Rising CO2 Concentrations Research Articles

The relationship between respiration, atmosphere and quality in intact and perforated mushroom pre‐packs

SummaryFresh ‘button’ mushrooms (Agaricus bisporus) were stored at 18°C in pre‐packs overwrapped with one of six polylvinyl chloride films. The effect of piercing the film with one to four pinholes (punctures) on the concentrations of CO2 and O2 in the pre‐pack atmosphere and the internal browning and CO2 production of the packed mushrooms were measured.The respiration, as measured by CO2 production, of mushrooms in intact packs was depressed by over 50% from the values observed in air, and varied considerably between the films used. There appeared to be an inverse relationship between respiration in the pre‐pack and internal browning. Carbon dioxide output of the packed mushrooms increased as a result of perforating the overwrapping film. The effect of perforations on the CO2 and O2 concentrations in the pre‐pack atmosphere and on the internal browning of packed mushrooms depended on the type of film used. It appeared that one or two pinholes in films which permitted low respiration rates when intact, caused a rise of CO2 concentration and an increase in internal browning, while little change was seen in O2 level; more pinholes led to a decrease in CO2 concentration, an increase in O2 concentration and some decrease in internal browning. Pre‐packed mushrooms overwrapped with a film which permitted a high level of respiration when intact showed decreased CO2 and increased O2 concentrations and some decrease in internal browning at all levels of perforation.The significance of the results is discussed in relation to previous work and to commercial practice.

Determination of Cardiac Output by Rebreathing Method ; with Special Reference to Its Reliability and Merit in Clinical Use

The PV^^co2, was determined graphically by the rate of rise in CO2 concentration while rebreathing pure oxygen. The reproducibility of consecutively determined PV^^co2 was fairly well and it correlated significantly with the PaCO2= directly measured from arterial blood. To make the procedure determining the cardiac output strictly non-bloody, PaCO2 was also determined indirectly by the end-tidal gas analysis. The CO2 output was measured conventionally. The PV^^co2 and PaCO2 were converted to their con-tent with CO2 dissociation curve for fully oxygenated blood, then the cardiac output was calculated applying these values to the Fick's formula. The range of the cardiac output determined consecutively during an hour was considered small enough to be included within the physiological fluctuation, and the cardiac output thus determined correlated significantly with that by direct Fick method. The cardiac output was significantly different between one another in three groups (healthy, ischemic heart disease and ischemic heart failure). The result agreed with that made by the dye dilution method and apexcardiogram. Having fairly good reproducibility and showing good accordance with the results by the other techniques, it was proved that this indirect Fick method is of great clinical use. Besides, the procedure does not give almost any mental or physical load to subjects.