The effect of dietary intake on apneic performance, cardiovascular and splenic responses during repeated breath holds

Abstract

Rationale:Static apnoeas performed after an overnight fast as opposed to postprandially have been evinced to improve apnoeic performance. However, no study has explored the effect of dietary intake on apnoeic performance, cardiovascular nor splenic responses over a series of repeated apnoeas. Method:Ten healthy adults attended the laboratory on three separate occasions (≥48-h apart) after: a 14-h fast (F14), 1-h post consumption of a high-calory-high-carbohydrate (HCHC) or a low-calory-low-carbohydrate (LCLC) based-meal. During each visit the subjects performed a hyperoxic rebreathing trial and a series of three repeated maximal static apnoeas. Heart rate, peripheral oxyhaemoglobin saturation (SpO2) and gas exchange were monitored continuously whereas splenic volume (SV) and haematology were assessed after the rebreathing and apnoeas. Results:At rest, after HCHC the respiratory exchange ratio (0.87±0.17,p≤0.043), expired minute volume of carbon dioxide (CO2) (HCHC,0.35±0.09L/min,p≤0.014) and SV (227±45mL,p≤0.031) were higher compared to F14 (0.71±0.08;0.23±0.04L/min;204±49mL) and LCLC (0.72±0.07;0.25±0.03L/min;199±49mL). A faster CO2 accumulation was recorded during the HCHC (96±35s) rebreathing trial (F14,162±42s,p=0.001;LCLC,151±23s,p=0.002). Longer apnoeas were reported in F14 compared with HCHC (apnoeas 1-3,p≤0.046) and LCLC (apnoeas 2-3,p≤0.006). After the first apnoea SV was lower in F14 (141±43mL,p=0.015) compared with HCHC (180±34mL). Moreover, following the third apnoea end-tidal partial pressure of oxygen and nadir SpO2 were lower in F14 (8.6±2.2kPa,p=0.028;77±13%,p=0.009) compared with HCHC (10.1±1.7kPa;84±9%). No differences were measured in end-apnoeic end-tidal partial pressure of CO2, heart rate nor haematology across diets. Conclusion:Fasting improved apnoeic performance with apnoeas being terminated at lower oxygen levels through altering the rate of CO2 accumulation but without affecting the cardiovascular responses.

Breath-Hold Diving Injuries — A Primer for Medical Providers

“…Fasting prior to breath-holding can help athletes prolong a breath hold due to the slower accumulation of CO 2 , at the risk of developing hypoxia due to significantly lower oxygen levels at the termination of a breath hold (15,16). When fasting is combined with light exercise, the breath hold duration also is increased.…”