Effects of varied vocal intensity on ventilation and energy expenditure in women and men

This study was completed to determine how ventilatory responses change by means of speech reading at three different sound pressure levels (SPL) as compared to quiet breathing prior to each task. The energy required to alter SPL was also studied and compared to energy expenditures during a quiet breathing condition. Twenty-four adults (12 women, 12 men) were studied while reading a standard passage at low, comfortable, and high SPLs for 7 minutes with quiet breathing periods between each task to achieve respiratory steady state and serve as a control to which the reading tasks were compared. The last 2 minutes of exhaled air for all speaking and quiet breathing tasks were collected using a Hans Rudolph mouth breathing face mask. A Sensor Medics V(max) 29(TM) series diagnostic instrument system measured all ventilatory responses and energy expenditures. Volume and timing alterations in ventilation were characterized by measuring tidal volume (V(T)), inspiratory time (T(I)), inspiratory flow rate (V(T)/T(I)), and expiratory time (T(E)). Average ventilation, energy expenditure, and adequacy of ventilation were measured using minute ventilation (V̇(E)), oxygen consumption (V̇O₂), carbon dioxide production (V̇CO₂), and partial pressure of end-tidal carbon dioxide (end-tidal PET(CO2)). Results indicated volume, timing, ventilation, and energy expenditure values remained closest to quiet breathing values for the comfortable SPL. Volume, ventilation, and energy expenditure were significantly greater for the high SPL and lower for the low SPL, compared to the baseline steady state, indicating that the low SPL causes a ventilatory deficit that was found to be paid back at the end of the speech task during the quiet breathing period. These results demonstrate that an individual's comfortable SPL is the last energy-requiring way to speech breathe. As SPL rises above or below comfortable SPL, speech breathing requires more energy.