Ventilatory responses to threshold loaded respiration in man

Area of Science:

• Respiratory Physiology
• Neurology

Background:

• Postoperative patients often experience respiratory difficulty beyond physical findings.
• This suggests impaired compensatory mechanisms, potentially pre-existing.
• Clinical assessment is limited by patient status.

Purpose of the Study:

• To develop a noninvasive method to assess respiratory system stress.
• To investigate the impact of increasing carbon dioxide (CO2) levels and inspiratory threshold loads on respiratory responses.
• To evaluate compensatory mechanisms in postoperative patients.

Main Methods:

• A noninvasive rebreathing test using a 7% CO2 and 93% O2 mixture.
• Sequential application of fixed pressure inspiratory threshold loads.
• Measurement of respiratory system response under increasing stress.

Main Results:

• Normal subjects exhibited incrementally depressed CO2 response with threshold loads.
• Patients with brain stem lesions showed significantly greater depression at higher loads.
• This indicates a reduced tolerance to increased breathing loads in these patients.

Conclusions:

• The developed test effectively stresses the respiratory system.
• Brain stem lesions may impair the ability to tolerate increased respiratory loads.
• This finding has implications for understanding postoperative respiratory distress.