The employer and insurer appeal from the compensation judge’s decision ordering the payment of rehabilitation expenses associated with exploring the possibility of retraining the employee as a certified nurse practitioner.  We affirm.

The employee is a resident of Wheaton, Minnesota.  After obtaining a two-year nursing degree, she began working as a registered nurse for the employer, St. Francis Medical Center, in Breckenridge, Minnesota.  On November 14, 1996, the employee sustained a work injury to her cervical spine, thoracic spine, and left arm.  As of the date of injury, the employee was working full time at a weekly wage of $651.38.  As a result of the work injury, the employee subsequently developed chronic pain syndrome and reflex sympathetic dystrophy of her left upper extremity.

The employer accommodated the employee in light duty work until April 30, 1998.  Subsequently, the employee sought nursing work with the assistance of a Qualified Rehabilitation Consultant (QRC).  In September 1998, the employee began working as an independent contractor conducting insurance physicals but this job provided only a very small income.  Rehabilitation efforts continued but the employee’s QRC was unable to identify any available nursing jobs within the employee’s restrictions in her labor market.  In 2000, the employee worked briefly in a second part-time job as a private duty nurse for an infant with cerebral palsy.

By 2002, the employee and her QRC began considering retraining, focusing on the field of physician’s assistant or nurse practitioner. A labor market survey for nurse practitioner positions done at that time revealed few openings for nurse practitioners in the local labor market and the employee’s QRC decided against recommending a retraining plan for the employee.  The employee continued to look for work as a registered nurse within her restrictions but was unable to find employment.

In September 2004, the employee began working part time for the Center for Natural Healing Arts (CNHA), a naturopathic “alternative medicine” clinic in Alexandria, Minnesota, 70 miles from her home.  Her duties included assisting with physical examinations and measurements.  The employee also performed blood draws at the clinic to be sent for testing at a medical facility.

In March 2006, the employee’s QRC prepared a retraining plan proposing that the employee be provided with four years of retraining at the Minnesota State University at Moorhead to complete a B.S.N. degree and an M.S. degree in nursing in order to qualify the employee to work as a certified nurse practitioner.  Estimated costs of the plan were $74,149.00.  The plan also contemplated that the employee would remain employed with CNHA after plan completion.

By September 2006, the employee was working up to three days a week at CNHA and was being paid $27.50 an hour.  She was also paid $50.00 a week travel allowance to assist in commuting expenses.  Between January 1, 2006, and April 11, 2006, the employee earned $11,231.27 from CNHA, averaging more than her date-of-injury weekly wage.

The employee’s medical restrictions as of October 2005 limited her to working alternate days, optimally no more than five or six hours per day, in sedentary employment with no squatting, crawling, crouching, climbing, or reaching above shoulder level.  She was to avoid extended periods in static positions and lifting was limited to 5 pounds occasionally and 20 pounds rarely.

The employer and insurer objected to the retraining plan, and a hearing was held before a compensation judge on September 13, 2006.  The employee and her QRC testified in support of the employee’s claims; David Berdahl, a vocational expert, testified for the employer and insurer.

In her findings and order dated November 28, 2006, the compensation judge found that the employee had failed to establish either that the retraining plan would result in reasonably obtainable employment or that retraining would provide her with an economic status greater than what was available to her through her employment with CNHA.^[1]

The employee’s employment with CNHA ended on February 20, 2007.  The employee started searching for work and within the next month had contacted all of the hospitals, clinics, and nursing homes within 70 miles of her home.  By October 2007, the employee had not found work within her restrictions and her QRC requested that job placement services be instituted.  A job placement plan and agreement was signed on October 25, 2007.  In early November, the employee was offered a position by an employer she had originally contacted in March 2007 and placement assistance was put on hold.

The job offer in November 2007 was for a position as Director of Quality Assurance for the Coteau des Prairies Hospital in Sisseton, South Dakota, working eight hours a day and three days a week with an hourly wage of $25.  The employee started the job on November 13, 2007.  The job exceeded the employee’s restrictions in that it required extended periods of sitting and typing and full eight-hour daily shifts.  The employee was able to perform the job, however, until July 2008, when a staff restructuring at the hospital resulted in additional duties outside the employee’s restrictions being added to the position.

Placement services were reinstituted in January 2009.  The employee eventually was offered a temporary job auditing medical records on site at various hospitals for a firm known as Q Mark.  This was a seasonal contract position expected to last about two months.  It was paid as piecework on a per chart audited basis with reimbursement of travel expenses.  The employee worked in this job during the spring of 2009 and earned about $16,000.00.

Because the Q Mark job was known to be temporary, placement services continued both during and after it.  The employee’s QRC also recommended that the employee’s rehabilitation plan be amended to again include exploration of retraining as a certified nurse practitioner.  The employer and insurer opposed this recommendation and the employee filed a rehabilitation request on July 23, 2009.  A rehabilitation response opposing the requested change was filed on July 24, 2009.

In August 2009, the employee’s treating physician modified her restrictions to permit her to work full eight-hour shifts.

An administrative conference on September 1, 2009, resulted in an administrative decision denying the employee’s rehabilitation request.  The employee filed a request for formal hearing on September 23, 2009.

Early in 2010, the employee was again offered the two-month seasonal job for Q Mark, although it is not clear from the record whether that temporary position had started as of the date of the hearing.  Despite an intensive job placement effort and job search through early February 2010, no other suitable employment has been found for the employee.

A hearing was held on April 21, 2010, before a compensation judge of the Office of Administrative Hearings.  The employee and her QRC, Ione Tollefson, testified at the hearing.  Ms. Tollefson testified that the number of employers in the employee’s labor market employing nurse practitioners had increased significantly since 2006.  She also testified that the number of opportunities in this field was expected to continue to grow.  In addition, it was her opinion that the recent change to the employee’s restrictions, allowing allow her to work eight-hour days, would increase her chances of finding part-time employment in the new field.  The employer and insurer offered no witnesses and relied on the opinion of David Berdahl from 2006.  Following the hearing, the compensation judge found that it was reasonable to allow a change of the employee’s rehabilitation plan to permit her QRC to perform a labor market survey and explore whether retraining as a nurse practitioner would be reasonable.  The employer and insurer appeal.

At the hearing, the employer and insurer argued that consideration of retraining as a certified nurse practitioner was foreclosed by the November 2006 findings and order. The compensation judge concluded that res judicata did not bar the employee’s request to modify the rehabilitation plan to permit a labor market survey and other steps in exploring retraining as a nurse practitioner in light of the changed circumstances since the 2006 hearing, including the employee’s loss of her job with CNHA, the prospect of greater employment opportunities as a nurse practitioner, and the modification of the employee’s restrictions.  The employer and insurer argue on appeal that the compensation judge erred.  They point out that the compensation judge in 2006 considered and denied a retraining plan for a four year program of training to qualify the employee for employment as a certified nurse practitioner, the same employment considered in the present rehabilitation request.

Res judicata or claim preclusion is essentially a finality doctrine in which “a final judgment on the merits bars a second suit for the same claim by parties.”  Kaiser v. Northern States Power Co., 353 N.W.2d 899, 902 (Minn. 1984).  The principles of res judicata are applicable in workers’ compensation proceedings.  Alexander v. Kenneth R. LaLonde Enters., 288 N.W.2d 18, 31 W.C.D. 407 (Minn. 1980).  Collateral estoppel, or issue preclusion, is a limited form of res judicata by which a prior judgment is conclusive in a later suit between the same parties as to determinative issues finally decided in the former suit.  Travelers Ins. Co. v. Thompson, 163 N.W.2d 289 (Minn. 1969).

However, the doctrine of res judicata applies in workers’ compensation cases only with respect to issues and claims that were in fact decided in an earlier decision.  Fischer v. Saga Corp., 498 N.W.2d 449, 48 W.C.D. 368 (Minn. 1993).  Where the question at the later hearing is one of benefit eligibility which depends on factual circumstances subsequent to the prior decision, the prior determination is res judicata only with respect to the period considered in the former hearing.  See, e.g., Hatfield v. Lenort, 69 W.C.D. 285 (W.C.C.A. 2009), and cases cited therein.  This principle is applicable to the issue of whether to approve a modification to a rehabilitation plan.  Cf., e.g., Burnette v. Episcopal Community Servs., slip op. (W.C.C.A. March 28, 1994) (a prior denial of job placement assistance predicated on a post-injury offer of suitable employment with the employer had no res judicata effect on a subsequent request to modify the employee’s rehabilitation plan to focus on outside job placement, where there was a change in circumstances affecting the suitability of the post-injury job with the employer).

The 2006 determination was based on factual findings that reflected the circumstances then present concerning the employee’s post-injury employment and labor market.  The factors on which the determination was based were ones which might change in the future, and the determination made in 2006 does not have res judicata effect if the employee’s circumstances have changed since that time. The compensation judge found that the employee’s situation has changed in material respects in the three and one half years since the 2006 findings and order. The employer and insurer contend that the changes are minimal and largely immaterial to the original reasons for the prior denial of retraining, and that the employee thus failed to meet her burden of proof.

We note that the prior decision was predicated in significant part on the comparison of the proposed new occupation with the post-injury employment the employee had at that time with CNHA.  That employment is no longer available and the employee has not been able to find work within her restrictions. As the compensation judge found, this is a significant change in the employee’s circumstances with respect to vocational rehabilitation.  The prior decision was also based on the nature of the labor market for nurse practitioner positions in 2006; the compensation judge in the present proceeding accepted expert testimony that these factors had changed.  Whether these changes are material is a question dependent in part on the weight of the evidence, on which we must generally give deference to the compensation judge’s conclusions.

The employer and insurer also argue that the employee’s claim is barred by this court’s earlier decision affirming the denial of the retraining claim. The employer and insurer characterize the decision as establishing the “law of the case” as being that retraining is never appropriate for the employee. The doctrine of law of the case seeks to maintain uniformity within a case by ensuring that a rule of law, once determined in that case, will not be differently applied at different stages of the case.  Cf., Black’s Law Dictionary, “Law of the Case,” 798 (5th ed. 1979).  The doctrine is inapplicable here as the issues resolved in the 2006 decision were factual and not questions of law.

In Poole v. Farmstead Foods, 42 W.C.D. 970 (W.C.C.A. 1989), this court identified several factors relevant to whether a proposed plan of retraining should be approved.  The employer and insurer argue that the compensation judge should have considered the Poole factors in deciding the employee’s claim.  They further argue that the evidence offered by the employee failed to establish a claim for retraining as a nurse practitioner when the Poole factors are applied.

The issue at the hearing, however, was not approval for a retraining plan.  The issue was whether the employee’s rehabilitation plan should be amended to permit the QRC to conduct a labor market survey and take other appropriate steps to explore and investigate retraining as a nurse practitioner as a reasonable rehabilitation option for the employee.  As we have previously noted, the standard of proof in such a case does not require an employee to address the Poole factors.  Johnson v. Arctic Cat, 64 W.C.D. 106 (W.C.C.A. 2004).  The employee has an impaired earning capacity as a result of the work injury and, as a result, she is entitled to an evaluation for purposes of developing a retraining plan.  Siltman v. Partridge River, Inc., 523 N.W.2d 491, 52 W.C.D. 282 (Minn. 1994).

Substantial evidence supports the compensation judge’s approval of the requested amendment to the employee’s rehabilitation plan, and we affirm.