Respiratory measurements

An NM3 respiratory profile monitor (Philips Respironics, CT), connected to a combined pressure and flow sensor with mainstream capnograph (Capnostat-5), was used [Fig. 1]. The flow and pressure measurements were from a fixed orifice pneumotachometer and differential pressure sensor, respectively. The expired CO₂ was measured using infrared absorption spectroscopy. The respiratory monitor was automatically calibrated for pressure, flow and CO₂ according to the factory-stored calibrations within the monitor. The NM3 monitor was connected to a Laptop (Dell Latitude, UK) with customised Spectra software (3.0.1.4; Grove Medical, UK). The data were exported from Spectra to Microsoft Excel (for Office 365, 2007 version) with a sampling output of 100 Hz for analysis and construction of volumetric capnograms.

a combined pneumotachograph and mainstream capnograph b Endotracheal tube c Ventilator tubing.