Transdiaphragmatic pressure can be measured in the critically ill to give a nonvolitional assessment of diaphragm contractility, but not all patients can be studied. At present, the relationship of twitch endotracheal tube pressure to transdiaphragmatic pressure is too variable to reliably represent a less invasive measure of diaphragm strength.

Many critically ill patients develop significant skeletal muscle weakness in the Intensive Care Unit (ICU), which ultimately may cause difficulties in weaning from mechanical ventilation and a protracted, expensive ICU stay. Reliable monitoring of muscle strength in this environment is difficult. The purpose of this study was to develop a reproducible, nonvolitional method of measuring adductor pollicis (AP) muscle function by magnetic stimulation of the ulnar nerve (MSUN) that could be applied to patients in the ICU and operating theater (OT). Fifty subjects (32 healthy control subjects [12 of whom were elderly], 12 ICU patients with critical illness [mean APACHE II score 20], and six otherwise healthy patients requiring minor surgery in the OT) received MSUN. In 12 of the normal subjects electrical stimulation of the ulnar nerve (ESUN) and MSUN were compared and AP twitch tension (Tw AP) and surface electromyogram (EMG) were measured. Close agreement was found between supramaximal Tw AP (median [95% CI] for MSUN 6.3 N [5-7.2 N] and ESUN 6.9 N [5.2-7.8 N] [p = NS]). Median (95% CI) values with MSUN for the 20 young and 12 elderly control subjects were 6.9 N (5. 3-7.4 N) and 7.1 N (4.4-9.8 N). Median (95% CI) Tw AP for the ICU group was 4.2 (2.2-6.7 N) and for the OT group was 5.8 (4-9.1 N). Tw AP was significantly reduced in ICU patients compared with age-matched controls (p = 0.01). MSUN can be used to measure neuromuscular function in both the laboratory and clinical settings including the ICU.

Assessment of diaphragm paralysis with oesophageal EMG and unilateral magnetic phrenic nerve stimulation. YM Luo, ML Harris, RA Lyall, A Watson, MI Polkey, J Moxham. #ERS Journals Ltd 2000. ABSTRACT: The purpose of this study was to establish a sensitive and reliable method of diagnosing diaphragm paralysis by recording the diaphragm compound muscle action potential (CMAP) using a multipair oesophageal electrode and unilateral magnetic phrenic nerve stimulation.An oesophageal electrode catheter was designed containing six coils (1 cm wide and 3 cm apart), creating an array of four sequential electrode pairs. The oesophageal catheter was taped at the nose with the proximal electrode pair 40 cm from the nares. Eight patients with unilateral (n=5) or bilateral (n=3) diaphragm paralysis were studied. Five to seven phrenic nerve stimulations were performed at 80% of maximum magnetic stimulator output and the CMAPs were recorded simultaneously from the four pairs of electrodes.In the five patients with unilateral diaphragm paralysis, the CMAP amplitudes and latencies were 1.160.29 mV and 7.61.5 ms for functioning sides. No diaphragm CMAP could be detected when stimulating nonfunctioning phrenic nerves.This study shows that diaphragm paralysis can be reliably diagnosed by unilateral magnetic stimulation combined with a multipaired oesophageal electrode. Eur Respir J 2000; 15: 596±599.

Lung volume reduction surgery can improve lung function in patients with emphysema. We report our anaesthetic experience, problems and the physiological data of eight patients. Our aims were prevention of air trapping and air leaks, good analgesia and early recovery and mobilization. We were able to achieve these aims using pressure limited ventilation, lumbar epidural diamorphine, propofol infusions and intensive physiotherapy. Hypoxia during one-lung ventilation was the main intraoperative problem. Air leaks, infection and pulmonary hypertension were the main postoperative problems.

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