PubMed · 10179491
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J M Mathias. 1998. Protocols help lower extubation times.. https://pubmed.ncbi.nlm.nih.gov/10179491/
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Exercise tolerance tests in athletes are usually performed to evaluate aerobic exertion capacity and to plan training. They are based on simultaneous measurement of expired gases (determination of ventilation threshold and of VO2max). They can also be used to seek a possible cardiovascular anomaly, particularly in case of clinical symptoms or anomalies on auscultation; findings based on electrocardiography (rhythm, repolarisation, etc.) and on blood pressure readings, however, can lead to suspicion of an early anomaly and direct complementary investigation.
Chronic respiratory failure is defined by the inability of the respiratory system to carry out the gas exchange needed to fulfill the body needs. Its diagnosis is based on arterial blood gas measurements. It is possible, however, for the physician to assume it from clinical symptoms. Measuring peak expiratory flow allows one to evaluate the degree of insufficiency. The pneumologist confirms the diagnosis with arterial blood gases measurement and determines its severity. Exercise tests evaluate the incapacity. A quality of life questionnaire assesses the respiratory handicap resulting from the patient's life comfort deficit. After diagnosis, the respiratory failure follow-up is performed by the general practitioner, with specialized investigations as often as necessary according to the severity of the respiratory failure.
Recently, synchronized modes of conventional mechanical ventilation became available for neonatal ventilatory support, but there has been little information regarding details of patient-ventilator interactions during pressure support, volume support, or any other volume-targeted modes of synchronized ventilation in newborn infants. Our objective was to obtain comparative data on patient-ventilator interactions and stability of delivered tidal volume (V(T)) for the different modes of synchronized mechanical ventilation in stable ventilated newborn infants. We examined the effects of pressure support ventilation (PSV) and volume guarantee (VG) modes of a prototype Dräger Babylog ventilator on peak and mean airway pressures (PIP and Paw), inspiratory time (t(in)), and V(T) in 23 ventilated newborn infants. Twelve infants were studied while on assist/control (AC) and 11 on synchronized intermittent mandatory ventilation (SIMV). Mean birth weight was 1,650 +/- 1,180 g, gestational age 31 +/- 6 weeks, and age at time of study was 19 +/- 26 days. Data for 400-600 breaths from each infant were downloaded directly from the ventilator pressure and volume-monitoring module, and analyzed using ANOVA for repeated measures. Mean values and breath-to-breath variability were compared for 20-min periods of AC or SIMV followed by PSV, PSV+VG, and back to baseline AC or SIMV. PSV and PSV+VG led to shorter t(in) and thus to lower Paw, compared to AC. Mean PIP was similar across all AC modes but more variable during VG, reflecting the servocontrol of PIP. V(T) did not differ between AC modes, but was significantly less variable with VG added. PSV and PSV+VG led to lower and less variable PIP and Paw, compared to SIMV, because t(in) was shorter and every breath was supported in PSV and PSV+VG. V(T) was similar in SIMV, PSV, and PSV+VG, but less variable with PSV+VG. Arterial blood gas tensions were similar across all ventilation modes. We conclude that the ventilator prototype functioned as intended. Breath-to-breath tidal volume variability was significantly reduced in VG modes, although not completely eliminated.