Figures
- Figure 1
a) Maximal (outer black loop) and tidal (inner purple loop) flow–volume loops at rest in our patient. The predicted values loop is shown as a dashed profile. b) SNIP traces at rest in our patient. c) MIP traces at rest in our patient. Please refer to the text for more details.
- Figure 2
Current practice on the suspicion of respiratory muscle dysfunction (especially of the diaphragm), outside the intensive care setting. The figure describes how a clinician or physiologist suspects and treats respiratory muscle dysfunction (especially unilateral and bilateral diaphragm weakness), outside the intensive care setting. PImax: maximal inspiratory pressure; TF: thickening fraction of the diaphragm; PSG: polysomnography; CPAP: continuous positive airway pressure; NPPV: noninvasive positive pressure ventilation; PaCO2: arterial carbon dioxide tension; SpO2: arterial oxygen saturation measured by pulse oximetry. Please refer to the text for more details.
Tables
- Table 1
Resting PFT in an upright sitting and supine position
Upright sitting position Supine position Measured LLN ULN Reference (mean value) % of reference Measured % of reference VC L 4.13 4.33 6.17 5.25 79% 2.70 51% TLC L 5.79 6.07 8.37 7.22 80% 4.17 58% FRC L 2.39 2.43 4.41 3.42 70% 1.65 48% IC L 3.40 3.47 98% 2.52 73% RV L 1.65 1.24 2.58 1.91 87% 1.47 77% ERV L 0.73 1.73 42% 0.18 10% RV/TLC % 29 19 37 28 102% 35 126% FEV1 L 3.07 3.32 5.00 4.16 74% FVC L 4.04 4.03 6.03 5.03 80% FEV1/VC %# 74 69 92 81 94% PEF L·s−1 8.11 7.59 11.57 9.58 85% FEF25% L·s−1 6.93 5.44 11.06 8.25 84% FEF50% L·s−1 3.52 3.14 7.48 5.31 66% FEF75% L·s−1 0.91 1.11 3.67 2.39 38% LLN: lower limit of normality; ULN: upper limit of normality; VC: vital capacity; TLC: total lung capacity; FRC: functional residual capacity; IC: inspiratory capacity; RV: residual volume; ERV: expiratory reserve volume; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; PEF: peak expiratory flow; FEFx%: forced expiratory flow measured after x% of the FVC has been exhaled. #: spirometric evidence of an obstructive ventilatory defect as defined by a reduced FEV1/VC ratio less than the fifth percentile of the predicted value [1].
- Table 2
Respiratory muscle pressure assessment
Measured LLN ULN Reference (mean value)# % of reference MIP sustained for 1 s (at RV) cmH2O 68 80 168 124 55% MIP at peak value (at RV) cmH2O 70 MEP sustained for 1 s (at TLC) cmH2O 166 149 317 233 71% MEP at peak value (at TLC) cmH2O Maximum SNIP cmH2O 52 81 129 105 50% MIP: maximal inspiratory pressure; MEP: maximal expiratory pressure; SNIP: sniff nasal inspiratory pressure. #: reference values taken from [2, 3].
- Table 3
Main differences between unilateral and bilateral diaphragmatic paralysis
Unilateral diaphragmatic paralysis Bilateral diaphragmatic paralysis Symptoms Usually asymptomatic
Possible dyspnoea on exertion and limited ability to exercise
Occasionally dyspnoea when supineUnexplained dyspnoea or recurrent respiratory failure
Considerable dyspnoea at rest, when supine, with exertion, or when immersed in water above their waist
Fatigue, hypersomnia, depression, morning headaches and frequent nocturnal awakenings
Subsegmental atelectasis and infections of the lower respiratory tractPFT VC ∼75% predicted
VC ∼55–65% predicted when supine
FRC usually preserved
TLC usually preservedVC ∼50% predicted
VC ∼30–50% predicted when supine
TLC ∼70–79% predicted (mild restriction)
TLC ∼30–50% predicted (moderate-to-severe restriction)
RV >predictedRME MIP ∼30–60% predicted
SNIP ∼30–60% predictedMIP <30% predicted
SNIP <30% predictedThreshold values to suspect diaphragmatic weakness:
MIP or sniff Pdi or Pdi,max ≤80 cmH2O in men, ≤70 cmH2O in women
SNIP ≤70 cmH2O in men, ≤60 cmH2O in womenRME: respiratory muscles evaluation. Please refer to the text for more details.
