Over recent years manufacturers have incorporated compliance software into non-invasive ventilators. This has primarily been aimed at reviewing compliance within the clinic setting. The reliability of these packages has been reviewed (1,2) and there have been reported use of the software to titrate settings in acute and home settings (2). We reviewed the value of built in ventilator software to indicate deterioration in patients prior to an emergency hospital admission. All patients with home Non Invasive Ventialtion (NIV) attending clinic have their ventilators downloaded. A record is made of compliance (hours of usage), tidal volume (TV), leak for the preceding month and arterial blood gas (ABG). This was compared to a similar dataset downloaded for the preceding week prior to an acute admission (3 neuro-muscular, 2 COPD, 4 COPD & obesity, 1 obesity (n=10). Only stable patients ( no admissions in the previous 3 months, using the ventilator for ≥5hrs per night at last clinic attendance ) were evaluated. The majority of admissions (n=7) were secondary to an respiratory exacerbation. Five patients were acidotic (pH 7.2 – 7.33). Six patients increased their NIV usage, while in 4 this fell. TV as a proportion of the baseline clinic volume dropped in 6 patients up to 49%, 6 days prior to admission. In a small series, it would appear that interrogating downloaded NIV compliance data could identify changes in key ventilator parameters up to a week prior to admission. If substantiated, using data to implement early therapeutic intervention to prevent subsequent deterioration could have an impact on patient care References 1. Contal, O et al 2012; 141(2):469–476 2. Rabec C et al Eur Respir J 2009; 34: 902–913.

Background and objective: ARDS is characterized by bilateral pulmonary infiltrates and refractory hypoxemia attributed to V/Q mismatch. We used dynamic CT to characterize changes in lung composition, regional perfusion and tissue distribution in patients with ARDS in comparison with healthy subjects.Methods: The Fick principle was applied to serial attenuation measurements constructed from sequential CT images acquired during the passage of a bolus of iodinated contrast medium in healthy subjects (n = 3) and patients with ARDS (n = 11). Perfusion was calculated by the Mullani-Gould method and mapped throughout both lungs. Gradients of perfusion and tissue density against vertical height were constructed.Results: In comparison with normal individuals, the tissue component of lungs from patients with ARDS was significantly increased (P < 0.05). Blood fraction was unchanged. There was a discernable gradient in tissue density from non dependent to dependent regions in the patients with ARDS that was significantly different from controls. The proportion of perfusion applied to consolidated areas (i.e. shunt) correlated significantly (P < 0.05) with the severity of hypoxaemia.Conclusions: In patients with ARDS there are changes in both lung composition and the distribution of tissue and perfusion that may account in part for the physiological changes that define the syndrome.

Rationale and Objectives. Pulmonary vascular control mechanisms are complex and likely to differ between species. We wish to quantify regional perfusion and the effects of gravity using computed tomography.Materials and Methods. Sequential density measurements following the administration of a bolus of iodinated contrast medium were acquired from four healthy human subjects and four dogs.Results. In humans, perfusion (Q) was linear throughout most of the range of vertical height, with an overall gradient of -2.6% cm(-1). However, when perfusion was normalized to "tissue" density (blood plus tissue: sQ(t)), maximum perfusion occurred around the mid-range of vertical height, being 9% (range 1-22%) greater than either the dorsal or ventral extreme. Within discrete transverse axial sections, concentric zones of perfusion centered on blood vessels were demonstrated. The relationship between sQt and vertical height in dogs was distinctly linear, with a gradient of -7.2% cm(-1). In dogs, the median gradient of Q was - 13.6% cm(-1) (range -9.7 to -17.1%).Conclusions. Differences in regional pulmonary perfusion, particularly the vertical gradient observed in humans and dogs, may in part reflect anatomic differences between the symmetric dichotomous branching structure of the human pulmonary vasculature and the more asymmetrical structure found in dogs.