Bruce P. Krieger

Evaluation of conventional criteria for predicting successful weaning from mechanical ventilatory support in elderly patients.

To assess whether the accepted weaning parameters (derived from middle-aged patients) are helpful in determining discontinuation of mechanical ventilatory support (MVS) in elderly patients, we retrospectively reviewed records of 269 patients greater than or equal to 70 yr who were weaned from MVS from January, 1984 through June, 1985 at one institution. Parameters studied included spontaneous respiratory rate, tidal volume, minute ventilation, maximal inspiratory pressure (MIP), pH, PaCO2, PaO2, and PaO2/FiO2. Two hundred forty-one patients (mean age 80 yr) were successfully weaned while 28 patients (mean age 80 yr) required reinstitution of MVS within 48 h. MIP and pH were statistically lower in the unsuccessfully weaned group, although the mean absolute differences were small (-32 vs. -38 cm H2O and 7.42 vs. 7.44 cm H2O, respectively). All parameters had good positive predictive values but poor negative predictive values (less than or equal to 22%) and only marginal diagnostic accuracy (58% to 86%). We conclude that strict adherence to previously published weaning parameters may not be applicable in deciding when to discontinue MVS in elderly patients.

Pulmonary artery rupture induced by a pulmonary artery catheter: a case report and review of the literature.

Placement and use of pulmonary artery catheters (PACs) carry potential risks. The authors describe a case of a patient who developed massive hemoptysis after placement of a PAC that caused a rupture of the pulmonary artery with pseudoaneurysm formation. Treatment was successfully achieved with transcatheter coil embolization. Pulmonary artery rupture and pseudoaneurysm formation are among the most serious complications of PAC use because of the associated risk of mortality. Patients with this complication may be asymptomatic or may present with variable amounts of hemoptysis immediately or days after using a PAC. The gold standard diagnostic test is pulmonary angiography, and the treatment of choice for most patients is transcatheter embolization. Physicians and other health care personnel handling these catheters should be familiar with the specific PAC balloon’s inflation limits to avoid complications that may injure the patient.

Oxygen desaturation and changes in breathing pattern in patients undergoing colonoscopy and gastroscopy.

The respiratory effect of diagnostic colonoscopy and upper endoscopy were studied in 32 elderly patients. Twenty-two underwent colonoscopy and 10 upper endoscopy. In the group undergoing upper endoscopy, 4 of 10 patients experienced a decrease in oxygen desaturation greater than or equal to 4% during the medication period; an additional 2 patients desaturated during the procedure. In the group undergoing colonoscopy, 12 of 22 patients experienced oxygen desaturation during the medication period; 3 other patients desaturated during the procedure. Mean SaO2 for each group was lowest (p less than 0.05) during the medication period. Central apneas occurred in 13 of the patients undergoing colonoscopy during the medication period; however, only 8 of these patients with apneas experienced desaturation greater than or equal to 4% and the periods of desaturation did not correlate with the periods of apneas. Oxygen desaturation greater than or equal to 4% occurs frequently during both upper endoscopy and colonoscopy in this elderly population. This is related to the effects of sedation; the procedure itself worsened the desaturation in only 16% of the patients. Furthermore, the desaturation did not correlate with changes in the breathing patterns of the patients. Low-flow oxygen and/or close monitoring of patients during and subsequent to administration of medication is advised.

Near-drowning: Epidemiology, pathophysiology, and initial treatment

Drowning is a major cause of accidental deaths, especially in children. The most serious pathophysiologic consequence of near-drowning is hypoxemia, which usually is due to aspiration-induced noncardiogenic edema. Therefore, initial resuscitative efforts need to be directed at establishing adequate oxygenation and ventilation, followed by rewarming and fluid administration. Although completely asymptomatic patients with normal vital signs, oxygenation and chest radiographs require only 4 to 6 hours of observation, many near-drowning victims will require at least 24 hours of observation. Despite these measures, approximately 25% of victims presenting to the Emergency Department will die and another 6% will develop neurological sequelae. Therefore, it is vital that better efforts be made by the community in promoting and instituting water safety programs.

Hyperinflation and Intrinsic Positive End-Expiratory Pressure: Less Room to Breathe

Clinically, the symptoms and limited exercise capabilities of patients with chronic obstructive pulmonary disease (COPD) correlate better with changes in lung volumes than with airflow measurements. The realization of the clinical importance of hyperinflation has been overshadowed for decades by the use of forced expiratory volume during 1 s (FEV1) and the ratio of the FEV1 to the forced expiratory vital capacity (FEV1/FVC) to categorize the severity and progression of COPD. Hyperinflation is defined as an elevation in the end-expiratory lung volume or functional residual capacity. When severe hyperinflation encroaches upon inspiratory capacity and limits vital capacity, it results in elevated intrinsic positive end-expiratory pressure (PEEPi) that places the diaphragm at a mechanical disadvantage and increases the work of breathing. Severe hyperinflation is the major physiologic cause of the resulting hypercarbic respiratory failure and patients’ inability to transition (i.e. wean) from mechanical ventilatory support to spontaneous breathing. This paper reviews the basic physiologic principles of hyperinflation and its clinical manifestations as demonstrated by PEEPi. Also reviewed are the adverse effects of hyperinflation and PEEPi in critically ill patients with COPD, and methods for minimizing or counterbalancing these effects.

Diaphragmatic flutter resulting in failure to wean from mechanical ventilator support after coronary artery bypass surgery.

Diaphragmatic dysfunction, most commonly elevation of the left hemidiaphragm and/or phrenic nerve paralysis, are well-known complications of coronary artery bypass grafting (CABG). Diaphragmatic flutter (DF) is an easily overlooked breathing pattern characterized by rapid (greater than 40 times/min) involuntary contractions of the diaphragm, at times superimposed on a more normal breathing pattern (dirhythmic breathing). Using respiratory inductive plethysmography, we were able to record this unusual ventilatory pattern in four patients after CABG. All procedures were performed via median sternotomy with topical hypothermia. Sternal complications were present in three cases (instability, dehiscence, infection). DF could not be suppressed by mechanical hyperventilation or patient volition. Weaning was unsuccessful until after DF abated. Diaphragmatic flutter may occur after CABG and should be considered as a cause of failure to wean from mechanical ventilator support in this setting.

When wheezing may not mean asthma: Other common and uncommon causes to consider

PREVIEW Asthma often is assumed to be the cause of wheezing. However, any process that narrows an airways aperture or increases airflow velocity through an orifice can produce wheezing. In this article, Dr Krieger reviews the differential diagnosis of wheezing and provides guidelines for recognizing conditions that produce wheezing but are not asthma.

Altitude-related pulmonary disorders

The major physiologic stress encountered at high altitude is caused by the occurrence of hypobaric hypoxia. In this article, acute and chronic pulmonocardiac adaptation to altitude is reviewed, including possible genetic differences among highlanders from the Himalayan versus the Andean Mountains. The origin, symptoms, and treatment of acute mountain sickness and high altitude pulmonary edema are outlined. In addition, the prediction and prevention of pulmonary complications that may be encountered or exacerbated during commercial airflight are noticed.

Respiratory Muscle Fatigue

Excerpt To the Editor:Murciano and colleagues (1) showed that tracheal occlusion pressure (P0.1) provided a better predictive index for successful extubation than classic weaning criteria in patien...