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 Consumables

Flow sensors. Proximal flow and pressure measurement

Flow sensor

Come closer! Proximal flow measurement

The proximal flow sensor has been the centerpiece of our ventilators since 1983. The whole ventilation process depends on the measurement and accuracy of the flow sensor, and they provide data from the airway opening.

Precise volume, flow, and pressure data is crucial to making a correct diagnosis and avoiding common side effects of inappropriate ventilation settings. It is also what enables some of our advanced technologies, such as the ASV and INTELLiVENT-ASV modes, IntelliSync+, and the P/V Tool.

Flow sensor

Accuracy is a must. Your patients depend on it

Our ventilators measure flow and pressure close to the patient's airway. Studies have shown that tidal volumes for ventilated patients should be determined with a flow sensor placed at the endotracheal tube (Cannon ML, Cornell J, Tripp-Hamel DS, et al. Tidal volumes for ventilated infants should be determined with a pneumotachometer placed at the endotracheal tube. Am J Respir Crit Care Med. 2000;162(6):2109-2112. doi:10.1164/ajrccm.162.6.99061121​, Gammage, Gary W.; Banner, Michael J.; Blanch, Paul B.; Kirby, Robert R. VENTILATOR DISPLAYED TIDAL VOLUME—WHAT YOU SEE MAY NOT BE WHAT YOU GET, Critical Care Medicine: April 1988 - Volume 16 - Issue 4 - p 454 2​)

Graphic illustration: woman thinking about a question

Do we have proof? Clinical evidence

Accurately determining the exhaled tidal volume (VTE) is crucial (Cannon ML, Cornell J, Tripp-Hamel DS, et al. Tidal volumes for ventilated infants should be determined with a pneumotachometer placed at the endotracheal tube. Am J Respir Crit Care Med. 2000;162(6):2109-2112. doi:10.1164/ajrccm.162.6.99061121​), especially in situations where only small tidal volumes are delivered (infants, neonates, and ARDS patients). With Hamilton Medical flow sensors, you can measure VTE close to the patient’s airway for a more precise value.

Benefits for you:

  • Proximal placement eliminates the effects of breathing circuit compliance on flow and volume measurements (Cannon ML, Cornell J, Tripp-Hamel DS, et al. Tidal volumes for ventilated infants should be determined with a pneumotachometer placed at the endotracheal tube. Am J Respir Crit Care Med. 2000;162(6):2109-2112. doi:10.1164/ajrccm.162.6.99061121​)
  • VTE measurement is subject to less resistance from the respiratory system (Nève V, Leclerc F, Noizet O, et al. Influence of respiratory system impedance on volume and pressure delivered at the Y piece in ventilated infants. Pediatr Crit Care Med. 2003;4(4):418-425. doi:10.1097/01.PCC.0000090289.98377.153​)
  • Fewer leaks occur that may alter the result (Al-Majed SI, Thompson JE, Watson KF, Randolph AG. Effect of lung compliance and endotracheal tube leakage on measurement of tidal volume. Crit Care. 2004;8(6):R398-R402. doi:10.1186/cc29544​)

Our flow sensor portfolio

We offer Hamilton Medical consumables for adult, pediatric, and neonatal patients. You can choose between reusable and single-use products, depending on your institutional policies.

Single-use proximal flow sensor for pediatric/adult patients

Single-use proximal flow sensor for pediatric/adult patients

  • Tube available in three different lengths 188, 260, and 330 cm
  • OD22/ID15, patient side
  • Calibration adapter
  • Tubing clip
Single-use proximal flow sensor for neonatal patients

Single-use proximal flow sensor for neonatal patients

  • Tube available in three different lengths 160, 188, and 310 cm
  • ID15, patient side
  • Calibration adapter
  • Tubing clip
Reusable proximal flow sensor for pediatric/adult patients

Reusable proximal flow sensor for pediatric/adult patients

  • Tube length: 188 cm
  • OD22/ID15, patient side
  • Calibration adapter
  • Tubing attachment straps
e-Catalog
Dr. Robert Lopez

Customer voices

Hamilton Medical single‑use flow sensors help us prevent cross-contamination because we don't have to worry about re-using the flow sensors on another patient.

Dr. Robert Lopez

Director of Respiratory Care until 2018
University Medical Center, Lubbock (TX), USA

Graphic illustration: baby with flow sensor

Good to know! How to use the flow sensor correctly

For more information

Document
Flow sensor technical specifications
English | 0.58 MB | 689568.02
Document
Tidal volumes for ventilated patients should be determined at the endotracheal tube
English | 0.08 MB | 689217.00
Document
Reprocessing Guide Flow sensor
English, German, French, Spanish, Italian, Russian, Turkish, Chinese | 1.46 MB | 624421.05
Document
Instructions for use adult/pediatric, flow sensor, single use
English, German, French | 0.76 MB | 624269.12
Show more

References

  1. 1. Cannon ML, Cornell J, Tripp-Hamel DS, et al. Tidal volumes for ventilated infants should be determined with a pneumotachometer placed at the endotracheal tube. Am J Respir Crit Care Med. 2000;162(6):2109-2112. doi:10.1164/ajrccm.162.6.9906112
  2. 2. Gammage, Gary W.; Banner, Michael J.; Blanch, Paul B.; Kirby, Robert R. VENTILATOR DISPLAYED TIDAL VOLUME—WHAT YOU SEE MAY NOT BE WHAT YOU GET, Critical Care Medicine: April 1988 - Volume 16 - Issue 4 - p 454

 

  1. 3. Nève V, Leclerc F, Noizet O, et al. Influence of respiratory system impedance on volume and pressure delivered at the Y piece in ventilated infants. Pediatr Crit Care Med. 2003;4(4):418-425. doi:10.1097/01.PCC.0000090289.98377.15
  2. 4. Al-Majed SI, Thompson JE, Watson KF, Randolph AG. Effect of lung compliance and endotracheal tube leakage on measurement of tidal volume. Crit Care. 2004;8(6):R398-R402. doi:10.1186/cc2954

Footnotes

 

Tidal volumes for ventilated infants should be determined with a pneumotachometer placed at the endotracheal tube.

Cannon ML, Cornell J, Tripp-Hamel DS, et al. Tidal volumes for ventilated infants should be determined with a pneumotachometer placed at the endotracheal tube. Am J Respir Crit Care Med. 2000;162(6):2109-2112. doi:10.1164/ajrccm.162.6.9906112

Many ventilators measure expired tidal volume (VT) without compensation either for the compliance of the ventilator circuit or for variations in the circuit setup. We hypothesized that the exhaled VT measured with a conventional ventilator at the expiratory valve would differ significantly from the exhaled VT measured with a pneumotachometer placed at the endotracheal tube. To investigate this we studied 98 infants and children requiring conventional ventilation. We used linear regression analysis to compare the VT obtained with the pneumotachometer with the ventilator-measured volume. An additional comparison was made between the pneumotachometer volume and a calculated effective VT. For infant circuits (n = 70), our analysis revealed a poor correlation between the expiratory VT measured with the pneumotachometer and the ventilator-measured volume (r(2) = 0.54). Similarly, the expiratory VT measured with the pneumotachometer did not correlate with the calculated effective volume (r(2) = 0.58). For pediatric circuits (n = 28), there was improved correlation between the expiratory VT measured with the pneumotachometer and both the ventilator-measured volume and the calculated effective VT (r(2) = 0.84 and r(2) = 0.85, respectively). The data demonstrate a significant discrepancy between expiratory VT measured at a ventilator and that measured with a pneumotachometer placed at the endotracheal tube in infants. Correcting for the compliance of the ventilator circuit by calculating the effective VT did not alter this discrepancy. In conventionally ventilated infants, exhaled VT should be determined with a pneumotachometer placed at the airway.

Ventilator displayed tidal volume: What you see may not be what you get.

Gammage, Gary W.; Banner, Michael J.; Blanch, Paul B.; Kirby, Robert R. VENTILATOR DISPLAYED TIDAL VOLUME—WHAT YOU SEE MAY NOT BE WHAT YOU GET, Critical Care Medicine: April 1988 - Volume 16 - Issue 4 - p 454

Influence of respiratory system impedance on volume and pressure delivered at the Y piece in ventilated infants.

Nève V, Leclerc F, Noizet O, et al. Influence of respiratory system impedance on volume and pressure delivered at the Y piece in ventilated infants. Pediatr Crit Care Med. 2003;4(4):418-425. doi:10.1097/01.PCC.0000090289.98377.15



OBJECTIVES

Tidal volume (VT) delivered to infants' airways are overestimated and pressure underestimated when measured in the ventilator and not at the Y piece. This study aimed at evaluating the influence of respiratory system impedance on expiratory VT (VTE) and pressure measurement difference.

DESIGN

Prospective observational study.

SETTING

Pediatric intensive care unit at a university hospital.

PATIENTS

Data were collected between February 2000 and October 2001 for 30 infants (range, 1-23 months) ventilated in the pressure-controlled or volume-controlled mode.

INTERVENTIONS

Measurements of VTE, pressure obtained at the same time at the Y piece and on the ventilator Servo 300, were collected in ventilated infants. Respiratory system impedance was calculated from data obtained at the Y piece. Circuit compliance was measured in vitro. VTEs were corrected for compressible volume.

MEASUREMENTS AND RESULTS

VTEs were overestimated by the Servo 300 in the pressure-controlled and volume-controlled modes (from 5% to 62% of the value displayed on Servo 300). Maximal inspiratory pressures were underestimated by the Servo 300 in the pressure-controlled mode (difference from -2 to +19 cm H(2)O). Measurement difference increased with increasing respiratory system impedance. Ventilator VTE corrected for circuit compliance did not offer a sufficiently accurate estimation of VTE at the Y piece.

CONCLUSIONS

VT and pressure measurements must be performed at the Y piece, especially in infants with increased respiratory system impedance (i.e., decreased respiratory system compliance or increased resistance). Correcting VTE for circuit compliance cannot replace measurement of VT at the Y piece.

Effect of lung compliance and endotracheal tube leakage on measurement of tidal volume.

Al-Majed SI, Thompson JE, Watson KF, Randolph AG. Effect of lung compliance and endotracheal tube leakage on measurement of tidal volume. Crit Care. 2004;8(6):R398-R402. doi:10.1186/cc2954



INTRODUCTION

The objective of this laboratory study was to measure the effect of decreased lung compliance and endotracheal tube (ETT) leakage on measured exhaled tidal volume at the airway and at the ventilator, in a research study with a test lung.

METHODS

The subjects were infant, adult and pediatric test lungs. In the test lung model, lung compliances were set to normal and to levels seen in acute respiratory distress syndrome. Set tidal volume was 6 ml/kg across a range of simulated weights and ETT sizes. Data were recorded from both the ventilator light-emitting diode display and the CO2SMO Plus monitor display by a single observer. Effective tidal volume was calculated from a standard equation.

RESULTS

In all test lung models, exhaled tidal volume measured at the airway decreased markedly with decreasing lung compliance, but measurement at the ventilator showed minimal change. In the absence of a simulated ETT leak, calculation of the effective tidal volume led to measurements very similar to exhaled tidal volume measured at the ETT. With a simulated ETT tube leak, the effective tidal volume markedly overestimated tidal volume measured at the airway.

CONCLUSION

Previous investigators have emphasized the need to measure tidal volume at the ETT for all children. When ETT leakage is minimal, it seems from our simulated lung models that calculation of effective tidal volume would give similar readings to tidal volume measured at the airway, even in small patients. Future studies of tidal volume measurement accuracy in mechanically ventilated children should control for the degree of ETT leakage.