Diaphragm function in patients with cervical cord injury or prior poliomyelitis infection

Abstract

Diaphragm function was evaluated in cervical cord injury patients (CCI), 1-3 years after injury (CCI1-3) and 10 years or more after injury (CCI(≥10)), as well as in a group of prior poliomyelitis infection patients (PPI), requiring intermittent positive pressure ventilation (IPPV) for about 6 h per night. Measurements included transdiaphragmatic pressure swings (ΔPdi) at rest, during maximal inspiratory efforts against closed airways (ΔPdi(max)) and during sniff manoeuvres (ie maximal inhalation through the nose, ΔPdi(sniff)), vital capacity normalized to age and height (VC(%pred)), tidal volume (Vt), relative inspiratory time (Ti/Ttot), breathing frequency (f(b)), and the tension-time index of the diaphragm (TTdi = ΔPdi/ΔPdi(max) x Ti/Ttot). The median VC(%pred) was 50% in the CCI1-3 group and 57% in the CCI(≥10) group, but only 28% in the PPI group. ΔPdi(max) values were similar for the CCI1-3 (11.8 kPa) and CCI(≥10) (11.9 kPa) groups, but were lower (7.1 kPa) in the PPI group. Due to the reduction in ΔPdi(max), the PPI group had higher ΔPdi/ΔPdi(max) values than the CCI groups, however, the TTdi was similar amongst the different groups studied. A submaximal exercise test in five cervical cord injury patients and in five polio patients with similar ΔPdi(max), ΔPdi(sniff) and TTdi values at rest revealed clear group differences with respect to force development, in that CCI patients showed significant increases in TTdi, while PPI demonstrated only minor changes. In CCI patients, an increase in ventilation was accompanied by an increase in ΔPdi/ΔPdi(max) while in contrast, the PPI patients showed no increase in ΔPdi/ΔPdi(max). We conclude that CCI patients, both recently and previously injured, have a similar maximal inspiratory force and are less impaired than the PPI patients. The TTdi at rest is similar in all groups, but the PPI patients react to inspiratory loads with little increases in TTdi, while the CCI patients increase their TTdi above fatiguing (0.15) levels. The different behaviours may be linked to loss of sensory pathways in the CCI patients.