Long form | Unit | Short form | Definition |
Tidal volume FRC | mL | V _{T,FRC} | Tidal volume preceding FRC_{p}. Average over the last 5 breaths pre-occlusion |
t_{I} prior to FRC | s | t _{I,FRC} | Inspiratory time preceding FRC_{p}. Average over the last 5 breaths pre-occlusion |
t_{E} prior to FRC | s | t _{E,FRC} | Expiratory time preceding FRC_{p}. Average over the last 5 breaths pre-occlusion |
t_{tot} prior to FRC | s | t _{T,FRC} | Total breath time preceding FRC_{p}. Calculated as t_{I}+t_{E} over 5 breaths pre-occlusion |
RR prior to FRC | L·min^{−1} | RR_{FRC} | Respiratory rate preceding FRC_{p}. Calculated from the t_{tot}-FRC parameter as RR=60/t_{tot} |
sd of EEL | mL | EELs | sd of EEL measured relative to the baseline EEL calculated over 5 breaths prior to each FRC occlusion manoeuvre |
Stability of EEL prior to FRC_{p} | % | EEEls% | Stability of EEL prior to FRC_{p}, i.e. EELs expressed as a % of V_{T,FRC}: EELs%=100×EELs/V_{T,FRC} |
% Change in EEL | % | ΔEEL% | Change in EEL post-preocclusion, expressed as % of mean V_{T} prior to occlusion |
Ambient pressure | kPa | P _{amb} | Ambient pressure |
Apparatus dead space | mL | DS _{app} | Apparatus dead space including the mask |
Occluded volume | mL | V _{occ} | Volume inspired above EEL at moment of occlusion |
Total occluded gas volume | mL | TOGV | Total occluded gas volume, including V_{occ} and DS_{app} (including the effective dead space of the mask) |
FRC_{pleth} | mL | FRC_{p} | Mean functional residual capacity, i.e. (TOGV−DS_{app}−V_{occ}) |
CV of FRC_{p} | % | FRC_{pCV} | Coefficient of variation (i.e. 100×(sd/mean)) of n accepted FRC_{p} manoeuvres |
No. of accepted FRC_{p} | FRC_{p,n} | Number of accepted FRC_{p} manoeuvres | |
Change in P_{ao,occ} | kPa | ΔP_{ao} | Mean change in P_{ao} during respiratory efforts against the airway occlusion measured between 5%–95% of troughs and peaks respectively |
Change in V_{pleth,occ} | mL | ΔV_{pleth} | Mean change in box volume during airway occlusion corresponding to ΔP_{ao} |
Maximal inspiratory pressure | kPa | P _{I,max} | Minimal absolute value in P_{ao} during inspiratory effort against the occlusion |
Maximal inspiratory pressure | kPa | P _{E,max} | Maximal absolute value in P_{ao} during expiratory effort against the occlusion |
t_{I} occluded | s | t _{I,occ} | Duration of the first inspiratory effort during airway occlusion (for use if assessing the strength of the Hering Breuer reflex). This parameter is only measured during EE occlusions. t_{I,occ} is measured from the start of inspiration (taken from the tidal volume trace) immediately before an EE occlusion until the end of the first inspiratory effort, when P_{ao} starts to rise during the occluded effort |
t_{E} occluded | s | t _{E,occ} | Duration of the first expiratory effort during airway occlusion. This parameter is only measured if EI occlusion is selected. The time is measured from the start of expiration (measured from the tidal volume trace) immediately before an EI occlusion, until P_{ao} starts to fall during the airway occlusion |
HBR-EE | % | HBR-EE | Strength of Hering Breuer Reflex calculated from end expiratory occlusion as 100×(t_{I,occ}−t_{I}FRC)/t_{I}FRC |
HBR-EI | % | HBR-EI | Strength of Hering Breuer Reflex calculated from end inspiratory occlusion as 100×(t_{E,occ}−t_{E}FRC)/t_{E}FRC |
Apparatus resistance | kPa·L·s^{−1} | R _{app} | Apparatus resistance |
Specific airway resistance | kPa·s^{−1} | sR_{aw} | See definition in text, which includes correction for apparatus resistance |
Specific airway conductance | 1/(kPa·s^{−1}) | sG_{aw} | Specific airway conductance. Calculated as sG_{aw}=1/sR_{aw} |
V _{eff} | mL | V _{eff} | Lung volume used to convert specific effective airway resistance (see text) |
V _{lv} | mL | V _{lv} | Volume to convert sR_{lv} (see text) |
V _{hv} | mL | V _{hv} | Volume to convert sR_{hv} (see text) |
Airway resistance | kPa·L·s^{−1} | R _{aw} | Effective airway resistance. Calculated as: R_{eff}=sR_{eff}/V_{eff} (where V_{eff}=effective volume above FRC at time of R_{eff} analysis – see text) |
Airway conductance | L·s·kPa^{−1} | G _{aw} | Airway conductance. Calculated as: G_{aw}=1/R_{aw} |
sR_{lv} | kPa·s^{−1} | sR_{lv} | Specific airway resistance at low lung volume (i.e. end inspiratory and initial expiratory values – see text) |
sR_{hv} | kPa·s^{−1} | sR_{hv} | Specific airway resistance at high lung volume (i.e. end inspiratory to initial expiratory values – see text) |
PEF during resistance | mL·s^{−1} | PEF | Peak tidal expiratory flow during resistance measurement as weighted mean from all accepted breaths |
PIF during resistance | mL·s^{−1} | PIF | Peak tidal inspiratory flow during resistance measurement as weighted mean from all accepted breaths |
No. of R_{aw} | R _{aw,n} | Number of accepted R_{aw} breaths | |
CV of sR_{aw} | % | sR_{aw}CV | Coefficient of variation of sR_{aw} |
Exp to ins sR_{aw} ratio | sR_{E/I} | Ratio of slope of end expiratory to initial inspiratory parts of the specific resistance loop, taken from above and below zero flow over a selected flow limit | |
Flow limit sR_{I} | % | %V_{R,I} | Percentage of inspiratory peak flow, used for calculation of sR_{lv} and sR_{hv} |
Flow limit sR_{E} | % | %V_{R,E} | Percentage of expiratory peak flow, used for calculation of sR_{lv} and sR_{hv} |
RR during R_{aw} | L·min^{−1} | RRR_{aw} | Respiratory rate during the resistance manoeuvre. The average over all breaths used in the resistance calculation is taken. Best is calculated from 60×(1/mean t_{I}+mean t_{E}) |
Tidal volume R_{aw} | mL | V _{T,Raw} |
Suggested suffixes to denote specific type of analysis etc. (particularly during R_{aw} measurements when so many options are available): eff: effective (e.g. R_{aw,eff}); E: expiratory; I: inspiratory; tot: total; hv: high volume; lv: low volume; X% assessment at specified pre cent of peak inspiratory or expiratory flow (e.g. R50%I=R_{aw} measured at 50% PIF, whereas sG75%E would be sG_{aw} at 75% PEF); EEL: end expiratory level.