The employee appeals the compensation judge’s determination that the employee did not sustain a work-related injury on December 8, 2004.  We affirm.

Kevin Southerland, the employee, worked for Kables, Inc./Slumberland Furniture, the employer, as a delivery person.  The employee’s duties were to load a delivery truck in the morning and deliver furniture to customers.  Every Wednesday, the employee, with the help of two other employees, Robert Wilkens and Ralph Galvin, unloaded a semi-trailer of furniture at the employer’s warehouse.  Chad Hagen, the warehouse manager, checked the furniture SCU numbers as the three employees brought the furniture into the warehouse.  After the furniture was unloaded, the four employees typically took a doughnut break for 15 to 30 minutes.  After the break, the employee and Mr. Wilkens would load the delivery truck and leave to make deliveries.

On Wednesday, December 8, 2004, the employee, together with Mr. Wilkens and Mr. Galvin, were unloading furniture from a semi-truck trailer.  In the process, the employee was struck on the left side of his chest by a sofa-sleeper weighing approximately 300 pounds.  When the unloading was completed, the group took a doughnut break.

At some point, the employee began coughing and had difficulty breathing.  The time the employee began coughing was disputed by the parties.  The employee testified that when the sofa struck his chest, he immediately suffered a loss of breath and began coughing and wheezing.  Mr. Wilkins also testified that immediately after the incident the employee was pale and was coughing a lot.  He testified the employee sat down in a chair and did not assist in unloading the remaining furniture from the trailer.  Mr. Hagen observed the employee struggle with a large sofa sleeper but did not see the employee get struck by the sofa sleeper.  After the sofa was unloaded, all four employees took part in a doughnut break which lasted approximately twenty minutes.  During the doughnut break, Mr. Hagen did not observe the employee coughing.  Approximately an hour after the truck was unloaded, Mr. Hagen testified the employee was sitting in a chair and coughing.  At some point, Mr. Hagen took the employee home.  Mr. Galvin testified the last piece of furniture on the trailer, a sofa, tipped as the employee was unloading it, but stated the sofa did not strike the employee.  During the doughnut break, Mr. Galvin stated he observed nothing unusual about the employee.  Mr. Galvin then left to do some paper work.  Mr. Galvin testified he returned to the warehouse approximately twenty minutes later and observed the employee coughing.

The employee went to the Hutchinson Medical Center on December 8, 2004, complaining of acute left-sided chest pain which developed at work.  The employee was seen by Colleen Caspers, a nurse practitioner, who ordered a blood test which the records reflect was obtained at 10:27 a.m.  Ms. Casper referred the employee to Dr. David Byron, and the employee was admitted to the hospital.  Dr. Byron recorded a history that the employee was working at Slumberland doing some lifting and had the sudden onset of left-sided chest pain.  Dr. Byron noted the employee smoked and used marijuana regularly.  The diagnosis was spontaneous pneumothorax.^[1]  With the assistance of Dr. H. Chris Remucal, Dr. Byron performed a chest tube thoracostomy.  The following day, the employee’s left lung again collapsed and Dr. Remucal reconnected the chest tube and later performed a chemical pleurodesis procedure.  The employee was discharged from the hospital on December 14, 2004.

Dr. Thomas Mulrooney reviewed the employee’s medical records at the request of the employer and insurer and prepared a medical report dated May 12, 2005.  The doctor was asked to assume the following facts: the employee was unloading furniture from a semi-trailer when the sofa began to tip off a two-wheeled cart; the employee caught the sofa with his arm and another employee then came to help and together they pushed the furniture upright; the employee did not believe that he was struck by the sofa or, if he was, the blow was light and did not leave any mark; following this incident, the employee entered the warehouse for a short break; about thirty minutes into the break, the employee began to cough vigorously and was taken home at about 11:00 a.m.  Based upon these hypothetical facts and his review of the medical records, Dr. Mulrooney opined the employee sustained a primary spontaneous pneumothorax.  The doctor stated this disorder is nearly always the result of rupture of congenital blebs.^[2]  Dr. Mulrooney stated heavy smoking appears to increase significantly the risk of spontaneous pneumothorax and the employee was a cigarette smoker.  The doctor stated pneumothorax was not a disorder that appears to be associated with effort.  Rather, in most cases, the onset of symptoms occurs when the victim is at rest, as was the case with the employee.  Dr. Mulrooney opined any connection with the furniture moving was coincidental and stated the exertion did not appear to have been extreme and there was no direct blow to the chest.  Had the pneumothorax been caused by a blow to the chest, Dr. Mulrooney opined it would have resulted in symptoms immediately and certainly in less than thirty minutes after the blow.  In any event, the doctor stated a light glancing blow would not cause a collapsed lung.

In an August 2006 medical report, Dr. Remucal stated the employee’s injury,

The employee filed a claim petition seeking medical expenses and wage loss benefits as a result of an alleged personal injury on December 8, 2004.  Following a hearing, the compensation judge issued a findings and order in which the judge found that in the process of unloading a sofa, the front bottom edge of the sofa struck the employee on the chest.  The compensation judge, however, adopted the opinions of Dr. Mulrooney and concluded the employee did not sustain a personal injury on December 8, 2004, and found the employee’s work activities were not a substantial contributing cause of the onset of his pneumothorax.  The employee appeals.

The employee contends the compensation judge’s adoption of Dr. Mulrooney’s opinions is clearly erroneous because the doctor lacked adequate foundation for his opinions.  The employee argues Dr. Mulrooney’s opinions were based on erroneous facts and facts not in evidence.  There is no question, the employee contends, that he struggled while unloading the sofa sleeper and the compensation judge found the employee was struck on the chest by the bottom edge of the sofa.  Since the judge found the employee was struck by the sofa, the employee asserts the timing of the events is critical because Dr. Mulrooney bases his opinions on the assumption the employee did not start coughing until at least thirty minutes after the incident.  This assumption, the employee asserts, is unsupported by substantial evidence.

The foundation for Dr. Mulrooney’s opinions, the employee contends, depends upon the doctor’s assumption that the employee did not start coughing until thirty minutes after the incident with the couch.  The thirty-minute time frame, the employee argues, presumably relies upon the timing of the events as related by Mr. Galvin and Mr. Hagen.  Mr. Galvin testified they began to unload the trailer at 8:30 a.m. on December 8, 2004.  Both Mr. Galvin and Mr. Hagen testified it normally took from one to one and half hours to unload the semi.  After the semi was unloaded, Mr. Galvin and Mr. Hagen testified they took a doughnut break and then did paperwork totaling forty-five minutes.  Mr. Hagen then gave the employee a ride home which took between three and ten minutes and his wife then drove him to the hospital.  The hospital records document that blood was drawn from the employee at 10:27 a.m.

The employee, Rob Wilkens, Ralph Galvin, and Chad Hagen each testified at the hearing.  Their recollections and observations did not all agree.  The employee and Mr. Wilkens testified the employee started coughing immediately after being struck in the chest by the sofa.  Mr. Gavin testified the sofa that struck the employee was the last one taken off the truck after which all four employees took a doughnut break.  Mr. Galvin testified the employee appeared normal at this time.  Mr. Galvin then went into his office to do paperwork and when he returned, he saw the employee sitting in a chair coughing.  Mr. Hagen also testified that he observed no problems with the employee during the doughnut break, following which he also left to do paperwork.  When he returned to the warehouse, he observed the employee sitting and coughing.  The compensation judge concluded it was most likely the employee started coughing some thirty minutes after the unloading was completed.  This conclusion is supported by the testimony of Mr. Galvin and Mr. Hagen.  Accordingly, Dr. Mulrooney’s assumption the employee starting coughing thirty minutes after the unloading incident is supported by substantial evidence.  We do not, however, find the exact timing of the events to be critical.

Dr. Mulrooney opined the employee sustained a spontaneous pneumothorax which was the result the of the rupture of congenital blebs.  The doctor stated the main risk factor for a spontaneous pneumothorax was cigarette smoking and the employee was a smoker.  Further, Dr. Mulrooney opined a spontaneous pneumothorax is not a disorder that is associated with effort.  Dr. Mulrooney stated in most cases the onset of symptoms occurs when the victim is at rest, which, again, is consistent with the testimony of Mr. Galvin and Mr. Hagen.  The history recorded by Dr. Byron was onset of chest pain while the employee was lifting and neither his examination records or those of Ms. Caspars document any external injury to the employee’s chest.  This is consistent with Dr. Mulrooney’s conclusion that a light-glancing blow to the chest would not be sufficient to cause a collapsed lung.  A fair reading of Dr. Mulrooney’s report establishes that the time the employee began coughing was not the only basis for his causation opinion.  The doctor concluded that absent significant trauma forceful enough to fracture a rib, the employee’s pneumothorax likely resulted from his cigarette smoking.  Dr. Mulrooney stated,

In this case, there was conflicting testimony from the lay witnesses and the expert medical witnesses.  The compensation judge adopted the opinions of Dr. Mulrooney over those of Dr. Remucal.  It is the responsibility of the compensation judge as a trier of fact to resolve conflicts in expert testimony.  See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  Dr. Mulrooney’s opinions were adequately founded and the compensation judge could reasonably rely upon them.  Accordingly, the compensation judge’s decision is supported by substantial evidence, and it must be affirmed.  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).