# Paced breathing causes tonic change rather than phasic modulation of superficial venous diameter

## TL;DR

Paced breathing changes vein diameter in a sustained way rather than a rhythmic one, suggesting it may not help improve venipuncture success.

## Contribution

The study provides novel evidence of respiratory modulation in peripheral superficial veins and identifies tonic changes as more dominant than phasic modulation.

## Key findings

- Respiratory modulation was confirmed in peripheral superficial veins, similar to the inferior vena cava.
- Tonic changes in baseline vein diameter were more dominant than phasic modulation during paced breathing.
- Paced breathing for 50 seconds did not enhance venous access compared to spontaneous breathing.

## Abstract

Respiratory modulation is generally observed in the inferior vena cava (IVC). If similar respiratory modulation exists in peripheral superficial veins, it would be possible to dilate the vein diameter by respiratory control. This may improve the success rate of venipuncture in clinical practices. Hence, the present study aimed to investigate the respiratory modulation in peripheral superficial veins.

This study included 21 healthy female volunteers (mean age 21.8 ± 0.9 years). Participants performed spontaneous breathing (SB) and paced breathing (PB). B-mode ultrasound imaging was used to continuously monitor the cutaneous veins of the left elbow fossa for 50 s.

Vein diameter demonstrated a clear modulation consistent with paced breathing, and the amplitude of vein diameter modulation was greater at 10 s-PB than at 3 s-PB. Additionally, PB affected the baseline of modulation (mean vein diameter). The baseline exhibited the largest diameter in SB, followed by 3 s-PB and 10 s-PB. The baseline for SB and 10 s-PB demonstrated a statistically significant difference (p = 0.03). Respiratory modulation was confirmed in peripheral superficial veins; however, tonic change in baseline diameter was dominant over phasic modulation. Even when vein diameter was most dilated at 10 s-PB, the diameter at that time was smaller than the mean diameter at SB.

This study demonstrated that the peripheral superficial vein diameter exhibited respiratory modulation, similar to the IVC. Although respiratory modulation of the IVC has been well documented in previous studies, the present findings provide novel evidence of this phenomenon in the peripheral superficial veins. Additionally, this study identified tonic changes in the mean vein diameter, which were more dominant than phasic modulations. Furthermore, the mean vein diameter during SB was greater than the maximum diameter observed during 10 s-PB. These findings suggested that PB for 50 s during venipuncture did not enhance venous access.