Fleur Tehrani v Hamilton Bonaduz AG & Ors.

Patent claims must be construed through the eyes of the skilled team and in light of the common general knowledge. An indefinite reference to control for “a next breath” does not require adjustment on every breath; it may refer to a later breath where the claim language permits that construction.

A claim requiring PEEP to be determined so as to keep the PEEP/FiO₂ ratio within a prescribed range does not necessarily require the ratio to be calculated. The relationship may be achieved by prescribing corresponding values or ranges.

For inventive step, a sequence of individually obvious modifications does not establish obviousness unless the collective performance of those steps would itself have been obvious. The patent was invalid, although claim 1 would have been infringed if valid.

The claimant was the proprietor of UK Patent No. 2,424,721, concerning automatic control of oxygenation and ventilation in mechanical ventilators. The defendants marketed ventilators incorporating the Intellivent-ASV System.

The claimant alleged infringement of claims 1 and 45. The defendants denied infringement and counterclaimed for revocation on grounds of lack of novelty, lack of inventive step and insufficiency.

The central issues were the construction of “a next breath”, whether claim 1 required calculation of the PEEP/FiO₂ ratio, whether the Intellivent-ASV System infringed, and whether the claims were invalid over the cited prior art.

1. Construction. The skilled person was properly considered as a skilled team comprising an engineer and a respiratory or critical care physician. The phrase “a next breath” did not mean only the immediately following breath or require adjustment on every breath. It covered a later breath, and the skilled person would generally expect a delay between determination and application of the control signals because of the risks of excessive PEEP and the physiological lag in oxygen measurement.
2. “Determined” meant ascertained or decided upon. Claim 1 did not require the PEEP/FiO₂ ratio to be calculated. A system could satisfy the claim by prescribing PEEP and FiO₂ values whose relationship necessarily fell within a prescribed range.
3. Infringement. The Intellivent-ASV System satisfied the “next breath” requirement. Its graphical relationship between PEEP and FiO₂ constituted a sufficiently narrow prescribed range for integer 1E when treatment was being increased. Claim 1 was therefore infringed on its normal construction. Claim 45 was not infringed because the system did not use the patient’s oxygen level to determine the required FiO₂, breathing frequency, ventilation and I:E ratio. The suggested indirect relationship through PEEP was unsupported by the evidence.
4. Validity. Neither claim lacked novelty over Anderson. Claim 1 lacked novelty over Waisel because the therapy continuum clearly and unambiguously disclosed a prescribed range of PEEP/FiO₂ ratios. Claim 45 was obvious over Waisel. The combination of the Tehrani Paper and US 268 did not make claim 45 obvious. A series of individually obvious steps could not establish obviousness without evidence that carrying out the steps collectively would have been obvious.
5. The insufficiency arguments did not arise on the findings made. The Patent was invalid. Had it been valid, claim 1 would have been infringed and claim 45 would not have been infringed.