Transcutaneous carbon dioxide measurements in fruits, vegetables and humans: A prospective observational study.

BACKGROUND: Transcutaneous carbon dioxide measurement (TcCO2) is frequently used as a surrogate for arterial blood gas sampling in adults and children with critical illness. Data from noninvasive TcCO2 monitoring assists with clinical decisions regarding mechanical ventilation settings, estimation of metabolic consumption and determination of adequate end-organ tissue perfusion. OBJECTIVES: To report TcCO2 values obtained from various fruits, vegetables and elite critical care medicine specialists. DESIGN: Prospective, observational, nonblinded cohort study. SETTINGS: Single-centre, tertiary paediatric referral centre and organic farmers' market. PARTICIPANTS: Vegetables and fruits included 10 samples of each of the following: red delicious apple (Malus domestica), manzano banana (Musa sapientum), key lime (Citrus aurantiifolia), miniature sweet bell pepper (Capsicum annuum), sweet potato (Ipomoea batatas) and avocado (Persea americana). Ten human controls were studied including a paediatric intensivist, a paediatric inpatient hospital physician, four paediatric resident physicians and four paediatric critical care nurses. INTERVENTIONS: None. MAIN OUTCOME MEASURES: TcCO2 values for each species and device response times. RESULTS: TcCO2 readings were measurable in all study species except the sweet potato. Mean ±â€ŠSD values of TcCO2 for human controls [4.34 ±â€Š0.37 kPa (32.6 ±â€Š2.8 mmHg)] were greater than apples [3.09 ±â€Š0.19 kPa (23.2 ±â€Š1.4 mmHg), P < 0.01], bananas [2.73 ±â€Š0.28 kPa (20.5 ±â€Š2.1 mmHg), P < 0.01] and limes [2.76 ±â€Š0.52 kPa (20.7 ±â€Š3.9 mmHg), P < 0.01] but no different to those of avocados [4.29 ±â€Š0.44 kPa (32.2 ±â€Š3.3 mmHg), P = 0.77] and bell peppers [4.19 ±â€Š1.13 kPa (31.4 ±â€Š8.5 mmHg), P = 0.68]. Transcutaneous response times did not differ between research cohorts and human controls. CONCLUSION: We found nonroot, nontuberous vegetables to have TcCO2 values similar to that of healthy, human controls. Fruits yield TcCO2 readings, but substantially lower than human controls.