The importance of monitoring the breathing pattern during sedation of children undergoing magnetic resonance scans is indicated in guidelines, but no appropriate magnetic resonance-compatible devices are available. We report preliminary findings from a technique referred to as remote pressure sensor respiratory plethysmography.

A data acquisition system was developed, enabling measurement of respiratory rate, plethysmogram amplitude, proportion of inspiratory time over cycle time, thoraco–abdominal phase shift and sigh rate. Correlation between plethysmogram amplitude and tidal volume was investigated on adult volunteers. Twenty-seven children undergoing sedation were monitored with remote pressure sensor respiratory plethysmography, in addition to SPO2 and PetCO2. Differences in monitoring parameters were searched for among three groups: patients who received chloral hydrate only (chloral succeeded, CS group), those who received a supplementation of sodium thiopental (chloral failed, CF group), and those who were sedated with sodium thiopental directly (no chloral, NC group). Correlations were searched for among monitoring parameters, and with total dose of thiopental. The long-term behaviour of respiratory rate, proportion of inspiratory time over cycle time and phase shift was studied.

Plethysmogram amplitude was found to correlate linearly with tidal volume (r > 0.92), with a slope varying up to 22%. While 11% of patients did not tolerate the capnometric probe and readings were discontinuous in 26%, all of them tolerated remote pressure sensor respiratory plethysmography belts. Sighs and non-respiratory movements of the torso could be distinguished on remote pressure sensor respiratory plethysmography waveforms. No significant inter-group differences were found in PetCO2, SPO2, respiratory rate and phase shift. Proportion of inspiratory time over cycle time was higher in the NC group when compared to the CS group (0.497 ± 0.03 vs. 0.463 ± 0.008; P = 0.02), the CF group being characterized by intermediate values (0.480 ± 0.008); when compared to the CS group, sigh rate was lower in the CF group (0.04 ± 0.04 vs. 0.14 ± 0.08; P = 0.04) and in the NC group (0.06 ± 0.05 vs. 0.14 ± 0.08, P = 0.03). A positive correlation was found between total dose of thiopental and proportion of inspiratory time over cycle time, with r = 0.4 and P = 0.04. A large baseline variability in phase shift was found. No long-term trends predictive of patient movement could be identified.

Breathing pattern monitoring is feasible through pneumatic devices, which are well tolerated. The resulting correlation with changes in tidal volume can be better when compared to visual inspection. Proportion of inspiratory time over cycle time and sigh rate convey information related to the state of the sedated patient. These results are not specific to the technology employed, and large-scale studies on the clinical usefulness of breathing pattern monitoring are motivated.

The postoperative monitoring and treatment of the patient undergoing aortic valve replacement is a complex challenge. Echocardiography is the only method which provides dynamic and real-time bedside imaging of the heart. Focused assessed transthoracic echocardiography has been shown to provide a usable window for cardiac imaging in a mixed ICU population. The aim of this study was to evaluate the feasibility of perioperative imaging of the heart and pleura according to the focused assessed transthoracic echocardiography protocol in patients scheduled for aortic valve replacement.

Thirty-five adult patients scheduled for aortic valve replacement were followed perioperatively with focused assessed transthoracic echocardiography examinations. A Vivid-7 echo-machine and a 2.5 MHz matrix transducer with second-harmonic imaging were used for data acquisition. The image quality for the cardiac window was graded 1–5 (1 = no image, 2 = poor and unusable image quality, 3 = usable image quality, 4 = good image quality and 5 = perfect image quality). A score ⩾3 equalled an image quality judged to be of sufficient quality to be interpreted and thereby to contribute to clinical decision-making.

All patients had at least one usable window preoperatively. At least one usable window was obtained in 88% of patients on the first postoperative day, and in 97% at discharge. The image quality changed over time, with the poorest quality being observed on the first postoperative day. The apical view with the patient in the left lateral position provided the best cardiac window on all occasions. The presence of drains did not significantly affect the achievability of a satisfactory examination. The number of patients with pleural effusion was relatively high. On the first postoperative day, 10 subjects had unilateral and one subject had bilateral pleural effusions. At discharge, 14 patients had unilateral and four patients had bilateral effusions.

We conclude that the image quality of the heart and pleura, according to the focused assessed transthoracic echocardiography concept, is sufficient to undergo interpretation and thereby contribute to the perioperative clinical decision-making in patients with aortic stenosis.