postural impairments secondary to unilateral diaphragm paralysis are unique. These patients should be specifically screened for asymmetrical presentations. The development of chronic pain from asymmetric muscle use is a common complaint in this population but not yet researched (Fig. 11.3). Recent research suggests that patients with unilateral diaphragm paralysis have increased balance impairments because their center of mass is disturbed with every breath on a coronal plane, rather than just a sagittal plane [9]. Compensations to correct for this added postural burden could lead to repetitive muscle stress resulting in pain.
Fig. 11.3
Common postural compensations/abnormalities with unilateral phrenic nerve injury. Previously healthy, fit 67-year-old man with left paralyzed phrenic nerve of >12-month duration. Phrenic nerve graft surgery ~4 months prior to these pictures. One PT visit thus far. (a) Subject’s trunk is shortened on the left. He reported no postural asymmetry problems before phrenic nerve injury. (b) Lateral side bending to left shows normal range of motion for the right rib cage and lower trunk (intact phrenic nerve). Patient shows normal weight shift of hips to the right when side bending to left. (c) Lateral side bending to the right shows moderate restrictions in left lower rib cage and lower trunk (left paralyzed phrenic nerve). Note: (1) increased effort in his face, (2) decreased elbow extension, (3) decreased shoulder flexion, and (4) decreased weight shift onto left lower extremity. These restrictions limit more than inspiratory lung volumes, such as limitations in balance, gait, and reach, and may lead to chronic pain from long-standing altered mechanics
Pediatrics
Special consideration must be made in pediatrics as their chest wall and spine have not yet matured. Chronic phrenic nerve paralysis may lead to hypoplasia of the rib cage on the side of the paralysis which in turn will contribute to scoliosis forces and increased likelihood of more pronounced asymmetric postural alignment throughout the trunk (Fig. 11.4). Balance compensations will increase the risk of repetitive stress injuries as the child matures, which could lead to pain. Recent research shows that patients with chronic low back pain have weaker diaphragms than controls [27]. Long-term research has not yet been done with children with pediatric phrenic nerve injuries but would suggest that maturing with a chronically weak or paralyzed diaphragm would predispose these children to an increased risk of developing low back pain.
Fig. 11.4
Pediatric postural impairments 1–1/2-year-old girl surviving a traumatic vaginal birth with resultant bilateral phrenic nerve injury (left more impaired than right). Note postural shift of her trunk to left side (increased weight bearing on left leg) and increased lateral trunk flexion to left (increased skin fold), both likely balance compensations. Long term, this posturing will lead to greater scoliotic forces on her developing spine and greater risk of repetitive stress injuries (pain)
Postural Stability
There are numerous functional presentations of postural instability. Four specific impairments are detailed below.
Balance
The contributions of the diaphragm to postural stability are well established; thus, the assessment of balance (postural instability) should be a routine screening module of the PT evaluation. There are numerous balance tests from simple sitting perturbation tests, to timed single-limb stance tests, to sophisticated computerized limits of stability tests. Balance tests should be chosen for their sensitivity to change, availability of resources, and specificity to each individual patient’s capabilities [28].
Gait
Postural control impairments may be reflected as abnormal gait patterns and are highly variable with this population. Patients with mild postural instability are likely to stiffen their trunks in an attempt to improve postural stability. Common gait deviations associated with rigid trunks include decreased arm swing, decreased trunk rotation, slower cadence, and shorter steps. This pattern is very similar to other physical impairments such as chronic low back pain, neuromuscular weakness (Parkinson’s, multiple sclerosis, stroke, etc.), incontinence, and lower gastrointestinal dysfunctions (constipation, irritability, etc.) [29–31]. Careful screening is needed to ascertain gait deviations due to phrenic nerve paralysis vs. other underlying problems.
Patients with severe postural instability can’t stiffen their trunk because of extreme weakness or motor control issues. Their trunk is too floppy, and their gait pattern typically shows deviations such as excessive arm swing and excessive trunk movements, especially in the coronal plane. If the trunk is markedly unbalanced, the patient may require an assistive device or may no longer be ambulatory.
Pain
A possible long-term consequence of altered motor plans is pain due to malalignment or overuse syndromes [32, 33]. Pain conditions may reflect overuse of the accessory muscles due to the diaphragm weakness (neck or chest pain) or due to postural instability (pain anywhere from neck to hips) [34]. Patients with unilateral diaphragm paralysis may have pain related to rotational (torsion) forces due to asymmetric and rotary forces across their spine. Compensatory trunk postural strategies could result in pain down in the knee or ankle joints. All patients should be screened for secondary pain conditions.
Continence
The deep abdominal muscle shell that controls intra-abdominal pressure is comprised of the diaphragm as the top dome, the transversus abdominis and multifidus as the long cylinder, and the pelvic floor as the bottom sling. When one of those four muscles is impaired, it impairs the function of the whole abdominal complex. Thus, diaphragm dysfunction is highly associated with pelvic floor consequences, such as incontinence, and should be screened in this population [6, 8].
Summary
Diaphragm paralysis has marked implications for motor dysfunction beyond breathing and endurance impairments and should be carefully assessed and documented preoperatively in order to accurately assess the long-term outcomes of the phrenic nerve graft surgery. However, because this surgery is so specialized, requiring many patients to travel a great distance, there is little likelihood that the same PT will do the pre- and post-surgery which may limit the reliability of the measures. Research is needed to determine the optimal pre-/posttests that could be performed reliably on a nationwide basis.
Physical Therapy Rehabilitation
PT Reassessment
Following phrenic nerve graft surgery and after the confirmation from the surgeon that it is safe to start rehabilitation, the patient should be reassessed by PT. If the patient was not seen by PT preoperatively, the PT evaluation described earlier in the chapter should be done. Two specific tests should be included in the postsurgical rehabilitation phase of PT: (1) integument restrictions and (2) diaphragm responsiveness.
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