The employee appeals the compensation judge’s finding that the proposed surgery is not causally related to the employee’s work injury, arguing that a prior finding of causation is res judicata on that issue.  The employee also appeals from the denial of his claim for payment for a medical consultation related to a cardiac condition.  We affirm, as modified.

On October 11, 2007, Daniel Hatfield, the employee, injured his left shoulder and neck while working as a laborer for Mark J. Lenort, the employer, who was insured for workers’ compensation liability by Farm Bureau Mutual Group, the insurer.  The employer operates a pig farm; the employee was injured as he hauled dead pigs from the pens.  The employer and insurer admitted liability for a left shoulder injury and a temporary cervical injury, and paid various workers’ compensation benefits.

The employee experienced acute pain in his neck and down his left arm to his hand.  He treated with Dr. Harry Miller at Fairmont Medical Center.  X-rays indicated degenerative changes at C5-6.  Dr. Miller referred the employee for a cervical MRI on October 26, 2007.  The MRI indicated degenerative changes at C5-6 and disc bulging with marginal osteophyte formation.  Dr. Miller noted that there was no herniated disc.  The employee underwent a bone scan on November 5, 2007, which indicated increased uptake at C5-6, a suspected degenerative change.  On examination, Dr. Miller noted an absent bicep-tricep reflex in the left arm.  The employee continued to experience neck pain and pain radiating into his left shoulder and down to the fingertips of his left hand, and also numbness and weakness in his left hand.  Dr. Miller prescribed pain medication and referred the employee to Dr. Michael Puumala, a neurosurgeon, for further evaluation.  Dr. Miller also indicated that the employee is a smoker and “may not be a significant candidate for surgical intervention unless he quits.”

Dr. Puumala examined the employee on December 17, 2007.  Based upon examination findings, Dr. Puumala detected a C6 radiculopathy and referred the employee for an additional MRI scan.  A January 13, 2008, MRI indicated findings at the C5-6 levels that were consistent with a C6 radiculopathy.  Dr. Puumala referred the employee for physical therapy.  The employee continued to experience neck and left arm pain.  During an examination of the employee on February 25, 2008, Dr. Puumala noted a decrease in the employee’s left bicep reflex, which he stated was an objective sign of C6 radiculopathy.  Dr. Puumala diagnosed degenerative disc disease at C5-6 with C6 left-sided radiculopathy, opined that the employee’s work injury was a substantial contributing factor to the employee’s condition, and recommended surgery at C5-6.  Dr. Puumala testified that the employee had undergone fairly extensive conservative treatment and therefore it was reasonable to consider surgery.  He proposed an anterior cervical discectomy and interbody fusion at C5-6.

On March 17, 2008, the employee filed a medical request for payment of expenses related to cervical fusion surgery.  The employer and insurer denied the request, arguing that the surgery was not reasonable and necessary.  On May 16, 2008, the employee was examined by Dr. David Florence at the employer and insurer’s request.  Dr. Florence noted that x-rays indicated degenerative changes at C5-6, and that the MRI indicated a C5-6 protrusion with no nerve root impingement.  He diagnosed neck and left shoulder pain with possible C6 radiculopathy, left hand numbness, nicotine dependence, depression, and functional overlay.  Dr. Florence concluded that the employee injured his left shoulder on October 11, 2007, and possibly developed neck symptoms as a result of chiropractic manipulation.  Dr. Florence recommended that the employee undergo an EMG to determine whether the employee’s left hand symptoms were radicular and whether there was radiculopathy at C6 on the left.  Even if the EMG was positive, Dr. Florence indicated that an anterior cervical discectomy and fusion might not be appropriate because of the employee’s osteopenia, or bone loss, and his smoking history, which would impair the healing process.

On May 13, 2008, the employee treated at Mayo Clinic/Fairmont Medical Center with Dr. Durga Giri for chest discomfort, “mainly tenderness around the left supraspinatus.”  The clinical notes indicate that his discomfort was around the left side of his neck radiating down the left shoulder; the clinical notes state that the employee was worried about possible heart disease.  The employee underwent an EKG, which was interpreted as being normal.

In a June 11, 2008, deposition, Dr. Puumala opined that the employee has pathology at C5-6, including numbness and absence of reflex, and that an EMG would not be necessary to confirm the diagnosis of radiculopathy at the C5-6 level.  Dr. Puumala also opined that a negative EMG would not necessarily preclude surgery.  He also opined that he did not see any evidence that the employee has osteopenia and that the employee’s smoking history would not preclude surgery.  He acknowledged that smoking “is known to reduce the efficacy of fusion,” but that the adverse effects of smoking have been decreased with the advent of improved medical technology.

A hearing was held on June 18, 2008.  In Findings and Order served and filed July 10, 2008, Compensation Judge Nancy Olson found that the employee’s work injury was a substantial contributing cause of his cervical spine condition for which Dr. Puumala recommended surgery, and rejected Dr. Florence’s opinion that the work injury was solely a temporary left shoulder injury.  Although the judge concluded that the need for the requested surgery was causally related to the employee’s injury, she accepted Dr. Florence’s opinion that the surgery was not reasonable and necessary at that time.  Based upon Dr. Florence’s opinion, the judge indicated that the employee should have an EMG and stop smoking prior to surgery.

On August 13, 2008, the employee underwent an EMG, which indicated a chronic/active left C7 radiculopathy with ongoing reinnervation and no evidence of a left arm mononeuropathy.  In an addendum report dated September 29, 2008, Dr. Florence indicated that there was irritation of the left C7 nerve root, but that it was healing and that there was no true radiculopathy.  Dr. Florence did not think the results were compatible with the employee’s symptoms of severe pain, and that the employee’s condition could be associated with functional overlay or depression.  Dr. Florence also opined that there were no findings to support surgery and that surgery would not be successful based upon the employee’s history of smoking and other findings, including osteopenia.

On August 18, 2008, the employee filed another medical request for approval of the proposed cervical fusion surgery, and also requested payment for the employee’s treatment at Fairmont Medical Center on May 13, 2008.  The employer and insurer denied the requests.  In October 2008, the parties reached a settlement that closed out chiropractic care, acupuncture, acupressure, physical therapy, chronic pain programs, MAPS treatment, and psychiatric and psychological treatment.  Claims for other medical expenses, including the proposed cervical fusion surgery, remained open.

The employee treated at Fairmont Medical Center with Dr. Giri for smoking cessation treatment.  As of September 2, 2008, the employee smoked half of a pack of cigarettes per day.  The employee testified that he stopped smoking as of September 12, 2008.

A hearing was held on December 18, 2008.  Compensation Judge Danny Kelly denied the employee’s medical request, finding that the proposed surgery was not reasonable and necessary or causally related to the employee’s work injury.  The employee appeals.

On appeal, the Workers' Compensation Court of Appeals must determine whether "the findings of fact and order [are] clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted."  Minn. Stat. § 176.421, subd. 1 (2008).  Substantial evidence supports the findings if, in the context of the entire record, "they are supported by evidence that a reasonable mind might accept as adequate."  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).  In addition, "a decision which rests upon the application of a statute or rule to essentially undisputed facts generally involves a question of law which [the Workers' Compensation Court of Appeals] may consider de novo."  Krovchuk v. Koch Oil Refinery, 48 W.C.D. 607, 608 (W.C.C.A. 1993), summarily aff’d (Minn. June 3, 1993).

The employee argues that the issue of whether the proposed surgery was causally related to his work injury has been determined and therefore, under principles of res judicata, the earlier determination of a causal relationship is final.  The employee also argues that the compensation judge erred by not considering the prior findings concerning surgery that pre-conditioned the proposed surgery on the employee undergoing an EMG and ceasing to smoke.  The employee argues that he has met all the pre-conditions that support the reasonableness of the proposed cervical fusion surgery.

Res judicata is a doctrine bringing finality to legal proceedings in which “a final judgment on the merits bars a second suit for the same claim” by the same parties.  Kaiser v. Northern States Power Co., 353 N.W.2d 899, 902 (Minn. 1984).  Principles of res judicata are applicable in workers’ compensation proceedings.  See, e.g., Alexander v. Kenneth R. LaLonde Enters., 288 N.W.2d 18, 31 W.C.D. 407 (Minn. 1980).  However, res judicata applies in workers’ compensation cases only with respect to issues specifically litigated and decided in prior proceedings.  See, e.g., Fischer v. Saga Corp., 498 N.W.2d 449, 450, 48 W.C.D. 368, 369 (Minn. 1993); see also Westendorf v. Campbell Soup Co., 243 N.W.2d 157, 158, 28 W.C.D. 460, 460 (Minn. 1976).

The res judicata effect of a prior workers' compensation determination is limited to those issues and facts material to, and determinative of, benefit eligibility and events or circumstances previously at issue and in existence as of the date of the prior hearing.  Where benefit eligibility depends upon factual circumstances subsequent to the prior hearing, the prior determination is res judicata only with respect to the period considered in the former hearing.  See, e.g., Saenger v. Liberty Carton Co., 316 N.W.2d 737, 34 W.C.D. 499 (Minn. 1982) (finding that the employee was not totally disabled and had retired from the labor market in 1977 did not preclude new determination of these issues for subsequent period); Sjerven v. Strite-Anderson Mfg. Co., 45 W.C.D. 469, 472-73 (W.C.C.A. 1991) (denial of temporary benefits res judicata only for the periods considered at the prior hearing); Tottenham v. Eaton Char-Lynn Corp., 43 W.C.D. 71 (W.C.C.A. 1990) (earning capacity); Drexler v. Armour & Co., 40 W.C.D. 430 (W.C.C.A. 1987) (withdrawal from labor market and lack of diligent job search).  Issues involving the need for, or the reasonableness or effectiveness of, medical treatment are among those which may be affected by changed circumstances so as to preclude a res judicata effect on determinations for subsequent periods.  See Duncan v. Contact Cartage, Inc., slip op. (W.C.C.A. 1994) (approval of request to change doctors affirmed “based on the changed circumstances” since prior denial of request); Cook v. Lloyd's Food Products, Inc., slip op. (W.C.C.A. Sept. 22, 1992) (prior finding denying need for surgery was not res judicata for later periods); Gullickson v. Commonwealth Elec. Co., slip op. (W.C.C.A. Nov. 28, 1989) (medical restrictions determined for a prior period were not res judicata for a subsequent period).

In this case, the hearing on the employee’s first surgery request was held on June 18, 2008.  Following that hearing, in unappealed findings served and filed July 10, 2008, a compensation judge determined that the employee’s work injury was causally related to the cervical spine condition for which Dr. Puumala recommended surgery.  The judge, however, concluded that surgery was not reasonable and necessary at that time, relying on Dr. Florence’s recommendation for an EMG study and smoking cessation before surgery was to be considered.

Since the first hearing, the employee has complied with the preconditions set out in the initial findings and order; he ceased smoking and has undergone an EMG which indicated a chronic left C7 radiculopathy.  Dr. Miller reviewed the results of the EMG and diagnosed a C7 radiculopathy.  Dr. Florence, however, reviewed the results of that EMG, and, in an addendum report dated September 29, 2008, indicated that there was irritation of the left C7 nerve root, but that it was healing and that there was no true radiculopathy.  Dr. Florence again recommended against surgery, opining that the employee’s physical, EMG and MRI findings did not provide support for proceeding with surgery.  The record contains no follow-up report by Dr. Puumala addressing the EMG results.

The compensation judge who presided at the second hearing reviewed the medical records generated since the first hearing, and noted the conflicting medical opinions, including Dr. Florence’s opinion issued after his review of the employee’s EMG results.  Based on the evidence in the record, the compensation judge could reasonably conclude that the employee’s circumstances have changed since the June hearing and, therefore, that he was not restricted by the initial findings concerning the issue of reasonableness and necessity of surgery.

The compensation judge accepted Dr. Florence’s opinion that there were no findings to support surgery and that surgery would not be successful based upon the employee’s history of smoking and other findings, including osteopenia.  The compensation judge found that Dr. Puumala had indicated a C6 radiculopathy, not a C7, and that he did not have foundation for his opinion since he had not reviewed the EMG results or Dr. Miller’s notes after the EMG.  While any alleged deficiencies in Dr. Puumala’s opinion go more to weight than foundation, they are factors for the compensation judge to evaluate.  See Drews v. Kohl’s, 55 W.C.D. 33 (W.C.C.A. 1996).  It is the compensation judge's responsibility, as trier of fact, to resolve conflicts in expert testimony.  Nord v. City of Cook, 360 N.W.2d 337, 342, 37 W.C.D. 364, 372 (Minn. 1985).  The compensation judge concluded that the employee presently lacks medical support for the recommended fusion surgery intended to relieve symptoms of C6 radiculopathy.  Substantial evidence supports that finding, and we affirm.  See Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).

We agree with the employee, however, that the compensation judge who presided at the second hearing in December 2008 could not decide anew on the causation issue.  As we have already noted, his determination that the employee has not established the need for surgery is supported by substantial evidence in the record.  But given the unappealed Finding No. 4, from the initial findings and order, served and filed July 10, 2008 - - that the employee’s “work injury is a substantial contributing cause of the Employee’s cervical spine condition for which Dr. Pummala is recommending cervical fusion,” - - the issue of causation was not at issue at the second hearing.

Neither party litigated the issue of causation at the second hearing.  At the hearing, the employer and insurer did not dispute causation, but instead argued that surgery was contraindicated.  In their appellate brief, the employer and insurer note that “[t]he issue before Judge Kelly was whether this surgery was reasonable and necessary regardless of Judge Olson’s prior ruling.”

Because the issue at the second hearing in December 2008 was whether the surgery was reasonable and necessary, the compensation judge’s reference to causation appears to be inadvertent and therefore we modify that finding to delete the reference to “causation.”  For clarification purposes, we modify Finding No.  17, in the findings and order issued on January 14, 2009, to read as follows:

The employee also appeals the compensation judge’s denial of the employee’s request for payment related to treatment at Fairmont Medical Center on May 13, 2008.  The employee argues that this clinical visit was compensable because it was necessary for diagnosis.  Referral for diagnostic testing to evaluate or rule out an alternative explanation or treatment for a work injury is generally compensable, whether or not the condition or diagnosis evaluated is found to be work-related.  Caizzo v. McDonald’s, 65 W.C.D. 378 (W.C.C.A. 2005).  The employee treats at Fairmont Medical Center for other medical conditions, not just for his work injury.  The employee sought treatment on May 13, 2008, regarding chest discomfort, “mainly tenderness around the left supraspinatus.”  The clinical notes indicate that the discomfort was around the left side of the neck radiating down the left shoulder and that the employee was worried about possible heart disease.  An EKG conducted at that time had normal results.

The compensation judge noted the employee’s history of atypical chest pain treatment and found that this clinical visit was related to a pre-existing condition.  The employee has been diagnosed in the past with mild coronary artery disease and has undergone angiograms.  The employee argues that he was being evaluated for “cervical neuralgia.”  The clinical note indicates that the employee “[i]s currently dealing with Workers’ Compensation with regards to further evaluation for cervical neuralgia,” not that he was being evaluated for cervical neuralgia at that time.  Where evidence is conflicting or more than one inference may reasonably be drawn from the evidence, the findings of the compensation judge are to be upheld.  Redgate v. Sroga's Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).  The compensation judge could reasonably conclude that the employee’s May 13, 2008, clinical visit was not related to his work injury, and we affirm.