In Reply:-We appreciate the concern of Mr. Moore and the Arrow [registered sign] Corporation relative to our study of the competency of hemostasis valves associated with introducer catheters. As a matter of fact, it was a similar letter sent to our ICU Medical Director that initiated a debate. Part of our faculty agreed with Arrow [registered sign], that a seal (obturator) over a seal (the valve) would provide additional safety by preventing fluid from leaking out through the valve and air entrainment in through the valve. Other clinicians believed that the obturator represented an additional expense to the patient and hospital with no tangible benefit to the patient. It was our decision to settle this dispute with data rather than rhetoric, and thus our study was performed.
In our study, we obtained 29 introducer catheters that had been used in ICU patients and 50 new valves from Arrow. We filled a closed system with saline solution and applied negative pressure to the valves, measuring the pressure at which the valves “failed” by entraining air into the system. We repeated the test with segments of pulmonary artery catheter (PAC), inserted short term and long term (8 days), and repeated measurements with an obturator cap in place. Our results demonstrated that the valves associated with introducer catheters remain competent to pressures far in excess of intrathoracic pressures that would be encountered clinically. Our data also demonstrated that using the obturator cap further augmented the protective effect of the valve by increasing the amount of negative pressure required to entrain air through most of the valves.
There were, however, two valves that initially demonstrated normal competency with negative pressures of -443 mmHg and -378 mmHg required to entrain air that dropped to -70 mmHg and -75 mmHg, respectively, after insertion of the PAC. Competency improved with removal of the PAC (to -430 mmHg and -378 mmHg), but when the obturator cap was applied, the failure pressure decreased to -242 mmHg and -133 mmHg. Thus, placement of the obturator cap actually worsened the function of these two hemostasis valves.
No laboratory study, including ours, can recreate every situation that might be encountered clinically. In our study we used a modest number of valves and subjected them to a few clinically relevant tests to determine the validity of the claim that obturator caps are necessary to maintain competency. Our data showed that the obturator cap is not necessary to maintain the competency of the hemostasis valves associated with Arrow [registered sign] introducer catheters and may actually degrade the function of the valves. If Arrow [registered sign] has data to suggest otherwise, we would be anxious to see it published.
Drew A. MacGregor, M.D.
Assistant Professor of Anesthesiology and Medicine;firstname.lastname@example.org
Phillip E. Scuderi, M.D.
Associate Professor of Anesthesiology; Wake Forest University School of Medicine; Winston-Salem, North Carolina 27157-1009
(Accepted for publication November 24, 1998.)