It is well established that in closing argument counsel is allowed broad latitude to draw reasonable inferences and conclusions from the evidence and disparities which may be found therein. See, e.g., Lebrecht v. Tuli (1985), 130 Ill. App.3d 457, 484, 473 N.E.2d 1322, appeal denied (1985), 106 Ill.2d 555; Oh Boy Grocers v. South East Food Liquor, Inc. (1979), 79 Ill. App.3d 252, 261, 398 N.E.2d 269, appeal denied (1980), 79 Ill.2d 632. In the case at bar, plaintiff argues that defense counsel improperly attacked her for being present in the courtroom during the trial.

( Pedrick v. Peoria Eastern R.R. Co. (1967), 37 Ill.2d 494, 510, 299 N.E.2d 504.) A jury's verdict will be overturned when it is against the manifest weight of the evidence. ( Lebrecht v. Tuli (1985), 130 Ill. App.3d 457, 473 N.E.2d 1322, appeal denied (1985), 106 Ill.2d 555.) A verdict is contrary to the manifest weight only if it is wholly unwarranted by the evidence, and not when the evidence is merely conflicting and the jury resolves the conflict. 130 Ill. App.3d at 471.

The general rule is that the standard of care must be established by expert testimony. ( Lebrechtv. Tuli (1985), 130 Ill. App.3d 457, 471, 473 N.E.2d 1322, appeal denied (1985), 106 Ill.2d 555.) Such expert testimony may be supplied by the defendant doctor himself.

Because this information is probative of the information available to defendant, the trial court did not err in admitting such testimony. Lebrecht v. Tuli (1985), 130 Ill. App.3d 457, 473 N.E.2d 1322, appeal denied (1985), 106 Ill.2d 555. • 13 Defendant argues that the trial court erred in admitting color photographs of lung tissue taken from plaintiff.

The doctrine of res judicata provides that a final judgment rendered by a court of competent jurisdiction on the merits is conclusive as to the rights of the parties and their privies and, as to them, constitutes an absolute bar to a subsequent action involving the same claim, demand or cause of action. ( Housing Authority v. YMCA (1984), 101 Ill.2d 246, 251, 461 N.E.2d 959; Lester v. Arlington Heights Federal Savings Loan Association (1985), 130 Ill. App.3d 233, 238, 474 N.E.2d 33, appeal denied (1985), 106 Ill.2d 555; Stratemeyer v. West (1985), 136 Ill. App.3d 1095, 1096, 484 N.E.2d 399, appeal denied (1986), 111 Ill.2d 579.) The doctrine of res judicata applies only to facts and conditions as they existed when the judgment was rendered.

As plaintiff chose not to pursue his remedies under the note, the doctrine of res judicata arises from the first suit to estop it from asserting those remedies in a subsequent suit. • 7 Plaintiff contends the doctrine of res judicata does not apply to the case at bar because the actions are not based on the same claim. Causes of action are identical where the evidence necessary to sustain a second verdict would sustain the first, i.e., where the causes of action are established upon a common core of operating facts. ( Lester v. Arlington Heights Federal Savings Loan Association (1985), 130 Ill. App.3d 233, 238, appeal denied (1985), 106 Ill.2d 555; Decatur Housing Authority v. Christy-Foltz, Inc. (1983), 117 Ill. App.3d 1077, 1081; Redfern v. Sullivan (1982), 111 Ill. App.3d 372, 376.) Here, both actions are essentially based on the existence of the sales contract and defendant's failure to pay it. The underlying debt of $20,989.13 is the foundation of both suits, and the fact that plaintiff now seeks additional interest does not change that fact.