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Background and objective Obstructive sleep apnoea is a prevalent and considerably underdiagnosed disease. The development of cost-effective, home-based, automatic diagnostic devices to improve the diagnosis accessibility is therefore essential. Methods In this study, a new portable polygraph (BTI-APNiA) was used to validate automatic scoring. This five-channel device records respiratory flow, oxygen saturation, heart rate, body position and snoring. The validation was performed in two phases. In the first phase, manual and automatic scorings of a new respiratory polygraphy (RP) device (BTI-APNiA) were compared. In the second phase, automatic analysis performed with BTI-APNiA was compared with manual scoring of a validated RP device (Embletta Gold). Results Phase I was completed by 424 patients (50.5% males, 52.2 ± 12.4 years, BMI of 25.4 ± 4.8 kg/m2 and Epworth Sleepiness Scale score of 8.0 ± 4.0). Manual and automatic analysis resulted in an apnoea–hypopnoea index (AHI) of 13.7 ± 12.7 and 14.0 ± 12.5 (P > 0.05), respectively. The interclass correlation coefficient (ICC) was 0.99 (P 0.05). The ICC was 0.68 (P < 0.01). Conclusion The automatic analysis of the BTI-APNiA is as accurate as manual analysis of AHI. This automatic analysis compared well with the manual analysis of a validated RP device (Embletta Gold).

The upper airways play a significant role in the tracheal flow dynamics. Despite many previous studies, however, the effect of the upper airways on the ventilation distribution in distal airways has remained a challenge. The aim of this study is to experimentally and computationally investigate the dynamic behaviour in the intratracheal flow induced by the upper respiratory tract and to assess its influence on the subsequent tributaries. Patient-specific images from 2 different modalities (magnetic resonance imaging of the upper airways and computed tomography of the lower airways) were segmented and combined. An experimental phantom of patient-specific airways (including the oral cavity, larynx, trachea, down to generations 6-8) was generated using 3D printing. The flow velocities in this phantom model were measured by the flow-sensitised phase contrast magnetic resonance imaging technique and compared with the computational fluid dynamics simulations. Both experimental and computational results show a good agreement in the time-averaged velocity fields as well as fluctuating velocity. The flows in the proximal trachea were complex and unsteady under both lower- and higher-flow rate conditions. Computational fluid dynamics simulations were also performed with an airways model without the upper airways. Although the flow near the carina remained unstable only when the inflow rate was high, the influence of the upper airways caused notable changes in distal flow distributions when the 2 airways models were compared with and without the upper airways. The results suggest that the influence of the upper airways should be included in the respiratory flow assessment as the upper airways extensively affect the flows in distal airways and consequent ventilation distribution in the lungs.

A partial-body plethysmograph was developed for measuring the respiratory flow of anesthetized mice during routine microimaging experiments performed in the close confines of an 89-mm-diameter, vertical-bore magnet. Respiratory flow patterns were used for synchronizing conventional T2-weighted spin-echo imaging with the respiratory cycle, thereby, significantly reducing motion-induced artifacts and increasing observed liver lesion contrast.

We measured purring in unrestrained intact pumas, cheetahs and domestic cats. Domestic cats, Felis silvestris f. catus, purr at a frequency of 26·3 ±; 1·95 (S.D.) Hz. The frequency at mid-expiration exceeds that at mid-inspiration by 2·4 ± 1·3 Hz. Purring frequency for individuals does not change with age. Purring can occur simultaneously with other vocalization. Two-channel acoustic measurements confirm that the primary mechanism for sound and vibration production is a centrally driven laryngeal modulation of respiratory flow. The diaphragm and other muscles appear to be unnecessary for purring other than to drive respiration.

In a lung model the rebreathing effects of different respiratory flow patterns (RFP) were studied in the coaxial Mapleson A (Lack) and D (Bain, Coax-II) systems during spontaneous breathing. In the Mapleson A system RFP was not found to have any impact. In the D systems FACO2 was higher with an RFP typical of halothane-anaesthetized patients than with an RFP with an exponentially decreasing expiratory flow and an end-expiratory flow pause (FTEP). The difference in FACO2 was 26% with a VF corresponding to 100 ml X min-1 X kg-1 body weight. The RFP in a non-anaesthetized volunteer was intermediate between these two patterns. Rebreathing decreased in the D systems with prolongation of FTEP and when a decelerating expiratory flow was used.

The validity of the Stenqvist-Sonander formula for calculating the end-expiratory fraction of carbon dioxide (FACO2) in the coaxial Mapleson D (Bain) systems was evaluated using a lung model for simulated spontaneous breathing with an optional respiratory wave form. Two different respiratory flow patterns were used, one representing relaxed breathing in a volunteer and one resembling the respiration found in halothane anaesthesia. Each pattern was used with five different fresh gas flows and three different respiratory rates. The formula was found to be quite accurate when the flow pattern of an awake volunteer was simulated, but it underestimated the observed FETCO2 value by about 10% in halothane breathing. It is concluded that the formula can be recommended for use in theoretical and educational situations but that it is too complicated for application in clinical practice.

A new flat-bodied pneumotachograph head is described which can be readily interposed between a commercially available endotracheal tube connector on one side and a suitable low dead space attachment on the other. The head was designed to enable the respiratory flow of infants and neonates to be measured both easily and accurately, and without adding appreciably to the work of breathing. The method used to heat the head, and to heat and humidify the inspired gases are also detailed. The underlying aim has been to record inspiratory and expiratory flow as accurately as is possible within the bounds of practical clinical measurement.