Petition nor Rehearing
Before Brand*, Chief Justice, and Rossman, Lusk, Latourette** and Tooze, Justices. *619TOOZE, J.■ Plaintiff petitions for a rehearing, presenting a number of assignments of error directed to our original opinion.
It is unnecessary for us to review in detail the evidence in the case, because practically all the essential facts are set forth in our former opinion. However, for the purposes of this opinion, we will hereinafter enlarge upon our statement of the evidence.
We have given careful consideration to the several assignments of error and to the briefs of the respective parties relating thereto. Although there is merit in some of the assignments, nevertheless, with one exception, they do not reach the heart of this case. We therefore refrain from discussing all the assignments, because, in our opinion, only one deserves serious consideration, and our decision thereon will be decisive of this matter.
Plaintiff alleges that this court erred “in holding that defendant’s negligence in allowing plaintiff to assume a horizontal position on her back on the cot while unconscious was not a proximate cause of the putrid abscesses”, and further, that “the court erred in holding that Dr. Tuhy’s testimony as to proximate cause was pure conjecture and highly speculative for the reason that Dr. Tuhy testified that the putrid lung abscesses were probably caused by the aspiration of infected pyorrheatic material while reposing on her back under anaesthesia following the extractions, and that all other causes of her putrid abscesses, while possible, were improbable.” (Italics ours.)
*620 It is elementary that to fix liability in a ease of this nature two things must concur and combine: (1) an act of negligence on the part of defendant: and (2) such act of negligence must be a proximate cause of the injury. If either of these elements is missing, there can be no liability. To warrant a recovery of damages, each and both of these constituents of a cause of action must be established by a preponderance of evidence.
At the outset it may be conceded that there is substantial evidence in the record to establish an act of negligence on the part of defendant in permitting plaintiff to lie on her back in the recovery room immediately following the teeth extraction operation. This is the act of negligence upon which plaintiff relies and upon which her entire case rests.
The decisive question then remains: Is there substantial evidence in the record tending to establish the fact that this act of negligence was a proximate cause of the injury of which plaintiff complains?
Ordinarily the question of whether a particular act was the proximate cause of the injury complained of is one for decision by the jury, and it is only where the facts are such that all reasonable men must draw the same conclusion from them that the question of proximate cause becomes one of law for the court. When the existence of proximate cause under the facts is challenged, it is for the court to say whether there is substantial evidence in the record sufficient to submit the question to the jury. Kukacka v. Rock, 154 Or 542, 544, 61 P2d 297; Miami Quarry Co. v. Seaborg Packing Co., 103 Or 362, 370, 204 P 492.
In determining the question whether there is substantial evidence in this case to support a finding that *621defendant’s act of negligence was the proximate cause of plaintiff’s injury, we must view the testimony in the light most favorable to her.
To establish proximate cause, plaintiff relies entirely upon the testimony of Dr. John E. Tuhy, a duly licensed physician and surgeon of the city of Portland. She has caused a complete transcript of his testimony given on the trial to be attached to her brief on rehearing. It is manifest from the record that if Dr. Tuhy’s testimony is insufficient as a matter of law to warrant the submission of the question of proximate cause to the jury, plaintiff’s cause of action against defendant must fail.
In our former opinion when discussing the question of proximate cause, we quoted to some extent from the testimony of Dr. Tuhy. We concluded that it was insufficient to establish the element of proximate cause. We have carefully reexamined that conclusion and in doing so have given additional and painstaking attention to all his testimony. Although we must and do assume as true all facts to which Dr. Tuhy testified, we are not required to, nor do we, assume the correctness of any of his conclusions or opinions unless they are based upon substantial evidence in the record.
To clarify the problem before us, we propose to quote at length from Dr. Tuhy’s testimony, setting out all of his testimony which, in our opinion, is material to the question of proximate cause.
Plaintiff suffered from an abscess of the upper lobe of the right lung. It was discovered when X-rays were taken in September and October, 1948. Dr. Tuhy operated Upon her “in order to drain the abscess”. Before the operation Dr. Tuhy examined plaintiff’s windpipe and bronchial tubes “with a lighted instrument”, *622to determine “if there were any foreign materials such-as tooth fragments and so on in the bronchial tube”. No tooth fragment “or anything of the like” was found. In reply to a question whether plaintiff suffered any permanent disability as the result of the abscess, Dr. Tuhy said: “I think there will be a slight permanent disability. * * # She would tend to be short of breath, more than the average person, so I would say that there was some slight permanent disability.”
Dr. Tuhy was then asked the following hypothetical question:
“Doctor, assuming that before July 10, 1948, Mrs. Wintersteen was in good health, and assuming that on or about July 10, 1948, she went to Dr. Semler’s office to have her teeth extracted, and that she had 17 teeth at that time, that at that time there were tartar deposits on and around her teeth and that she had a pyorrheatic condition of the mouth, and further assuming that about eleven o’clock on July 10, 1948, all her 17 teeth were removed at one time, she being under a general anesthetic, and assuming that she was thereafter taken onto a cot in Dr. Semler’s office, and that about 11:15 or so that morning her husband first saw her after she went in for her surgery, and that he saw her lying on this cot in a horizontal position, that is, on her back, with her head tilted to the right, and that he observed that her eyes were shut and that she was motionless, and he tried talking to her without any response, and that he nudged her without any response, and then he continued standing over her for a period of approximately five minutes or more, and then assume that on or about July 19, 1948, Mrs. Wintersteen returned to the office of Dr. Semler and advised a nurse there named Jane Schamel that she had been suffering since about July 13, 1948, from repeated and severe coughing spells and that she was bringing up a greenish bile-like substance and she felt that she was losing *623weight because she wasn’t able to take any food, and that the only food that she was able to take was mill?:, and that she was also taking anacin. Then, Doctor, assume that these same complaints continued thereafter, and then that she went to the St. Vincents Hospital, where those pictures were taken—those X-rays were taken—on September 2, 1948, that you have examined and testified about. Doctor, would you have an opinion as to whether or not the lung abscess that was shown on those X-rays of September 2, 1948 was connected or resulted from the extraction of Mrs. Wintersteen’s teeth?” (Italics ours.)
Defendant at this point objected upon the ground that the hypothetical question did not contain a statement of all the material facts, particularly the time element, and upon other grounds which we deem unnecessary to mention. After some discussion between court and counsel, plaintiff requested and received permission of the court to modify the question by stating the time element without reciting the question. Whereupon, the following question was directed to the witness:
“Doctor, assuming the same circumstances that I set out to you in that question, and further, that Mrs. Wintersteen was administered a general anesthetic about eleven A.M. on July 10, 1948, and that her husband found her in the position mentioned at about 11:15 AM. on that same day, and that he then stood over her for a period of approximately five minutes or more and that she was in this same prone position, that is, a horizontal position on her back, with her head tilted to the right, during that whole time he was standing over her, and further, assume that the dentist who extracted the teeth used complete and proper dental procedures in connection with the blocking of the throat at the time the teeth were removed; under those circumstances, Doctor, do you have an opinion as
*624to whether or not Mrs. Wintersteen’s lnng abscesses were caused by anything connected with the extractions?” (Italics onrs.)
To this question the Doctor replied:
“Yes, I believe that the lung abscesses were due to the aspiration of infected material from her pyorrhea, either .during or following the extractions when she was under the influence of general anesthesia.” (Italics ours.)
At this point we think it should be emphasized that in order to establish the necessary element of proximate cause in this case, the evidence must tend to show that the aspiration of infected material, if there was such aspiration, occurred during the short period of time plaintiff rested in the recovery room following the operation. If it occurred during the operation, then defendant’s act of negligence hereinbefore noted could not possibly be the proximate cause of plaintiff’s injury. We make note of the fact that the Doctor stated that it may have occurred not only during the operation, as well as following, but also that it was “when she was under the influence of general anaesthesia.”
The following question was then directed to Dr. Tuhy:
“Doctor, assuming that when her teeth were taken out, that is, at the time the teeth actually were extracted, proper dental procedures were followed, so as to eliminate that possibility, then is it your opinion that by reason of the position she had on the couch these abscesses developed?”
An objection was made and sustained to this question, and then the following question was propounded:
‘ ‘ Doctor, would you care to pick out any incident in that hypothetical question that I mentioned to you to connect up the lung abscesses with the extraction?” (Italics'ours.)
*625Dr. Tuhy replied:
“The prompt appearance following the extractions under general anesthesia of the symptoms of coughing and expectoration of this material [referring to a time one or two days following the extractions] certainly from experience would lead me to think that it was quite likely that she had aspirated this infected material. When a person is wider general anesthesia and there is infected material draining from the mouth or sinuses after a tonsillectomy one of the worst positions that you may assume is a flat or horizontal one, because material will go down the mouth and between the vocal cords and into the windpipe. It won’t do that in a person who is awake because normal reflexes will make that person spit out the stuff before it goes into the windpipe, but where these reflexes are depressed by anesthesia or insulin shock the infected material will lodge in the portion of the lung in the back.” (Italics ours.)
The witness further testified as follows:
“Q You first treated Mrs. Wintersteen at Mat-son Memorial in a surgical way for the abscess in the upper part of the right lung?
“A That is correct.
“Q Do you have an opinion, Doctor, as to what caused that abscess ?
“A I believe that it followed a suppurative pneumonia due to the aspiration of foreign material in the mouth incident to extractions.”
Later in his direct examination Dr. Tuhy testified that plaintiff had a putrid lung abscess, which he described as one where the pus has a foul odor. He also expressed it as his opinion that following an operation involving the throat or mouth, a patient should be placed in a head-down position, because, as he said:
“Well, if a person has had an operation on the mouth or nose or throat and is unconcious and is *626allowed simply to lie flat on Ms back or perhaps reclining with Ms head up, the secretions are much more apt to go down into the windpipe and into the lungs than if they are properly suctioned out and allowed to drain by gravity while he is recovering from the anesthesia(Italics ours.)
Thereupon, another hypothetical question was directed to the witness. The following are the proceedings in connection therewith:
“Q I would like to ask you this question Doctor: Assuming that before July, 1948, Mrs. Wintersteen was in good health and assuming that on or about July 10, 1948, she went to Dr. Semler’s office to have her teeth extracted and that she had seventeen teeth at that time and that at that time there were tartar deposits on or around her teeth and that she had a pyorrhetie [sic] condition of her mouth, and further assuming that about eleven o’clock on that day all of her seventeen teeth were removed at one time and under general anaesthesia, and assuming further that thereafter and on that same day her husband found her in what is called a lay-out room lying on her back in a horizontal position with her mouth turned to the right, and that her eyes were closed and that she was motionless and that he tried talking to her without response from her and that he shook her without response from her, and assuming further that she had been given this general anaesthesia about eleven o’clock that morning and that her husband continued standing over her for a period of about five or more minutes after eleven-fifteen and that during tMs entire period she did not—she continued in the same state that I have mentioned, and that after ah out five or more minutes she got up, opened her eyes and then her husband assisted her in a sitting position and then, Doctor, assume that on or about July 19, 1948, Mrs. Wintersteen returned to the office of Dr. Semler and advised the nurse there whose name was Jane Schamel that she had been *627suffering since about July 13, 1948, from repeated and severe coughing spells and that she was bringing up a greenish bile-like substance, and that she felt lake she was losing weight because she wasn’t able to take any food and that the only food that she was able to take was milk and that she was also taking aspirin; then assume, Doctor, that on or about September 2nd or September 1st she went to the St. Vincent’s Hospital and then that those X-rays were taken on September 2nd which you have seen and observed and testifiefid [sic] about, Doctor, under all those circumstances would you have an opinion as to the time that these lung abscesses were contracted?
“MR. EASLEY: That has all been gone over. We have been over this already, your Honor. I think it is repititious [sic]. The doctor will probably admit that he answered the same identical question yesterday.
“THE COURT: The date of the contracting, I didn’t recall was gone into. If it was—is that the object of your question?
“MR. KORN: Yes, your Honor.
“MR. EASLEY: The actual date?
“MR. KORN: Yes.
“MR. EASLEY: I understood that the doctor had limited it to the teeth extractions on the 10th, but then maybe I was wrong.
“Q (by Mr. Korn) Do you have an opinion on that, Doctor?
“A Yes.
“Q What is that opinion?
“A I would conclude that Mrs. Wintersteen a couple of days after these extractions had developed the syinptoms of what we call a suppurative pneumonia which was a forerunner of the lung abscess and that, further, the suppurative pneumonia was in all probability caused by the aspiration of infected material from her mouth, either during the procedure or immediately afterward, *628especially since her position during the period of recovery from anaesthesia would not be considered proper medically since in such a position and under general anaesthesia she would be more likely to aspirate such material when she was unconscious.
“Q Then do you have an opinion as to the probabilities of the time element as to the aspiration of those materials?
“A It could have occurred either during the extractions or in the period of unconsciousness under general anaesthesia afterward, and I don’t think that I could say when it was more likely to have occurred.
“Q What are the probabilities, Doctor?
“A I would say that if the dentist who did the extractions had used all the usual precautions during the extensions [sic], suction of infected material, packing of the throat and so on, if he had used all those precautions and then she had been laid out in this horizontal position on her back, that it was very likely that this infected material had gone down afterwards when she was on the couch.
“Q And are those the probabilities to your knowledge, Doctor?
“A Yes.” (Italics ours.)
It is noted that in the Doctor’s reply to the question he again stated that “in all probability” the aspiration occurred either during the operation or immediately afterward, and while plaintiff was “under general anaesthesia” and “when she was unconscious.” We also observe that in his answer to the second question relating to the time element, he repeated that the “probabilities” were it “could have occurred either during the extraction” or “in the period of unconsciousness under general anaesthesia afterwards.” (Italics ours.) His statement: “and I don’t think I could say when it was more likely to have occurred”, is significant.
*629His later assertion “that it was very likely that this infected material had gone down afterwards when she was on the conch”, must be considered in the light of his prior answers which were in substance to the effect that it occurred, if it occurred at all, while plaintiff was “under general anaesthesia” and “when she was unconscious.” Moreover, it is obvious that there is a decided inconsistency between his last statement and that made immediately prior thereto that, “I don’t think that I could say when it was more likely to have occurred.” Considering his prior replies and the foundation upon which they were based, is it not manifest that his opinion as to what was “very likely” or “probable” constituted but a mere guess on his part and is purely speculative?
An opinion of a medical expert that a result is “probable” or “very likely” presents no question for jury determination, unless it is based upon facts and, in the light of all the evidence in the case, is reasonably sustainable. In McKay v. State Ind. Acc. Com., 161 Or 191, 87 P2d 202, Mr. Justice Lusk, in writing the opinion of the court, rejected the testimony of a medical expert who had testified that “heart failure” at a particular specified time was “probable”. When such medical “opinion” is plainly opposed to reason, it fails to constitute substantial evidence for any purpose.
Upon cross-examination, Dr. Tuhy was examined as to the causes of lung abscesses. Several possibilities as to how plaintiff’s lung abscess may have been caused by the pyorrhea, other than the manner claimed in this ease, were developed, and. admitted by the witness. Thereafter, he testified as follows:
“Q Now you have already told the jury and *630the Court that the trachea is sort of a tree-like device, we call it the windpipe?
“A Yes, the windpipe is simply a tube that divides into the main bronchial tubes and into many other bronchial tubes.
“Q Nature has fixed the trachea so that the likelihood of outside matter getting in is limited?
“A That is correct.
“Q In other words, what is the device up there at the head of the trachea which protects the trachea, what is that called?
“A The epiglottis is sort of a trapdoor business where the vocal cords lead into the windpipe. The epiglottis helps tend to cover the progress of the cords so that foreign matter doesn’t go into the windpipe but goes into the esophagus.
“Q In other words, nature had protected the lungs from'the foreign objects?
“A Yes, in that way and in other ways, too.
“Q Now it is a fact, Doctor, in natural or induced sleep that particular reflex at the mouth of the trachea is the last to go away and the first to return, isn’t that right, in the normal physical reflexes?
“A Yes, the cough reflex is not lost in fairly deep anaesthesia, in the third plane of anaesthesia, generally.
“Q So that this cough reflex—and that is what we are talking about—remains because nature has this coughing device to keep things out of your lungs, too, and that is it, isn’t it?
“A No, there are others—of course, if material does get down into the windpipe there are nerve endings which stimulate coughing and tend to expel it. Then there are others—shall I go into them?
“Q No, because I am primarily interested in the ones at the head of the trachea.
“A Yes.
“Q So that reflex, in induced sleep or normal sleep if the reflex is going to go it will be the last *631reflex to go because of the lung protection it affords?
“A Well, I would say that the cough reflex is effective in ordinary sleep but that it is depressed or absent in anaesthesia, and especially in deep anaesthesia.
“Q You wouldn’t say that the cough reflex in sleep is as good as it is when you are awake?
“A I would say that it isn’t as good in deep sleep. In ordinary light sleep if anything gets down in there, a person will cough, I would say, just as well as if he is awake; but in profound sleep under the influence of alcohol or sedatives or narcotics, the reflex would definitely be depressed.
“Q So it is all a matter of degree?
“A That is correct.” (Italics ours.)
The theory of the doctor, as well as of plaintiff in this case, is that plaintiff’s cough reflexes were depressed by the anaesthesia, so that they did not operate to prevent foreign material from entering the lung cavity by way of the windpipe. From the foregoing testimony of the witness, it is evident that the cough reflex is not ordinarily lost in light or fairly deep anaesthesia, but only in “deep anaesthesia” or “profound sleep under the influence of alcohol * *
In reference to anaesthesia and its effects, the witness testified:
“Q Doctor, you are talking about anaesthesia. This anaesthesia is proportioned to the job to be done?
“A That is correct.
“Q And the more anaesthesia given, the more the tendency is to become deeper in sleep; the more anaesthesia you give the more the reflexes disappear?
“A Yes, that is correct.
“Q Now, then, for a comparatively short operation of, say, ten or fifteen minutes, in fact, the *632time differential or interval between the time that the person goes into the chair and the time that she is given oxygen and led into a room, a matter of less than an hour—in fact, you have been told about the facts of this case and you know that she went into the chair at a quarter to eleven, that is, she was led into the room at a quarter to eleven, she went down the hall to the bathroom, she came back, she took off her coat and earrings—you have heard all this.
“A Yes.
“Q Well, she was administered—she was prepared for the anaesthesia and she was administered the anaesthesia, seventeen teeth were extracted, she was then administered oxygen, which was normal, isn’t that right, to bring them out of the sleep?
“A It is commonly done, yes. ■
“Q So they are artificially induced to sleep and artificially brought out of it?—[objection] * * * And then she stayed five or ten minutes, in other words, the anaesthesia time—the recovery time is approximately the anaesthesia time, and then she was helped out, walked down the stairs, took a cab and got into the 5100 block north of Burnside on Mallory Street by noon. In other words, an hour and fifteen minutes between the time that she went into the room and did all of this until the time she got clear out to the north end. It would be your considered opinion that she was in very light cmaesthesia?
“A Not necessarily.
“Q Why?
“A It would depend on the anaesthetic agent. There are some anaesthesias that are quickly acting and quickly go away that may produce fairly deep anaesthesia.
“Q What about nitrous oxide?
“A Nitrous oxide, one may get fairly deep anaesthesia and recovery is fairly prompt.
*633“Q With, those facts in mind, wouldn’t you say that the probabilities are that the anaesthesia wasn’t deep?
“A Could you tell me about her status, the state of her pupillary reflexes, for example, and whether she did cough during the extractions and so on? I think I could answer better.
‘ ‘Q There will be evidence that there was never any coughing.
“A There was never any coughing. Well, I would thixik that would be a point in favor of the cough reflex being depressed.
“Q Why is that?
“A Because lying in this horizontal position, it would be almost inevitable.
“Q We are talking about sitting in the chair with the anaesthesia, nitrous oxide.
am m m m m
“THE WITNESS: If a person has had extractions a certain amount of blood will go down the back of the throat which they should, of course, spit up or have it suctioned out, usually both, and if they lie under anaesthesia on their back, I would say it is almost inevitable for some material to go down there. Now if they are under very light anaesthesia, just almost awake, that will get them to coughing. They will try to set up and cough, and cough and spit this stuff out. If they are under fairly deep anaesthesia the material is apt to go down unobstructed.” (Italics ours.)
The undisputed facts show that plaintiff was administered nitrous oxide; that before the operation was entirely completed, oxygen was used to restore her to consciousness, the amount of oxygen being regulated so that recovery was coincident with the end of the operation. When plaintiff had sufficiently recovered from the anaesthesia, the operation being com*634pleted, she got out of the dental chair and with the assistance of the nurse walked to the recovery room.
From the foregoing statement of the evidence, it is patent that plaintiff was not under “fairly deep” nor “deep” anaesthesia while in the recovery room. She had come out from under the anaesthesia before she left the dental chair; so much so, in fact, that she was able to walk, with assistance, to the recovery room. There is no substantial evidence in the record that she was “unconscious” at any time after the operation was completed. The testimony of her husband as to what was said and done in the recovery room falls far short of being substantial evidence to establish the essential fact that plaintiff was “unconscious” at that time, or even that she was sound asleep, and his testimony is the only testimony in the record which relates to the few moments plaintiff was lying on the cot. This testimony is summarized in the hypothetical questions, supra.
Our search of the record fails to disclose any medical testimony to the effect that one who has been administered nitrous oxide, recovery from which is fairly prompt, and who has been given oxygen to hasten consciousness (and who has recovered consciousness to the extent of being able to walk with assistance from the dental chair to the resting room), may again lapse into a state of unconsciousness from the effects of the drug theretofore used. Common sense teaches us that one who has been restored to consciousness after anaesthesia will, for a short time at least, remain drowsy and not wish to be disturbed. The fact that within a period of five minutes, more or less, after lying down, plaintiff was able to get up, walk through the dental offices to the elevator, and leave the build*635ing, the nurse having done nothing in the meantime to hasten wakefulness, also is significant.
The most that can be claimed for the testimony of plaintiff’s husband is that it affords the basis for a speculative inference, another doubtful link in the chain of causation; a “speculative inference”, because from this testimony alone, considered in the light of the entire record, it is manifest that the jury would necessarily be compelled to resort to mere guess to find that plaintiff was “unconscious under general anaesthesia”, with her cough reflexes depressed, at the time in question. To eliminate all the other possibilities mentioned in our former opinion as to time and cause, and as an essential step in pinpointing “aspiration of infected material” during the brief time plaintiff was in the recovery room, it is necessary to depend entirely upon Mr. Wintersteen’s testimony.
Plaintiff’s case upon proximate cause must first pass the test of whether there is substantial evidence to show “unconsciousness under general anaesthesia” on her part while she was resting immediately following the operation. “Unconsciousness under general anaesthesia” is the sole basis for Dr. Tuhy’s inference that aspiration likely occurred while plaintiff was so lying down. We again repeat his answer to the hypothetical question: “It could have occurred either during the extractions or in the period of unconsciousness under general anaesthesia afterward * * (Italics ours.) It is obvious from the record that Dr. Tuhy’s deduction was based upon an erroneous premise, a premise which finds no substantial support in the evidence. As we point out in our former opinion and as further demonstrated herein, Dr. Tuhy’s opinion was purely speculative.
*63615. In 15 Am Jnr 413, Damages, § 22, the following rules are stated:
“The damages recovered in any case must he shown with reasonable certainty both as to their nature and in respect of the cause from which they proceed. No recovery can he had where it is uncertain whether plaintiff suffered any damages unless it is established with reasonable certainty that the damages sought resulted from the act complained of. Hence, no recovery can be had where resort must he had to speculation or conjecture for the purpose of determining whether the damages resulted from the act of which complaint is made or from some other cause, or where it is impossible to say what, if any, portion of the damages resulted from the fault of the defendant and what portion from the fault of the plaintiff himself.” (Italics ours.)
Also see Becker v. Tillamook Bay Lbr. Co. et al., 194 Or 134, 142, 240 P2d 237; Allen et ux. v. McCormick, 193 Or 604, 612, 238 P2d 220; Spain v. Oregon-Washington R. & N. Co., 78 Or 355, 369, 153 P 470, Ann Cas 1917E, 1104.
The conclusion we reached in our former opinion that plaintiff had failed, as a matter of law, to establish the element of proximate cause is correct, and we adhere to the result therein announced.
The petition for rehearing is denied.