Work of Breathing in Infants With Respiratory Insufficiency
Work of Breathing in Infants With Respiratory Insufficiency
Twenty infants were evaluated. Demographics are shown in Table 1 . A total of 52 patients were approached for entry into the study. Twenty-two consented with two being removed before entry into the study due to clinical changes leading to ineligibility after consent was obtained. There was greater tendency of parents to assent for participation if their infant was on CPAP compared with HFNC at the start of the study (P=0.09). All study subjects tolerated the procedures. A total of 12 102 breaths were analyzed; this is the total number of breaths from the 20 patients on the four different modes of therapy. There was a high degree of asynchronous breathing at all four levels of support.
Eighty-two percent of the study subject—respiratory mode combinations displayed clustering (VRS <0.25; k-means clustering with k=2 centers) in which a proportion of breaths either occurred predominantly out-of-phase (relative asynchrony) or in-phase (relative synchrony). (Figures 1 and 2). This has not been previously reported. There was a greater tendency to demonstrate two-cluster pattern breathing with infants on nCPAP compared with HFNC (P<0.01) and in infants with higher mean phase angles measurements (P=0.01), though the clinical impact of the change on VRS was small and unlikely to be clinically meaningful (0.05 for HFNC vs nCPAP; 0.011 maximum impact of phase angle). Seventy-two percent of the phase angle distributions were random. The study was not prospectively designed to investigate this newly detected phenomenon and factors that may influence this occurrence may not have been included in the study protocol.
(Enlarge Image)
Figure 1.
Example patient no. 1: histogram and scatter representation of the phase angles for one of the patients studied on nasal CPAP 6 cmH2O.
(Enlarge Image)
Figure 2.
Example patient no. 2: histogram and scatter representation of the phase angles for one of the patients studied on nasal CPAP 6 cmH2O.
Phase angle, labored breathing index and phase relation of the total breath means for all breaths for each mode of therapy are presented in Figures 3, 4, 5.
(Enlarge Image)
Figure 3.
Mean phase angle and 95% confidence interval results for all analyzed breaths in each group studied. Note: lower phase angle value indicates greater chest–abdomen synchrony.
(Enlarge Image)
Figure 4.
Mean labored breathing index and 95% confidence interval results for all analyzed breaths in each group studied. Note: labored breathing index: closer to 1 relates to greater chest–abdomen synchrony.
(Enlarge Image)
Figure 5.
Mean phase relation total breath and 95% confidence interval results for all analyzed breaths in each group studied. Note: phase relation of total breath: lower numbers relate to greater chest–abdomen synchrony.
The mean phase angle across the four different support levels varied between 80–140°, demonstrating significant ongoing WOB in the study population. There were different degrees of variability in the phase angle across the study group with 10% of patients on HFNC 3 lpm, 30% on HFNC 5 lpm, 20% nCPAP 5 cmH2O and 40% nCPAP 6 cmH2O. The highest phase angle values were seen in the measurements made on HFNC of 3 lpm, followed by HFNC of 5 lpm, nCPAP of 5 cmH2O and finally nCPAP of 6 cmH2O, which had the lowest phase angle measured (P<0.01). Although statistically significant because of the sensitivity associated with the large number of breaths measured, the overlap of the 95% confidence interval for the phase angle parameters, especially between HFNC 5 lpm, nCPAP 5 cmH2O and nCPAP of 6 cmH2O, suggest that there is a lack of a clinical meaningful difference (Figure 3). At the time that the infants were receiving HFNC of 3 lpm, they had less breath-to-breath variation when compared with the other three modes of therapy; however, they had the highest mean phase angle. The percentage of breaths with a phase angle >90 was greater in HFNC 3 lpm>HFNC 5 lpm>nCPAP 5 cmH2O>nCPAP 6 cmH2O (P<0.01).
The mean relative labored breathing index showed statistical differences (P≤0.001), but the clinically similar means and high degree of overlap of the 95% confidence interval suggest a lack of clinical meaningful differences (Figure 4). Similarly, the mean phase relation of total breath was statistically different (P<0.01) though with clinically similar means and high degree of overlap of the 95% confidence interval (Figure 5).
The composite data for the uncalibrated inspired volume revealed that HFNC of 3 lpm had a mean size breath that was 11.8% smaller when compared with HFNC of 5 lpm (P=0.01); 23.2% smaller when compared with nCPAP of 5 cmH2O (P<0.01); and 21.3% smaller when compared with nCPAP of 6 cmH2O (P<0.01). The median size breath for HFNC of 5 lpm was 11.4% smaller when compared with the mean size breath of nCPAP of 5 cmH2O (P=0.19); 9.4% smaller when compared with nCPAP of 6 cmH2O (P=0.22). The mean breath size of nCPAP of 5 cmH2O was 1.9% smaller when compared with nCPAP of 6 cmH2O (P=0.78).
Results
Twenty infants were evaluated. Demographics are shown in Table 1 . A total of 52 patients were approached for entry into the study. Twenty-two consented with two being removed before entry into the study due to clinical changes leading to ineligibility after consent was obtained. There was greater tendency of parents to assent for participation if their infant was on CPAP compared with HFNC at the start of the study (P=0.09). All study subjects tolerated the procedures. A total of 12 102 breaths were analyzed; this is the total number of breaths from the 20 patients on the four different modes of therapy. There was a high degree of asynchronous breathing at all four levels of support.
Eighty-two percent of the study subject—respiratory mode combinations displayed clustering (VRS <0.25; k-means clustering with k=2 centers) in which a proportion of breaths either occurred predominantly out-of-phase (relative asynchrony) or in-phase (relative synchrony). (Figures 1 and 2). This has not been previously reported. There was a greater tendency to demonstrate two-cluster pattern breathing with infants on nCPAP compared with HFNC (P<0.01) and in infants with higher mean phase angles measurements (P=0.01), though the clinical impact of the change on VRS was small and unlikely to be clinically meaningful (0.05 for HFNC vs nCPAP; 0.011 maximum impact of phase angle). Seventy-two percent of the phase angle distributions were random. The study was not prospectively designed to investigate this newly detected phenomenon and factors that may influence this occurrence may not have been included in the study protocol.
(Enlarge Image)
Figure 1.
Example patient no. 1: histogram and scatter representation of the phase angles for one of the patients studied on nasal CPAP 6 cmH2O.
(Enlarge Image)
Figure 2.
Example patient no. 2: histogram and scatter representation of the phase angles for one of the patients studied on nasal CPAP 6 cmH2O.
Phase angle, labored breathing index and phase relation of the total breath means for all breaths for each mode of therapy are presented in Figures 3, 4, 5.
(Enlarge Image)
Figure 3.
Mean phase angle and 95% confidence interval results for all analyzed breaths in each group studied. Note: lower phase angle value indicates greater chest–abdomen synchrony.
(Enlarge Image)
Figure 4.
Mean labored breathing index and 95% confidence interval results for all analyzed breaths in each group studied. Note: labored breathing index: closer to 1 relates to greater chest–abdomen synchrony.
(Enlarge Image)
Figure 5.
Mean phase relation total breath and 95% confidence interval results for all analyzed breaths in each group studied. Note: phase relation of total breath: lower numbers relate to greater chest–abdomen synchrony.
The mean phase angle across the four different support levels varied between 80–140°, demonstrating significant ongoing WOB in the study population. There were different degrees of variability in the phase angle across the study group with 10% of patients on HFNC 3 lpm, 30% on HFNC 5 lpm, 20% nCPAP 5 cmH2O and 40% nCPAP 6 cmH2O. The highest phase angle values were seen in the measurements made on HFNC of 3 lpm, followed by HFNC of 5 lpm, nCPAP of 5 cmH2O and finally nCPAP of 6 cmH2O, which had the lowest phase angle measured (P<0.01). Although statistically significant because of the sensitivity associated with the large number of breaths measured, the overlap of the 95% confidence interval for the phase angle parameters, especially between HFNC 5 lpm, nCPAP 5 cmH2O and nCPAP of 6 cmH2O, suggest that there is a lack of a clinical meaningful difference (Figure 3). At the time that the infants were receiving HFNC of 3 lpm, they had less breath-to-breath variation when compared with the other three modes of therapy; however, they had the highest mean phase angle. The percentage of breaths with a phase angle >90 was greater in HFNC 3 lpm>HFNC 5 lpm>nCPAP 5 cmH2O>nCPAP 6 cmH2O (P<0.01).
The mean relative labored breathing index showed statistical differences (P≤0.001), but the clinically similar means and high degree of overlap of the 95% confidence interval suggest a lack of clinical meaningful differences (Figure 4). Similarly, the mean phase relation of total breath was statistically different (P<0.01) though with clinically similar means and high degree of overlap of the 95% confidence interval (Figure 5).
The composite data for the uncalibrated inspired volume revealed that HFNC of 3 lpm had a mean size breath that was 11.8% smaller when compared with HFNC of 5 lpm (P=0.01); 23.2% smaller when compared with nCPAP of 5 cmH2O (P<0.01); and 21.3% smaller when compared with nCPAP of 6 cmH2O (P<0.01). The median size breath for HFNC of 5 lpm was 11.4% smaller when compared with the mean size breath of nCPAP of 5 cmH2O (P=0.19); 9.4% smaller when compared with nCPAP of 6 cmH2O (P=0.22). The mean breath size of nCPAP of 5 cmH2O was 1.9% smaller when compared with nCPAP of 6 cmH2O (P=0.78).
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