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Biomedical subjects

J H Modell

Publications and source records attributed to J H Modell.

At least 37 records · Page 2Linked to original sources
PubMed1984

Titration of PEEP by the arterial minus end-tidal carbon dioxide gradient.

It was shown in dogs that intrapulmonary physiologic shunt (Qsp/Qt), arterial oxygen tension (PaO2), total static respiratory compliance (CT), oxygen delivery (O2AV), cardiac output (Qt), and arterial minus end-tidal carbon dioxide gradient (PaCO2-PetCO2) undergo statistically significant deterioration when oleic acid is injected into the pulmonary artery. Positive end-expiratory pressure (PEEP) therapy reduced Qsp/Qt and PaCO2-PetCO2 gradient and increased PaO2. The CT did not show any consistent pattern of improvement with the application of PEEP. The Qt and the O2AV progressively decreased as PEEP was increased. The application of additional PEEP beyond that which minimized the PaCO2-PetCO2 gradient produced a statistically significant increase in the PaCO2-PetCO2 gradient, but this was not reflected by concomitant changes in Qsp/Qt or PaO2 in spite of a further decrease in Qt. Thus, the PaCO2-PetCO2 gradient may be a more sensitive indicator of excessive PEEP than is Qst/Qt or PaO2, since it should be smallest when there is maximal recruitment of perfused or functional gas units without overdistention of alveolar areas contributing to dead space. Also, the use of the PaCO2-PetCO2 gradient permits the rapid titration of PEEP without the need for a pulmonary artery catheter.

Animals↗
PubMed1984

Pulmonary aspiration--effects of volume and pH in the rat.

To evaluate the effect of volume of aspirates with different pHs on mortality associated with pulmonary aspiration, hydrochloric acid solutions were injected into the tracheas of 336 Sprague-Dawley rats. The rats were divided randomly into 33 groups, were observed for 96 hr after aspiration, and were not resuscitated. Deaths were divided into two groups: early, less than 30 min after aspiration, and late, greater than 4 hr after aspiration. Late deaths, accounting for 22% of all fatalities, occurred exclusively in animals aspirating solutions with a pH less than 2.5. These late deaths indicated progressive lung damage as opposed to acute cardiorespiratory failure, which early deaths suggested. Low volume pulmonary aspirates (0.3 ml/kg) with extremely low pH (1.0) resulted in a high mortality rate (90%). Conversely, higher volume pulmonary aspirates (1.0-2.0 ml/kg) with a higher pH (greater than or equal to 1.8) resulted in a low mortality rate (14%). These data demonstrate an important interaction between pH and volume of aspirates: even low volumes have a high mortality rate if pH is very low, whereas if gastric fluid is effectively buffered, then much higher volumes than previously thought can be tolerated. This suggests that the routine use of nonparticulate antacids may be indicated in patients at risk from aspiration of stomach contents and should not be withheld because of concern of increasing gastric volume.

Anesthesia, General↗
PubMed1983

Effectiveness of CPAP by mask for pulmonary edema associated with hypercarbia.

We describe continuous positive airway pressure (CPAP) by mask to reduce hypercarbia in two patients who had pulmonary edema due to congestive heart failure. In such patients, beside reducing venous return and filling pressures, CPAP improves compliance and decreases the work of breathing, thereby improving effective ventilation. Hence, CPAP may be useful to combat not only hypoxemia but also hypercarbia that is associated with pulmonary edema.

Aged↗
PubMed1983

Continuous positive airway pressure is beneficial in treatment of smoke inhalation.

This study demonstrates that continuous positive airway pressure (CPAP) improves pulmonary function after smoke inhalation by dogs. Sixteen dogs were anesthetized with iv sodium pentobarbital. Arterial and mixed venous blood gas tensions; carboxyhemoglobin concentration (COHgb); mean systemic arterial (MAP), mean pulmonary arterial (MPAP), and pulmonary arterial wedge (WP) pressures; heart (HR) and respiratory (f) rates; cardiac output (CO); and airway pressure (Paw) were measured. Intrapulmonary physiologic shunt (Qsp/Qt) and pulmonary (PVR) and systemic (SVR) vascular resistances were calculated. The animals then breathed an aerosol of smoke and were divided randomly into 2 groups. The treatment group breathed spontaneously on 8-torr CPAP whereas the control group continued to breathe spontaneously at ambient pressure. After inhalation of smoke, Qsp/Qt, MPAP, PVR, COHgb, HR, and f rose, whereas PaO2 and MAP fell in untreated animals. When CPAP was applied, PaO2 and Qsp/Qt returned nearly to baseline values. Mean f also was significantly lower in the treated animals. We found that the early institution of CPAP improves oxygen exchange in the lungs after the inhalation of smoke.

Animals↗
PubMed1983

Continuous positive airway pressure improves oxygenation in dogs after the aspiration of blood.

Fourteen dogs were anesthetized, intubated, and breathed room air spontaneously. We then instilled 2 ml/kg of fresh nonheparinized donor blood into their tracheas. Seven dogs received no treatment and served as controls (group A); respiratory rate (RR) increased from 25 +/- 11 (mean +/- SD) to 103 +/- 33 breath/min, HR decreased from 179 +/- 28 to 136 +/- 42 beat/min, PaO2 decreased from 82 +/- 10 to 30 +/- 4 torr, pulmonary venous admixture (Qsp/Qt) increased from 0.14 +/- 0.10 to 0.72 +/- 0.06, and venous oxygen tension (PVO2) decreased from 46 +/- 4 to 22 +/- 5 torr 10 min after the aspiration of blood; all changes were statistically significant (p less than .05). After 4 h, RR and HR returned to control values, but PaO2 was only 58 +/- 10 torr. Cardiac output, oxygen consumption (VO2), and pulmonary and systemic BP and resistances were not significantly affected. Thirty-five min after the other 7 dogs aspirated blood (group B), 10 cm H2O of continuous positive airway pressure (CPAP) was applied while they breathed spontaneously. CPAP reduced Qsp/Qt to 0.31 +/- 0.10 and 0.15 +/- 0.11 30 and 90 min after its application, respectively (p less than .05). By 4 h, the PaO2 of group B dogs was 81 +/- 15 torr (p less than .05 compared with group A). CPAP also increased arteriovenous oxygen content difference (C[a-v]O2) compared with the nontreated dogs. Four hours after the aspiration of blood, all dogs were extubated. Twenty-four hours later, arterial blood gases were normal in all dogs of both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Positive end-expiratory pressure (PEEP) and cerebrospinal fluid pressure during normal and elevated intracranial pressure in dogs.

The effect of up to 15 cm H2O positive end-expiratory pressure (PEEP) on cerebrospinal fluid pressure (Pcsf) was investigated in five anaesthetised, mechanically ventilated dogs during normal and then elevated (40-50 cm H2O) intracranial pressure (ICP). Stepwise elevations of PEEP in 5 cm H2O increments resulted in small rises in Pcsf at normal ICP and in significantly larger rises when ICP was elevated. The regression equations for the relationships between Pcsf and end-expiratory pressure (EEP) were as follows: Pcsf = 12.95 + 0.82 EEP for normal ICP, and Pcsf = 46.41 + 2.06 EEP for elevated ICP. Mean PaCO2 rose from 39.7 +/- 2.5 to 47.6 +/- 5.0 torr during normal ICP, and from 34.2 +/- 2.9 to 50.9 +/0- 5.3 torr at elevated ICP as PEEP was elevated to 15 cm H2O. We conclude that PEEP raised Pcsf, and that this increase is more severe under conditions of elevated ICP. The rise in Pcsf due to PEEP may be explained by either the rise in intrathoracic pressure or the rise in PaCO2, or both.

Animals↗
PubMed1980

Near-drowning: correlation of level of consciousness and survival.

This paper reports a retrospective review of 121 cases of near-drowning treated at university hospitals in Miami and Gainesville. The series included 57 adults and 64 children who were classified into three categories, Category A (Awake), Category B (Blunted) and Category C (Comatose), based on their level of consciousness on arrival at the primary hospital. Results based on the total 121 patients showed 87 per cent survived with apparently normal brain function, two per cent survived with impaired brain function and 11 per cent died. The survival rate of all patients who were awake when they entered the hospital was significantly greater than that of both those who were admitted and blunted consciousness (p = 0.05) and those who were comatose when admitted (p less then 0.0001). Further, the group whose members had blunted consciousness had a significantly greater number of normal survivors than the group whose members were comatose on admission (p less than 0.002). All treated adults survived without permanent neurological damage and only three surviving children in the series suffered residual brain damage. Whether the course of the seven patients, three adults and four children, who died without return of brain function, would have been altered by deliberate attempts to preserve the brain is a matter of speculation.

Adult↗
PubMed1978

Evaluation of criteria for discontinuing mechanical ventilatory support.

Thirty-three patients who required short-term postoperative mechanical ventilatory support were studied to compare different criteria established to initiate weaning from mechanical ventilation. Intermittent mandatory ventilation criteria (i.e., decreasing mechanical respirator rate as long as the arterial (pHa) remains above 7.35) and conventional criteria (ie, vital capacity greater than 15 ml/kg and peak negative pressure greater than 20 cm H2O) were compared to determine which would more rapidly predict a patient's ability to sustain total spontaneous respiration. All patients were eventually weaned from mechanical ventilation and had their tracheas extubated. Twenty-one patients maintained a pHa of greater than 7.35 during total spontaneous ventilation before they would, or could, meet conventional criteria for initiating a trial of spontaneous respiration (P less than .001). Seven patients simultaneously met both criteria for maintaining total spontaneous ventilation and the remaining five patients met conventional criteria before intermittent mandatory ventilation criteria. In the latter group, the pHa decreased below 7.35 during spontaneous respiration but in only one patient did it fall below 7.30. Our findings suggest that a patient's ability to maintain a pHa of greater than 7.35 while decreasing the frequency of mechanical ventilator breaths is more accurate than peak negative pressure and vital capacity for predicting ability to sustan adequate spontaneous respiration.

Adolescent↗
PubMed1978

Biology of drowning.

The near-drowning victim must be treated immediately for ventilatory insufficiency, hypoxia, and the resulting acidosis. The cause and pathophysiologic changes of pulmonary insufficiency vary, depending on the tpe and volume of fluid aspirated. Success or failure of the overall resuscitative effort frequently depends on the adequacy of prompt emergency resuscitation and on effective intensive pulmonary care. Each patient should be evaluated and treated individually, since abnormalities of multiple organ systems can occur, their degree and form varying considerably from patient to patient (28).

Acid-Base Equilibrium↗