Accuracy of height estimation and tidal volume setting using anthropometric formulas in an ICU Caucasian population

Impact of sex on use of low tidal volume ventilation in invasively ventilated ICU patients-A mediation analysis using two observational cohorts

Background

Studies in patients receiving invasive ventilation show important differences in use of low tidal volume (V_T) ventilation (LTVV) between females and males. The aims of this study were to describe temporal changes in V_T and to determine what factors drive the sex difference in use of LTVV.

Methods and findings

This is a posthoc analysis of 2 large longitudinal projects in 59 ICUs in the United States, the ‘Medical information Mart for Intensive Care III’ (MIMIC III) and the ‘eICU Collaborative Research DataBase’. The proportion of patients under LTVV (median V_T < 8 ml/kg PBW), was the primary outcome. Mediation analysis, a method to dissect total effect into direct and indirect effects, was used to understand which factors drive the sex difference. We included 3614 (44%) females and 4593 (56%) males. Median V_T declined over the years, but with a persistent difference between females (from median 10.2 (9.1 to 11.4) to 8.2 (7.5 to 9.1) ml/kg PBW) vs. males (from median 9.2 [IQR 8.2 to 10.1] to 7.3 [IQR 6.6 to 8.0] ml/kg PBW) (P < .001). In females versus males, use of LTVV increased from 5 to 50% versus from 12 to 78% (difference, –27% [–29% to –25%]; P < .001). The sex difference was mainly driven by patients’ body height and actual body weight (adjusted average causal mediation effect, –30% [–33% to –27%]; P < .001, and 4 [3% to 4%]; P < .001).

Conclusions

While LTVV is increasingly used in females and males, females continue to receive LTVV less often than males. The sex difference is mainly driven by patients’ body height and actual body weight, and not necessarily by sex. Use of LTVV in females could improve by paying more attention to a correct calculation of V_T, i.e., using the correct body height.

Computational evaluation of rebreathing and effective dead space on a helmet-like interface during the COVID-19 pandemic

The coronavirus disease 2019 (COVID-19) is a potentially severe acute respiratory infection caused by severe acute respiratory syndrome coronavirus 2. The potential for transmission of this disease has led to an important scarcity of health-care resources. Consequently, alternative solutions have been explored by many physicians and researchers. Non-invasive Ventilation has been revealed as one alternative for patients with associated acute respiratory distress syndrome. This technique is being used in combination with helmet-like interfaces because of their versatility and affordability. However, these interfaces could experience important problems of CO2 rebreathing, especially under low flow rate conditions. This work proposes a Computational Fluid Dynamics method to accurately characterize the fluid flow in a pre-design environment of helmet-like interfaces. Parameters as effective dead space, rebreathing, pressure, or temperature field distribution are quantified and analysed in detail in order to study the performance and feasibility of such devices to relieve the effects of respiratory infections.

Exploring the Impact of Obesity on Health Care Resources and Coding in the Acute Hospital Setting: A Feasibility Study

Obesity is costly, yet there have been few attempts to estimate the actual costs of providing hospital care to the obese inpatient. This study aimed to test the feasibility of measuring obesity-related health care costs and accuracy of coding data for acute inpatients. A prospective observational study was conducted over three weeks in June 2018 in a single orthopaedic ward of a metropolitan tertiary hospital in Queensland, Australia. Demographic data, anthropometric measurements, clinical characteristics, cost of hospital encounter and coding data were collected. Complete demographic, anthropometric and clinical data were collected for all 18 participants. Hospital costing reports and coding data were not available within the study timeframe. Participant recruitment and data collection were resource-intensive, with mobility assistance required to obtain anthropometric measurements in more than half of the participants. Greater staff time and costs were seen in participants with obesity compared to those without obesity (obesity: body mass index ≥ 30), though large standard deviations indicate wide variance. Data collected suggest that obesity-related cost and resource use amongst acute inpatients require further exploration. This study provides recommendations for protocol refinement to improve the accuracy of data collected for future studies measuring the actual cost of providing hospital care to obese inpatients.

A Comparison of Three Methods of Height Estimation and Their Impact on Low Tidal Volume Ventilation in a Mixed Ethnicity Intensive Care Unit: A Real-World Experience

Background

Height measurement is crucial for calculating predicted body weight (PBW) and establishing low tidal volume ventilation (LTVV). However, standing height is usually unavailable in critically ill patients and supine height may be difficult to obtain.

Objective

We investigated whether there were any significant differences in tidal volumes (VT) obtained using PBW derived from supine, forearm, and lower leg lengths in an intensive care unit (ICU) setting.

Methods

Supine, forearm and lower leg lengths were measured in 100 mechanically ventilated patients. Limb lengths were converted to height and PBW calculated using published formulae. The 6 mL/kg VT for the supine (sVT), forearm (fVT), and lower leg (lVT) methods were compared to each other and to visually estimated VT (estVT).

Results

Forearm length produced the greatest height estimate, leading to a significantly greater tidal volume fVT (437.6 ± 62.1 mL) compared with sVT (385.5 ± 63.8 mL) and lVT (369.1 ± 66.4 mL), (p < .001). There was no significant difference between lVT and sVT, (p = .169). On Bland Altman analysis, the lowest bias was found between lVT and sVT (−16.4 ± 36.0 mL, 95% limits of agreement (LOA) [−86.9, 54.1]), whereas fVT had a bias of 52.1 ± 41.5 mL, 95% LOA [−29.1, 133.4] compared to sVT. The fVT was significantly greater than sVT and lVT in all sexes and ethnic groups (p < .05).

Conclusion

Lower leg length may be a suitable alternative to supine height to facilitate the application of LTVV in an ICU setting.

Height Prediction From Ulna Length of Critically Ill Patients

BACKGROUND

Ulna length (UL) has been used in mathematical formulas to predict the body height of healthy and sick individuals. However, the evaluation of its use with patients admitted to intensive care units (ICU) is scarce. The objective of this study was to develop a mathematical equation to estimate critically ill patients' height using the UL measure and to evaluate its agreement with measured standing height.

METHODS

This cross-sectional study was performed at the ICU of a tertiary hospital in Brazil. A total of 100 patients aged ≥18 years who had their body height measured before ICU admission were enrolled. The equation was developed through multiple linear regression, and its agreement was assessed through paired Student's t test and Bland-Altman plot.

RESULTS

The following formula was obtained: height in cm = 153.492 - (7.97 × sex [sex: male = 1, female = 2]) + (0.974 × UL [in cm]). The difference between means of measured height (MH) and height estimated from UL was not significant (166.26 ± 8.75 cm and 166.30 ± 5.29 cm, respectively, P = .96), and a significant correlation (r = 0.624, P < .001) was detected. In the Bland-Altman analysis, UL was in agreement with MH; however, there was a significant bias (P < .001) suggesting that it may be disproportional and dependent on the average's height value.

CONCLUSION

The mathematical equation for height estimation using UL developed in this study matched the MH of critically ill patients. However, we suggest more studies for its validation.