Case No. IP-2019-000196

For a next breath – integers 1C and 1G 50.According to claim 1 the apparatus which controls the ventilator seeks to reduce the difference between the measured oxygen level of the patient and a desired value (integer 1D). This is done by adjusting FiO2 (1D). PEEP is also determined and the ratio of PEEP/FiO2 is kept within a prescribed range, while the oxygen level of the patient is maintained above a predefined value (1E).51.The output data (1B) and thereby the control signals (1F) set the required FiO2 and PEEP for “a next breath” of the patient (1C and 1G).52.The point in issue was whether “a next breath” should be construed to mean “the next breath”, implying that the control signals adjust FiO2 and PEEP for every breath of the patient. Alternatively “a next breath” just means a breath some time in the future.53.It is therefore necessary to identify the moment which would be followed by “a next breath” to make sense of the claim. I do not believe this was in dispute, but anyway it can only be the moment at which the FiO2 and PEEP are both determined such that the ratio between may be kept within a prescribed range.54.As I have indicated above, it was part of the skilled person’s CGK that manual adjustment of PEEP should be done incrementally at intervals of no less than 20 minutes to avoid the danger to the patient of excessive PEEP. It was also part of his or her CGK that there was a significant lag between a change in FiO2 and a change in the patient’s blood oxygen level. Hamilton argued that in consequence the skilled person would expect that there will be a lag between the determination of desired FiO2 and PEEP and control signals to change them. This will imply a corresponding lag between determinations. If not, the patient’s blood oxygen level and PEEP are liable to be driven up or down, dangerously overshooting the target.55.I find this persuasive. According to the ordinary meaning of the claim, use of the indefinite article in integers 1C and 1G – “a next breath” – does not rule out adjustments of FiO2 and PEEP at every breath. But the skilled person would also understand that this need not be the case. The adjustment may take place for some later breath. The skilled person’s appreciation of the potential danger of such adjusting at each breath would also lead to an understanding that in practice there will usually be a delay between the “determination” required by integers 1D and 1E on the one hand, and the provision of control signals of integer 1G, to give the required FiO2 and PEEP of integer 1C, on the other hand.56.Professor Tehrani relied on an exemplary embodiment in the specification in which the interval for the system’s decision whether to alter PEEP and FiO2 was 0.75 seconds. The claim does not exclude operation with decisions at that frequency but neither does the claim require it. PEEP is determined to keep a ratio of PEEP/FiO 2 within a prescribed range – integer 1E 57.It was common ground that “determined” means ascertained or decided upon. Both FiO2 and PEEP are ascertained and the PEEP/FiO2 ratio is kept within, or brought within, a prescribed range.58.No prescribed range is identified. Professor Rees pointed out that, although not mentioned in the Patent, there are necessary maxima and minima for PEEP and FiO2. PEEP will fall between atmospheric pressure and typically 30-50cm H2O. FiO2 must be between 21% (the oxygen content of air) and 100%. If those limits determine the prescribed range of integer 1E, any ventilator is bound to keep the PEEP/FiO2 ratio within that range.59.Alternatively, if 1E is intended to refer to a narrower and clinically preferred range of ratios, the Patent does not disclose what that is. It may be that the clinician in the team would know the desirable ranges for PEEP and FiO2 and by extension the preferred range of ratios. But then the range would be part of the CGK.60.There was a dispute as to whether claim 1 requires the PEEP/FiO2 ratio to be calculated. In his first witness statement Professor Rees said this:“167. The claim does not require determination (whether by setting or calculation) of the PEEP/FiO2 ratio, only that PEEP is determined to keep the ratio within a range. The skilled person would appreciate that if one is presented with values for PEEP and FiO2 then the ratio between them is also known, therefore, prescribing PEEP and FiO2 values also prescribes the ratio (and, naturally, if one has values for the ratio and one of PEEP or FiO2 then the missing term is still ‘known’ as it is defined by the relationship between them). This means that when PEEP and FiO2 are controlled in relation to one another the ratio between them is controlled. In my opinion, determining PEEP to maintain the ratio of PEEP and FiO2 within a prescribed range, in practice, would be satisfied by a system that manages patient oxygenation within thresholds or set limits, reflecting clinically desirable values of PEEP and FiO2. This could be achieved by setting PEEP and FiO2 according to values held in a table or database. In such a system the PEEP/FiO2 ratio of the desirable values will inevitably be within a set (or prescribed) range of ratios, despite the ratio not actually being calculated as part of the control program. The claim would also be satisfied by a system that simply calculates the PEEP/FiO2 ratio and compares this to a predetermined maximum and minimum value but I do not think the claim is limited to such a system.”61.Professor Tehrani drew attention to paragraph [0052] of the specification:“[0052] After the determination of the required FiO2, the procedure of adjusting the PEEP value is started at F in step 282. In this step, the ratio of PEEP/FiO2 is calculated.”62.Paragraph [0052] is part of a long passage in the specification describing an embodiment of the invention. Claim 1 undoubtedly encompasses a system in which the PEEP/FiO2 ratio is calculated. Professor Rees’ point, however, was that calculation is not necessary. One way of maintaining the ratio within limits would be to prescribe limits to each of PEEP and FiO2 such that the ratio between the two is always within a prescribed range. Since the range can be anything, this seems to me to make sense. Integer 1E of claim 1 does not specify calculation of the PEEP/ FiO2 ratio. I find that claim 1 covers a system that will achieve the ratio without calculation although it includes a system that calculates the ratio.