High-flow nasal cannula (HFNC) is a method of non-invasive respiratory support used to decrease the effort of breathing (EOB) in patients with a wide variety of respiratory diseases in the pediatric intensive care unit. While its use has shown association with decreased rates of mechanical ventilation, there is a paucity of data examining its direct effect upon objective measurements of EOB. This study will aim to evaluate objective measurements of EOB in response to different levels of HFNC support, characterize the natural course of respiratory diseases treated with HFNC, evaluate changes in EOB secondary to the administration of supplemental medical therapies used in conjunction with HFNC, and compare different physiologic metrics for quantifying EOB in patients on HFNC.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
21
Measurements of effort of breathing will be obtained at flow rates of 0.5, 1.0, 1.5, and 2.0 L/kg/min. Adequate time will be allowed at each flow rate for stabilization of EOB and flow levels will be trialed in a random order, each being trialed for approximately 5 minutes.
Measurements of effort of breathing will be obtained at flow rates of 0.5, 1.0, 1.5, and 2.0 L/kg/min. Adequate time will be allowed at each flow rate for stabilization of EOB and flow levels will be trialed in a random order, each being trialed for approximately 5 minutes.
Children's Hospital Los Angeles
Los Angeles, California, United States
Percent Change in Pressure-rate Product (PRP) as a Function of Increasing HFNC Flow Rate on Both Types of HFNC Delivery System (FP and VT)
PRP is a validated objective metric of effort of breathing which is derived from the product of the peak-to-trough change in esophageal pressure (in cmH20) and the respiratory rate (breaths per minute). The percent change in PRP is derived from the quotient of the absolute PRP at increased HFNC flow rates (1.0, 1.5, and 2.0 L/kg/min) divided by the absolute PRP at a baseline HFNC flow rate (0.5 L/kg/min). Percent change in PRP was used because a) there was a large degree of heterogeneity in baseline absolute PRP values in our study population based upon patient size, disease severity, and time point of illness, and b) we allowed for repeated measures on the same patient which would bias absolute PRP values in favor of those who were measured more frequently. It was not pre-specified to compare the two different HFNC delivery systems.
Time frame: median percent change in PRP over 5 minute measurement period
Pressure-rate Product (PRP) as a Function of Increasing HFNC Flow Rate on Both Types of HFNC Delivery System (FP and VT)
PRP is a validated objective metric of effort of breathing which is derived from the product of the peak-to-trough change in esophageal pressure (in cmH20) and the respiratory rate (breaths per minute). These values were obtained from 5 minute flow titration periods. For this outcome, the PRP was obtained for all titrations on both types of HFNC delivery system (FP and VT). It was not pre-specified to compare the two different HFNC delivery systems.
Time frame: median PRP over a 5 minute period
Phase Angle as a Function of Increasing HFNC Flow Rate on Both Types of HFNC Delivery System (FP and VT)
Phase angle is a measure of asynchrony between thoracic and abdominal breathing compartments that has correlated with increased effort of breathing. It is derived by measuring the relative expansion of these two breathing compartments and describing the synchrony between them as an angle (theta). For this outcome, the phase angle was obtained for all titrations on both types of HFNC delivery system (FP and VT). It was not pre-specified to compare the two different HFNC delivery systems.
Time frame: median phase angle over a 5 minute period
Percent Change in Pressure-rate Product (PRP) From Baseline as a Function of Increasing HFNC Flow Rate, Comparing Different HFNC Delivery Systems
For this outcome, a subgroup of patients (N=12) were examined who had PRP measurements obtained on two different HFNC delivery systems (Fisher \& Paykel (FP) and Vapotherm (VT)) in back-to-back flow titration periods. With one exception, patients were first studied on the FP and then transitioned to the VT HFNC delivery system.
Time frame: median PRP over a 5 minute period
Percent Change in Pressure-rate Product (PRP) From Baseline as a Function of Increasing HFNC Flow Rate, Comparing Weight-Stratified Subgroups on Both Types of HFNC Delivery System (FP and VT)
To assess the relationship between patient size and dose-response of HFNC flow rate, we compared subgroups stratified by weight (patients \<8 kg and \>8 kg). For this outcome, the median percent change in PRP was obtained for all titrations on both types of HFNC delivery system (FP and VT). It was not pre-specified to compare the two different HFNC delivery systems.
Time frame: medain percent change in PRP over a 5 minute period
Maximum Percent Change in Pressure-rate Product (PRP) From Baseline as a Function of Increasing HFNC Flow Rate, Comparing Weight-Stratified Subgroups on Both Types of HFNC Delivery System (FP and VT)
Exploratory analysis of patients by further stratified weight groupings (\<5 kg, 5-8 kg, and \>8 kg) was performed to determine the greatest observed benefit of HFNC flow titration in patients of different sizes. For this outcome, the maximum percent change in PRP was obtained for all titrations on both types of HFNC delivery system (FP and VT). It was not pre-specified to compare the two different HFNC delivery systems.
Time frame: median of the maximum percent change in PRP over a 5 minute period
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