Sellers William F S
Broadgate House, 22 Broadgate, Great Easton, Leicestershire, LE16 8SH UK.
Allergy Asthma Clin Immunol. 2017 Jun 29;13:30. doi: 10.1186/s13223-017-0202-0. eCollection 2017.
Current pressurised metered dose asthma inhaler (pMDI) propellants are not inert pharmacologically as were previous chlorofluorocarbons, have smooth muscle relaxant' partial pressure effects in the lungs and inhaled hydrofluoroalkane 134a (norflurane) has anaesthetic effects. Volumes of propellant gas per actuation have never been measured.
In-vitro studies measured gas volumes produced by pMDIs on air oxygen (O) levels in valved holding chambers (VHC) and the falls in O% following actuation into lung ventilator delivery devices.
Volumes of propellant gas hydrofluoroalkane (HFA) 134a and 227ea and redundant chlorofluorocarbons (CFC) varied from 7 ml per actuation from a small salbutamol HFA inhaler to 16 ml from the larger. Similar-sized CFC pMDI volumes were 15.6 and 20.4 ml. Each HFA salbutamol inhaler has 220 full volume discharges; total volume of gas from a small 134a pMDI was 1640 ml, and large 3885 ml. Sensing the presence of liquid propellant by shaking was felt at the 220th discharge in both large and small inhalers. Because of a partial pressure effect, VHC O% in air was reduced to 11% in the smallest 127 ml volume VHC following 10 actuations of a large 134a salbutamol inhaler. The four ventilator delivery devices studied lowered 100% oxygen levels to a range of 93 to 81% after five actuations, depending on the device and type of pMDI used.
Pressurised inhaler propellants require further study to assess smooth muscle relaxing properties.
当前的压力定量吸入器（pMDI）推进剂在药理上并非像以前的氯氟烃那样呈惰性，在肺部具有平滑肌舒张的分压效应，且吸入的氢氟烷烃134a（诺氟烷）具有麻醉作用。每次按压喷出的推进剂气体体积从未被测量过。
体外研究测量了pMDI在带阀储物罐（VHC）中对空气氧（O）水平产生的气体体积，以及在启动进入肺通气输送装置后O%的下降情况。
氢氟烷烃（HFA）134a和227ea以及多余的氯氟烃（CFC）推进剂气体体积各不相同，从小型沙丁胺醇HFA吸入器每次按压喷出7毫升到大型的16毫升不等。类似尺寸的CFC pMDI体积分别为15.6毫升和20.4毫升。每个HFA沙丁胺醇吸入器有220次全量喷出；小型134a pMDI喷出的气体总体积为1640毫升，大型的为3885毫升。在大小吸入器中，第220次喷出时通过摇晃能感觉到液体推进剂的存在。由于分压效应，在一个大型134a沙丁胺醇吸入器按压10次后，最小127毫升体积的VHC中的空气O%降至11%。所研究的四种通气输送装置在按压五次后将100%的氧水平降至93%至81%的范围，这取决于所使用的装置和pMDI类型。
压力定量吸入器推进剂需要进一步研究以评估其平滑肌舒张特性。
